**Department of Health and Human Services**

**Muscular Dystrophy Coordinating Committee**

**Action Plan for the Muscular Dystrophies**

**Plan developed by the:**

**Muscular Dystrophy Coordinating Committee**

**Scientific Working Group**

**August 16-17, 2005**

**Bethesda, Maryland**

**Approved by the:**

**Muscular Dystrophy Coordinating Committee**

**December 2005**

**Muscular Dystrophy Coordinating Committee**

**Action Plan for the Muscular Dystrophies**

**Table of Contents**

**I. Introduction**

A. The Muscular Dystrophies 1

B. Muscular Dystrophy Coordinating Committee (MDCC) 3

Purpose of the MDCC 3

The MDCC Research and Education Plan for the NIH 3

C.  Muscular Dystrophy Coordinating Committee Scientific Working

> Group 4

MDCC SWG Charge 4

MDCC SWG Process 4

Goal for the MDCC SWG Planning Process 5

**II. Muscular Dystrophy Research Planning Process Participants**

> A. Scientific Working Group Composition 6

Mechanisms of Muscular Dystrophy Subgroup 6

Diagnosis and Screening of Muscular Dystrophy Subgroup 6

Therapy of Muscular Dystrophy Subgroup 6

Living with Muscular Dystrophy Subgroup 7

Research Infrastructure for Muscular Dystrophy Subgroup 7

B. Outside Consultant 7

C. Muscular Dystrophy Coordinating Committee Membership 7

> D. National Institutes of Health Staff Participants 8

**III. Mechanisms of Muscular Dystrophy**

A. Introduction 10

B. Recent Research Advances 11

Duchenne/Becker Muscular Dystrophy 11

Myotonic Dystrophy 13

Facioscapulohumeral Muscular Dystrophy 14

Laminopathies 14

Congenital Muscular Dystrophies 15

Calpainopathies 16

Defects in Membrane Repair 16

Oculopharyngeal Muscular Dystrophy 17

C. Research Objectives 17

Disease-Specific Pathogenic Mechanisms 18

General Pathogenic Mechanisms 20

Infrastructure Needs 21

D.  Matrix of Research Objectives in Mechanisms of Muscular 23

> Dystrophy

**IV. Diagnosis and Screening of Muscular Dystrophy**

A. Introduction 24

B. Recent Research Advances 25

Improved Molecular Diagnosis in Duchenne/Becker Muscular Dystrophy 25

Dysferlin Expression Testing on Peripheral Blood Monocytes 25

Western Blot Approaches to Diagnosis of Limb Girdle Muscular Dystrophy
25

Identification of the Role of Alpha-Dystroglycan in Muscular Dystrophy
and

> Use of Screening Tests for Abnormal Glycosylation 26

Development of Mutation Testing for Myotonic Dystrophy Type 2 27

Improved Diagnostic Testing in Facioscapulohumeral Muscular Dystrophy 27

C. Research Objectives 28

Technology for Diagnostic Testing 28

Resources for the Research Community Related to Diagnosis 29

Muscle Imaging as a Diagnostic Tool 31

Epidemiology Studies Based on Genetic Diagnosis 32

Neonatal Testing for Muscular Dystrophy 32

E.  Matrix of Research Objectives in Diagnosis and Screening in

> Muscular Dystrophy 34

**V. Therapy of Muscular Dystrophy**

A. Introduction 35

B. Recent Research Advances 36 Corticosteroid Use 36

Muscle Growth Factor Modulation 36

Cell-Based Therapy 37

Improvement in Understanding of Pathogenesis 38

Advances in Genetic Diagnosis 39

Viral Vector Gene Replacement Therapy 39

Gene Correction/Gene-Based Therapy 40

Alternative Pathways (Indirect Genetic Complementation) 41

Respiratory Care Guidelines 42

C. Research Objectives 42

Corticosteroids and Anti-Inflammatory Drugs 43

Growth Factor Modulation 44

Cell-Based Therapy 44

Viral Vector Gene Therapy 46

Gene Repair 48

High-Throughput Screening and Translational Research 48

Cardiopulmonary Care 49

Infrastructure Needs 50

D. Matrix of Research Objectives in Therapy of Muscular Dystrophy 52

**VI. Living with Muscular Dystrophy**

A. Introduction 54

B. Recent Research Advances 55

Corticosteroids in Duchenne Muscular Dystrophy 55

Application of Non-Invasive Ventilation and Cough-Assist Techniques 55

Early Recognition of and Advances to Treat Sleep-Disordered Breathing 56

Improved Techniques for Diagnosis and Testing 56

Early Diagnosis and Management of Cardiomyopathy 56

Management of Gastrointestinal Dysfunction 57

Nutritional Management of Obesity and Cachexix 57

Application of Assistive Technologies 58

Improved Understanding of Cognitive Defects 58

Recognition of Decreased Bone Mineral Content in Duchenne Muscular

Dystrophy and its Management 58

Documentation of the Benefits of Physical Activity and Exercise in
Slowly

Progressive Muscular Dystrophies 59

Multi-Disciplinary Approach to Diagnosis, Treatment, and Management 59

C. Research Objectives 59

Quality of Life Measures in Muscular Dystrophy 60

Clinical Endpoints in Natural History Studies and Clinical Trials 60

Consensus Guidelines for the Clinical Management of the Muscular

> Dystrophies 61

Benefits and Risks of Exercise and Physical Activity 62

Understanding and Managing the Secondary Consequences of Muscular

Dystrophy 63

Patient and Family Education and Social Participation in the

> Community and Physician Training 64

D. Matrix of Research Objectives in Living with Muscular Dystrophy 66

**VII. Research Infrastructure Needs for Muscular Dystrophy**

A. Introduction 67

B. Currently Available Research Resources 68

Resources for Mechanistic Studies in Muscular Dystrophy 68

Resources for Diagnosis and Screening and Therapeutic Development 69

Resources for Reducing the Clinical Burden of Disease 71

Resource Centers for Muscular Dystrophy 72

Resources for Education and Training 72

Resources for Muscular Dystrophy in Europe 74

C. Needed Research Resources 76

Preclinical Research Infrastructure 76

Clinical Research and Trial Infrastructure 78

Communication and Education 81

D.  Matrix of Research Objectives in Research Infrastructure Needs for

> Muscular Dystrophy 84

**VIII. action plan Implementation, Tracking, and Assessment**

A. Plan Implementation 85

B. Plan Tracking 86

C. Plan Assessment 86

**Muscular Dystrophy Coordinating Committee**

**Action Plan for the Muscular Dystrophies**

**Tables**

**Table 1:** Matrix of Research Objectives in Mechanisms of Muscular

> Dystrophy 23

**Table 2:** Matrix of Research Objectives in Diagnosis and Screening in

> Muscular Dystrophy 34

**Table 3:** Matrix of Research Objectives in Therapy of Muscular
Dystrophy 52-53

**Table 4:** Matrix of Research Objectives in Living with Muscular
Dystrophy 66

**Table 5:** Matrix of Research Objectives in Research Infrastructure
Needs for

Muscular Dystrophy 84

**Muscular Dystrophy Coordinating Committee**

**Action Plan for the Muscular Dystrophies**

**Summary Listing of Research Objectives**

Note: Research Objectives are grouped so that thematically related
objectives appear together within each of the five topics. Their
sequential order does not reflect any prioritization of the Research
Objectives.

**[Mechanisms of Muscular Dystrophy]{.underline}**

**Disease-Specific Pathogenic Mechanisms**

-   *Research Objective 1:* Define the role that disrupted signal
    transduction pathways play in the pathogenesis of Duchenne and
    Becker muscular dystrophies and assess their viability as
    therapeutic targets (Long Term; Low Risk).

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-   *Research Objective 2:* Define post-transcriptional mechanisms that
    lead to muscle (and other tissue) phenotypes in myotonic dystrophy
    and evaluate the role of DNA repair/replication/recombination
    mechanisms in microsatellite expansion (Medium Term; Intermediate
    Risk).

-   *Research Objective 3:* Define the molecular pathogenetic mechanisms
    that lead to facioscapulohumeral muscular dystrophy (Long Term; High
    Risk).

-   *Research Objective 4:* Establish mouse (and cellular) models for
    facioscapulohumeral muscular dystrophy, specific to emerging
    candidate genes and/or disease genomics, to understand the
    epigenetic mechanisms and for the development of novel intervention
    strategies (Long Term; Intermediate Risk).

-   *Research Objective 5:* Define the multiple divergent effects that
    single mutations in nuclear envelope proteins exert on different
    tissues in Emery-Dreifuss muscular dystrophy and other laminopathies
    (Medium Term; High Risk).

-   *Research Objective 6:* Determine the pathogenic pathways that are
    downstream from PABPN1 protein nuclear aggregate formation in
    oculopharyngeal muscular dystrophy (Medium Term; Intermediate Risk).

**General Pathogenic Mechanisms**

-   *Research Objective 7:* Support continued gene identification and
    biochemical characterization of rare and understudied forms of
    muscular dystrophy (Medium Term; Low Risk).

-   *Research Objective 8:* Define the roles of inflammation, oxidative
    stress, and disrupted calcium homeostasis as primary or secondary
    pathogenic mechanisms in the muscular dystrophies (Medium Term; Low
    Risk).

-   *Research Objective 9:* Characterize defects in post-translational
    processing and resulting pathogenetic mechanisms in the congenital
    muscular dystrophies and related disorders (Short Term; Intermediate
    Risk).

-   *Research Objective 10:* Define biochemical mechanisms involved in
    membrane instability and membrane repair in dystrophic muscle (Long
    Term; Low Risk).

-   *Research Objective 11:* Elucidate apoptotic mechanisms occurring in
    the muscular dystrophies as potential targets for therapeutic
    intervention (Long Term; Low Risk).

**Infrastructure Needs**

-   *Research Objective 12:* Establish invertebrate, other vertebrate,
    and alternative model systems to study pathogenetic mechanisms of
    gene/RNA/protein defects that cause muscular dystrophies in humans
    (Long Term; Intermediate Risk).

-   *Research Objective 13:* Establish mouse models for dystrophies
    where none exist, and expand development of mouse models that modify
    disease phenotype to identify/study disease modifying genes (Long
    Term; Intermediate Risk).

**[Diagnosis and Screening of Muscular Dystrophy]{.underline}**

**Technology for Diagnostic Testing**

-   *Research Objective 1:* Develop minimally invasive diagnostic
    techniques for muscular dystrophies where appropriate (Medium Term;
    Intermediate Risk).

-   *Research Objective 2:* Develop definitive gene tests for muscular
    dystrophies for which genetic testing is not yet available (Short
    Term; Low Risk to Long Term; Low Risk).

-   *Research Objective 3:* Establish mechanisms for muscular dystrophy
    patients to obtain accurate genetic counseling (Short Term; Low
    Risk).

-   *Research Objective 4:* Establish the specificity and sensitivity of
    diagnostic tests for the muscular dystrophies (Long Term;
    Intermediate Risk).

**Resources for the Research Community Related to Diagnosis**

-   *Research Objective 5:* Encourage submission of new mutation and
    polymorphism data for muscular dystrophy genes to public databases
    (Short Term; Low Risk).

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-   *Research Objective 6:* Support disease-specific registries with
    detailed genetic, structural and functional information regarding
    phenotypic effects in other organ systems, as well as structural and
    functional information regarding phenotypic effects in other organ
    systems, as well as pathological and clinical information. Foster
    cooperation between registries, neuromuscular research centers, and
    academic diagnostic centers (Long Term; Intermediate Risk).

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-   *Research Objectives 7-9:* Optimize utilization of muscle biopsy
    materials for research by:

    -   Developing IRB language to assist investigators with use of
        archived or prospectively collected diagnostic muscle biopsies
        (Short Term; Low Risk).

    -   Fostering shared use of stored and prospectively collected
        diagnostic muscle biopsies by the research community (Short
        Term; Low Risk).

    -   Further developing new techniques for evaluation of muscle
        samples (such as Western blot analysis of very small quantities,
        proteomics, and laser capture microscopy) and, where
        appropriate, moving them into the diagnostic algorithm (Medium
        Term; Intermediate Risk).

**Muscle Imaging as a Diagnostic Tool**

-   *Research Objective 10:* Develop and validate the role of muscle
    imaging in diagnostic evaluation or as an endpoint measure for
    clinical trials (Long Term; High Risk).

**Epidemiology Studies Based on Genetic Diagnosis**

-   *Research Objective 11:* Establish current and accurate incidence
    and prevalence data for genetically confirmed forms of muscular
    dystrophy (Long Term; Intermediate Risk).

**Neonatal Testing for Muscular Dystrophy**

-   *Research Objective 12:* Develop methods for newborn screening of
    the muscular dystrophies. Explore the social and ethical issues
    involved in offering neonatal screening for muscular dystrophy and
    develop techniques that would make screening practical (Long Term;
    Intermediate Risk).

**[Therapy of Muscular Dystrophy]{.underline}**

**Corticosteroids and Anti-Inflammatory Drugs**

-   *Research Objective 1:* Optimize the use of prednisone as a
    treatment for Duchenne muscular dystrophy (Long Term; Low Risk).

-   *Research Objective 2:* Determine the mechanism of action of the
    corticosteroids in muscular dystrophy in order to develop new,
    potentially more efficacious agents (Medium Term; High Risk).

-   *Research Objective 3:* Examine the efficacy of existing
    anti-inflammatory drugs for treatment of muscular dystrophy (Medium
    Term; Low Risk).

**Growth Factor Modulation**

-   *Research Objective 4:* Expand insulin-like growth factor 1 (IGF1)
    preclinical studies and the scope of ongoing clinical trials and
    understand IGF1's local effects in muscle and other tissues (Short
    Term; Low Risk).

-   *Research Objective 5:* Identify alternative mechanisms of myostatin
    inhibition and establish their potential as therapeutics through
    preclinical testing in animal models of various types of muscular
    dystrophy (Medium Term; Intermediate Risk).

**Cell-Based Therapy**

-   *Research Objective 6:* Achievement of adequate immunosuppression to
    support myoblast transplant therapy (Medium Term; Low Risk)

-   *Research Objective 7:* Define, through basic and preclinical
    translational studies, the therapeutic potential of alternative
    muscle progenitor cells (Medium Term; Intermediate Risk).

-   *Research Objective 8:* Define, through basic and preclinical
    translational studies, the therapeutic potential of embryonic stem
    cells (Medium Term; Low Risk).

**Viral Vector Gene Therapy**

-   *Research Objective 9:* Conduct large animal model testing to
    determine optimal AAV serotypes for human gene therapy clinical
    trials (Short Term; Low Risk).

-   *Research Objective 10:* Improve the efficiency of gene therapy
    delivery in the muscular dystrophies, while minimizing the immune
    response to both gene product and delivery vehicle (Medium Term;
    Intermediate Risk).

-   *Research Objective 11:* Evaluate the clinical endpoints needed for
    and ethical issues associated with Phase I/II gene therapy and all
    clinical trials (Medium Term; Intermediate Risk).

**Gene Repair**

-   *Research Objective 12:* Evaluate the safety and efficacy of stop
    codon readthrough and exon skipping agents through additional
    translational studies and clinical trials (Long Term; Intermediate
    Risk).

-   *Research Objective 13:* Develop novel agents to improve efficacy of
    current gene repair strategies or to open new strategies (Medium
    Term; High Risk).

**High-Throughput Screening and Translational Research**

-   *Research Objective 14:* Identify new strategies to implement
    translational research projects for muscular dystrophy (Short Term;
    Low Risk).

-   *Research Objective 15:* Expand high-throughput, small molecule
    screening efforts for promising therapeutic targets and identify
    novel targets for drug development (Short Term; Low Risk).

**Cardiopulmonary Care**

-   *Research Objectives 16-18:* Improve treatment for cardiopulmonary
    consequences in muscular dystrophy patients by:

    -   Developing guidelines based on evidence and/or current practice
        standard of care (Short Term; Low Risk).

    -   Assessing the value of FDA-approved agents for cardiopulmonary
        complication prevention (Long Term; Low Risk).

    -   Improving management of cardiomyopathy, conduction block, and
        arrhythmia (Long Term; Intermediate Risk).

**Infrastructure Needs**

-   *Research Objective 19:* Develop the animal models, assays, and
    tools necessary for preclinical translational research projects that
    focus upon rapidly moving the accumulated mechanistic knowledge into
    clinical practice (Medium Term; Intermediate Risk).

-   *Research Objective 20:* Improve the availability and distribution
    network for appropriate mouse models of muscular dystrophy (Short
    Term; Low RIsk).

-   *Research Objective 21:* Ensure the availability and use of large
    animal models for the later stages of preclinical development (Long
    Term; Low Risk).

**[Living with Muscular Dystrophy]{.underline}**

**Quality of Life Measures in Muscular Dystrophy**

-   *Research Objective 1:* Identify and evaluate the quality of life
    and burden of disease measurement tools that are currently available
    (Short Term; Low Risk).

-   *Research Objective 2:* Develop disease-specific quality of life and
    burden of disease measures where gaps in existing measures are found
    (Medium Term; Low Risk).

**Clinical Endpoints in Natural History Studies and Clinical Trials**

-   *Research Objective 3:* Determine the sensitivity of clinical
    endpoints to changes in disease severity (Medium Term; Low Risk).

-   *Research Objective 4:* Determine the magnitude of changes in
    endpoints which are clinically meaningful to patients and family
    members (Medium Term; Low Risk).

-   *Research Objective 5:* Study the interrelationship of clinical
    endpoints for specific muscular dystrophies (Long Term; Low Risk).

-   *Research Objective 6:* Develop standardized data collection
    approaches nationally using clinically meaningful, readily
    obtainable parameters; develop a minimum data set for national data
    gathering efforts (Medium Term; Intermediate Risk).

**Consensus Guidelines for the Clinical Management of the Muscular
Dystrophies**

-   *Research Objective 7:* Develop consensus guidelines for clinical
    management using Duchenne muscular dystrophy as a model (Short Term;
    Low Risk).

-   *Research Objective 8:* Develop consensus guidelines for the
    clinical management of other muscular dystrophies (Medium Term; Low
    Risk).

**Benefits and Risks of Exercise and Physical Activity**

-   *Research Objective 9:* Determine the benefits and risks of varied
    exercise approaches in muscular dystrophies and develop
    scientifically based recommendations concerning optimal exercise,
    physical activity, and recreation (Medium Term; Intermediate Risk).

**Understanding and Managing the Secondary Consequences of Muscular
Dystrophy**

-   *Research Objective 10:* Assess the prevalence of secondary
    conditions in muscular dystrophy using existing longitudinal data
    collection efforts (Short Term; Low Risk).

-   *Research Objective 11:* Assess the natural history of secondary
    conditions in muscular dystrophy using existing longitudinal data
    collection efforts (Medium Term; Low Risk).

-   *Research Objective 12:* Assess the effectiveness of clinical
    management approaches to prevent and treat secondary conditions
    using existing multi-center collaborative networks and clinically
    meaningful outcomes (Medium Term; Intermediate Risk).

-   *Research Objective 13:* Define the neuropsychological and
    neurobehavioral profiles that impact on quality of life and
    caregiver burden and identify useful interventions (Medium Term;
    Intermediate Risk).

**Patient and Family Education and Social Participation in the Community
and**

**Physician Training**

-   *Research Objective 14:* Establish annual educational conferences
    for patients and families focused on specific muscular dystrophies
    (Short Term; Low Risk).

-   *Research Objective 15:* Identify strategies to improve patient
    integration into educational systems (Short-term; Low Risk).

-   *Research Objective 16:* Identify strategies to improve vocational
    outcomes and reduce social isolation (Medium Term; Intermediate
    Risk).

-   *Research Objective 17:* Develop strategies to improve physician
    effectiveness in communicating with and managing the care of
    patients with muscular dystrophy (Short Term; Low Risk).

**[Research Infrastructure Needs for Muscular Dystrophy]{.underline}**

**Preclinical Research Infrastructure**

-   *Research Objective 1:* Facilitate research (discovery, validation,
    and dissemination) of the biochemical pathways involved in muscular
    dystrophy (Medium Term; Intermediate Risk).

-   *Research Objective 2:* Establish standardized endpoints for
    preclinical trials in both mouse models, and the dog model, and
    ensure that facilities are available that enable testing of drugs
    and other therapeutic approaches (Long Term; Low Risk).

-   *Research Objective 3:* Create a mechanism to maintain mouse models
    of muscular dystrophy at approved vendors in a live state, available
    for easy and rapid importation into academic colonies (Medium Term:
    Low Risk).

-   *Research Objective 4:* Develop optimized models for mechanistic
    studies of specific muscular dystrophies, including models
    appropriate for therapeutic development screens (Medium Term; High
    Risk).

-   *Research Objective 5:* Encourage the development of cell-based
    assays that target aspects of pathogenesis and pathophysiology in
    the muscular dystrophies, to enable high throughput drug screening
    (Medium Term; High Risk).

**Clinical Research Infrastructure**

-   *Research Objective 6:* Establish a focus panel for molecular
    diagnostics of the muscular dystrophies, with the charge of
    developing consensus standards and approaches for molecular testing,
    screening, interpretation of results, and genetic counseling (Long
    Term; Low Risk).

-   *Research Objective 7:* Identify, develop, and encourage the use of
    standardized instruments to measure quality of life, cognitive, and
    central nervous system function using existing databases and
    potentially develop new common element databases to extend research
    capabilities (Medium Term; Intermediate Risk).

-   *Research Objective 8:* Monitor, coordinate, and communicate the
    rehabilitation and educational assessment activities of the various
    Federal agencies, voluntary, and patient advocacy groups (Long Term;
    Low Risk).

**Communication and Education**

-   *Research Objective 9:* Design and implement a web site that
    provides information and links to all existing resources in both the
    USA and internationally (Short Term; Low Risk).

-   *Research Objective 10:* Establish a USA equivalent of the European
    Neuromuscular Centre's disease focus meetings to link to and
    communicate with European and other international networks or groups
    (Short Term; Low Risk).

-   *Research Objective 11:* Increase the number and scientific breadth
    of basic scientists and clinicians involved in translational
    research in the muscular dystrophies (Long Term; Intermediate Risk).

-   *Research Objective 12:* Provide a publicly accessible listing of
    available training grants and resources so that opportunities for
    physicians and scientists are transparent (Short Term; Low Risk).

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-   *Research Objective 13:* Stimulate international collaborations and
    infrastructure sharing to ensure that opportunities are exploited
    and resources are used to maximum advantage, particularly in cases
    of novel opportunity or for the rare and/or understudied muscular
    dystrophies (Short Term; Intermediate Risk).

**Introduction**

The Muscular Dystrophy Coordinating Committee Scientific Working Group
was formed in the spring of 2005 and charged with developing
recommendations for specific Research Objectives for the muscular
dystrophies. The focus of the Muscular Dystrophy Coordinating Committee
Scientific Working Group was to identify scientific opportunities in the
areas of disease mechanisms, diagnosis and screening, therapy, living
with muscular dystrophy, and research infrastructure. This "Action Plan
for the Muscular Dystrophies" was designed to specifically identify
currently feasible, high-priority Research Objectives that could be used
by the Muscular Dystrophy Coordinating Committee and the muscular
dystrophy scientific community to coordinate research activities in
order to achieve the goal of timely detection, diagnosis, treatment, and
prevention of all of the muscular dystrophies.

**A. The Muscular Dystrophies**

Muscular dystrophy refers to a group of hereditary, progressive
degenerative disorders causing weakness of the skeletal or voluntary
muscles. There are many different forms of muscular dystrophy, which
differ in their age of onset, penetrance, severity, and pattern of
muscles affected. Most types of muscular dystrophy are not simply muscle
disorders, but rather multisystem disorders with manifestations in a
variety of body systems, including the heart, gastrointestinal system,
endocrine glands, skin, eyes, brain, and other organ systems. The major
forms of muscular dystrophy include Duchenne/Becker, limb girdle,
congenital, facioscapulohumeral, myotonic, oculopharyngeal, distal, and
Emery-Dreifuss. Although some forms first become apparent in early
childhood, others may not appear until middle age or later.

Duchenne muscular dystrophy, the most common form of muscular dystrophy
in children, is an X-linked, severe and progressive degenerative
myopathy with early childhood onset. Muscle fiber degeneration and
replacement by fibrous tissue and fat occurs in the skeletal muscles and
in the heart. Cognitive dysfunction can also occur. It is caused by
mutations in the gene encoding dystrophin, resulting in the absence or
deficiency of this protein. Becker type muscular dystrophy, which is
also caused by mutations in the dystrophin gene, has onset in
adolescence or adulthood with a less severe course of progression. An
animal model, the mdx mouse, is extensively used to study these
disorders.

Number range CHAPTERThe limb girdle muscular dystrophies all show a
similar distribution of muscle weakness, affecting both upper arms and
legs. Many forms of limb girdle muscular dystrophy have been identified,
showing different patterns of inheritance: autosomal recessive
(designated LGMD1) or autosomal dominant (LGMD2). In an autosomal
recessive pattern of inheritance, an individual receives two copies of
the defective gene, one from each parent. In an autosomal dominant
disease, the disorder can occur in either sex when an individual
inherits a single defective gene from either parent. The recessive limb
girdle muscular dystrophies are more frequent than the dominant forms,
and may be more severe. Limb girdle muscular dystrophy can have a
childhood onset, although more often symptoms appear in adolescence or
young adulthood. The dominant limb girdle muscular dystrophies usually
show adult onset. Some of the recessive forms have been associated with
defects in proteins that make up the dystrophin-glycoprotein complex.
Mutations in one component of the dystrophin-glycoprotein complex, the
sarcoglycans, can lead to the forms of limb girdle muscular dystrophy
known as LGMD2C, 2D, 2E, and 2F. Defects in caveolin 3, a protein that
associates with the dystrophin-glycoprotein complex, lead to LGMD1C,
while mutations in dysferlin, a protein that is thought to interact with
caveolin 3, cause LGMD2B. Mutations in genes not related to the
dystrophin-glycoprotein complex are implicated in other forms of limb
girdle muscular dystrophy. For example, mutations in the enzymatic
protein calpain 3 lead to LGMD2A.

Myotonic dystrophy is the most common form of muscular dystrophy. It is
dominantly inherited and characterized by muscle hyperexcitability
(myotonia), muscle wasting and weakness, cataracts, hypogonadism,
cardiac conduction abnormalities and other developmental and
degenerative manifestations frequently including cognitive dysfunction.
Penetrance can be variable. Myotonic dystrophy can be caused by
mutations in different genes, but the characteristics are quite similar.
Type 1 myotonic dystrophy (DM1) is caused by expansion of a CTG triplet
repeat in an untranslated region of the dystrophia myotonica protein
kinase gene (DMPK) on chromosome 19, while type 2 (DM2) is caused by
expansion of a CCTG repeat in the first intron of the zinc finger
protein-9 gene (ZNF9) on chromosome 3. Repeat number in the myotonic
dystrophies increases in subsequent generations (anticipation). DM1 also
has congenital and childhood onset forms; these early appearing forms of
the disease differ mechanistically from the adult form only in
exhibiting larger CTG repeats that, in turn, trigger earlier appearance
of symptoms. Those patients that survive early onset DM1 frequently
exhibit morbidity and mortality in the third and fourth decades relating
to cardiopulmonary involvement.

Facioscapulohumeral muscular dystrophy is an autosomal dominant
progressive degenerative disease that initially affects the muscles of
the face (facio), shoulders (scapulo), and upper arms (humeral),
followed by the muscles of the feet, pelvic girdle, and abdomen.
Affected individuals may also suffer from hearing loss. Onset and
progression of the disease is variable and often the weakness is
asymmetrical in affected individuals. Life expectancy is typically
within normal range, but the disease can lead to severe disability.
Nearly all cases are associated with deletions of tandem repeats, termed
D4Z4, in a distal region of chromosome 4 (4q35).

Number range CHAPTERThe congenital muscular dystrophies are a
heterogeneous class of disorders, and include several disorders with a
range of symptoms. Muscle degeneration can be mild or severe, and may be
restricted to skeletal muscle, or paired with effects on the brain and
other organs. Defects in the protein merosin are responsible for about
half of the cases in the U.S. Mutations in one of the integrin proteins
gives rise to another form of congenital muscular dystrophy. Defects in
the proteins called fukutin and fukutin-related protein cause the most
common forms of congenital muscular dystrophy found in Japan. All of
these proteins are thought to have some relationship to the
dystrophin-glycoprotein complex. Some forms of congenital muscular
dystrophy, including Fukuyama muscular dystrophy, muscle-eye brain
disease, and Walker-Warburg syndrome are due to defective glycosylation
of one of the proteins in the dystrophin-glycoprotein complex
(alpha-dystroglycan) and show severe brain malformations, such as
lissencephaly (a "cobblestone" appearance to part of the brain) and
hydrocephalus (an excessive accumulation of fluid in the brain). Other
forms, including the merosin-absent form and rigid spine syndrome, do
not have major brain malformations associated with the disease. The
molecular basis for many forms of congenital muscular dystrophy remains
unknown.

Number range CHAPTERSeveral other forms of muscular dystrophy also
occur. Oculopharyngeal muscular dystrophy, which causes weakness in the
eye, throat, and facial muscles, followed by pelvic and shoulder muscle
weakness, has been attributed to a short triplet repeat expansion in the
nuclear polyadenylate binding protein 1 gene (PABPN1), a gene involved
in translating the genetic code into functional proteins. Inheritance
follows either autosomal dominant or autosomal recessive patterns.
Polyalanine tract expansion from a norm of 10 to 12-17 residues causes
aggregation of filamentous intranuclear inclusions in skeletal muscle
which appear to precipitate the disease. This disease is most common
in people of French-Canadian descent or people of Hispanic descent from
certain regions of the Southwest. Miyoshi myopathy, one of the distal
muscular dystrophies, causes initial weakness in the calf muscles, and
is caused by defects in the protein dysferlin, which is the same gene
responsible for LGMD2B, reinforcing the idea that progress against one
form of muscular dystrophy should be informative to other forms. There
are two forms of Emery-Dreifuss muscular dystrophy---an X-linked and an
autosomal dominant form. Emery-Dreifuss muscular dystrophy is
characterized by weakness in the shoulder girdle and lower legs, as well
as the development of contractures in regions of the body, particularly
the elbows, Achilles tendons, and neck. Defects in proteins that make up
the nucleus, including emerin, and lamin A/C, are implicated in the
disorder.

**B. Muscular Dystrophy Coordinating Committee**

The establishment of the Muscular Dystrophy Coordinating Committee
(MDCC) was a major provision of the Muscular Dystrophy Community
Assistance, Research, and Education Amendments of 2001 (the MD-CARE Act,
Public Law 107-84). Number range CHAPTERIn accordance with the MD-CARE
Act, the Committee is composed of ten members from Government agencies
and five members from the public. Government agencies with an interest
in muscular dystrophy research and education, including components of
the Department of Health and Human Services and the Department of
Education, are represented. The Department of Defense is also
represented since it received an appropriation for muscular dystrophy
research in its FY 2003 Appropriations bill. Dr. Stephen Katz, Director
of the National Institute of Arthritis and Neuromuscular and Skin
Diseases, chairs the MDCC. A roster of the MDCC is included in this
report, immediately following this Introduction.

**Purpose of the MDCC**

The MD-CARE Act specified that the Muscular Dystrophy Coordinating
Committee shall coordinate research activities across the National
Institutes of Health and with other Federal health programs and
activities relating to the various forms of muscular dystrophy,
including Duchenne, myotonic, facioscapulohumeral muscular dystrophy,
and other forms of muscular dystrophy. The MD-CARE Act also charged the
Muscular Dystrophy Coordinating Committee with the task of developing a
plan for conducting and supporting research and education on muscular
dystrophy through the National Institutes of Health, and periodically
reviewing and revising the plan. The Act specified that the plan shall:
(a) provide for a broad range of research and education activities
relating to biomedical, epidemiological, psychosocial, and
rehabilitative issues, including studies of the impact of such diseases
in rural and underserved communities; (b) identify priorities among the
programs and activities of the National Institutes of Health regarding
such diseases; and (c) reflect input from a broad range of scientists,
patients, and advocacy groups.

**The MDCC Research and Education Plan for the NIH**

Based upon recommendations from the MDCC, a scientific working group was
convened in October 2003 to identify research goals in muscular
dystrophy. These research goals formed the basis for the Muscular
Dystrophy Research and Education Plan for the NIH, which was approved by
the MDCC and submitted to Congress in August 2004. This plan provided
broad guidelines for the NIH on research priorities for the muscular
dystrophies.

At the December 2004 meeting of the MDCC, the Committee agreed that the
Muscular Dystrophy Research and Education Plan for the NIH provided
broad-based guidance, but that a second scientific working group should
be convened to refine the current plan and to develop and prioritize
specific aims for the entire muscular dystrophy research community.

**C. Muscular Dystrophy Coordinating Committee Scientific Working
Group**

Based upon the MDCC recommendation at its December 2004 meeting, a
second Muscular Dystrophy Coordinating Committee Scientific Working
Group (MDCC SWG) was appointed. MDCC members were asked to nominate
individuals with the appropriate expertise and commitment to serve on
the MDCC SWG. Participants were selected to ensure that all of the major
types of muscular dystrophy were represented, and that there was
sufficient expertise relevant to the topic areas presented in the
Research and Education Plan. Twenty-four muscular dystrophy basic and
clinical researchers and physicians from outside the NIH participated in
the MDCC SWG. Subgroups were formed for each of the five major topics of
the existing MDCC Research and Education Plan for the NIH: Mechanisms of
Muscular Dystrophy, Diagnosis and Screening of Muscular Dystrophy,
Therapy of Muscular Dystrophy, Living with Muscular Dystrophy, and
Research Infrastructure Needs for Muscular Dystrophy. The MDCC SWG, in
coordination with NIH Staff, developed this "Action Plan for the
Muscular Dystrophies."

**MDCC SWG Charge**

The charge of the MDCC SWG was to:

-   Refine and focus the major topics of the MDCC Research and Education
    Plan for the NIH into specific goals that can be addressed by the
    NIH and other organizations.

-   Prioritize these goals and recommend, where a scientific basis
    exists, a sequence for addressing them.

-   Identify additional obstacles and barriers to the progress of
    muscular dystrophy research and treatment as well as other
    outstanding opportunities, noting those that are likely to be
    addressed through ongoing research and programs, and those that
    might benefit from additional emphasis.

The MDCC SWG was specifically asked to identify Research Objectives that
may help achieve the detection, diagnosis, treatment, and prevention of
the muscular dystrophies. The MDCC SWG was to consider all types of
muscular dystrophy and identify Research Objectives that were
high-priority needs for the field.

**MDCC SWG Process**

Each of the 24 extramural scientists and physicians appointed to the
MDCC SWG was assigned to one of the five subgroups; two co-chairs were
appointed in each subgroup. A roster of the MDCC SWG is included in this
report, immediately following this Introduction.

The scope of each subgroup was defined by the five major topics in the
existing MDCC Research and Education Plan for the NIH. For guidance, the
topic subgroup members were provided with copies of both the MDCC SWG
charge and the existing MDCC Plan. Through a process of conference calls
and electronic communications, each of the five topic subgroups
identified: (a) Recent Research Advances that have created new
opportunities for progress in the muscular dystrophies and (b) specific
Research Objectives in the area of their subgroup assignment.

Prior to the meeting that was held on August 16-17, 2005, each of the
MDCC SWG topic subgroups reached a consensus on the Research Objectives
that their subgroup would put forward and prepared a draft report
document. At the meeting, each subgroup presented their draft report and
used the discussions among the entire MDCC SWG to modify their Research
Objectives. The recommendations of each subgroup then were presented and
finalized on the second day of the meeting. At the meeting, and in
subsequent discussions with the subgroups, the final recommendations and
Research Objectives were formatted into a time-risk matrix, indicating
the length of time required to achieve the objective and the relative
risk in terms of success.

Subsequent to the MDCC SWG, NIH program and policy staff combined the
five separate working group documents into a cohesive action plan, and
returned the draft chapters and matrices to the MDCC SWG subgroups for
final editing and concurrence. The final draft report was submitted to
the MDCC and discussed at the November 9, 2005 MDCC meeting. After a
14-day comment period and additional revision, MDCC members voted to
approve the Action Plan for the Muscular Dystrophies in December 2005.

**Goal for the MDCC SWG Planning Process**

The MDCC SWG planning process drew upon the expertise and judgment of
leading basic and clinical researchers and physicians in the field of
muscular dystrophy. The result is a comprehensive Action Plan for the
Muscular Dystrophies that can be used as a guide for progress in the
management of these devastating diseases. Implementation of this Action
Plan requires the efforts of not only the NIH, but also the involvement
and coordination of efforts by all Federal, academic, professional, and
patient advocacy group partners committed to the goal of reducing the
clinical burden of the muscular dystrophies. Mechanisms will be
developed to increase communication and coordination among the Federal
agencies and advocacy organizations with a vested interest in the
muscular dystrophies and to implement, track, and assess progress in
attaining the Research Objectives identified by this Action Plan for the
Muscular Dystrophies. The MDCC will be instrumental as a starting point
for these activities.

**Muscular Dystrophy Research Planning Process Participants**

**A. scientific working Group composition** (\* denotes subgroup
co-chairs)

**Mechanisms of Muscular Dystrophy Subgroup**

\*Kevin P. Campbell, Ph.D., Investigator**,** Howard Hughes Medical
Institute**,** and Professor and Head**,** Department of Physiology and
Biophysics**,** University of Iowa

\*Thomas A. Rando, M.D., Ph.D., Associate Professor, Department of
Neurology, Stanford University School of Medicine

Melissa Spencer, Ph.D., Associate Professor, Departments of Neurology
and Pediatrics, University of California, Los Angeles

Maurice S. Swanson, Ph.D., Professor, Department of Molecular Genetics
and Microbiology, College of Medicine, University of Florida

Howard J. Worman, M.D., Associate Professor, Department of Medicine and
Department of Anatomy and Cell Biology, Columbia University College of
Physicians and Surgeons

**Diagnosis and Screening of Muscular Dystrophy Subgroup**

\*Kevin M. Flanigan, M.D., Associate Professor, Department of Neurology,
and Eccles Institute of Human Genetics, University of Utah

\*Katherine Mathews, M.D., Department of Pediatric Neurology, University
of Iowa Hospitals and Clinics

Steven A. Moore, M.D., Ph.D., Professor, Department of Pathology,
University of Iowa

Rabi Tawil, M.D., Associate Professor, Department of Neurology,
Neuromuscular Disease Center, University of Rochester Medical Center

**Therapy of Muscular Dystrophy Subgroup**

\*Elizabeth M. McNally, M.D., Ph.D., Associate Professor**,**
Departments of Medicine and Human Genetics, University of Chicago

\*Jerry R. Mendell, M.D., Director, Center for Gene Therapy, Kurtz
Professor of Neurology and Pediatrics, Columbus Children's Research
Institute

Langdon L. Miller, M.D., Chief Medical Officer, Clinical Development,
PTC Therapeutics

Hansell H. Stedman, M.D., Associate Professor, Department of Surgery,
University of Pennsylvania

Kathryn Wagner, M.D., Ph.D., Assistant Professor, Department of
Neurology, Johns Hopkins University School of Medicine

**Living with Muscular Dystrophy Subgroup**

\*Susan Iannaccone, M.D., Director, Department of Neurology, University
of Texas Southwestern Medical Center at Dallas

\*Craig M. McDonald, M.D., Professor**,** Department of Physical
Medicine and Rehabilitation and Pediatrics, and Director NIDRR
Rehabilitation Research and Training Center in Neuromuscular Diseases,
University of California, Davis Medical Center

Doug W. Biggar, M.D., F.R.C.P.(C), Professor of Pediatrics**,**
University of Toronto, and Physician Director**,** Musculoskeletal
Program**,** Bloorview MacMillan Children's Centre

Veronica J. Hinton, Ph.D., Assistant Professor of Neuropsychology**,**
Department of Neurology, Columbia University

Michael Rose, M.D., F.R.C.P., Consultant and Senior Lecturer in
Neurology, Department of Neurology, King's Neurosciences Centre, King's
College London

**Research Infrastructure for Muscular Dystrophy Subgroup**

\*Eric P. Hoffman, Ph.D., Director, Center for Genetic Medicine,
Children's National Medical Center

\*Richard T. Moxley III, M.D., Department of Neurology, Neuromuscular
Disease Center

University of Rochester Medical Center

Kate Bushby, M.D., F.R.C.P., Professor, Institute of Human Genetics and
Newcastle Muscle Center, University of Newcastle upon Tyne

John W. Day, M.D., Ph.D., Professor, Department of Neurology**,**
Institute of Human Genetics, University of Minnesota

H. Lee Sweeney, Ph.D., Chairman, Department of Physiology, School of
Medicine, University of Pennsylvania

**B. Outside Consultant**

David C. Rubinsztein M.B Ch.B, B.Sc.(Hons), Ph.D., FRCPath, FMedSci,
Professor of Department of Medical Genetics, Cambridge Institute for
Medical Research

**C. Muscular Dystrophy Coordinating Committee Membership**

Stephen I. Katz, M.D., Ph.D., Director, National Institute of Arthritis
and Musculoskeletal and Skin Diseases, National Institutes of Health,
and Chair, Muscular Dystrophy Coordinating Committee

Duane Alexander, M.D., Director, National Institute for Child Health and
Human Development, National Institutes of Health

Col. Kenneth Bertram, M.D., Director, Congressionally Directed Medical
Research Programs, US Army Research and Materiel Command, Department of
the Army

Edward A. Brann, M.D., M.P.H., Director, Division of Human Development
and Disability, National Center for Birth Defects and Developmental
Disabilities, Centers for Disease Control and Prevention

Donavon Decker, Advocate

Mary Jean Duckett, Acting Deputy Director, Disabled and Elderly Health
Programs Group, Center for Medicaid and State Operations, Centers for
Medicare and Medicaid Services

Patricia A. Furlong, President, Parent Project Muscular Dystrophy

Sharon E. Hesterlee, Ph.D., Director, Research Development, Muscular
Dystrophy Association

Story Landis, Ph.D., Director, National Institute of Neurological
Disorders and Stroke**,** National Institutes of Health

Merle McPherson, M.D., M.P.H., Director, Division of Services for
Children with Special Health Needs, Maternal and Child Health Bureau,
Heath Resources and Services Administration

Patricia A. Morrissey, Ph.D., Commissioner, Administration on
Developmental Disabilities, Administration on Children and Families

Daniel P. Perez, President and Chief Executive Officer,
Facioscapulohumeral Society, Inc.

Philip Sheridan, M.D., Medical Officer, Center for Drug Evaluation and
Research, Food and Drug Administration

Bradley R. Stephenson, Advocate

Steven James Tingus**,** M.S., C.Phil., Director, National Institute on
Disability and Rehabilitation Research, Office of Special Education and
Rehabilitative Services (OSERS), Department of Education

John D. Porter, Ph.D., Program Director, National Institute of
Neurological Disorders and Stroke, National Institutes of Health, and
Executive Secretary, Muscular Dystrophy Coordinating Committee

**D. National Institutes of Health Staff Participants**

Robin A. Conwitt, M.D., Program Officer**,** Clinical Trials Group**,**
National Institute of Neurological Disorders and Stroke, National
Institutes of Health

John Fakunding, Ph.D., Director, Heart Research Program, DHVD**,**
National Heart, Lung, and Blood Institute, National Institutes of Health

Laurie Gutmann, M.D., Program Officer**,** Clinical Trials Group**,**
National Institute of Neurological Disorders and Stroke, National
Institutes of Health

James W. Hanson, M.D., Director, Center for Developmental Biology and
Perinatal Medicine, National Institute of Child Health and Human
Development, National Institutes of Health

Lisa Kaeser, J.D., Senior Program Analyst, Office of Program and Public
Liaison, National Institute of Child Health and Human Development,
National Institutes of Health

Cheryl A. Kitt, Ph.D., Director, Extramural Program, National Institute
of Arthritis and Musculoskeletal and Skin Diseases, National Institutes
of Health

Yvonne T. Maddox, Ph.D., Deputy Director**,** National Institute of
Child Health and Human Development**,** National Institutes of Health

Glen Nuckolls, Ph.D., Director, Muscle Disorders and Therapies Program,
National Institute of Arthritis and Musculoskeletal and Skin Diseases,
National Institutes of Health

Mary Lou Oster-Granite, Ph.D., Temporary Chief and Health Scientist
Administrator, Mental Retardation and Developmental Disabilities Branch,
National Institute of Child Health and Human Development, National
Institutes of Health

Audrey S. Penn, M.D., Deputy Director, National Institute of
Neurological Disorders and Stroke, National Institutes of Health

Wilma A. Peterman, M.S., Senior Program Analyst, National Institute of
Arthritis and Musculoskeletal and Skin Diseases, National Institutes of
Health

Heather I. Rieff, Ph.D., Office of Science Policy and Planning**,**
National Institute of Neurological Disorders and Stroke, National
Institutes of Health

Daphné A. Robinson, Ph.D., American Association for the Advancement of
Science Fellow, Office of Science Policy and Planning, National
Institute of Neurological Disorders and Stroke, National Institutes of
Health

Lynn M. Rundhaugen, M.P.H., Program Analyst, National Institute of
Neurological Disorders and Stroke, National Institutes of Health

Paul A. Scott, Ph.D., Director, Office of Science Policy and Planning,
National Institute of Neurological Disorders and Stroke, National
Institutes of Health

Edmund M. Talley, Ph.D., Program Director, National Institute of
Neurological Disorders and Stroke, National Institutes of Health

Robert Zalutsky, Office of Science Policy and Planning, National
Institute of Neurological Disorders and Stroke, National Institutes of
Health

**Mechanisms of Muscular Dystrophy**

**a. INTRODUCTION**

The muscular dystrophies comprise a group of diseases that are
genetically, biochemically, and clinically diverse. While they were
initially grouped based on pathological similarities, and subdivided by
mode of inheritance, age of onset, and distribution of affected muscles,
the classification of the dystrophies has been refined over the past two
decades by identification of the genetic and biochemical basis of a
large number of disorders. A major challenge for research on the
mechanisms of muscular dystrophy is to begin to enumerate the various
pathogenetic cascades and to identify commonalities and divergences. In
fact, the pathologic changes that initially lead to the classification
of these different diseases as "muscular dystrophies" are extremely
diverse, with few central features that are shared by all. Among the
most reliable of those changes would be the end-stage changes of
fibrosis, fatty infiltration, variation in fiber size, and evidence of
prior degeneration and regeneration (i.e. centrally located nuclei).
However, none of these are specific for the dystrophies, as a group they
do not reflect early pathogenetic mechanisms, and the particular
combination of pathologic findings varies enormously among the different
groups lumped together under the general category of "muscular
dystrophies." Therefore, it is likely that deeper understandings of
pathogenetic mechanisms will result in a further reclassification of
these diseases.

Several major conclusions have emerged in terms of disease mechanisms.
It seems likely that there will be shared pathogenetic mechanisms among
groups of dystrophies, but that there will also be very divergent
pathogenetic mechanisms among others. Those muscular dystrophies that
are due to mutations in genes encoding dystrophin, sarcoglycans, and
laminin may converge very far "upstream" in terms of the mechanisms that
lead to muscle cell death, with rounds of degeneration and regeneration,
leading ultimately to muscle wasting and progressive weakness. Similar
mechanisms may also account for pathologic changes in those congenital
muscular dystrophies that are associated with glycosylation defects in
alpha-dystroglycan. By contrast, mechanisms leading to the
characteristic pathologic changes in myotonic dystrophy,
facioscapulohumeral muscular dystrophy, dystrophies associated with
mutations in nuclear membrane proteins, and dystrophies related to
mutations in calpain, dysferlin, and caveolin 3 are likely to have very
different pathogenetic cascades.

Central to the challenge of studying disease mechanisms is the
importance of considering each disorder biochemically, rather than just
pathologically. This challenge is highlighted by the fact that there is
an incomplete understanding of the function of most proteins that are
deficient or defective in the dystrophies, either in muscle cells
specifically or in cells in general. Dystrophin is clearly necessary for
maintaining a stable complex of proteins that link the extracellular
matrix with intracellular cytoskeletal elements and signaling proteins,
but the fact that even in this most highly penetrant of disorders,
muscles that are deficient in dystrophin show highly variable levels of
disease activity among different muscle groups, over time, and across
species suggests that the pathogenetic mechanisms are complex.

Mutations in nuclear membrane proteins present as diseases of both
muscle and other tissues, highlighting the fact that the muscular
dystrophies need to be considered as more systemic diseases and that
pathogenetic mechanisms may be best understood by studying tissues other
than muscle. The effects of mutations that cause facioscapulohumeral
muscular dystrophy and myotonic dystrophy clearly do not relate to a
single protein deficiency, and the pathogenetic mechanisms in these
disorders have required exploration beyond the simple
single-gene-mutation/single-protein-deficiency paradigm. In the
post-genomic era, the wealth of information that is becoming available
from expression profiling and proteomic studies serves as the starting
point for studies of pathogenetic mechanisms of disease.

The ultimate value for mechanistic studies in muscular dystrophy lies in
the identification of appropriate targets for therapeutic development.
The degree to which the muscular dystrophies have common pathogenic
mechanisms will determine the scope of any therapeutic strategy.
Comparative studies to understand similarities and differences in the
pathogenesis of the different muscular dystrophies may facilitate the
development of individual treatments with applicability to a range of
types and identify cases where type-specific therapy development is
necessary.

**B. RECENT Research ADVANCES**

The mechanisms underlying the muscular dystrophies are diverse. The
precipitating mechanisms and downstream pathogenesis of those
dystrophies that are associated with mutations in genes encoding
components of the dystrophin-glycoprotein complex appear to exhibit
important commonalities and have testable models that support
hypothesis-driven research. Despite this, the precise means by which the
loss of one or more dystrophin-glycoprotein complex members translates
into muscle fiber death are not yet fully understood. Mechanistic
knowledge is considerably less advanced for facioscapulohumeral muscular
dystrophy, myotonic dystrophy, Emery-Dreifuss muscular dystrophy, and
those limb girdle muscular dystrophies that are not associated with
dystrophin-glycoprotein complex defects.

**Duchenne/Becker Muscular Dystrophy**

*Reductions of nitric oxide synthase exacerbates disease pathogenesis.*
Neuronal nitric oxide synthase (nNOS) is a nitric oxide producing enzyme
that is associated with the sarcolemma and a component of the
dystrophin-glycoprotein complex. The loss of dystrophin in Duchenne
muscular dystrophy results in displacement of nNOS protein from the
sarcolemma, reduced nitric oxide release from dystrophic muscle, and
decreased circulating nitric oxide levels. There are at least three
identified downstream effects of this reduction of NOS that may
contribute to the pathogenesis in Duchenne muscular dystrophy:

-   The normal release of nitric oxide from muscle fibers promotes local
    vasodilation to overcome the alpha-adrenergic stimulation that
    accompanies exercise. The loss of muscle nitric oxide production in
    muscular dystrophy results in localized ischemia, which may be a
    contributing factor to disease pathogenesis.

-   Nitric oxide serves as an anti-inflammatory agent in muscle. Loss of
    this function has been shown to contribute to muscle pathogenesis in
    the mdx mouse model of muscular dystrophy.

-   Nitric oxide causes release of hepatocyte growth factor, a protein
    capable of activating muscle precursor cells (satellite cells). The
    subsequent loss of nitric oxide production in dystrophinopathy can
    act through this mechanism to reduce adequacy of repair mechanisms
    and thereby exacerbate pathogenesis.

*Dystrophin-deficient muscle exhibits enhanced susceptibility to
oxidative stress.* Dystrophic myogenic cells in culture show an
increased susceptibility to free radical-mediated stress. In addition,
pre-necrotic mdx mouse muscle shows evidence of increased oxidative
stress prior to the onset of any other visible dystrophic changes.
Collectively, these findings suggest that free radicals released by
immune cells, or due to mitochondrial calcium overload in muscle fibers,
may contribute to pathogenesis.

*Cellular proteases contribute to muscle cell death.* Membrane damage in
dystrophic muscle allows intracellular enzymes to leak out (detected as
elevated serum creatine kinase) and also may lead to abnormally high ion
accumulation within muscle fibers. While the issue of elevated free
calcium levels in mdx mouse and Duchenne patient muscles is
controversial, calcium dependent proteases (calpains) show both elevated
concentration and activity in mdx muscles at the peak of muscle
necrosis. Calpain concentration is also increased in Duchenne patient
muscles. Correspondingly, the suppression of calpains with an endogenous
inhibitor (calpastatin) reduces disease severity. The role of calcium
overload and calpain activation in the pathogenesis of the other
muscular dystrophies is currently unclear.

Recent studies have implicated other proteases in the pathogenesis of
muscular dystrophy. Inhibition of serine proteases (using Bowman-Birk
Inhibitor) leads to attenuation of dystrophic symptoms. Clinical trials
are being planned to test this drug in Duchenne muscular dystrophy
patients (National Institute of Neurological Disorders and Stroke).

*Dystrophic muscle shows aberrations in signaling pathways.* While the
predominant theory is that loss of dystrophin results in a mechanical
weakening of the sarcolemmal membrane, it is clear that loss of
dystrophin has other deleterious effects on muscle cell function and
viability. For example, muscle mass can be increased in the mdx mouse
through myostatin inhibition, but the increased mass does not translate
into an increase in the specific force that the muscle can generate.
Therefore, it is likely that dystrophin serves more than just a
mechanical/structural function in the cell.

Dystrophin and the dystrophin-glycoprotein complex proteins have several
identified signaling functions and loss of the complex in muscular
dystrophy has been associated with alterations in multiple signal
transduction pathways. Some of these changes may be due to the
compensatory upregulation of other proteins with signaling functions,
like integrins, and some may be directly related to the loss of
dystrophin.

Recent studies have identified specific cell signaling pathways
associated with the dystrophin-glycoprotein complex and corresponding
signaling aberrations of these pathways in dystrophic muscle, including:

-   JNK kinase, a member of the stress-activated MAP kinase family, is
    associated with the dystrophin-glycoprotein complex. JNK
    phosphorylates and inactivates NFATc, a protein important in muscle
    gene transcription. Through its NFATc activity, JNK regulates muscle
    gene transcription and activity of this kinase is increased in mdx
    mouse muscle. Deflazacort, a corticosteroid shown to be beneficial
    in treating Duchenne muscular dystrophy, may over-ride the
    deleterious effects of JNK activation by increasing NFAT expression.

-   ERK kinase and p38 kinase activities are elevated in
    dystrophin-deficient mouse muscle. But, it is not yet clear if
    activation of these kinases contributes to muscular dystrophy.

-   NFΚB is elevated in both pre-necrotic mdx mouse muscle and Duchenne
    patient biopsies. Elevated NFΚB might, in turn, increase the level
    of pro-inflammatory cytokines in the muscle environment, thus
    triggering increased inflammation and exacerbating muscle damage.
    Genetically modified mice with increased NFΚB activity show muscle
    wasting.

-   The AKT pathway is activated in response to normal
    alpha-dystroglycan-laminin interactions. It is hypothesized that
    loss of AKT signaling through this pathway may decrease cell
    survival or cell size in the muscular dystrophies.

*Inflammation exacerbates the pathogenesis of mdx muscle.* Muscles from
both Duchenne muscular dystrophy and the mdx mouse have elevated
inflammatory cell infiltration and increased inflammatory mediators such
as cytokines and chemokines. Reductions in cytokine/chemokine level or
in either the activation or concentration of inflammatory cells slow the
pathogenesis of muscular dystrophy. In addition, there is a correlation
between prednisone treatment and reductions in all inflammatory cell
populations, suggesting that the anti-inflammatory actions of prednisone
are one reason that this drug is beneficial in Duchenne muscular
dystrophy. Anti-inflammatory activity of the steroids is likely due to
reductions in the cellular adhesion molecules that are important for
immune cell extravasation to the muscle.

Taken together, recent research on perturbations of cell signaling
pathways in muscular dystrophy has identified several novel targets for
drug design.

**Myotonic Dystrophy**

*Unstable microsatellite expansions cause myotonic dystrophy types 1 and
2*. Myotonic dystrophy is the most prevalent form of muscular dystrophy
in adults. There are two forms of myotonic dystrophy, DM1 and DM2. While
many pathological features are shared, DM1 is the more severe disease,
particularly in the congenital form. DM1 is associated with a (CTG)~n~
expansion in the 3' untranslated region of the *DMPK* gene, while DM2
results from a (CCTG)~n~ expansion in the first intron of *ZNF9*. The
discovery that myotonic dystrophy is caused by structurally related
microsatellite expansions in different genes suggests that the repeat
expansions themselves are intrinsically toxic.

*The pathogenesis of myotonic dystrophy is RNA-mediated*. Early
mechanistic studies on the pathogenesis of myotonic dystrophy suggested
that disease might be mediated by a toxic RNA effect. While it is
dominantly inherited, the repeat expansions are located in non-coding
regions and myotonic dystrophy mutant allele transcripts accumulate in
the nucleus in ribonuclear foci. Conclusive evidence for a toxic RNA
effect was provided by the development of *HSA*^LR^ transgenic mice,
which carry a CTG expansion in the 3' untranslated region of the human
skeletal actin gene. Only those mice that actively express this
transgene develop myotonic dystrophy-associated muscle defects and
transgene expression levels directly correlate with the severity of
muscle pathology.

*RNA splicing mis-regulation is a downstream pathogenic event in
myotonic dystrophy*. One of the pathways that is adversely affected by
expression of toxic DM1 and DM2 RNAs is RNA alternative splicing. During
postnatal development, fetal exons must be excluded from mRNAs in order
to generate adult isoforms; this regulation is controlled by two sets of
antagonistic splicing factors, the CELF and MBNL protein families.
Expression of DM1 and DM2 mutant transcripts results in the
sequestration of the MBNL proteins which normally promote adult splicing
patterns. Thus, myotonic dystrophy most likely is an RNA splicing
disease in which fetal isoforms are retained in the adult.

*Development of myotonic dystrophy mouse models*. The future development
of therapies for myotonic dystrophy will be facilitated by the
generation of disease models which faithfully recapitulate
characteristic features of the human disease phenotype. Several new
mouse lines (*Mbnl1* knockout and CUGBP1 transgenic) faithfully model
many of the multi-systemic defects associated with human myotonic
dystrophy.

*Role of DNA mismatch repair genes and genetic recombination in the
generation of microsatellite expansions*. Somatic mosaicism of the
myotonic dystrophy DNA repeats can be recapitulated in both mouse and
cell culture models. The mismatch repair genes *Msh2*, *Msh3*, and
*Pms2* are required to generate these DNA expansions. Recent work also
indicates that the DM2 repeats are unusually active recombination
hotspots that are prone to expansion.

*Congenital myotonic dystrophy.* Early appearing myotonic dystrophy is
seen only for DM1. The molecular basis for early onset lies in the
finding that inherited unstable DNA sequences can become larger in each
subsequent generation. Congenital and childhood-onset DM1 correlates
with CTG repeat size with not other apparent mechanistic differences
from the adult disorder. Recognition of the childhood-onset form is
important because of associated conduction system abnormalities.

**Facioscapulohumeral Muscular Dystrophy**

*Most cases of facioscapulohumeral muscular dystrophy are associated
with the loss of subtelomeric DNA repeat units (D4Z4) from chromosome
4q.* In contrast to most monogenic disorders, in which the genetic
lesion typically affects the structure or function of a specific
protein, there is evidence that facioscapulohumeral muscular dystrophy
is associated with a complex epigenetic mechanism involving the
contraction of a subtelomeric macrosatellite repeat. In 95% of patients,
the D4Z4 repeat is contracted to an array of 1 to 10 units, while
unaffected subjects have up to 100 units. The D4Z4 repeat contains the
DUX4 gene, which encodes a double homeobox-containing protein. Some
familial cases have been reported that do not link to 4qter, but a
second locus for facioscapulohumeral muscular dystrophy has yet to be
identified. The pathogenic mechanisms underlying muscle weakness and
degeneration remain unresolved.

The potential role of the tandem repeat reduction in modulation of
transcription of nearby genes has been the subject of intensive
investigation. A putative repressor complex has been identified that
binds to D4Z4. In muscle of patients with facioscapulohumeral muscular
dystrophy, a distance-dependent transcriptional upregulation was found
for three genes, FRG2, FRG1, and ANT1, located near the repeat units.
However, in independent follow-up studies, the upregulation of these
genes could not be confirmed. Hence, considerable controversy exists
over whether the loss of D4Z4 repeat units in facioscapulohumeral
muscular dystrophy leads to loss of repression of genes near the D4Z4
locus.

*Molecular models for* *facioscapulohumeral muscular dystrophy*. Several
models have been proposed by which the contraction of the D4Z4 repeat
leads to changes in gene expression and the multi-system pathologies
associated with this disease. These models include altered gene
expression as a consequence of either: (a) the structure of D4Z4 repeats
and their interaction with local chromatin or the nuclear lamina, (b)
changes in D4Z4 methylation, or (c) expression and activity of DUX4.
Critical data pertaining to these or other models may be gained by
identifying the mutations outside of the 4q region that are associated
with a small percentage of facioscapulohumeral muscular dystrophy
patients. There is a significant need for model systems that will
facilitate testing of these hypotheses and for a better understanding of
the pathophysiology of this disease.

**Laminopathies**

*Mutations in lamins A and C cause muscular dystrophy and other
diseases.* A relatively recent revolution occurred in the field of
muscle pathophysiology when mutations in the nuclear envelope proteins,
emerin and lamins A and C, were shown to cause muscular dystrophy
(Emery-Dreifuss muscular dystrophy and limb girdle muscular dystrophy
type 1B) and dilated cardiomyopathy. This set the stage for analyzing
nuclear protein involvement in other hereditary diseases, and since
1999, nuclear lamin A/C mutations have been shown to have tissue/organ
system consequences beyond the striated muscle disorder. These diseases
include lipodystrophy syndromes, peripheral neuropathy (Charcot Marie
Tooth type 2) and syndromes with features of premature aging.

*Mutations in the lamins A and C cause mechanical problems with the
nucleus and abnormal cellular responses to stress.* Several studies have
shown that nuclei containing the lamin A and C mutations associated with
muscular dystrophy and other diseases have various abnormalities in
architecture, protein dynamics and response to heat and mechanical
stress. These studies suggest, but do not yet prove, that susceptibility
to mechanical stress-induced injury may be part of the
pathophysiological mechanism of how mutations in lamins A and C cause
muscular dystrophy.

*Nuclear lamins may be involved in transcription control.* Several
studies have suggested that nuclear lamins A and C are important in
processes including DNA replication, cell cycle regulation, and
transcriptional control. However, none of these studies thus far have
uncovered mechanistic details. Nonetheless, the results of such studies
have led to the hypothesis that mutations in lamins A and C and other
nuclear envelope proteins may cause disease by inducing tissue-specific
abnormalities in gene expression, possibly activating or deactivating
important cell signal transduction pathways.

*Lamin contributions to nuclear envelope protein structure.* The
complete three-dimensional structures of the nuclear lamins A and C, or
any other intermediate filament protein, are not known. In the past few
years, some advances have been made in determining the three-dimensional
structures of various domains of the nuclear lamins and other nuclear
envelope proteins. These studies have provided some clues about possible
functions and how mutations may cause different human diseases.

*Mouse models of mutations in nuclear envelope proteins.* Several mouse
models, specifically lamin A/C knockout and knock-in mice, have been
developed for human muscular dystrophies and other diseases caused by
lamin A/C mutations. While these models do not precisely mimic the
corresponding human disorders, they have been extremely useful to
investigators in studying pathogenic mechanisms of the laminopathies.

**Congenital Muscular Dystrophies**

*Glycosylation defects in limb girdle and congenital muscular
dystrophies.* The post-translational modification of sarcolemmal
proteins represents a new focus for mechanistic studies of muscular
dystrophy. Several genes that encode either known or putative
glycosylation enzymes have been causally associated with various types
of muscular dystrophy. The pathogenic mechanisms of these diseases
converge into abnormal glycosylation. In particular, mutations in
glycosyltransferase enzymes cause a novel group of human muscular
dystrophies, the dystroglycanopathies, which appear to share the primary
biochemical mechanism of hypoglycosylation of alpha-dystroglycan, with
decreased ability to bind its extracellular matrix ligands (laminin and
agrin). Specific mutated genes and their resultant disorders include
Large (congenital muscular dystrophy type 1D), fukutin (Fukuyama-type
congenital muscular dystrophy), fukutin-related protein (congenital
muscular dystrophy type 1C and limb girdle muscular dystrophy type 2I),
and protein-O-mannosyltransferase 1 (Walker-Warburg Syndrome).

The scope of the dystroglycanopathies exceeds the skeletal muscle
consequences, as multi-system effects (e.g., eye and brain) are frequent
in this group of disorders. One example is Walker-Warburg syndrome,
which is characterized by congenital muscular dystrophy and a wide range
of other organ system symptoms. It is likely that the
glycosyltransferases implicated in muscular dystrophy have targets in
addition to the ubiquitously expressed alpha-dystroglycan and that these
may contribute to the observed phenotypic diversity.

**Calpainopathies**

*Calpain 3 is mutated in limb girdle muscular dystrophy type 2A.*
Calpain 3 is the muscle-specific member of the calcium dependent
protease family. Diseases that result from deletions, translocations,
and point mutations in calpain 3 have been identified in patients with
limb girdle muscular dystrophy type 2A. Most of the disease-causing
mutations reduce either protein expression level or protease activity.

*Identification of calpain 3 localization and binding partners.* Calpain
3 is believed to be localized in the cytosol, although it has never been
successfully immunolocalized due to the non-specificity of available
antibody reagents. Some of the endogenous substrates of calpain 3 have
been identified and these include talin, ezrin, and filamin. Titin is
both the substrate and the only known binding partner of calpain 3.
Association with titin may be important for stabilizing the enzyme and
regulating its activity. Mutations in titin that result in muscular
dystrophy produce destabilization and reduced accumulation of calpain 3.
Furthermore, some mutations in the calpain 3 gene that are associated
with limb girdle muscular dystrophy type 2A result in loss of anchorage
of calpain 3 to titin.

*Morphological features of the calpainopathies differ from other
muscular dystrophies.* Pathogenesis in calpain 3 mutations appears to be
different from other limb girdle muscular dystrophies since a
compromised plasma membrane is not a feature of the disease;
paradoxically, patients with calpain 3 mutations exhibit elevated serum
creatine kinase. While there is some muscle degeneration in patients
lacking calpain 3, calpainopathy is mainly a wasting disease with
atrophy as a key component. Biopsies of limb girdle muscular dystrophy
type 2A patients show accumulation of subsarcolemmal NFΚB and elevated
apoptosis. Muscle biopsies also show areas of degeneration and
regeneration, abundant, disorganized mitochondria, and lobulated fibers.

*Development of mouse models for calpainopathy.* Mice lacking calpain 3
replicate the phenotypic features of limb girdle muscular dystrophy type
2A, including atrophy, small areas of degeneration/regeneration,
disorganized mitochondria, and lobulated fibers, but do not exhibit
apoptosis as an early feature of the pathology. In addition, calpain 3
knockout mice show abnormal sarcomere formation and organization.
Mechanistically, calpain 3 appears to act upstream of the ubiquitin
ligases. In turn, their role is likely to release myofibrillar and
cytoskeletal proteins from the organized myofibrillar complex. Insoluble
protein aggregates have been detected in calpain 3 knock out muscles
suggesting that calpain deficiency is likely a disease of excessive
protein accumulation rather than excessive protein degradation.

**Defects in Membrane Repair**

*Dysferlin mutations cause muscular dystrophy and myopathy.* Dysferlin
is a transmembrane protein that is mutated in limb girdle muscular
dystrophy type 2B and an allelic variant, Myoshi myopathy. The finding
that the identical dysferlin mutation causes these two different muscle
disease phenotypes supports a role for genetic background/modifier genes
in the pathogenesis of the dysferlinopathies. Recent studies show that
dysferlin functions in membrane repair and that defective repair
represents a novel mechanism of muscle degeneration. In contrast to many
of the other muscular dystrophies, where the mutated protein leads to
loss of sarcolemmal structural integrity, the dysferlinopathies then are
a consequence of compromised sarcolemmal repair mechanisms.

*Dysferlin distribution is altered in dystrophin-glycoprotein
complex-based muscular dystrophies.* Dysferlin is normally associated
with the sarcolemma, but is displaced to the cytoplasm in several types
of muscular dystrophy. In the converse situation of dysferlin mutations,
the dystrophin-glycoprotein complex is not disrupted.

*Emergence of the concept of a membrane repair complex.* Evidence
suggests that dysferlin may be one component of a complex or pathway
that is necessary for sarcolemmal repair. It has been demonstrated that
dysferlin interacts with caveolin 3. Caveolins are proteins associated
with invaginations of the plasma membrane; caveolin 3 is specifically
expressed in muscle. Mutations in caveolin 3 cause limb girdle muscular
dystrophy type 1C and rippling muscle disease. Dysferlin also interacts
with annexin 1 and 2, which are calcium and phospholipids binding
proteins involved in clustering vesicles and lipid rafts. A more
complete understanding of the proteins and the molecular mechanisms of
muscle membrane repair may accelerate advances in muscular dystrophy
research.

**Oculopharyngeal Muscular Dystrophy**

*The PABPN1 protein is prone to formation of intranuclear aggregates.*
Patients with oculopharyngeal muscular dystrophy exhibit characteristic
nuclear inclusions specific to skeletal muscle cells. Since PABPN1
appears to function in multiple cell types, the mechanisms behind the
skeletal muscle specificity are unclear. Expansion of the CGC repeat in
PABPN1 from 10 to greater than 12 copies has been associated with the
disease. Recent studies have shown that normal PABPN1 is inherently
aggregation-prone when expressed in an in vitro model. Cytoplasmic
displacement of overexpressed normal or mutant PABPN1 reduces
intranuclear aggregate formation. Muscle pathology may not only be due
to nuclear aggregation of PABPN1, as microarray studies have shown that
over 200 genes are overexpressed following PABPN1 overexpression, with
several overexpressed proteins co-aggregating with PABPN1. Finally,
studies show that PABPN1 protein is not irreversibly sequestered into
aggregates; the dynamic state of the intranuclear aggregates suggests
that there are potential avenues for treatment even well after disease
onset.

*PABPN1 protein aggregates may be mechanistic in oculopharyngeal
muscular dystrophy.* The appearance of nuclear aggregates of PABPN1
protein correlates with cellular toxicity in oculopharyngeal muscular
dystrophy. PABPN1 aggregates are degraded by the ubiquitin-proteosome
pathway; the activity of this pathway may explain the late onset of the
disease and pathway inhibition has been shown to increase aggregate
formation in an in vitro model. In cell-based models, inhibition of the
ubiquitin-proteosome pathway with inducers of the chaperone, HSP70,
reduced aggregate formation and cell death.

*Development of a transgenic model of* *oculopharyngeal muscular
dystrophy.* Transgenic expression of human PABPN1 containing the normal
(10 alanines) or disease-causing (17 alanines) number of repeats
targeted to skeletal muscle of mice yielded skeletal muscle-specific
pathology resembling that in oculopharyngeal muscular dystrophy
patients. Transgenic mice with the high residue number presented with
progressive muscle weakness that was accompanied by intranuclear
aggregates and apoptotic muscle nuclei. Reduction of the polyalanine
aggregate burden with doxycycline treatment resulted in a substantial
delay and attenuation of histopathology in the mouse model.

**C. RESEARCH Objectives**

There is compelling evidence that the precipitating mechanisms and
pathogenesis of the various types of muscular dystrophy exhibit both
disease-specific and conserved properties. A comparative understanding
of the convergence and divergence of pathogenic cascades that lead to
muscle degeneration will help identify the best targets for therapeutic
development in single muscular dystrophies, as well as potentially allow
the emergence of novel therapies with applicability to more than one
disease. For all of the muscular dystrophies, how the primary disease
mechanisms interact with the ongoing myogenic cell-based regeneration
also should be carefully considered, as the status of endogenous
regeneration has the potential to substantially affect the design,
timing, and efficacy of treatments.

**Disease-Specific Pathogenic Mechanisms**

The initial genetic mechanisms that are responsible for the various
types of muscular dystrophy are diverse, ranging from single gene
mutations to the expansion or contraction of DNA repeat sequences that,
in turn, may alter the expression or post-transcriptional processing of
other genes. An understanding of disease-specific pathogenic mechanisms
may accelerate the development the most optimal therapies.

-   *Research Objective 1:* Define the role that disrupted signal
    transduction pathways play in the pathogenesis of Duchenne and
    Becker muscular dystrophies and assess their viability as
    therapeutic targets (Long Term; Low Risk).

Rational drug design to specific molecular targets, particularly cell
signaling pathways, has proven successful in a variety of disorders such
as cancer and atherosclerosis. Recent studies suggest that there is an
opportunity to develop dystrophinopathy treatments that have their basis
in signal transduction pathways that either support muscle cell survival
or lead to muscle cell death. As in other diseases, aberrant signaling
may be responsible for some of the deleterious consequences of muscular
dystrophy. To this end, additional effort should be directed toward
defining the downstream signaling pathways controlled by components of
the dystrophin-glycoprotein complex and understanding which are affected
in the dystrophin-glycoprotein complex-based muscular dystrophies. The
roles of altered nNOS and NFΚB signaling may be particularly important.
Studies of models of muscle atrophy and regeneration also may facilitate
the identification of signaling cascades that are potential therapeutic
targets.

-   *Research Objective 2:* Define post-transcriptional mechanisms that
    lead to muscle (and other tissue) phenotypes in myotonic dystrophy
    and evaluate the role of DNA repair/replication/recombination
    mechanisms in microsatellite expansion (Medium Term; Intermediate
    Risk).

Studies should be initiated to clarify the potential roles of RNA
mis-splicing, and other post-transcriptional/translational processes in
myotonic dystrophy as they relate to abnormalities of skeletal muscle,
the brain (cognitive impairment, hypersomnolence, effects of personality
and behavior), endocrine/other systems (frontal balding,
hypogammaglobulinemia), the visual system (cataracts), cardiac muscle,
and the skeleton (talipes).

Understanding the relative roles of DNA mismatch repair, recombination,
and replication in microsatellite expansion is relevant to dissecting
the mechanisms underlying myotonic dystrophy. Research objectives should
include defining the role of DNA mismatch repair proteins in the
mechanism of triplet repeat expansion, testing chemical modifiers of
instability in mouse models, and creating tools that allow for the
rational design of therapeutic agents to modulate genetic instability.

-   *Research Objective 3:* Define the molecular pathogenetic mechanisms
    that lead to facioscapulohumeral muscular dystrophy (Long Term; High
    Risk).

Defining the molecular mechanisms by which a reduction in repeats at the
D4Z4 translates into the multi-system symptoms seen in
facioscapulohumeral muscular dystrophy has been difficult. Elucidation
of the function of the allelic variants (A and B) at D4Z4 may help
advance understanding of disease mechanisms. If perturbations of
chromatin structure and/or derepression of gene expression ultimately
figure into pathogenesis, there are some other diseases that could help
inform researchers in this field. A potentially important avenue of
research is the analysis of the chromatin structure at the D4Z4 locus,
including methylation and/or binding of specific repressors or
activators. Such chromatin conformational changes have been suggested as
a possible disease mechanism, presumably affecting the regulation of
expression of other genes. Since the issue of altered regulation of
genes in the vicinity of D4Z4 remains controversial, there is a need for
careful studies using microarrays or other techniques, to determine if
genes near the D4Z4 repeat units on chromosome 4q, or at more distant
locations on this chromosome, are upregulated or downregulated in
facioscapulohumeral muscular dystrophy. The expression and function of
the D4Z4 gene, DUX4, should be analyzed.

The association of 4qter with the nuclear lamina and the potential role
of this association upon gene expression profiles should be explored.
Genetic causes for facioscapulohumeral muscular dystrophy, other than
the D4Z4 contraction (such as non-chromosome 4 linked cases), should be
investigated in available patients.

-   *Research Objective 4:* Establish mouse (and cellular) models for
    facioscapulohumeral muscular dystrophy, specific to emerging
    candidate genes and/or disease genomics, to understand the
    epigenetic mechanisms and for the development of novel intervention
    strategies (Long Term; Intermediate Risk).

Although the pathogenic mechanism of facioscapulohumeral muscular
dystrophy is unknown, it is becoming increasingly well established that
epigenetic, including nuclear localization, gene expression modulation
due to the D4Z4 repeat contraction is the main culprit. As such, as this
mechanism is unique among the muscular dystrophies, its elucidation is
instrumental to understanding the pathogenic pathways and the design of
evidence-based therapeutic (and preventive) strategies. Accordingly,
generation of cellular and animal model systems is important. These
models should comprise not only specific *cis*-candidate genes, but also
genomic models, carrying the complete chromosome 4q subtelomere. The
gene-specific models can probably reflect parts of the clinical
phenotype, while at best the genomic models can produce faithful models
for the full facioscapulohumeral muscular dystrophy spectrum.

-   *Research Objective 5:* Define the multiple divergent effects that
    single mutations in nuclear envelope proteins exert on different
    tissues in Emery-Dreifuss muscular dystrophy and other laminopathies
    (Medium Term; High Risk).

Advances in the molecular biology of the laminopathies are relatively
recent, but provide new opportunities for understanding the mechanisms
of these multi-system diseases. Elucidation of the three-dimensional
structures and structure-function relationships of nuclear envelope
proteins, particularly those mutated in human diseases, will aid
understanding of pathogenic mechanisms. Likewise, high-resolution
imaging studies of nuclei and nuclear migration in cells with lamin A/C
mutations during development and in response to mechanical stress may
provide critical insights. It will be important to determine the
downstream cellular responses that are caused by mutations in lamins A
and C and other nuclear envelope proteins, with a possible focus on
characterizing cell signal transduction pathways. This information may
help appreciate the diversity of the multi-system consequences of the
laminopathies. Finally, statistically meaningful, exploratory studies of
alterations in the transcriptome and proteome of various cell types and
tissues from animal models and human subjects with lamin A/C mutations
will help evaluate alternative mechanisms not yet uncovered by other
approaches.

-   *Research Objective 6:* Determine the pathogenic pathways that are
    downstream from PABPN1 protein nuclear aggregate formation in
    oculopharyngeal muscular dystrophy (Intermediate Term; Medium Risk).

While a strong association has been established between intranuclear
aggregation of mutant PABPN1 protein and the pathogenesis of
oculopharyngeal muscular dystrophy, there is little understanding of the
cellular and molecular events that trigger myofiber death. Moreover, the
basis for the muscle group specificity that is so characteristic of
oculopharyngeal muscular dystrophy is completely unknown. The existence
of an animal model based upon validated disease mechanisms provides an
excellent opportunity to better understand the basis of this disease and
to, through translational research effort, develop appropriate
therapeutics. This model may also facilitate the identification of
biomarkers to be used in presymptomatic detection and monitoring of
clinical trials.

**General Pathogenic Mechanisms**

The identification of mechanisms that are conserved among multiple types
of muscular dystrophy may represent the most rapid and efficient means
of fostering drug development for these rare disorders.

-   *Research Objective 7:* Support continued gene identification and
    biochemical characterization of rare and understudied forms of
    muscular dystrophy (Medium Term; Low Risk).

The candidate gene approach has opened the door for mechanistic studies
in the muscular dystrophies. Yet only about 40% of limb girdle muscular
dystrophy cases show linkage to a known disease gene. These data support
the continuation of linkage analysis and positional cloning efforts.

-   *Research Objective 8:* Define the roles of inflammation, oxidative
    stress, and disrupted calcium homeostasis as primary or secondary
    pathogenic mechanisms in the muscular dystrophies (Medium Term; Low
    Risk).

Although the role of inflammation in the pathogenesis of muscular
dystrophy has been controversial, emerging data support a role for
inflammation in the downstream pathogenesis of at least some of the
muscular dystrophies. Further advances in this field will require the
identification of the specific immune effectors that contribute to
pathogenesis and the pinpointing of specific therapeutic targets. There
is a clear need to understand what makes dystrophic muscle more
susceptible to oxidative stress, and to appreciate how this feature
contributes to the pathogenesis. Methods for mitigating the effects of
oxidative stress should be explored as a therapeutic approach.

-   *Research Objective 9:* Characterize defects in post-translational
    processing and resulting pathogenetic mechanisms in the congenital
    muscular dystrophies and related disorders (Short Term; Intermediate
    Risk).

The congenital muscular dystrophies represent genetically and clinically
heterogeneous neuromuscular disorders. Disruption of normal
post-translational processing of alpha-dystroglycan represents a novel
pathological mechanism and understanding of the protein defects
responsible for dystrophic muscle changes may yield new insights into
treatment of congenital muscular dystrophy. The ectopic expression of
GalNAc transferase restores the membrane localization of
dystrophin-associated proteins and protects skeletal muscle from damage
in dystrophin-deficient mice, thereby supporting a putative role for
membrane biochemical approaches for therapeutic intervention in Duchenne
muscular dystrophy. Finally, understanding the role of hypoglycosylation
in non-contractile tissue involvement (e.g., brain) may be particularly
critical in dissecting the underlying disease mechanisms.

-   *Research Objective 10:* Define biochemical mechanisms involved in
    membrane instability and membrane repair in dystrophic muscle (Long
    Term; Low Risk).

The pathogenesis of many of the muscular dystrophies has long been
thought to involve destabilization of the sarcolemma. The development of
novel therapeutic approaches could be informed by an understanding of
the role of dysferlin and its associated proteins in repairing membrane
breaks that arise in the dystrophin-glycoprotein complex-based muscular
dystrophies as a consequence of muscle contraction.

-   *Research Objective 11:* Elucidate apoptotic mechanisms occurring in
    the muscular dystrophies as potential targets for therapeutic
    intervention (Long Term; Low Risk).

While muscle fiber necrosis has long been established as a final pathway
in the pathogenesis of the muscular dystrophies, there is evidence that
programmed cell death, or apoptosis, may play an important role. Studies
are needed to define the cascade of events responsible for apoptotic
muscle fiber death in muscular dystrophy. Findings that dystrophin,
sarcoglycan, lamin, and emerin mutations may alter signaling pathways to
increase apoptosis provides compelling evidence that apoptosis may be a
conserved pathogenic mechanism in the muscular dystrophies and thus a
potentially important common target for therapeutic intervention. Recent
data from laminin-alpha2-deficient mice suggest that anti-apoptosis
therapy may indeed be a possible route to amelioration of disease.

**Infrastructure Needs**

While a separate group evaluated infrastructure needs (see
Infrastructure Needs for Muscular Dystrophy), specific objectives that
were viewed as important to elucidating disease mechanisms are covered
here.

-   *Research Objective 12:* Establish invertebrate, other vertebrate,
    and alternative model systems to study pathogenetic mechanisms of
    gene/RNA/protein defects that cause muscular dystrophies in humans
    (Long Term; Intermediate Risk).

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-   *Research Objective 13:* Establish mouse models for dystrophies
    where none exist, and expand development of mouse models that modify
    disease phenotype to identify/study disease modifying genes (Long
    Term; Intermediate Risk).

Development of new mouse and other (invertebrate, cell-based, etc.)
model organisms that better replicate the human muscular dystrophy
phenotypes may allow investigators to gain better insight into disease
mechanisms and provide improved means for therapeutic development.
Adequate access to appropriate models represents a potential roadblock
to research. Improved high-throughput, pre-clinical cell- and
animal-based models would also facilitate drug efficacy testing. The
identification of compounds that are effective in the treatment of
muscle disease has been hindered by the lack of high-throughput systems
and easily obtainable and standardized outcome measures in mice.
Development of these models, using imaging or other easily performed
assays, would facilitate the identification of new therapies.

-   *Research Objective 14:* Establish repositories of
    tissues/cells/serum from muscular dystrophy patients to allow
    confirmation of pathogenic mechanism data that is derived from
    animal studies (Short Term; Low Risk).

Animal models provide vitally important tools to dissect the pathogenic
mechanisms of the muscular dystrophies, but do not fully reflect the
human disease. Hypotheses and mechanistic data originating from studies
of animal models therefore require validation through cell-based studies
of the human disease. Repositories represent a mechanism of ensuring
that researchers engaged in mechanistic studies have adequate access to
human tissues.

**D. Matrix of Research Objectives in Mechanisms of Muscular Dystrophy**

+-----------+------------------+------------------+------------------+
|           | **Short Term**   | **Medium Term**  | **Long term**    |
|           |                  |                  |                  |
|           | **(0-3 years)**  | **(4-6 years)**  | **(7-10 years)** |
+-----------+------------------+------------------+------------------+
| **High    |                  | -   Define the   | -   Define the   |
| Risk**    |                  |     multiple     |     molecular    |
|           |                  |     divergent    |     pathogenetic |
|           |                  |     effects that |     mechanisms   |
|           |                  |     single       |     that lead to |
|           |                  |     mutations in |     fac          |
|           |                  |     nuclear      | ioscapulohumeral |
|           |                  |     envelope     |     muscular     |
|           |                  |     proteins     |     dystrophy    |
|           |                  |     exert on     |                  |
|           |                  |     different    |                  |
|           |                  |     tissues in   |                  |
|           |                  |                  |                  |
|           |                  |   Emery-Dreifuss |                  |
|           |                  |     muscular     |                  |
|           |                  |     dystrophy    |                  |
|           |                  |     and other    |                  |
|           |                  |                  |                  |
|           |                  |    laminopathies |                  |
+-----------+------------------+------------------+------------------+
| **Int     | -   Characterize | -   Define       | -   Establish    |
| ermediate |     defects in   |     post         |                  |
| Risk**    |     po           | -transcriptional |    invertebrate, |
|           | st-translational |     mechanisms   |     other        |
|           |     processing   |     that lead to |     vertebrate,  |
|           |     and          |     muscle (and  |     and          |
|           |     resulting    |     other        |     alternative  |
|           |     pathogenetic |     tissue)      |     model        |
|           |     mechanisms   |     phenotypes   |     systems to   |
|           |     in the       |     in myotonic  |     study        |
|           |     congenital   |     dystrophy    |     pathogenetic |
|           |     muscular     |     and evaluate |     mechanisms   |
|           |     dystrophies  |     the role of  |     of           |
|           |     and related  |     DNA          |                  |
|           |     disorders    |     rep          | gene/RNA/protein |
|           |                  | air/replication/ |     defects that |
|           |                  |                  |     cause        |
|           |                  |    recombination |     muscular     |
|           |                  |     mechanisms   |     dystrophies  |
|           |                  |     in           |     in humans    |
|           |                  |                  |                  |
|           |                  |   microsatellite | -   Establish    |
|           |                  |     expansion    |     mouse (and   |
|           |                  |                  |     cellular)    |
|           |                  | -   Determine    |     models for   |
|           |                  |     the          |     fac          |
|           |                  |     pathogenic   | ioscapulohumeral |
|           |                  |     pathways     |     muscular     |
|           |                  |     that are     |     dystrophy,   |
|           |                  |     downstream   |     specific to  |
|           |                  |     from PABPN1  |     emerging     |
|           |                  |     protein      |     candidate    |
|           |                  |     nuclear      |     genes and/or |
|           |                  |     aggregate    |     disease      |
|           |                  |     formation in |     genomics, to |
|           |                  |                  |     understand   |
|           |                  |  oculopharyngeal |     the          |
|           |                  |     muscular     |     epigenetic   |
|           |                  |     dystrophy    |     mechanisms   |
|           |                  |                  |     and for the  |
|           |                  |                  |     development  |
|           |                  |                  |     of novel     |
|           |                  |                  |     intervention |
|           |                  |                  |     strategies   |
|           |                  |                  |                  |
|           |                  |                  | -   Establish    |
|           |                  |                  |     mouse models |
|           |                  |                  |     for          |
|           |                  |                  |     dystrophies  |
|           |                  |                  |     where none   |
|           |                  |                  |     exist, and   |
|           |                  |                  |     expand       |
|           |                  |                  |     development  |
|           |                  |                  |     of mouse     |
|           |                  |                  |     models that  |
|           |                  |                  |     modify       |
|           |                  |                  |     disease      |
|           |                  |                  |     phenotype to |
|           |                  |                  |                  |
|           |                  |                  |   identify/study |
|           |                  |                  |     disease      |
|           |                  |                  |     modifying    |
|           |                  |                  |     genes        |
+-----------+------------------+------------------+------------------+
| **Low     |                  | -   Support      | -   Define the   |
| Risk**    |                  |     continued    |     role that    |
|           |                  |     gene         |     disrupted    |
|           |                  |                  |     signal       |
|           |                  |   identification |     transduction |
|           |                  |     and          |     pathways     |
|           |                  |     biochemical  |     play in the  |
|           |                  |                  |     pathogenesis |
|           |                  | characterization |     of Duchenne  |
|           |                  |     of rare and  |     and Becker   |
|           |                  |     understudied |     muscular     |
|           |                  |     forms of     |     dystrophies  |
|           |                  |     muscular     |     and assess   |
|           |                  |     dystrophy    |     their        |
|           |                  |                  |     viability as |
|           |                  | -   Define the   |     therapeutic  |
|           |                  |     roles of     |     targets      |
|           |                  |                  |                  |
|           |                  |    inflammation, | -   Define       |
|           |                  |     oxidative    |     biochemical  |
|           |                  |     stress, and  |     mechanisms   |
|           |                  |     disrupted    |     involved in  |
|           |                  |     calcium      |     membrane     |
|           |                  |     homeostasis  |     instability  |
|           |                  |     as primary   |     and membrane |
|           |                  |     or secondary |     repair in    |
|           |                  |     pathogenic   |     dystrophic   |
|           |                  |     mechanisms   |     muscle       |
|           |                  |     in the       |                  |
|           |                  |     muscular     | -   Elucidate    |
|           |                  |     dystrophies  |     apoptotic    |
|           |                  |                  |     mechanisms   |
|           |                  |                  |     occurring in |
|           |                  |                  |     the muscular |
|           |                  |                  |     dystrophies  |
|           |                  |                  |     as potential |
|           |                  |                  |     targets for  |
|           |                  |                  |     therapeutic  |
|           |                  |                  |     intervention |
+-----------+------------------+------------------+------------------+

**DIAGNOSIS AND SCREENING IN MUSCULAR DYSTROPHY**

**A. INTRODUCTION**

Rapid and accurate diagnosis of the muscular dystrophies reduces
unnecessary testing, decreases stress of uncertainty about diagnosis,
allows accurate genetic counseling, and is necessary before specific
disease treatments can be considered. Accurate diagnosis of the muscular
dystrophies is closely related to an understanding of the molecular
mechanisms underlying the disease (see the chapter on Mechanisms of
Muscular Dystrophy, for a thorough discussion of this topic).
Identification of the causative gene has led to specific genetic tests
for many types of muscular dystrophy. For example, despite the technical
hurdle of the large size of the dystrophin gene, molecular diagnosis of
Duchenne and Becker muscular dystrophies through mutation analysis is
now quite accurate. For other forms of muscular dystrophy, accurate and
specific diagnoses require tissue-based testing. For example, abnormal
staining for merosin in skin or muscle makes a diagnosis of merosin
negative congenital muscular dystrophy. These tissue-based tests can
also indicate a general category of muscular dystrophy. For example,
abnormal glycosylation of alpha-dystroglycan in a patient with
congenital muscular dystrophy can be the result of mutation in one of at
least six different genes.

For other muscular dystrophies, development of precise diagnostic
procedures has been more difficult. For example, in myotonic dystrophy
type 2 the large size and instability of the repeat expansion have made
mutation testing difficult. For facioscapulohumeral muscular dystrophy,
diagnostic testing has been challenging, in large part due to the lack
of understanding of the mechanisms of the disease. As the underlying
causes and molecular mechanisms of the different forms of muscular
dystrophy are better understood, new approaches to molecular diagnosis
will likely follow. Advances in molecular technology will facilitate
test development.

Streamlining testing procedures and using the least invasive tests are
priorities to reduce costs and risk to patients. Minimally invasive
diagnostic approaches such as muscle imaging, or testing on easily
accessible tissues (blood, skin) should continue to be explored and
developed. To achieve these goals, advances in technology are often
needed.

Wide availability of logical testing algorithms is desirable, to
decrease unnecessary pain, expense and delay in diagnosis for patients
and families. Access to genetic counseling is also a critical component
of diagnostic and screening systems.

Neonatal screening is technically possible for some forms of muscular
dystrophy, however, a number of social and ethical issues need to be
explored to decide if widespread use is feasible or desirable.

Diagnostic testing at facilities that are engaged in research will allow
development of databases that record de-identified genetic and clinical
data. Mutation databases and disease-specific registries will facilitate
the identification of cohorts for clinical trials. Muscle biopsy samples
collected during diagnostic evaluation are an increasingly limited
resource. Because of the importance of these tissues for neuromuscular
research, a common database of available materials is desirable.

The ultimate goal of all diagnostic and screening procedures is improved
clinical management for patients. It will be important to have accurate
and widely available diagnostic procedures in place if a clear benefit
for early intervention in treating these diseases is demonstrated.

**B. Recent Research Advances**

In the past 5-10 years, there have been significant advances in
diagnostic approaches to the muscular dystrophies. The identification of
new genes has facilitated the development of molecular-based diagnostic
testing, and new technologies have been developed to improve the
diagnosis of a number of forms of muscular dystrophy. Sensitivity and
specificity have not been established for some of these tests. There is
also not consensus on the appropriate diagnostic algorithm in using the
available tests.

**Improved Molecular Diagnosis in Duchenne/Becker Muscular Dystrophy**

Genetic analysis of the dystrophin gene is complicated by its large size
and complex regulation (79 exons and spread over 2.2 million base pairs
of genomic DNA, including 8 promoters). The latest molecular approaches
to dystrophin gene analysis are now diagnostic in approximately 95% of
cases. If widely applied, use of these techniques would almost eliminate
the need for diagnostic muscle biopsies in Duchenne/Becker muscular
dystrophy, facilitate accurate genetic counseling, and identify
appropriate patients for participation in therapeutic trials that are
based upon the precise type of mutation.

Clinically available tests now include approaches to identifying small
or point mutations. These use an initial screening paradigm (e.g.,
single-stranded conformational polymorphism and denaturing high
performance liquid chromatography), followed by either limited
sequencing or direct sequencing (e.g., single condition
amplification/internal primer sequencing or SCAIP). Multiplex ligation
dependent probe amplification (MLPA) and multiplex amplifiable probe
hybridization (MAPH) have improved deletion/duplication testing.

The increasing use of these tests has also defined the limits of genomic
DNA-based analysis by highlighting the prevalence of intronic mutations
that result in pseudoexon insertions, which may account for up to 5% of
dystrophin mutations and will continue to require mRNA-based (RT-PCR)
diagnostic methods.

**Dysferlin Expression Testing on Peripheral Blood Monocytes**

Mutations in the dysferlin gene are associated with a variety of
clinical presentations; most commonly patients present with either
limb-girdle weakness (limb girdle muscular dystrophy type 2B) or distal
weakness (Miyoshi myopathy). Limb girdle muscular dystrophy type 2B is
estimated to account for approximately 15% of the limb girdle muscular
dystrophy patients in North America. As with dystrophin, mutation
detection from genomic DNA has proven difficult because of the large
size of the gene. The availability of a non-invasive dysferlin
expression analysis in blood monocytes has facilitated the diagnosis of
the dysferlinopathies, although information about the specificity and
sensitivity of these tests is quite limited.

**Western Blot Approaches to Diagnosis of Limb Girdle Muscular
Dystrophy**

Western blot analysis of dystrophin has played a role in Duchenne/Becker
muscular dystrophy testing for a number of years. More recently, an
expanded role for western blotting in the diagnosis of limb girdle
muscular dystrophy and congenital muscular dystrophy has been described.
This appears to be most important for calpain 3 in limb girdle muscular
dystrophy type 2A and dysferlin in limb girdle muscular dystrophy type
2B. Extensive work on calpain 3 has recently been published that
establishes sensitivity and specificity parameters using molecular data
as the gold standard for diagnosis. This work will need independent
confirmation before becoming widely accepted. Similar analyses are
needed for dysferlin. To accomplish this, support is needed for western
blot and molecular diagnostic evaluation of a large cohort of limb
girdle muscular dystrophy patients with dysferlinopathy, as identified
by immunostaining. Procedures for the miniaturization of western blot
techniques have also been published in recent years. Broader application
of this methodology will lead to more effective use of biopsy tissues.

**Identification of the Role of Alpha-Dystroglycan in Muscular Dystrophy
and Use of Screening Tests for Abnormal Glycosylation**

Shortly after the discovery of dystrophin and its role in Duchenne and
Becker muscular dystrophies, a membrane-associated complex of proteins
was discovered and characterized. Mutations in several components of
this dystrophin-glycoprotein complex were subsequently determined to
cause autosomal recessive subtypes of limb girdle muscular dystrophy (in
particular, the sarcoglycanopathies: limb girdle muscular dystrophy
types 2C, 2D, 2E, and 2F). Central proteins of the
dystrophin-glycoprotein complex, alpha- and beta-dystroglycan, are
encoded by a single gene, and to date, no dystroglycan mutations have
been identified in patients. The absence of a class of muscular
dystrophy specifically linked to dystroglycan mutations may have its
basis in the finding that targeted deletion of dystroglycan in mice is
early embryonic lethal.

In a surprising twist on the standard pathophysiology in the muscular
dystrophies, protein deficiency or partial deficiency of
dystrophin-glycoprotein complex proteins, several genes have been
discovered in the past five years that encode glycosyltransferases (or
putative glycosyltransferases) that are necessary for the
O-mannosylation of alpha-dystroglycan. Mutations in these genes account
for Fukuyama congenital muscular dystrophy, Walker-Warburg syndrome,
muscle-eye-brain disease, and at least two additional forms of
congenital muscular dystrophy (types 1C and 1D), and limb girdle
muscular dystrophy type 2I. The pathogenesis for each of these disorders
now appears to be hypo-glycosylation of alpha-dystroglycan, leading to
muscular dystrophy with or without brain and eye developmental
abnormalities.

The responsible genes for the glycosylation-related muscular dystrophies
are reviewed in the chapter on Mechanisms of Muscular Dystrophy.
Antibodies are available that recognize alpha-dystroglycan only when it
is fully glycosylated, and thereby represent useful diagnostic tools for
evaluating muscle biopsies either by immunostaining or western blotting.
Two of these genes have common mutations that make genetic diagnosis
relatively easy. In Japanese populations there is a founder
retrotransposal insertion in fukutin in \> 85% of mutant alleles of
Fukuyama congenital muscular dystrophy patients. More than 95% of
Fukuyama congenital muscular dystrophy patients carry the
retrotransposon on at least one chromosome. In limb girdle muscular
dystrophy type 2I populations of European descent, there is a common
point mutation in the fukutin-related protein gene that accounts for
nearly 80% of mutant alleles. In addition, the fukutin-related protein
gene has a single coding exon that makes sequencing easy and relatively
inexpensive.

**Development of Mutation Testing for Myotonic Dystrophy Type 2**

The myotonic dystrophy type 2 (DM2) locus was mapped to chromosome 3
(3q21.3), and the mutation was identified as an unstable (CCTG)n
expansion in intron 1 of zinc-finger protein 9 gene. Whereas normal
individuals have less than 30 CCTG repeats, individuals with DM2 have
75-11,000 repeats. DM2 mutation detection has proved problematic because
of the large size of repeat expansion (average 5,000 repeats) and
somatic instability of the expansion. Modified Southern blot protocols
have an overall sensitivity of about 80%. A three-step procedure has
been proposed to include: (a) PCR-based allele sizing across DM2; the
presence of two normal sized alleles excludes DM2, (b) Southern blot
analysis, and (c) DM2 repeat assay. The three-step procedure is highly
sensitive (98%) but is not widely available. Two recently described
simplified protocols, one involving pulsed-field gel electrophoresis
followed by semi-quantitative Southern blot and the second utilizing
long PCR, appear to be as sensitive as the three-step procedure.

**Improved Diagnostic Testing in Facioscapulohumeral Muscular
Dystrophy**

Facioscapulohumeral muscular dystrophy is a genetically complex disease
and, despite identification of the genetic mutation approximately 13
years ago, the mechanisms and specific gene or genes involved in
pathogenesis are unknown. Diagnostic testing is laborious, dependent on
Southern blot technology, and complex to interpret in many cases. There
is a need for more streamlined testing, which will likely be advanced by
an improved understanding of the pathogenesis of facioscapulohumeral
muscular dystrophy.

In the past 5 years, diagnostic testing for facioscapulohumeral muscular
dystrophy has become increasingly sophisticated and complex. A deletion
of a 3.3 kb repeat sequence on chromosome 4 (4q35; a deletion involving
the subtelomeric D4Z4 tandem repeat array) is associated with the
facioscapulohumeral muscular dystrophy phenotype. This observation
provided a basis for clinical diagnostic testing. The clinical use of
this diagnostic test is complicated due to cross reactivity with a
highly similar repeat sequence on chromosome 10q, interchromosomal
exchange, heterogeneous chromosomes, and complex rearrangements that
affect the binding site of a pulsed-field gel electrophoresis DNA marker
(p13E11) that is used in the diagnostic test.

A major improvement in diagnosis was the discovery that the chromosome
10q fragments could be digested away (BlnI digest). Diagnosis was still
complicated by the fact that it is common for individuals to have more
than 2 of the 10-type or 4-type repeat sequences because of
interchromosomal exchange. The next advance in the diagnostic evaluation
was the development of a "dosage test" that estimates the ratio of
10-type and 4-type sequences. This allows some degree of certainty that
a short (disease-associated) fragment is actually on chromosome 4.

More recently, it has been reported that the short fragment must be in a
particular environment on chromosome 4q, designated 4q35A. This
observation, assuming that it is confirmed by additional groups, further
refines the interpretation of diagnostic testing in facioscapulohumeral
muscular dystrophy.

Because of the complexity of the algorithm and mechanics of testing,
there is a need for improved documentation, training, and education for
professionals (physicians, neurologists, and genetic counselors) on
interpretation of genetic testing for facioscapulohumeral muscular
dystrophy.

**C. Research Objectives**

**Technology for Diagnostic Testing**

DNA-based diagnostic testing is now available for some major muscular
dystrophies (Duchenne, facioscapulohumeral, oculopharyngeal, and
myotonic dystrophy). Genetic testing should be developed for other
muscular dystrophies as well. Central diagnostic labs, which are
equipped to develop and make such tests readily available, could play a
key role in this effort. However, other muscular dystrophies will still
require muscle biopsy for diagnosis. In some cases, alternative,
minimally invasive techniques are available, but are not yet in
widespread use. Large studies are also needed to confirm the validity of
the currently available testing paradigms.

-   *Research Objective 1:* Develop minimally invasive diagnostic
    techniques for muscular dystrophies where appropriate (Medium Term;
    Intermediate Risk).

Some patients may always require diagnosis by means other than molecular
analyses. Muscle biopsy has the disadvantages of being expensive,
invasive, inducing anesthesia risks, and only minimal muscle may be
available for testing in advanced disease. The use of minimally invasive
techniques should be further developed and expanded, since these
approaches are much more acceptable to patients, less expensive to
perform, and valuable as diagnostic tools or as screening tests to
direct subsequent DNA-based testing. Skin biopsy has been used to
demonstrate target protein abnormalities in a number of muscular
dystrophies. In dystrophinopathy, the absence or abnormal dystrophin
expression in erector pili smooth muscle of the skin can be demonstrated
by a simple skin punch biopsy. However, since this procedure was first
described, whole dystrophin gene screening has been developed, rendering
the skin test obsolete. Congenital muscular dystrophy with laminin
alpha2 deficiency can be diagnosed by the absence of alpha2
immunostaining in skin arrector pili smooth muscles, cutaneous nerves,
and corium. Absence or deficiency of collagen VI can be demonstrated in
muscle or skin fibroblast cultures to diagnose Ullrich congenital
muscular dystrophy. Absence of emerin protein, demonstrated in skin by
immunohistochemistry, and in blood leukocytes, by immunoblot, can be
used to diagnose Emery-Dreifuss muscular dystrophy. Support should be
given to expanding and validating these minimally invasive techniques.

-   *Research Objective 2:* Develop definitive gene tests for muscular
    dystrophies for which genetic testing is not yet available (Short
    Term; Low Risk to Long Term; Low Risk).

Novel disease genes are frequently being discovered, but clinicians
often find it difficult to obtain access to genetic testing. Both
clinical and basic research would be facilitated by the targeted
development of useful muscle disease diagnostic testing. Particular
attention should be given to supporting central diagnostic research
laboratories that are integrated into the larger muscle disease research
community, and have the ability to rapidly respond to the need for the
development of such tests. Several research laboratories are capable of
developing such testing, but lack support to do so. Such centralized
testing facilities have been developed by consortia in the United
Kingdom, resulting in the centralized provision of diagnostic services,
to the benefit of patients and researchers.

-   *Research Objective 3:* Establish mechanisms for muscular dystrophy
    patients to obtain accurate genetic counseling (Short Term; Low
    Risk).

As genetic diagnosis is increasingly available, the need for accurate
genetic counseling becomes highlighted. Genetic counseling is an ethical
imperative when genetic information is being provided to a patient or
family, in the clinic or as part of a research effort. The creation of
better literature, brochures and training materials is needed to aid
patients, families, and health care professionals. In the setting of
research, demonstration that genetic counseling is available should be a
mandatory element prior to approval of a project and funding to support
counseling should be available. The opportunity to study the settings
and timing of genetic counseling and the efficacy of this counseling.

-   *Research Objective 4:* Establish the specificity and sensitivity of
    diagnostic tests for the muscular dystrophies (Long Term;
    Intermediate Risk).

New diagnostic tests for muscular dystrophies are constantly being
developed. In addition to new tests using established technology, there
are new technologies being introduced (e.g., micro-Western blot
analysis, proteomics, gene chip technology, and laser capture
microscopy). These diagnostic tests move rapidly to the clinical arena
because of the clinical need. The diagnostic accuracy of the tests is
often based on limited published data from a single laboratory. This is
true, for example, in the use of "A" and "B" alleles in
facioscapulohumeral muscular dystrophy and for monocyte dysferlin
expression in limb girdle muscular dystrophy type 2B. Large studies need
to be supported and published to confirm the validity of diagnostic
testing in muscular dystrophy. Pathologists have a long history of
working together to establish quality control and optimal techniques for
new tests, and it will be important to draw on this expertise and
perspective. Success in achieving this goal will likely require the use
of archived samples.

**Resources for the Research Community Related to Diagnosis**

A theme that runs through many of the goals involving diagnosis and
screening in the muscular dystrophies is the need for coordination and
communication between experienced neuromuscular clinicians,
neuropathologists with expertise in muscular dystrophy, and molecular
diagnostic laboratories. Increased coordination could result in common
algorithms for diagnostic evaluation of patients and a shared database
of the diagnostic tests that are available for muscular dystrophy,
including genetic, muscle-based, imaging, and tests in other tissues.
The muscular dystrophy research community benefits from the ready
availability of molecular diagnostic testing. However, when clinical
testing is performed, the aggregate data is frequently not available to
the research community. Investigators should be encouraged to submit
data to existing databases to facilitate sharing of this data.

-   *Research Objective 5:* Encourage submission of new mutation and
    polymorphism data for muscular dystrophy genes to public databases
    (Short Term; Low Risk).

-   *Research Objective 6:* Support disease-specific registries with
    detailed genetic, pathological and clinical information. Foster
    cooperation between registries, neuromuscular research centers, and
    academic diagnostic centers (Long Term; Intermediate Risk).

Mutation databases have considerable utility in fostering better
diagnosis (i.e., evaluation of disease-causing mutations versus simple
polymorphisms), facilitating genetic counseling, and promoting research
(from the informative value of individual cases, such as in-frame Becker
mutations aiding development of mini-/micro-dystrophin constructs,
through the value of aggregate data in studying the influence of
polymorphisms/haplotypes on disease processes). Several academic groups
that offer clinical or research testing services make an effort to
provide public access to their well-annotated databases containing a
variety of de-identified information. Such databases exist for a variety
of disorders, and include the Leiden Muscular Dystrophy pages
([www.dmd.nl](http://www.dmd.nl/)), the Utah Genome Center Dystrophin
Mutation Tables (<http://www.genome.utah.edu/DMD/mutation_tables.cgi>),
and the Inherited Peripheral Neuropathies Mutation Databases
(<http://www.molgen.ua.ac.be/CMTMutations/>).

In contrast, commercially available testing organizations do not, in
general, routinely present information on novel mutations, which may
shed light on disease pathogenesis or approaches to therapy. Academic
testing centers have, in general, demonstrated greater commitment to
this goal. Databases developed and annotated by consortia of researchers
should be encouraged and supported in order to provide stakeholders with
accurately annotated and easily accessible information useful for
diagnostic, genetic counseling, and research purposes. Such databases,
in association with natural history information, will be of benefit to
the muscular dystrophy community as a whole.

-   *Research Objectives 7-9:* Optimize utilization of muscle biopsy
    materials for research by:

    -   Developing IRB language to assist investigators with use of
        archived or prospectively collected diagnostic muscle biopsies
        (Short Term; Low Risk).

    -   Fostering shared use of stored and prospectively collected
        diagnostic muscle biopsies by the research community (Short
        Term; Low Risk).

    -   Further developing new techniques for evaluation of muscle
        samples (such as Western blot analysis of very small quantities,
        proteomics, and laser capture microscopy) and, where
        appropriate, moving them into the diagnostic algorithm (Medium
        Term; Intermediate Risk).

Muscle biopsy material is a precious resource that is often in limited
supply for the research community. This will be increasingly true as
non-invasive or minimally invasive diagnostic approaches are developed.
There is not currently a readily accessible supply of either control
muscle or muscle from patients with a genetically confirmed diagnosis.
General algorithms for the appropriate diagnostic evaluation of patients
with muscle disease and for handling of biopsy specimens should be
agreed upon, maintained in a readily accessible format and updated
regularly. Implementing this goal will require several steps.

First, neurologists and pathologists need to be educated about the
appropriate diagnostic evaluation of patients and handling of muscle
biopsies, including what samples to harvest and provision for long-term
storage of frozen muscle for possible future diagnostic evaluation and
research. General algorithms for the appropriate diagnostic evaluation
of patients with muscle disease should be agreed upon, maintained in a
readily accessible format and updated regularly. Such algorithms could
be posted on the website suggested below, or on the Senator Paul D.
Wellstone Muscular Dystrophy Collaborative Research Center websites.

Some centers already have stored muscle biopsy materials collected over
many years for diagnostic purposes. It would facilitate the use of this
stored muscle for research, if uniform national protocols, guidelines,
or language for the use of archived material was available for
submitting to various Institutional Review Boards (IRBs). While IRBs
vary, having some model language posted would reduce one hurdle in using
archived muscle. It may also be helpful to have available to researchers
and clinicians model IRB language to get permission to use prospectively
collected muscle in research.

Shared use of these stored materials would be greatly facilitated by the
development of a common set of data about the muscle samples in an
integrated national database for query by investigators with specific
questions. To set up such a database would require support for the data
entry and support for database maintenance. In addition, there would
have to be guidelines about information required prior to release of
muscle.

For continued investigator access to tissues and patients, and to
continue to develop improved approaches to diagnostic evaluation, it is
critical that diagnostic testing remain within the academic realm. For
this to happen, it is important that different labs offering
pathological or genetic evaluation be integrated so that the clinician
doesn't have to collect multiple samples to be sent sequentially to
different laboratories.

Muscle biopsy has the potential for contributing to diagnostic
evaluation and understanding of pathophysiology through emerging
technology. These include Western blot analysis of very small
quantities, proteomics, and laser capture microscopy. Further
development of these techniques should be supported and, where
appropriate, moved into the diagnostic algorithm.

**Muscle Imaging as a Diagnostic Tool**

It is often difficult to distinguish between an inherited dystrophic
process and an acquired myopathy on clinical grounds alone. This is of
utmost importance, since patients for whom the diagnosis is not clear
may receive unnecessary and potentially toxic treatment or may have
curative treatments delayed or withheld. While there is potential for
distinguishing the muscular dystrophies that have sarcolemmal
instability from those that do not, there is considerable debate as to
whether modern imaging techniques will prove valuable in the diagnosis
of specific types of muscular dystrophy (e.g., is MRI better than a
clinical exam at distinguishing the different dystrophy types?). Even if
imaging does not emerge as a widely useful diagnostic tool, it has
potential for therapeutic monitoring in clinical trials.

-   *Research Objective 10:* Develop and validate the role of muscle
    imaging in diagnostic evaluation or as an endpoint measure for
    clinical trials (Long Term; High Risk).

Several methods of muscle imaging (CT, MRI, MR spectroscopy, and DEXA)
have been utilized in the inherited and acquired myopathies. Both CT and
MRI are being utilized to identify areas of greatest pathology in order
to improve the yield of muscle biopsies. This is mainly applicable to
the inflammatory myopathies, where the pathology is often spotty and
multifocal; muscle imaging also can identify sarcolemmal damage. Muscle
imaging (MRI, CT, DEXA) can also be used to measure regional or total
body muscle mass as a surrogate outcome measure in clinical trials.
There have also been several studies suggesting that patterns of
skeletal muscle involvement determined by MRI may be useful in
distinguishing among the different muscular dystrophies. Most of these
studies looked at MRI patterns in a single muscular dystrophy or
compared small sample numbers in two dystrophies. It is not clear at
this point how sensitive such a procedure would be, given the phenotypic
variability within a given dystrophic process, and more importantly,
whether imaging is more sensitive than a thorough bedside neuromuscular
exam in discerning a characteristic pattern of involvement.

Priorities for future research in muscle imaging include clarifying the
sensitivity and specificity of muscle imaging in muscular dystrophies
from inflammatory myopathies, and in accurately and reliably
distinguishing between specific muscular dystrophies.

**Epidemiology Studies Based on Genetic Diagnosis**

Knowledge about incidence and prevalence of genetically confirmed types
of muscular dystrophy is valuable in developing reasonable algorithms
and novel treatments for specific diagnoses. As specific genetic tests
become available, we have the opportunity to determine the epidemiology
of these diseases.

-   *Research Objective 11:* Establish current and accurate incidence
    and prevalence data for genetically confirmed forms of muscular
    dystrophy (Long Term; Intermediate Risk).

Efforts are underway to determine the epidemiology of Duchenne/Becker
muscular dystrophy through the MDSTARnet project funded by the CDC. The
system could be expanded to include additional muscular dystrophies. A
multicenter effort to characterize a large cohort of limb girdle
muscular dystrophy patients will be submitted for publication in the
near future. These efforts need to be expanded in other forms of
muscular dystrophy.

**Neonatal Testing for Muscular Dystrophy**

Advances in technology have made neonatal screening approaches feasible.
Neonatal screening for Duchenne muscular dystrophy, however, raises many
issues. Duchenne muscular dystrophy is treatable, but not yet curable,
and the treatment (corticosteroids) has only been proven efficacious in
older individuals. Potential benefits to the families and patients
include the shortening of the diagnostic odyssey, the opportunity for
family and lifestyle planning based on the diagnosis, and the
opportunity of participation in presymptomatic clinical trials aimed at
early intervention strategies. Potential burdens include the
psychological burden of knowledge, in a presymptomatic child, of the
presence of an incurable condition, potential ramifications to insurance
status, and issues of consent.

-   *Research Objective 12:* Develop methods for newborn screening of
    the muscular dystrophies. Explore the social and ethical issues
    involved in offering neonatal screening for muscular dystrophy and
    develop techniques that would make screening practical (Long Term;
    Intermediate Risk).

Efforts to address some of these issues have been initiated by NICHD
with the support of the Centers for Disease Control, but these
activities need continued support. A consensus among stakeholders should
be attempted, including determining parental attitudes toward neonatal
testing. Another goal is to develop sensitive and specific methods for
neonatal diagnosis using recent improvements in technology. An example
is the development of genomic and proteomic methods for the screening
and diagnosis of Duchenne muscular dystrophy based on blood spots. The
CDC has several activities underway to research the complex issues
related to newborn screening for Duchenne/Becker muscular dystrophy. CDC
conducted an expert review panel to identify the research priorities and
issues related to newborn screening for Duchenne/Becker muscular
dystrophy. CDC currently funds a pilot newborn screening project, with
emphasis on studying the challenges related to informed consent in the
neonatal period. In addition, CDC is funding a pilot program for infant
screening for Duchenne/Becker muscular dystrophy in pediatricians'
offices. CDC funds a national survey effort that will collect
information on the attitudes of parents of males with Duchenne/Becker
muscular dystrophy toward newborn screening for Duchenne/Becker muscular
dystrophy. CDC is also funding a research project to study how parents
of health newborn males weigh the different factors related to newborn
screening for conditions without an effective early treatment such as
Duchenne/Becker muscular dystrophy.

D.  **Matrix of Research Objectives in Diagnosis and Screening in**

> **Muscular Dystrophy**

+-----------+------------------+------------------+------------------+
|           | **Short Term**   | **Medium Term**  | **Long term**    |
|           |                  |                  |                  |
|           | **(0-3 years)**  | **(4-6 years)**  | **(7-10 years)** |
+-----------+------------------+------------------+------------------+
| **High    |                  |                  | Develop and      |
| Risk**    |                  |                  | validate the     |
|           |                  |                  | role of muscle   |
|           |                  |                  | imaging in       |
|           |                  |                  | diagnostic       |
|           |                  |                  | evaluation or as |
|           |                  |                  | an endpoint      |
|           |                  |                  | measure for      |
|           |                  |                  | clinical trials  |
+-----------+------------------+------------------+------------------+
| **Int     |                  | -   Develop      | -   Establish    |
| ermediate |                  |     minimally    |     the          |
| Risk**    |                  |     invasive     |     specificity  |
|           |                  |     diagnostic   |     and          |
|           |                  |     techniques   |     sensitivity  |
|           |                  |     for muscular |     of           |
|           |                  |     dystrophies  |     diagnostic   |
|           |                  |     where        |     tests for    |
|           |                  |     appropriate  |     the muscular |
|           |                  |                  |     dystrophies  |
|           |                  | -   Optimize     |                  |
|           |                  |     utilization  | -   Support      |
|           |                  |     of muscle    |                  |
|           |                  |     biopsy       | disease-specific |
|           |                  |     materials    |     registries   |
|           |                  |     for research |     with         |
|           |                  |     by further   |     detailed     |
|           |                  |     developing   |     genetic,     |
|           |                  |     new          |     structural   |
|           |                  |     techniques   |     and          |
|           |                  |     for          |     functional   |
|           |                  |     evaluation   |     information  |
|           |                  |     of muscle    |     regarding    |
|           |                  |     samples      |     phenotypic   |
|           |                  |     (such as     |     effects in   |
|           |                  |     Western blot |     other organ  |
|           |                  |     analysis of  |     systems, as  |
|           |                  |     very small   |     well as      |
|           |                  |     quantities,  |     pathological |
|           |                  |     proteomics,  |     and clinical |
|           |                  |     and laser    |     information. |
|           |                  |     capture      |     Foster       |
|           |                  |     microscopy)  |     cooperation  |
|           |                  |     and, where   |     between      |
|           |                  |     appropriate, |     registries,  |
|           |                  |     moving them  |                  |
|           |                  |     into the     |    neuromuscular |
|           |                  |     diagnostic   |     research     |
|           |                  |     algorithm    |     centers, and |
|           |                  |                  |     academic     |
|           |                  |                  |     diagnostic   |
|           |                  |                  |     centers      |
|           |                  |                  |                  |
|           |                  |                  | -   Establish    |
|           |                  |                  |     current and  |
|           |                  |                  |     accurate     |
|           |                  |                  |     incidence    |
|           |                  |                  |     and          |
|           |                  |                  |     prevalence   |
|           |                  |                  |     data for     |
|           |                  |                  |     genetically  |
|           |                  |                  |     confirmed    |
|           |                  |                  |     forms of     |
|           |                  |                  |     muscular     |
|           |                  |                  |     dystrophy    |
|           |                  |                  |                  |
|           |                  |                  | -   Develop      |
|           |                  |                  |     methods for  |
|           |                  |                  |     newborn      |
|           |                  |                  |     screening    |
|           |                  |                  |     for the      |
|           |                  |                  |     muscular     |
|           |                  |                  |     dystrophies. |
|           |                  |                  |     Explore the  |
|           |                  |                  |     social and   |
|           |                  |                  |     ethical      |
|           |                  |                  |     issues       |
|           |                  |                  |     involved in  |
|           |                  |                  |     offering     |
|           |                  |                  |     neonatal     |
|           |                  |                  |     screening    |
|           |                  |                  |     for muscular |
|           |                  |                  |     dystrophy    |
|           |                  |                  |     and develop  |
|           |                  |                  |     techniques   |
|           |                  |                  |     that would   |
|           |                  |                  |     make         |
|           |                  |                  |     screening    |
|           |                  |                  |     practical.   |
+-----------+------------------+------------------+------------------+
| **Low     | -   Develop      |                  |                  |
| Risk**    |     definitive   |                  |                  |
|           |     gene tests   |                  |                  |
|           |     for muscular |                  |                  |
|           |     dystrophies  |                  |                  |
|           |     for which    |                  |                  |
|           |     genetic      |                  |                  |
|           |     testing is   |                  |                  |
|           |     not yet      |                  |                  |
|           |     available    |                  |                  |
|           |                  |                  |                  |
|           | -   Establish    |                  |                  |
|           |     mechanisms   |                  |                  |
|           |     for muscular |                  |                  |
|           |     dystrophy    |                  |                  |
|           |     patients to  |                  |                  |
|           |     obtain       |                  |                  |
|           |     accurate     |                  |                  |
|           |     genetic      |                  |                  |
|           |     counseling   |                  |                  |
|           |                  |                  |                  |
|           | -   Encourage    |                  |                  |
|           |     submission   |                  |                  |
|           |     of new       |                  |                  |
|           |     mutation and |                  |                  |
|           |     polymorphism |                  |                  |
|           |     data for     |                  |                  |
|           |     muscular     |                  |                  |
|           |     dystrophy    |                  |                  |
|           |     genes to     |                  |                  |
|           |     public       |                  |                  |
|           |     databases    |                  |                  |
|           |                  |                  |                  |
|           | -   Optimize     |                  |                  |
|           |     utilization  |                  |                  |
|           |     of muscle    |                  |                  |
|           |     biopsy       |                  |                  |
|           |     materials    |                  |                  |
|           |     for research |                  |                  |
|           |     by           |                  |                  |
|           |     developing   |                  |                  |
|           |     IRB language |                  |                  |
|           |     to assist    |                  |                  |
|           |                  |                  |                  |
|           |    investigators |                  |                  |
|           |     with use of  |                  |                  |
|           |     archived or  |                  |                  |
|           |                  |                  |                  |
|           |    prospectively |                  |                  |
|           |     collected    |                  |                  |
|           |     diagnostic   |                  |                  |
|           |     muscle       |                  |                  |
|           |     biopsies     |                  |                  |
|           |                  |                  |                  |
|           | -   Optimize     |                  |                  |
|           |     utilization  |                  |                  |
|           |     of muscle    |                  |                  |
|           |     biopsy       |                  |                  |
|           |     materials    |                  |                  |
|           |     for research |                  |                  |
|           |     by fostering |                  |                  |
|           |     shared use   |                  |                  |
|           |     of stored    |                  |                  |
|           |     and          |                  |                  |
|           |                  |                  |                  |
|           |    prospectively |                  |                  |
|           |     collected    |                  |                  |
|           |     diagnostic   |                  |                  |
|           |     muscle       |                  |                  |
|           |     biopsies by  |                  |                  |
|           |     the research |                  |                  |
|           |     community    |                  |                  |
+-----------+------------------+------------------+------------------+

**Therapy of Muscular Dystrophy**

**A. Introduction**

In the last five years, there have been some important advances in
development of therapeutics for the muscular dystrophies. However, in
terms of improved management of muscular dystrophy patients, the
advancement has been slow, with very little of the promise from animal
efficacy studies actually translating into new treatments for patients.
As a result of continued questions about treatment, even the use of
corticosteroids in Duchenne muscular dystrophy, which is considered
standard of care, occurs in only 60% of the patients. The ability to
obtain genetic diagnoses in many of these diseases has enhanced the
possibility for good clinical trials, especially in diseases with
phenotypic variation. The continued challenges of finding treatments and
proceeding with clinical trials are multiple. Despite these challenges,
there are now more potential therapies being explored at the level of
preclinical studies and clinical trials than ever before. The strategy
of maintaining this broad-based, parallel pursuit of the most promising
therapies for the muscular dystrophies is a vitally important research
objective.

Challenges faced in preclinical development for the muscular dystrophies
include the difficulty of establishing and maintaining good animal
models. Preclinical studies have yielded important advances in
understanding some of the key muscle growth factors and their signaling
pathways, as well as the regulatory mechanisms underlying muscle
fibrosis. These aspects of the pathogenesis of muscular dystrophy may
represent among the most directly addressable targets for novel therapy
development. Other advances include identification of those muscle
progenitor cells with the best potential for cell-based therapies, a
rapid evolution in technologies for gene correction or gene-based
therapy, identification of targets for indirect gene complementation
through understanding of genes that may play complementary roles to
those in the dystrophin-glycoprotein complex, and a better understanding
of the gene constructs, promoters, and delivery systems needed for viral
vector therapies. While animal studies have been invaluable in
therapeutic development efforts, efforts have to be taken to determine
if strategies that delay onset of disease in mice also slow progression
in humans when administered after the onset of symptoms.

The establishment of guidelines for respiratory care for patients with
Duchenne muscular dystrophy, both practice-based and evidence-based, in
cooperation with the American Thoracic Society, clearly can enhance
quality of life in a more uniform fashion for many of these patients.
This approach sets an important standard for the multidisciplinary
management of the muscular dystrophy patient.

The continued development and application of possible therapeutics to
patients with a variety of muscular dystrophies will require focus on a
variety of areas. With the convergence of therapeutic insights and
technologies, the ability to obtain precise molecular diagnoses of
disease, and the synergism provided by joint efforts of academic
researchers, small and large pharmaceutical companies, and support from
federal agencies and non-profit organizations, there is considerable
opportunity and promise for the emergence of new, effective therapies
for the muscular dystrophies. Beyond the identification of targets for
the development of new therapies, there is a real need to reassess the
strategies for moving from mechanistic understanding to clinically
effective treatments. Investigators and funding agencies should consider
a research paradigm shift, at least in part, from the hypothesis-driven
approach that has been vital for key discoveries in pathogenic
mechanisms to a goal-driven approach designed to select and focus upon
those therapeutic strategies with the best potential and move them
forward into clinical trials.

Regularly updated information about Federally and privately supported
clinical research in human volunteers is available at:
[http://www.clinicaltrials.gov](http://www.clinicaltrials.gov/).
ClinicalTrials.gov includes information about a trial\'s purpose, who
may participate, locations, and phone numbers for more details.

**B. Recent Research Advances**

There are few effective treatments available for muscular dystrophy.
Current efforts to develop novel therapies include both generalized and
gene-specific strategies. Generalized strategies aim at common points in
the pathogenesis of muscular dystrophy, and their products may have
therapeutic potential for several of the muscular dystrophies. These
strategies include sarcolemmal stabilization, sarcolemmal repair, and
enhancement of normal muscle regenerative mechanisms. By contrast,
gene-specific strategies rely upon detailed knowledge of the molecular
defect in a particular type of muscular dystrophy and thus their
benefits are likely to be disease-specific; these include the
replacement or repair of a defective gene or use of
pharmaceuticals/small molecules to bypass the mutation site and produce
a truncated, but adequately functional protein. Recently, there has been
substantial effort to translate animal model efficacy data into clinical
trials for muscular dystrophy.

**Corticosteroid Use**

Corticosteroids have become the standard of care for Duchenne muscular
dystrophy, acting to delay the loss of independent ambulation, delay the
onset of cardiac and respiratory failure, and reduce the occurrence of
skeletal defects. Approximately 60% of Duchenne muscular dystrophy
patients in the USA are taking corticosteroids. Although practice
parameters have been published, several competing treatment regimens are
in use in USA, Canada, and Europe, including prednisone (0.75
mg/kg/day), deflazacort (0.9 mg/kg/day), and intermittent deflazacort
(10 days on/10 days off, 0.75 mg/kg/day). There is unequivocal evidence
that both prednisone and deflazacort are beneficial over a 6-month
period, based on double-blind controlled clinical trials; the two drugs
appear to be equally effective in head-to-head studies. Retrospective
analysis suggests that corticosteroids can prolong ambulation by 2 to 3
years, but the numbers of patients walking longer than the norm is not
well defined. Difficulties in management of side effects remain a
barrier to corticosteroid use in many patients. A phase III clinical
trial to determine whether a high-dose weekly course of prednisone
therapy is safer than and at least as effective as daily dose therapy in
Duchenne muscular dystrophy is being conducted by an international
consortium (The Cooperative International Neuromuscular Research Group
(CINRG)).

**Muscle Growth Factor Modulation**

*Myostatin inhibition.* Myostatin is an endogenous negative regulator of
muscle growth. The rationale for therapeutic development based upon
myostatin is that muscle growth inhibitor blockade could enhance muscle
regeneration. In the past five years, the myostatin signaling pathway
has been elucidated, thereby providing multiple sites for drug
targeting. Inhibiting myostatin has been shown to induce muscle
regeneration in chronic injury models, including the mdx mouse. Since
the function of myostatin is conserved across species, myostatin
inhibition may have beneficial effects in human muscle disease.

A phase I/II multicenter clinical trial using a myostatin blocking
antibody (MYO-029) has been started (Wyeth Pharmaceuticals). Subjects
with several types of muscular dystrophy (Becker muscular dystrophy,
autosomal recessive limb-girdle muscular dystrophy, and
facioscapulohumeral muscular dystrophy), with differing pathogenic
mechanisms, have been entered into the myostatin trial; inclusion
criteria are restricted (18 years of age or older and ambulatory
patients only). While a blocking antibody may have only limited
applicability in chronic muscle disease, the parallel translational and
clinical studies will provide an important test of the myostatin
strategy and support development of alternative means of blocking the
myostatin signaling cascade (e.g., with orally bioavailable small
molecules).

*Insulin-like growth factor 1.* Following a strategy that is the
converse to myostatin inhibition, the therapeutic potential of
upregulating a positive regulator of muscle development and
regeneration, insulin-like growth factor 1 (IGF1), has been extensively
studied in the mdx mouse. Transgenic overexpression of mIGF1 in mdx
muscle fibers reduces the breakdown of dystrophic muscle during the
acute phase of degeneration and increases muscle mass. Subcutaneous
injection of IGF1 in mdx mice reverses exercise-related fatigue and
improves contractile function. Collectively, its combined activity of
promoting muscle regenerative capacity and preventing necrosis makes
IGF1 particularly attractive as a potential treatment for muscular
dystrophy. A recent study in dystrophic mice showed that a combinatorial
strategy, gene therapy with both dystrophin and IGF1, represents a clear
improvement over results obtained with the dystrophin gene construct
alone. A clinical trial of IGF1 linked to IGF binding protein 3
(SomatoKine), is planned for myotonic dystrophy patients (University of
Rochester). Due to its regeneration-enhancing mechanism, SomatoKine may
have general applicability as a treatment for the muscular dystrophies.
In addition, discovery programs are ongoing to find small molecules that
can upregulate muscle-specific IGF1.

**Cell-Based Therapy**

The goal of cell-based therapy designs is to repopulate dystrophic
muscle with cells that are capable of either fusing with existing muscle
fibers, or forming muscle fibers de novo, and then go on to express the
defective gene. The cell-based therapy strategies that are currently
under investigation differ in the source of muscle precursor cells.

*Myoblast transplantation.* Muscle is a regenerative organ; upon
activation, a resident satellite cell population forms muscle precursor
cells or myoblasts. Although ongoing regeneration is a characteristic
feature of muscular dystrophy, it ultimately fails to match the
progressive muscle degeneration. Genetically normal myoblasts can be
isolated from normal subjects, expanded in culture, and then delivered
by direct injection into dystrophic muscles. The rationale for this
approach is that muscle function may be restored provided that
sufficient numbers of normal myoblasts are delivered, overcome muscle
fibrosis, hypo-vascularity, and/or any host immune response, and proceed
to form new muscle fibers.

Phase I/II trials are ongoing using myoblast transplantation. In these
studies, myoblasts are derived from healthy, genetically related donors
and injected into selected target muscles. Immunosuppression is a key to
long-term survival of myoblasts and FK506 seems to be of benefit.
However, the therapeutic potential for myoblast transfer has yet to be
demonstrated. Important hurdles to the success of myoblast
transplantation are: (a) identification of cell populations with the
greatest potential for myogenesis, (b) the limited treatment potential
of direct muscle injection (systemic delivery potential of satellite
cells is poor and myoblast dispersement from single injection sites is
limited), (c) initiation of treatment early enough to avoid the
complications of fibrosis and poor perfusion of the dystrophic muscle
target, and (d) developing protocols to prevent rejection of
transplanted cells. Recent studies suggest that autologous transfer of
myoblasts from unaffected to affected muscles may have therapeutic value
in facioscapulohumeral and oculopharyngeal muscular dystrophies.

*Other muscle progenitor cells.* Recently, additional populations of
muscle progenitor cells (i.e., the side population (SP) cells in muscle
and bone marrow) have been identified using cell sorting technology. It
remains a considerable debate to what degree bone marrow-derived cells
can differentiate into muscle. Recent studies suggest that, with Notch
transcription factor modulation, bone marrow-derived cells can be
induced to develop into muscle cells. Bone marrow cells may be better
than the progenitor cells that reside in skeletal muscle at overcoming
the hurdle of systemic delivery. Yet, key successes with bone marrow
cells have failed to be reproduced in mouse models by some groups.

Progenitor cells that are derived from muscle are an active area of
investigation and may hold promise. While recent studies suggest that
they have considerable potential for repopulating dystrophic muscle and
their in vitro expansion can yield therapeutically relevant numbers of
cells for transplantation, a concern about possible transformation
during in vitro expansion and subsequent tumorgenicity remains. Clearly,
embryonic-derived stem cells are known to have considerable ability to
differentiate and develop into muscle. Embryo-derived cells offer the
additional advantage that they are likely to avoid issues related to
immune-mediated rejection.

**Improvement in Understanding of Pathogenesis**

While advances in mechanistic understanding of the muscular dystrophies
are reviewed in the chapter on Mechanisms of Muscular Dystrophy, two
specific advances that may rapidly drive therapeutic development are
summarized here.

*Glycosyltransferases.* Sarcolemmal proteins, such as
alpha-dystroglycan, link the sarcolemma to the extracellular matrix
through binding of its carbohydrate moieties with the basal lamina
proteins (in the case of alpha-dystroglycan, to laminin alpha2). The
enzymes responsible for modifying cell surface glycoproteins and
glycolipids have recently been recognized to be implicated in limb
girdle and congenital muscular dystrophies. Glycosyltransferase
deficiency may also play a significant role in hereditary
cardiomyopathy. Fukutin-related protein (FKRP) mutations result in limb
girdle muscular dystrophy type 2I and congenital muscular dystrophy type
1C. It is estimated that limb girdle muscular dystrophy type 2I is one
of the most common forms of limb girdle muscular dystrophy worldwide.
Therapies addressing the hypo-glycosylation of alpha-dystroglycan may
have value independent of replacement of the defective gene.

*Dysferlin and its role in muscle membrane repair.* Mutations in the
gene encoding dysferlin are common causes of limb girdle muscular
dystrophy, having been described in patients throughout the world. A
mouse model lacking dysferlin was generated and the skeletal muscle from
this mouse displays abnormal resealing of laser-generated tears in the
plasma membrane. A number of genetic defects that lead to muscular
dystrophy arise from defects of plasma membrane stability, and these
defects include mutations in dystrophin and the sarcoglycans. In
contrast, mutations in dysferlin lead to muscular dystrophy by a defect
in plasma membrane repair. Therefore, this represents a novel mechanism
for muscular dystrophy. Therapy aimed at stabilizing muscle plasma
membrane may be less effective for dysferlin-mediated dystrophy.
Understanding how membrane repair occurs could lead to therapy for many
forms of muscular dystrophy. Dysferlin is a key molecule in dissecting
this process.

**Advances in Genetic Diagnosis**

Most dystrophin mutations that cause Duchenne muscular dystrophy are
large deletions or insertions that cause codon reading frameshifts (58%)
or small frameshifts or point mutations (41%), with the remainder due to
duplications. About a third of new Duchenne muscular dystrophy patients
have de novo mutations, obviating the need for diagnosis and screening
programs. There has been substantial progress in structure-function
studies of dystrophin. Not all domains of dystrophin are equally
essential for generating a functional protein. Mutations leading to the
absence of spectrin repeats in the rod domain, but with C-terminal and
cysteine-rich domain preservation, may cause a milder Becker muscular
dystrophy. The understanding of molecular structure-function from basic
science studies and recent progress in genotype-phenotype correlations
represent an important base for therapeutic development.

A precise molecular diagnosis (i.e., exact information on the nature of
the mutation) is essential for many of the putative therapies that are
moving into clinical trials. Advances in sequencing of the dystrophin
gene have expanded clinical diagnostic capabilities, now including at
least 30% of patients with Duchenne muscular dystrophy that might
otherwise be excluded from clinical trials. Gene sequencing of the
dystrophin gene has expanded clinical diagnostic capabilities and
allowed identification of small mutations, including nonsense mutations
sought for clinical trials. The genetic basis of the majority of the
muscular dystrophy and congenital myopathies is now known. Through a
combination of commercially available testing and research laboratories,
genetic diagnosis is now also available for the majority of patients.
Other advances in molecular diagnosis of the muscular dystrophies, and
the Research Objectives for this area, are compiled in the chapter on
Diagnosis and Screening in Muscular Dystrophy.

**Viral Vector Gene Replacement Therapy**

Several clinical trials designed to replace defective genes in Duchenne
muscular dystrophy or autosomal recessive limb girdle muscular dystrophy
are in planning stages (Columbus Children's Research Institute, National
Institute of Neurological Disorders and Stroke, and Asklepios
Biopharmaceuticals). Considerable progress has been made in gene therapy
constructs, construct delivery vectors, and promoter optimization.

*Micro-dystrophins for AAV somatic gene therapy.* Due to its large size,
full length dystrophin constructs cannot be accommodated in AAV vector.
To circumvent this problem, systematic studies have identified micro-
and mini-dystrophins that are functional in mdx mice. This approach
began with the identification of a truncated dystrophin in a Becker
patient that was still ambulatory in the 7^th^ decade of life. Other
smaller dystrophins have been described in mild Becker patients and
there is evidence for a deletional \"cold spot\" 5\' to the intron 44,
with the suggestion that ascertainment bias has precluded the clinical
recognition of asymptomatic in-frame (and \"in-phase\") deletions. These
Becker muscular dystrophy mini-dystrophins (and mini-utrophins) have
been extensively studied in vivo in the mdx and double null
(dystrophin-deficient/utrophin knock-out) mouse. Meanwhile, germline
gene transfer studies have suggested that the C-terminal dystrophin
binding sites for syntrophin and dystrobrevin might be \"expendable\".
This finding has been further exploited in the construction of
micro-dystrophin cassettes that subsequently have been tested in mdx
mice by both germline and somatic gene transfer, notably in the context
of rAAV vectors. Dystrophin constructs appropriately sized for
integration into AAV, with at least 4 spectrin-like repeats, appear to
have the capacity to reverse much of the histopathology and contractile
dysfunction characteristic of the mdx mouse model. There are not, as
yet, any reports of micro-dystrophin construct efficacy in the large
animal model.

*Optimization of AAV vectors.* Recombinant AAV (rAAV) vectors now have a
greatly expanded repertoire, including the serotypes AAV1-AAV9. Many of
these are potentially applicable for clinical trials in muscle disease.
Although AAV2 is the only serotype studied in clinical trials to date,
preclinical studies have suggested that the efficiency of muscle
transduction may be higher with other naturally occurring and
\"synthetic\" serotypes. Although switching serotypes will mandate an
uncertain amount of additional regulatory scrutiny, improved
transfection efficiency may be a compelling rationale. Most testing of
the alternative serotypes has have been limited to mice or young
hamsters, but they have shown promise in these systems for systemic gene
transfer following intravenous delivery. In a notable recent study, dogs
previously sensitized to AAV2 had efficient hepatic transduction with
AAV8. This has not yet been replicated with muscle as the target tissue;
likewise, transduction efficiency and potential myositis in a large
animal previously exposed to the same AAV serotype has not yet been
addressed. Recent data suggest that alternative methods of vector
delivery may dramatically alter the relative transduction efficiencies
of the various serotypes, potentially obviating the need for a switch
from AAV2.

*Optimization of AAV enhancers, promoters and target genes.*
Muscle-specific promoters (e.g., muscle-specific creatine kinase) in
experimental gene therapy may ensure greater safety, although these
express poorly in heart and diaphragm when compared to cytomegalovirus
(CMV) promoter. Ubiquitous over-expression of utrophin is non-toxic in
mice, although the levels are lower than generally expected with CMV.
There is, however, another possible theoretical advantage to
muscle-specific expression of AAV-encoded proteins, the potential
avoidance of immune recognition of the transgene product. Direct
evidence for this is limited; more recent studies using other transgenes
have shown evidence for strong humeral and cellular immune responses
despite the use of a muscle-specific promoter. There is also a potential
trade-off between attaining high-level expression versus tissue
specificity. Micro-dystrophin coding cassettes have been optimized to
fit into AAV while retaining much of the protein product functionality,
but leave very little room for promoter engineering.

**Gene Correction/Gene-Based Therapy**

Many of the mutations in dystrophin that cause Duchenne muscular
dystrophy act to cause either a deletion or a premature stop codon in
messenger RNA that is located within the rod/spectrin repeat domain of
dystrophin. Since the important binding domains of dystrophin are
preserved, these mutations are amenable to emerging gene correction
technology.

*Stop codon therapy.* Approximately 15% of the mutations that cause
Duchenne muscular dystrophy are due to point mutations in the coding
sequence that cause premature termination of transcription (stop
codons), leading to a truncated, non-functional protein product. Members
of the aminoglycoside class of antibiotics produce readthrough of these
premature stop codons to produce a nearly intact dystrophin. One of
these drugs, gentamicin, increases dystrophin expression in mdx mice by
10-20%. Small clinical trials with Duchenne muscular dystrophy patients
have been conducted with gentamicin with varying results (in one study,
serum creatine kinase levels decreased following a 14 day course without
demonstration of dystrophin expression). A new gentamicin trial is
underway in Duchenne muscular dystrophy (Columbus Children's Research
Institute).

Current drug development efforts are aimed at identifying orally
bioavailable agents that can promote stop codon readthrough with
improved pharmacokinetics and reduced toxicity. PTC124, a compound
developed via a high-throughput screen for stop codon suppression
activity and structural optimization by medicinal chemistry, has been
shown to induce dystrophin expression and to improve functional
endpoints in mdx mice. PTC124 has completed Phase I clinical testing in
healthy volunteers and is currently in Phase II clinical trials (PTC
Therapeutics). An observed hierarchy of responsiveness to the
suppression of different stop codon types suggests that drugs may need
to be matched to each of the three stop codon sequences; accordingly,
back-up compounds are being examined that may offer alternative
readthrough characteristics.

*Modulation of transcription and translation: exon skipping.* The
process of RNA splicing normally assembles each of 79 exons into a
dystrophin-encoding messenger RNA in skeletal muscle; alternative
combinations of these exons are selected to generate other
tissue-specific dystrophin isoforms (e.g., Dp71 in brain and Dp116 in
peripheral nerve). Since alternative splicing depends upon recognition
of exon boundaries, it is possible to manipulate the normal gene
splicing mechanisms in order to prevent the transcription of the
mutation-containing exon that otherwise would interfere with generation
of a functional dystrophin protein. This therapeutic development
strategy has been designated as exon skipping.

Targeted skipping of mutation-containing exons could theoretically
benefit 70-80% of Duchenne muscular dystrophy patients, but also may
have applicability in other muscular dystrophies. By skipping exons in
the rod/spectrin repeat domain of dystrophin, the resulting dystrophin
product would still contain the functionally essential actin- and
beta-dystroglycan-binding functional domains and potentially convert a
severe Duchenne to a milder Becker muscular dystrophy phenotype. A
specific antisense oligonucleotide or small nuclear RNA would be needed
in order to mask each mutation-containing exon. Recent advances in exon
skipping therapy development include improved chemistry (i.e.,
2\'-O-methyl antisense oligonucleotides (2OMeAO)) and demonstration that
systemic delivery can restore dystrophin expression and partially
reverse the mdx phenotype. Alternatively, AAV delivery of small nuclear
U7 RNA now has been shown to increase dystrophin expression in the mdx
mouse and in vitro in Duchenne cell lines. Clinical trials using the
antisense oligonucleotide exon skipping strategy are expected to start
soon in Australia and Europe (ProSensa, Glaxo SmithKline, University of
Western Australia, Imperial College of Medicine, and Leiden University).

Taken together, these designer therapies require knowledge of the
specific gene defect in each patient, increasing the importance of
patient registries with a precise molecular diagnosis for registrants.

**Alternative Pathways (Indirect Genetic Complementation)**

Several pathways are being explored for their ability to combat elements
of muscle degeneration in muscular dystrophy. Nitric oxide signaling in
skeletal muscle has both vasodilation and anti-inflammatory roles; these
roles are lost in both Duchenne muscular dystrophy and its animal
models. Transgenic overexpression of neuronal nitric oxide synthase
(nNOS) 3 (NOS3) in the mdx mouse reduces muscle pathology. The precise
mechanisms underlying this success are being explored. Overexpression of
NOS3 has a similar effect in ameliorating fibrosis in the hearts of mdx
mice. Manipulation of the cellular localization and activity level of
NOS3 has potential for muscular dystrophy therapeutic development.

Increased utrophin expression, whether mediated by transgenesis or viral
delivery, can improve dystrophic pathology in mdx mice. The rationale
for upregulation of the endogenous utrophin gene is that utrophin serves
the same function as dystrophin, but at a very restricted site, the
neuromuscular junction. The upregulation of utrophin along the entire
sarcolemma, effectively replacing dystrophin, is also being attempted
using small-molecule approaches.

Increased expression of an alternatively spliced form of integrin
alpha7, the major laminin-binding integrin of mature muscle, improves
the severely dystrophic phenotype of mdx/utrophin knock-out mice. The
rationale for upregulation of alpha7 integrin using small molecules is
that it, like the dystrophin-glycoprotein complex, normally provides a
trans-sarcolemmal linkage to the extracellular matrix, such that
increasing the density of alpha7 integrin protein in the sarcolemma may
functionally compensate for the projected mechanical stabilization
function of dystrophin.

Other putative targets for genetic compensation or "booster gene"
therapy (and their specific targets) include a disintegrin and
metalloprotease 12 (ADAM12) and acetyl-N-galactosamine (GalNAc)
transferase (membrane stabilization), agrin (basement membrane formation
in laminin alpha2 congenital muscular dystrophy), and calpastatin
(blockade of necrosis). In addition to potentially functioning as
isolated therapies, genetic compensation strategies may be useful as
co-therapies to increase the chance of success of cell- or gene
repair-based therapies.

**Respiratory Care Guidelines**

Clinical management of patients with muscular dystrophy often is
variable in the nature and quality of care that is provided. Much of the
care is anecdotal, occurring in the absence of clear guidance from
established practice parameters. Recently, consensus guidelines were
published for the respiratory care of Duchenne muscular dystrophy
patients. These are practice-based guidelines, as the ability to
generate evidence-based guidelines was limited due to the relatively
rare nature of Duchenne muscular dystrophy. The respiratory care
guidelines provide precise recommendations for the timing and extent of
respiratory examinations and care, from initial diagnosis through end of
life directives. The process that produced these guidelines serves as a
model for developing consensus practice parameters that address the
multi-system involvement seen for many of the muscular dystrophies.

**C. Research Objectives**

Although the underlying molecular defects have been characterized for
many of the muscular dystrophies, these remain among the most difficult
diseases to treat. However, there are now more potential therapies for
muscular dystrophy at various stages of development than ever before. In
part, this is a consequence of the improved understanding of pathogenic
mechanisms (see the chapter on Mechanisms of Muscular Dystrophy) and the
focused efforts toward translation of this knowledge into animal
efficacy studies and then clinical trials. The Research Objectives
identified here include not only a focus on the key steps needed for
maturation of specific strategies, but also the recognition that efforts
must be broad-based, since it is unclear as to which approaches, or
combination of approaches, may ultimately prove to be the most effective
in the treatment of muscular dystrophy. Combination therapies that, for
example, simultaneously counter muscle necrosis/fibrosis and correct or
replace the mutated gene, likely represent the best opportunity for
effective treatment of muscular dystrophy.

**Corticosteroids and Anti-Inflammatory Drugs**

Corticosteroids represent the standard of care for Duchenne muscular
dystrophy and remain the only treatment that has been established as
producing a functional delay in the disease course.

-   *Research Objective 1:* Optimize the use of prednisone as a
    treatment for Duchenne muscular dystrophy (Long Term; Low Risk).

While corticosteroids represent the only beneficial treatment for
Duchenne muscular dystrophy, many remaining questions regarding the use
of corticosteroids have not been answered or even addressed. An
extremely important remaining question is the potential benefit of
corticosteroids given early in the course of Duchenne muscular dystrophy
(e.g., ages 1 or 2) to establish if muscle degeneration/loss would be
prevented by early administration. The side effects of the
corticosteroids remain a significant prohibitory factor for some
patients and physicians. Efforts to idealize drug dosing regimens and to
establish the long-term benefits and side effects are important in
patient management. It has been proposed that prednisone given in
regimens other than daily dosing is equally beneficial to daily doses of
prednisone or deflazacort, but with fewer side effects. These
alternative dosing regimens require testing in a controlled trial.

The potential long-term benefits (e.g., prolonged ambulation and
improved pulmonary and/or cardiac function versus their substantial side
effects, especially osteoporosis and cataracts) of corticosteroids have
not yet been addressed in a prospective study. One complication for such
studies is the identification of validated, short-term surrogate
endpoint measures that are predictive of enhanced ambulation years after
the end of a clinical trial. The effects of corticosteroid use on
respiratory musculature decline and cardiomyopathy should be determined
in a prospective, double-blind study. The continuing value of
corticosteroid use in patients who are beyond the loss of ambulation is
advocated by some, but requires systematic study.

-   *Research Objective 2:* Determine the mechanism of action of the
    corticosteroids in muscular dystrophy in order to develop new,
    potentially more efficacious agents (Medium Term; High Risk).

The precise mechanism by which the corticosteroids delay progression of
Duchenne muscular dystrophy is unknown. Although these agents have
substantial anti-inflammatory activity, it is unclear whether this
represents their primary mode of action in muscular dystrophy. Recent
studies suggest that deflazacort may act by calcineurin-NFAT cell
signaling pathways to promote muscle cell survival. In order to improve
upon what is currently the standard of care for muscular dystrophy, it
is important to determine the mechanism of action of the corticosteroids
in dystrophic muscle, exploit medicinal chemistry to design new drugs to
enhance therapeutic potential and minimize side effects, and move these
drugs into controlled clinical trials to test against the current
standard of care. Although the corticosteroids did not show efficacy for
facioscapulohumeral muscular dystrophy in a small pilot trial,
engineering steroid structure to exploit muscle cell survival activity
may yield agents that have broad spectrum efficacy for treatment of the
muscular dystrophies.

-   *Research Objective 3:* Examine the efficacy of existing
    anti-inflammatory drugs for treatment of muscular dystrophy (Medium
    Term; Low Risk).

Gene expression profiling has considerably broadened our understanding
of the spatial and temporal properties of inflammatory cell involvement
in muscular dystrophy. Completely blocking inflammation, however, has
deleterious consequences because some inflammatory cell types are
essential for muscle regeneration. Several recent studies have
identified specific pro-inflammatory signaling pathways and mononuclear
cell types as contributors to the pathogenesis of muscular dystrophy.
This specific knowledge of pro-inflammatory pathways in muscular
dystrophy should be exploited in selective preclinical and clinical
testing of the efficacy of Food and Drug Administration (FDA)-approved
anti-inflammatory agents.

**Growth Factor Modulation**

Skeletal and cardiac muscles utilize a variety of cytokines and growth
factors to modulate muscle precursor cell proliferation, commitment to
the myogenic lineage, myoblast fusion and differentiation into myotubes,
and muscle fiber growth. The balance among positive and negative growth
regulators determines muscle status between the extremes of hypertrophy
and atrophy. Recent knowledge of the signaling pathways that regulate
myogenesis during muscle development and regeneration provides a novel
opportunity for the design of new treatments for the muscular
dystrophies.

-   *Research Objective 4:* Expand insulin-like growth factor 1 (IGF1)
    preclinical studies and the scope of ongoing clinical trials, and
    understand IGF1's local effects in muscle and other tissues (Short
    Term; Low Risk).

There is significant preclinical data that IGF1 stimulates muscle
regeneration and ameliorates muscular dystrophy in mouse models.
However, IGF1 has effects on multiple tissues throughout the body.
Restricted expression or utilization of IGF1 for treatment of muscular
dystrophy is an achievable goal. Preparations of IGF1 and IGF1 binding
protein 3 are currently entering clinical trials in myotonic dystrophy.
Screens are ongoing for small-molecule inducers of muscle-specific IGF1.
Other modes of delivery, such as adeno-associated viral vectors (AAV),
in additional disease settings, should be clinically studied. There also
is a clear need to understand the long-term effects of IGF1 on muscle
regenerative capacity.

-   *Research Objective 5:* Identify alternative mechanisms of myostatin
    inhibition and establish their potential as therapeutics through
    preclinical testing in animal models of various types of muscular
    dystrophy (Medium Term; Intermediate Risk).

A neutralizing antibody to myostatin has entered clinical trials in
adult muscular dystrophy, including Becker, facioscapulohumeral, and
some limb girdle muscular dystrophies. Muscular dystrophies at different
stages and severity may have different responses to this potential
growth-inducing drug, and failure or success in one disease category may
not easily translate to another. This necessitates separate clinical
trials for growth regulators in the different muscular dystrophies and
at different stages of disease. In addition, myostatin inhibition by a
neutralizing antibody requires long-term parenteral administration.
Development of orally bioavailable small molecules that might inhibit
myostatin production should be explored. Multiple other drug targets in
the myostatin signaling pathway, such as natural or modified inhibitory
complex proteins, are known and might be developed for clinical trials.

**Cell-Based Therapy**

The major hurdles to myoblast transfer therapy for muscular dystrophy
include the lack of dispersion of cells after direct muscle injection,
immune rejection, and poor cell survival. Moreover, only a small
population of transplanted cells actually contributes to muscle
regeneration. Use of alternative bone marrow or embryonic stem cell
populations as donor cells will require the selective induction of the
skeletal muscle lineage in cultures prior to transplantation,
appropriate expression of tissue-specific endogenous genes in donor
cells after transplantation, and effective integration of differentiated
skeletal muscle cells into the targeted muscle. Autologous cell therapy
approaches are useful in some situations (potentially in the muscular
dystrophies with selective muscle group targeting, such as
facioscapulohumeral and oculopharyngeal, where muscle progenitor cells
could be harvested from unaffected muscles) and do not have the same
requirements for immunosupression. The focus for cell-based therapeutic
development needs to be upon the isolation of cell populations with
optimal potential to efficiently home to and successfully engraft in
muscle after systemic delivery.

-   *Research Objective 6:* Achievement of adequate immunosuppression to
    support myoblast transplant therapy (Medium Term; Low Risk)

Myoblast transfer therapy development, based upon transfer of
dystrophin-competent myoblasts from the fathers of Duchenne muscular
dystrophy patients, failed in the early 1990's. Recent advances support
renewed efforts to exploit natural muscle regenerative mechanisms by
transferring myoblasts expressing the defective gene. For myoblast-based
studies, ongoing phase I/II safety studies will continue. The emphasis
for the next five years should be upon determining whether sufficient
cells can be transferred and remain viable so as to improve muscle
function. Targeted therapy, aiming for engraftment of particular muscle
groups, will likely see success. Immunosuppressive co-therapy will
utilize agents useful for other organ transplantation.

If myoblast transfer therapy is to be viable for muscular dystrophy,
there are several issues besides immune rejection that must be resolved.
Some of these issues are common to all cell-based therapy strategies, so
progress with one specific approach may aid others. In the longer term,
there is a need to develop better delivery mechanisms so that therapy is
not restricted to direct injection of isolated muscle groups. Treatment
of young children or newborns with muscular dystrophy has the advantage
of the reduced numbers of myoblast injections necessary for relatively
small muscles and the improved efficacy due to the later appearance of
fibrosis, but does invoke a need for newborn screening. Conversely,
treatment of very young children raises a number of ethical questions
should these studies begin too soon without sufficient documentation
that engrafted cells can survive long term. These issues may have the
consequence of limiting cell-based clinical studies to older, more
affected individuals for whom this therapy may be less effective due to
excessive muscle degeneration and fibrosis.

-   *Research Objective 7:* Define, through basic and preclinical
    translational studies, the therapeutic potential of alternative
    muscle progenitor cells (Medium Term; Intermediate Risk).

-   *Research Objective 8:* Define, through basic and preclinical
    translational studies, the therapeutic potential of embryonic stem
    cells (Medium Term; Low Risk).

Therapeutic development with alternative muscle progenitor and embryonic
stem cells likely will remain animal based for several years. This
belief is based on the need to determine the full capability of these
cells and their optimal sources. An advantage of using progenitor or
stem cells is that the potential for blood-borne delivery, which
eliminates the dispersion problem seen with myoblast transfer.

Markers should be developed to facilitate isolation of cell populations
with the best myogenic and engraftment potential, and these markers and
cell preparations should become widely available to researchers to
advance the field. Human counterparts of those murine cells with optimal
therapeutic potential should be studied in culture models. It is
reasonable to expect that human transplantation studies with alternative
muscle progenitor cells may commence within approximately 5 years.
Combination therapies, such as pairing cell-based therapy with
strategies to maximize the myogenic potential of transplanted cells
(e.g., via induction of muscle-specific transcription factors or
myostatin inhibition) may be required to increase the efficacy of this
approach to the level where it can have a measurable functional impact
for patients.

**Viral Vector Gene Therapy**

The barriers to successful gene therapy include identification of
optimal gene constructs (i.e., functional constructs of a size that fits
into delivery vectors), promoters, and AAV serotypes, resolution of
problems with protein and vector immunogenicity, and scale-up to large
animal models, where immune status and vascular and muscle biology
represent better approximations for the subsequent human trials. As a
consequence of the progress with gene constructs and muscle-specific
promoters, the focus for future studies should be on the other issues
identified here.

-   *Research Objective 9:* Conduct large animal model testing to
    determine optimal AAV serotypes for human gene therapy clinical
    trials (Short Term; Low Risk).

Identification and testing of alternative AAV serotypes was highly
successful for dystrophin-glycoprotein complex gene delivery in small
animal models (e.g., the improvement of AAV6 and AAV8 over AAV2), but
findings have not yet been reproduced in a large animal model. One
potential mechanism for species-specific results is the possibility that
the vasculature of small rodents is intrinsically leaky. Duchenne is the
only muscular dystrophy with a well-established large animal genetic
model and could serve as a paradigm for other muscular dystrophies.
Recent studies show that limb-wide vector delivery is both safe and
highly efficient in large animals when novel vascular access approaches
are used. Parallel studies using isolated cardiac perfusion in situ have
demonstrated similar progress. Interestingly, the isolated perfusion
approaches work with both adenovirus and AAV, suggesting that it may be
valuable to revisit the issues of cloning capacity and \"gutted\"
vectors for full-length dystrophin replacement.

The large animal approaches were first pioneered in rodent systems,
reiterating the need for continued, parallel investigation in models of
various sizes. The canine models for Duchenne muscular dystrophy could
potentially be used to address a wide range of clinically relevant
endpoints (e.g., limb, respiratory, and cardiac muscle function)
following either local or systemic administration of molecular therapy.
There is no published study of clinical efficacy in the canine Duchenne
model with any molecular therapy. In hemophilia, demonstration of
efficacy and safety in the dog model has been critical to the FDA
regulatory process. Hemophilia B serves as a clear example of FDA action
in the context of AAV-based therapy and should guide developmental work
for muscular dystrophy. Overall, it is still reasonable to expect that
an approach must work first in a rodent system before large animal
studies are fully justified; however, it should also be recognized that
success in the small animal is not necessarily a reliable predictor of
scale-up potential.

-   *Research Objective 10:* Improve the efficiency of gene therapy
    delivery in the muscular dystrophies, while minimizing the immune
    response to both gene product and delivery vehicle (Medium Term;
    Intermediate Risk).

The initial developmental stages for gene therapy in muscular dystrophy
relied upon direct injections into selected muscles. Based upon
experience from these preclinical gene therapy studies, isolated muscle
injection has limited therapeutic value, while development of systemic
delivery poses considerable risks. Research emphasis on an intermediate
approach, isolated limb perfusion: (a) allows the use of the
contralateral limb as a control, (b) offers the potential to minimize
liver and germ line vector delivery, and (c) faces fewer regulatory
hurdles than systemic gene transfer. Viewed as an intermediate step,
preclinical translational studies and clinical trials using limb
perfusion can help identify any unforeseen toxicities/complications and
determine the reasonable expectations for systemic therapeutic efficacy.
Since isolated limb therapies can improve quality of life by extending
ambulation and/or allowing retention of leg or arm/hand usage, this
strategy may be viewed by researchers and patients as more than simply
an intermediate step toward systemic therapy.

Since there is variable, low-level protein expression from many
dystrophin gene mutations, the recognition of dystrophin as a foreign
protein may vary widely from patient to patient. Hemophilia B studies
have revealed clear immunological differences between point mutational
and deletional nulls. While most Duchenne muscular dystrophy patients
have deletions, there is only one described deletional null animal
model. Since point mutational dystrophin nulls are leaky, as
demonstrated at the transcriptional level, data on immune response to
\"non-self\" proteins in the genetic disease models must be viewed with
caution. Gene therapy directed at upregulation of putative compensatory
proteins (e.g., utrophin and alpha7beta1 integrin) that are normally
expressed in Duchenne patients would avoid this complication.

Vector capsid antigenicity has been a problem in the rAAV clinical
trials. There is a clear need for model systems for investigation of the
cell-mediated immune response to vector capsid antigen in muscle, and
the potential role of transient immunosuppressive strategies to
circumvent this response.  Furthermore, studies in mice have
demonstrated differences in the immune response to a given rAAV vector
based on the route of administration. 

-   *Research Objective 11:* Evaluate the clinical endpoints needed for,
    and ethical issues associated with, Phase I/II gene therapy and all
    clinical trials (Medium Term; Intermediate Risk).

If successful molecular therapy evolves from one of the multiple
strategies under development, patients with far advanced disease may be
excluded because of their accumulated loss of muscle tissue, unless
muscle regeneration can be enhanced. In addition, the characteristic
fibrosis in dystrophic muscle may also be rate-limiting for many
potential therapies unless slowed by a co-treatment. Defining validated
outcome measures is essential to tracking disease course and assessing
efficacy of clinical interventions. The following measures are viewed as
important for the various stages of therapeutic development: cell-based
(markers), animal-based (markers, imaging, histopathology, strength, and
function), human subjects (imaging, markers, clinically meaningful
endpoints including strength, ambulation, spine deformity, cardiac
function, pulmonary function, quality of life), non-muscle endpoint
determination, and pharmacokinetic studies.

The bioethical issues associated with phase I/II clinical trials require
debate. These initial trials are safety studies and lack outcome
measures based on clinically meaningful endpoints to patients. In these
clinical studies, the potential risks may outweigh the benefits and
could preclude patients from later clinical trials when technology has
advanced the field to a higher level. On the other hand, these initial
clinical experiments must be carried out in order to get to more
meaningful studies.

**Gene Repair**

Two gene repair strategies are currently under investigation:
pharmaceutical-based stop codon readthrough and antisense
oligonucleotide-based exon skipping. Stop codon readthrough had its
basis in the initial discovery that aminoglycoside antibiotics could
bypass the premature stop codons that are seen in about 15% of Duchenne
muscular dystrophy patients. This technology is relatively mature and is
in clinical trials with both gentamicin and an oral agent (PTC124)
generated through a rational drug design strategy. Studies show
substantial potential for antisense oligonucleotide-based targeted
removal of one or more exons from a gene transcript to skip over
disease-causing mutations and produce a shortened, but in-frame,
transcript. This approach may be applicable for up to 80% of Duchenne
muscular dystrophy patients, warranting additional effort to move the
strategy forward through translational research and clinical trials.

-   *Research Objective 12:* Evaluate the safety and efficacy of stop
    codon readthrough and exon skipping agents through additional
    translational studies and clinical trials (Long Term; Intermediate
    Risk).

-   *Research Objective 13:* Develop novel agents to improve efficacy of
    current gene repair strategies or to open new strategies (Medium
    Term; High Risk).

Important remaining steps in advancing the stop codon readthrough
strategy are to complete ongoing phase I/II safety trials and move into
controlled evaluation of the efficacy of the most promising agents in
Duchenne muscular dystrophy patients. Depending upon the efficiency that
these agents show in clinical trials, exploration of additional novel
oral stop codon therapeutics may be required. As exon skipping moves
into phase I/II trials, the key research issues are to refine
oligonucleotide chemistry, obtain high efficiency systemic delivery,
maintain continuous antisense oligonucleotide expression (improving in
vivo antisense oligonucleotide stability or otherwise circumventing the
need for reinjection strategies based upon oligonucleotide and
dystrophin half-life), and resolve regulatory issues that now require
each new oligonucleotide sequence to be treated as a separate IND.

**High-Throughput Screening and Translational Research**

While there is considerable mechanistic understanding of many of the
muscular dystrophies, a therapy that pre-dates much of this knowledge,
corticosteroids, remains the standard of care for Duchenne muscular
dystrophy and there are few, if any, effective treatments for the other
muscular dystrophies. Efforts should be focused upon new strategies to
translate knowledge of the pathogenic mechanisms in muscular dystrophy
into testable therapeutics.

-   *Research Objective 14:* Identify new strategies to implement
    translational research projects for muscular dystrophy (Short Term;
    Low Risk).

Much of the substantial mechanistic data that has been developed through
hypothesis-driven studies of the dystrophin-glycoprotein complex-based
muscular dystrophies has yet to translate into therapeutics. There is a
considerable need for the entire research community to focus efforts on
the milestone-driven drug screening and therapeutic development
strategies that are used by the pharmaceutical industry. By directing
preclinical therapy development efforts toward those efficacy and
toxicology/biodistribution studies that are necessary for FDA
investigational new drug (IND) approval, candidate therapeutics can be
more rapidly culled and, as appropriate, moved into controlled clinical
trials. Since no specific putative therapy has yet emerged as a "leading
candidate," and combination therapy is likely to be necessary, care
should be taken to ensure that development of multiple therapeutic
strategies continues to proceed in parallel.

-   *Research Objective 15:* Expand high-throughput, small molecule
    screening efforts for promising therapeutic targets and identify
    novel targets for drug development (Short Term; Low Risk).

Several endogenous proteins have shown efficacy in targeting steps in
the pathogenesis of muscular dystrophy. These include utrophin (a
structural/functional analog of dystrophin normally with very restricted
expression in muscle), integrin alpha7 (a transmembrane protein that, in
parallel with dystrophin, links the sarcolemma to the extracellular
matrix), myostatin (a negative regulator of muscle growth; its
inhibition accelerates muscle regeneration), and IGF1 (a positive
regulator of muscle growth; its activation accelerates muscle
regeneration).

The transcriptional start site for the major striated muscle isoform of
utrophin (A) has been identified and constructs for use in promoter
analysis developed. More recently, a second isoform has been identified
(B-utrophin) and its promoter have been identified and cloned. A
reporter fragment of the A-utrophin promoter has been engineered into a
line of transgenic mice to allow for in vivo screening. Isolated
promoter fragments have been used in vitro for both high-throughput and
targeted screens for low molecular weight transcriptional upregulators.
The role for heregulin in transcriptional regulation of utrophin was
identified in this way, and therapeutic efficacy studies in the mdx
mouse have provided proof-of-concept for this general approach. One
European effort has focused on a high-throughput screening approach for
utrophin upregulation
([www.vastox.com/research/muscular_dystrophy.html](http://www.vastox.com/research/muscular_dystrophy.html)),
but there has been little public discussion of an analogous approach to
involve US-based partners.

A priority for research is to support targeted approaches, such as that
for utrophin upregulation, or consider adding incentives for industry to
participate in a high-throughput screening effort directed at endogenous
proteins that can counter the inherited gene defects in the muscular
dystrophies. Recognition and coordination with ongoing efforts in other
countries is essential to maximize the impact of limited resources.

**Cardiopulmonary Care**

Because many of the genes responsible for muscular dystrophy have shared
functions in skeletal and cardiac muscle, patients often develop
conduction block, arrhythmia, and cardiomyopathy. Standard
cardiopulmonary therapy is quite effective at reducing the symptoms
associated with and reducing mortality from congestive heart failure,
but has not been systematically evaluated to ensure the best quality of
care.

-   *Research Objectives 16-18:* Improve treatment for cardiopulmonary
    consequences in muscular dystrophy patients by:

    -   Developing guidelines based on evidence and/or current practice
        standard of care (Short Term; Low Risk).

    -   Assessing the value of FDA-approved agents for cardiopulmonary
        complication prevention (Long Term; Low Risk).

    -   Improving management of cardiomyopathy, conduction block, and
        arrhythmia (Long Term; Intermediate Risk).

Practice guidelines for the cardiopulmonary care of muscular dystrophy
patients should be developed, as was previously done for pulmonary care
in Duchenne muscular dystrophy. Guidelines for both cardiovascular and
pulmonary care should be provided to neuromuscular disorder clinics and
be made readily available to patients/families through websites for
health care provider/patient-based education. The absence of information
on the natural history of cardiomyopathy in susceptible populations of
muscular dystrophy patients also represents an important gap in
knowledge.

The mainstay of therapy for cardiomyopathy in the adult population
relies on angiotensin converting enzyme (ACE) inhibitors or angiotensin
receptor blockade. When used in combination with beta blockade,
mortality is significantly reduced. Additional agents that are effective
in adult populations with cardiomyopathy are spironolactone and digoxin.
Diuretics also are used as needed for symptoms of fluid overload.
Cardiopulmonary care in the pediatric muscular dystrophy patient has
generally lagged that in adults. A recent study suggested that early
institution of ACE inhibitors reduced the onset of cardiomyopathy in
Duchenne muscular dystrophy. Early combination therapy (ACE inhibitor
and beta blockade) would be expected to be even more beneficial and
requires assessment in controlled clinical trials.

There is a real need for improved cardiac care guidelines in all
muscular dystrophy patients.

Guidelines for the use of internal defibrillators have been developed in
the adult cardiomyopathy population, but not for pediatric muscular
dystrophy patients. Cardiomyopathy patients with left ventricular
ejection fraction of less than 30% are receiving implanted cardiac
defibrillators. Alternative options for pediatric muscular dystrophy
patients include external defibrillators. Even in the adult population
of myotonic dystrophy patients, there is a real question as to when
implanted defibrillators are appropriate.

**Infrastructure Needs**

While the needs for infrastructural support for research in the muscular
dystrophies are reviewed in the chapter on Infrastructure Needs for
Muscular Dystrophy, specific objectives that were viewed as particularly
important to developing new therapies are covered here.

-   *Research Objective 19:* Develop the animal models, assays, and
    tools necessary for preclinical translational research projects that
    focus upon rapidly moving the accumulated mechanistic knowledge into
    clinical practice (Medium Term; Intermediate Risk).

-   *Research Objective 20:* Improve the availability and distribution
    network for appropriate mouse models of muscular dystrophy (Short
    Term; Low RIsk).

-   *Research Objective 21:* Ensure the availability and use of large
    animal models for the later stages of preclinical development (Long
    Term; Low Risk).

The availability of appropriate animal models for efficacy studies and
assays for high-throughput screening represents a potential obstacle to
development of new treatments for the muscular dystrophies. It is at
least as important to reject drugs and therapeutic strategies at an
early stage, thereby saving valuable resources, as it is to identify
those strategies with the most promise to move into controlled clinical
trials. Among large animal models, the deletional null dog model may
allow informative preclinical studies of a wide range of molecular
therapies for dystrophinopathies. There are other canine and/or feline
models for laminin and sarcoglycan gene mutations that, if further
developed, would provide additional disease-specific systems for
critical studies in these forms of muscular dystrophy. In addition,
there are models for potentially related conditions, such as
cardiomyopathy, that could be optimized for translational studies, via
further genetic analysis and colony expansion.

**D. Matrix of Research Objectives in Therapy of Muscular Dystrophy**

+-----------+------------------+------------------+------------------+
|           | **Short Term**   | **Medium Term**  | **Long term**    |
|           |                  |                  |                  |
|           | **(0-3 years)**  | **(4-6 years)**  | **(7-10 years)** |
+-----------+------------------+------------------+------------------+
| **High    |                  | -   Determine    |                  |
| Risk**    |                  |     the          |                  |
|           |                  |     mechanism of |                  |
|           |                  |     action of    |                  |
|           |                  |     the          |                  |
|           |                  |                  |                  |
|           |                  |  corticosteroids |                  |
|           |                  |     in muscular  |                  |
|           |                  |     dystrophy in |                  |
|           |                  |     order to     |                  |
|           |                  |     develop new, |                  |
|           |                  |     potentially  |                  |
|           |                  |     more         |                  |
|           |                  |     efficacious  |                  |
|           |                  |     agents       |                  |
|           |                  |                  |                  |
|           |                  | -   Develop      |                  |
|           |                  |     novel agents |                  |
|           |                  |     to improve   |                  |
|           |                  |     efficacy of  |                  |
|           |                  |     current gene |                  |
|           |                  |     repair       |                  |
|           |                  |     strategies   |                  |
|           |                  |     or to open   |                  |
|           |                  |     new          |                  |
|           |                  |     strategies   |                  |
+-----------+------------------+------------------+------------------+
| **Int     |                  | -   Identify     | -   Improve      |
| ermediate |                  |     alternative  |     treatment    |
| Risk**    |                  |     mechanisms   |     for          |
|           |                  |     of myostatin |                  |
|           |                  |     inhibition   |  cardiopulmonary |
|           |                  |     and          |     consequences |
|           |                  |     establish    |     in muscular  |
|           |                  |     their        |     dystrophy    |
|           |                  |     potential as |     patients by  |
|           |                  |     therapeutics |     improving    |
|           |                  |     through      |     management   |
|           |                  |     preclinical  |     of           |
|           |                  |     testing in   |                  |
|           |                  |     animal       |  cardiomyopathy, |
|           |                  |     models of    |     conduction   |
|           |                  |     various      |     block, and   |
|           |                  |     types of     |     arrhythmia   |
|           |                  |     muscular     |                  |
|           |                  |     dystrophy    | -   Evaluate the |
|           |                  |                  |     safety and   |
|           |                  | -   Define,      |     efficacy of  |
|           |                  |     through      |     stop codon   |
|           |                  |     basic and    |     readthrough  |
|           |                  |     preclinical  |     and exon     |
|           |                  |                  |     skipping     |
|           |                  |    translational |     agents       |
|           |                  |     studies, the |     through      |
|           |                  |     therapeutic  |     additional   |
|           |                  |     potential of |                  |
|           |                  |     alternative  |    translational |
|           |                  |     muscle       |     studies and  |
|           |                  |     progenitor   |     clinical     |
|           |                  |     cells        |     trials       |
|           |                  |                  |                  |
|           |                  | -   Improve the  |                  |
|           |                  |     efficiency   |                  |
|           |                  |     of gene      |                  |
|           |                  |     therapy      |                  |
|           |                  |     delivery in  |                  |
|           |                  |     the muscular |                  |
|           |                  |     dystrophies, |                  |
|           |                  |     while        |                  |
|           |                  |     minimizing   |                  |
|           |                  |     the immune   |                  |
|           |                  |     response to  |                  |
|           |                  |     both gene    |                  |
|           |                  |     product and  |                  |
|           |                  |     delivery     |                  |
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|           |                  |     I/II gene    |                  |
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+-----------+------------------+------------------+------------------+

Therapy of Muscular Dystrophy matrix is continued on next page.

+-----------------+-----------------+-----------------+-----------------+
|                 | **Short Term**  | **Medium Term** | **Long term**   |
|                 |                 |                 |                 |
|                 | **(0-3 years)** | **(4-6 years)** | **(7-10         |
|                 |                 |                 | years)**        |
+-----------------+-----------------+-----------------+-----------------+
| **Low Risk**    | -   Expand      | -   Define,     | -   Optimize    |
|                 |                 |     through     |     the use of  |
|                 |    insulin-like |     basic and   |     prednisone  |
|                 |     growth      |     preclinical |     as a        |
|                 |     factor 1    |                 |     treatment   |
|                 |     (IGF1)      |   translational |     for         |
|                 |     preclinical |     studies,    |     Duchenne    |
|                 |     studies and |     the         |     muscular    |
|                 |     the scope   |     therapeutic |     dystrophy   |
|                 |     of ongoing  |     potential   |                 |
|                 |     clinical    |     of          | -   Improve     |
|                 |     trials, and |     embryonic   |     treatment   |
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|                 |     other       |     an          |     n muscular  |
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|                 |     for human   |     to support  |                 |
|                 |     gene        |     myoblast    |    complication |
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|                 |     clinical    |     therapy     |                 |
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|                 |                 |                 |                 |
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|                 |                 |                 |                 |
|                 |    consequences |                 |                 |
|                 |     in muscular |                 |                 |
|                 |     dystrophy   |                 |                 |
|                 |     patients by |                 |                 |
|                 |     developing  |                 |                 |
|                 |     guidelines  |                 |                 |
|                 |     based on    |                 |                 |
|                 |     evidence    |                 |                 |
|                 |     and/or      |                 |                 |
|                 |     current     |                 |                 |
|                 |     practice    |                 |                 |
|                 |     standard of |                 |                 |
|                 |     care        |                 |                 |
|                 |                 |                 |                 |
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|                 |                 |                 |                 |
|                 |    availability |                 |                 |
|                 |     and         |                 |                 |
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|                 |     mouse       |                 |                 |
|                 |     models of   |                 |                 |
|                 |     muscular    |                 |                 |
|                 |     dystrophy   |                 |                 |
+-----------------+-----------------+-----------------+-----------------+

**Living with Muscular DystrophY**

**A. Introduction**

The muscular dystrophies are multi-system disorders affecting many body
systems besides the musculoskeletal system. Individuals with muscular
dystrophy experience not only the principal effects on muscle
degeneration, but also many secondary conditions, some of which are
serious conditions of their own. Thus, the individual's quality of life
is affected not only by muscle weakness and loss of mobility, but also
by conditions including bone deformities, breathing disorders,
cardiomyopathy, and cognitive decline, to name just a few. Many of these
conditions negatively impact one another, complicating the ability to
manage the disease. Taken together, the multi-system involvement in
muscular dystrophy has significant detrimental effects on the day-to-day
lives of patients, and may lead to social isolation. Clearly, the "whole
body" approach to the disease needs to be considered as appropriate
interventions are assessed and developed.

There is currently no treatment that can stop or reverse the progression
of muscular dystrophy. Other than corticosteroids, which can slow the
progression of some aspects of Duchenne muscular dystrophy, most
therapies are aimed at treatment of specific symptoms and focus on
rehabilitation and enhancing quality of life for patients. The
development of assistive technologies and specific interventions has
positively impacted quality of life for many individuals, but more
research is needed to develop beneficial therapeutic approaches. In
particular, the benefits and risks of exercise need to be determined.
One particular challenge in developing interventions is the lack of
quality of life measures for these diseases. Adequate measures of
quality of life and disease burden, and clinical endpoints for disease,
need to be developed.

In addition to the impact of the muscular dystrophies on the patients,
these debilitating diseases have a significant effect on the quality of
life of families and caregivers. Beginning with an uncertain and/or
lengthy diagnostic process, and continuing as the disease progresses,
family members face difficult decisions and significant stresses on a
daily basis. Advances in diagnosis have somewhat lessened this burden
and opened the possibility of neonatal testing to allow for family
planning. The availability of genetic testing means that parents and
families may seek advice from genetic counselors. It is critical to
provide sufficient means to educate families and improve their quality
of life, in addition to managing the disease in patients themselves.

Achieving progress in the topic area of Living with Muscular Dystrophy
represents a substantial challenge to the research community, in large
part due to the coordination that must occur among patients and their
families, multiple types of health care practitioners, various
professional organizations of physicians and other health care
providers, patient advocacy organizations, and governmental agencies at
federal, state, and local levels. While the challenge here is to
identify the best opportunities and most pressing needs, the ultimate
challenge will be to achieve the degree of coordination that is
necessary to achieve these objectives.

**B. Recent Research Advances**

Important advances have been made to improve the quality of life for
muscular dystrophy patients and their families. These include reduction
in the diagnostic odyssey that has been commonly associated with
muscular dystrophy, better understanding of the impact of muscular
dystrophy on both patients and family members, and improved diagnosis
and management of the secondary consequences of these diseases. In
addition, improvements have been made in a variety of interventions,
including medical and surgical management, rehabilitation and allied
health strategies, assistive technologies, psychosocial management,
education strategies, and vocational rehabilitation. Collectively, these
advances, and their associated infrastructure, create new opportunities
for improving the quality of life for patients living with muscular
dystrophy.

**Corticosteroids in Duchenne Muscular Dystrophy**

Recent reviews and practice parameter guidelines suggest that physicians
should offer corticocosteroids as a treatment for Duchenne muscular
dystrophy. These studies have shown that corticocosteroids significantly
increase muscle strength, performance, and pulmonary function and slow
the progression of weakness in boys with Duchenne muscular dystrophy.
However, corticosteroids are also associated with weight gain,
cushingoid facial appearance, acne, short stature, excessive hair growth
and behavioral changes. More studies are needed to determine the optimal
dose, dosing schedule, and age to begin treatment, in order to improve
function with the least number of side effects. Studies are also needed
to determine if corticosteroids have a beneficial effect on cardiac,
respiratory, gastrointestinal, and cognitive function in patients with
Duchenne muscular dystrophy. Better measures of quality of life and
patient reported outcomes are needed to assess the effect of these
compounds. Further studies are also needed to assess functional
measures, in particular to better understand the milestones of disease
progression.

**Application of Non-Invasive Ventilation and Cough-Assist Techniques**

Breathing disorders are recognized as the leading cause of mortality in
neuromuscular disease.

Although the natural histories of the various types of muscular
dystrophy differ with respect to time course and muscle groups involved,
respiratory muscle weakness in varying degrees is common to many of
these diseases. Weakness in both inspiratory and expiratory muscles
leads to a progressive reduction in vital capacity, and changes in the
compliance of the lungs and the chest wall contribute to the restrictive
pattern of pulmonary function. Over time, hypercarbia, which initially
occurs only at night, is seen during the day as well. Thus, a vicious
cycle of muscle weakness, nocturnal sleep disturbance, and hypercarbia
leading to worsening muscle weakness ensues. Even with appropriate
treatment of nocturnal respiratory disturbances, respiratory muscle
weakness can progress to the point where 24 hour/day ventilatory support
is needed.

Recently, chronic mechanical ventilation with either nocturnal
ventilation and/or daytime intermittent ventilation has been
increasingly employed in patients with more severe muscular dystrophies.
This management has been shown to reduce arterial CO~2~ and increase
arterial O~2~, decrease symptoms of respiratory failure, reduce
morbidity and mortality, and improve quality of life. Twenty-four-hour
per day noninvasive respiratory support has been suggested as a
methodology that can prolong survival (once the maximum benefit from
using nocturnal ventilation has been reached) and improve quality of
life when compared with standard tracheostomy ventilation. A number of
other mechanical cough-assist approaches act to increase cough
expiratory flows and help mobilize secretions. The provision of these
pulmonary technologies to patients remains variable despite increasing
literature supporting the use of these interventions in persons with
severe restrictive lung disease due to neuromuscular weakness. The
impact of such technologies on burden of care measures and quality of
life remain important issues.

**Early Recognition of and Advances to Treat Sleep-Disordered
Breathing**

During the 1980's, symptoms of sleep disordered breathing and the health
risks of its late diagnosis were recognized. Non-invasive ventilation
was complicated to achieve, but seemed to be associated with fewer risks
than tracheostomy for neuromuscular patients. In the 1990's, new
technology made non-invasive ventilation easier to use, facilitating the
study of sleep hypoventilation. Advances in the technology and wider
availability of the polysomnogram, as well as cheaper screening
procedures, resulted in large descriptive studies showing unequivocally
that early intervention with nocturnal ventilation results in many
benefits for patients. Technology has influenced treatment greatly, from
the availability of properly sized pediatric interfaces to the
development of laptop size ventilators that are easily portable and
socially acceptable. Improved study design occurred parallel to the
technology development, so that decisions can now be evidence based.

**Improved Techniques for Diagnosis and Testing**

[]{.mark}

While advances in diagnostic testing are reviewed in depth in the
chapter on Diagnosis and Screening in Muscular Dystrophy, it is
important to highlight here how these advances have contributed in
positive ways to "living with muscular dystrophy." New genomics and
proteomics technologies have made it feasible to provide a specific
diagnosis for many patients. Accurate diagnosis, in turn, has made it
possible to provide life-saving treatment for some individuals---such as
female Duchenne carriers with cardiomyopathy---who otherwise may not
have sought treatment. The availability of accurate diagnosis also has
given some individuals access to genetic counseling, although more
widely available counseling is needed. In addition, the use of genetic
diagnosis has opened the door for the possibility of prenatal testing.
Advances in prenatal testing technology---including the use of Chorionic
villus sampling, rapid PCR diagnosis of single cells removed at the
blastocyst stage, and maintained viability of blastocysts following
removal of a single cell---has made prenatal testing and embryo
selection feasible for a wide range of conditions. Anecdotal reports
suggest that this methodology has been used by several muscular
dystrophy families to avoid the birth of affected children.

**Early Diagnosis and Management of Cardiomyopathy**

Cardiomyopathy is evident in Duchenne and Becker muscular dystrophy,
myotonic muscular dystrophy, selected subtypes of limb girdle muscular
dystrophy, and Emery-Dreifuss muscular dystrophy. Newer imaging
approaches such as tissue Doppler echocardiography and magnetic
resonance imaging have made earlier detection of cardiomyopathy in
muscular dystrophies possible. Clinicians are recognizing the importance
of early treatment of cardiomyopathy in Duchenne muscular dystrophy with
angiotensin converting enzyme inhibitors (e.g. Enalapril, perindopril,
etc.) to delay the onset and slow the progression of left ventricular
dysfunction. Other agents typically used in adult cardiomyopathy such as
beta blockers, diuretics, and digitalis may also have a role in the
treatment of dystrophy-related cardiomyopathy, but more investigation is
needed. Conduction abnormalities (such as prolongation of the PR
interval, abnormal axis, and infranodal conduction abnormalities) may
also be seen in myotonic muscular dystrophy. These patients may benefit
from implantation of a cardiac pacemaker. Emery-Dreifuss muscular
dystrophy patients may experience atrial paralysis, atrial fibrillation,
and atrial flutter. Conduction disturbances may also involve the
infranodal conduction system, resulting in slow junctional escape
rhythms or complete heart block. While aggressive treatment of
cardiomyopathy in muscular dystrophies may improve morbidity and
mortality, the impact of such treatment on functional status and quality
of life are not known.

**Management of Gastrointestinal Dysfunction**

Swallowing disorders (dysphagia) are often associated with muscular
dystrophies, with swallowing problems reported in 30-50% individuals
with myotonic dystrophy, approximately 20% of individuals with Duchenne
muscular dystrophy and limb girdle muscular dystrophy, and in 6% of
those with facioscapulohumeral dystrophy. Slowly progressive dysphagia
is one of two cardinal symptoms of oculopharyngeal muscular dystrophy
(eyelid ptosis is the other). The swallowing difficulties in individuals
with muscular dystrophy are frequently due to impairment of esophageal
motility, which causes problems with slow transverse of the food bolus
through the esophagus. Transpharyngeal transit time may be delayed as
well. Some individuals may also have problems at the diaphragm
associated with hiatal hernias and with reflux. Reflux can produce
burning pain, difficulty with further swallowing, and may also involve
aspiration pneumonia. Improved diagnosis of these conditions has
occurred with the implementation of quantitative videodynamic swallowing
studies, where differences in food consistency and head positioning can
be studied as well as aspiration risk. Placement of a gastrostomy tube
may be indicated in the case of aspiration risk. A recent analysis of
the Cochrane Neuromuscular Disease Group trials register concluded that
no trials have adequately evaluated treatments for dysphagia in chronic
muscle disease.

**Nutritional Management of Obesity and Cachexia**

Muscular dystrophies are associated with the loss of skeletal muscle,
gain of excess body fat, and changes in energy metabolism and physical
activity over time. A reduction in 24-hour energy expenditure, decreased
fat-free mass and increased fat mass in ambulatory subjects with slowly
progressive muscular dystrophies has been documented. The ability to
measure body composition has improved with the application of imaging
techniques such as dual-energy x-ray absorptiometry, bioelectrical
impedance, and magnetic resonance imaging.

Nutrition, obesity, and obesity-related conditions are understudied in
all of the muscular dystrophies. It is not clear at this stage whether a
single approach toward nutrition is optimal given the different age of
onset, sex, and age of muscular dystrophy patients. There appears to be
a high incidence of obesity in individuals with Duchenne muscular
dystrophy, as well as other muscular dystrophies. Fat tissue often
increases at the time of transition to a wheelchair due to reduced daily
energy expenditure related to activity. Corticosteroid therapy also may
be a factor. The advantages of reduction of excess adipose tissue
include a lessening of the burden on already weakened muscles and
potential improvement in mobility and ease of breathing. During the
later stages of Duchenne muscular dystrophy, there is a rapid decline in
body weight due to a hypermetabolic state. As a result, energy and
protein requirements may be substantially higher during the later stages
of disease. Placement of a feeding gastrostomy tube for enteral
supplementation has been shown to be critical in patients with cachexia,
hypermetabolic state, dysphagia, and profound weakness which limits
self-feeding.

**Application of Assistive Technologies**

Modern assistive technology has been a major force in improving the
quality of life for disabled persons. Such technology provides people
with an improved means of communication, mobility, and control over
their environment and gives people with complex physical disabilities an
alternative way to perform many tasks that enhance independence. Great
technological innovations have been achieved over the past decade, which
have enormous potential for enhancing the lives of people with muscular
dystrophies. To identify the technical solution needed in each case, it
is essential to look at the individual's ability and the environment in
which the technology will be used. Appropriate use of assistive
technology (e.g., service dogs for children with muscular dystrophy) may
not only enhance the individual's abilities, but may have positive,
unpredicted consequences, such as helping with socialization. Awareness
and knowledge of assistive technology are key factors in supporting
empowerment of people with disabilities, and contribute to the success
of assistive technology solutions.

**Improved Understanding of Cognitive Defects**

Gains in our understanding of the neuropsychological consequences of
muscular dystrophies include more detailed descriptions of the
neurocognitive profile. New understanding of cognitive deficits in
Duchenne muscular dystrophy patients include an understanding of the
general intellectual downward shift, characterization of selective
verbal deficits particularly those affecting short term verbal memory,
resulting consequences on reading ability, changes in developmental
trajectory such that the verbal deficits are less severe with age, and
observations that the relative verbal weakness occurs across
intellectual level. Data demonstrating decreased brain metabolic
functioning, particularly in the cerebellum and medial temporal
cortices, suggests potential areas of involvement and mechanisms
underlying the defects. Studies examining the associations of cognitive
functioning with mutation position have suggested that distal mutations
disrupting production of alternatively spliced isoforms of dystrophin
(Dp71 and Dp140) are more likely to be associated with severe cognitive
deficits. Associated behaviors include increased social skill deficits
and anxiety and depressive symptoms. For myotonic dystrophy, profiles
vary according to age of onset, such that affected children present with
mental retardation while adult onset forms of disease cause dementia. In
general, executive functions are preferentially impaired. Brain changes
include evidence of white matter lesions, neurofibrillary tangles and
increases of tau protein, as well as decreased metabolic functions in
the frontal and temporal areas of the brain. Associated behaviors
include increased avoidant personality. For congenital muscular
dystrophy and facioscapulohumeral muscular dystrophy, the cognitive
effects are less clear; reports have suggested a range of intellectual
function.

**Recognition of Decreased Bone Mineral Content in Duchenne Muscular
Dystrophy and its Management**

Bone health is frequently compromised in boys with Duchenne muscular
dystrophy; fractures of long bones are more common. Fractures have
negative effects on their quality of life and may contribute to the loss
of ambulation. Duchenne muscular dystrophy patients also have reduced
bone mineral density, which may be exacerbated by corticosteroid
treatment. Corticosteroids may also increase the risk of vertebral
compression fractures. Vitamin D and calcium contribute to overall bone
health, but have not been proven to reduce the risk of low-impact
fractures.

Issues that require further study in Duchenne muscular dystrophy include
the natural history of bone health, identification of risk factors that
that predict the likelihood of a low-impact fracture, determination of
the contribution of Vitamin D and calcium to bone health, and the impact
of weight bearing exercise on bone strength. The role of bisphosphonates
has not been documented. Developing strategies to prevent and treat
reduced bone mineral density will require multicenter, collaborative
studies where standardized, clinical and laboratory data on boys with
Duchenne muscular dystrophy is collected. Clinical trials will hopefully
document both improved bone health and quality of life for boys with
Duchenne muscular dystrophy. Elucidation of the prevalence of
osteoporosis in other forms of muscular dystrophy is also of critical
importance.

**Documentation of the Benefits of Physical Activity and Exercise in
Slowly Progressive Muscular Dystrophies**

Three significant problems frequently noted by persons with slowly
progressive muscular dystrophies are muscle weakness, difficulty
exercising, and fatigue. These issues lead to reductions in physical
activity and an increased sedentary existence in muscular dystrophy
populations, putting individuals at long-term risk for coronary artery
disease, obesity, osteoporosis, and mental health issues such as
anxiety, depression or reduced self-esteem. Reduction in functional
muscle mass in individuals with neuromuscular diseases and associated
functional impairments are the result of both atrophy of disuse
secondary to a sedentary life style and muscle degeneration secondary to
the disease. This reduction of functional muscle mass likely results in
further reductions in activity levels. Endurance exercise or aerobic
training may be helpful to reverse the negative effects of the
de-conditioned state. Increased physical activity in persons with
muscular dystrophies, through exercise or other therapeutic approaches,
is likely to contribute directly to improved community locomotion,
community integration, and improved ability to participate in a greater
diversity of recreational options. In addition to general and preventive
health benefits, physical activity may provide a number of
disease-specific benefits in the disabled due to direct effects on
cardiac, pulmonary, and musculoskeletal impairments.

**Multi-Disciplinary Approach to Diagnosis, Treatment, and Management**

In the last few years, it has been recognized that there are a number of
management interventions that can alter the natural history of Duchenne
muscular dystrophy and other childhood onset muscular dystrophies, so
that the majority of people affected can be expected to live into adult
life. Four areas that are key to the proper multidisciplinary management
of muscular dystrophies are the improvement, maintenance, and support of
muscle strength and function; prevention and management of spinal
deformity; the management of respiratory complications; and the
prevention and treatment of cardiomyopathy. To make advances in these
areas, a team approach to disease management---involving neurology,
physical medicine and rehabilitation, orthopedic surgery, nutrition,
gastroenterology, pulmonology, respiratory therapy, cardiology, physical
and occupational therapy, psychology, and genetics---is needed. Such a
team approach has had an impact on the life expectancy of Duchenne
muscular dystrophy over the past three decades, has reduced secondary
complications in muscular dystrophies, and has likely positively
affected the quality of life in affected persons and family members.

**C. Research Objectives**

There is a substantial burden of disease experienced by persons with
muscular dystrophy and their families beginning with delayed, uncertain,
or erroneous diagnosis, and continuing as the disease progresses. The
goals for research on the topic of "living with muscular dystrophy" are
to reduce or eliminate this diagnostic odyssey, to improve quality of
life for patients and family members, to provide for improved clinical
management of primary and secondary disease consequences, and to
establish mechanisms to educate patients and family, thereby reducing
their psychosocial burden and isolation from society.

**Quality of Life Measures in Muscular Dystrophy**

Adequate quality of life and burden of disease measures for persons with
muscular dystrophies and family members are essential to understand and
address disease progression and rehabilitation challenges and to
facilitate clinical trials.

-   *Research Objective 1:* Identify and evaluate the quality of life
    and burden of disease measurement tools that are currently available
    (Short Term; Low Risk).

-   *Research Objective 2:* Develop disease-specific quality of life and
    burden of disease measures where gaps in existing measures are found
    (Medium Term; Low Risk).

Many existing quality of life and burden of disease measures cover
domains that are highly relevant to persons with muscular dystrophies
and their family members. A web-based catalog of measures that are
specific to muscular dystrophy would be useful to clinical researchers.
It would include domains covered, age range, sensitivity, reliability,
validity, psychometric properties, language translations (and validity
of multi-lingual versions of outcome measures), and references.
Disease-specific quality of life and burden of disease measures should
be developed where gaps exist.

**Clinical Endpoints in Natural History Studies and Clinical Trials**

Current understanding of the applicability of clinical endpoints (e.g.,
strength, activities, function, participation, quality of life, and
burden of disease) to natural history studies and clinical trials is
incomplete. Due to the progressive nature of the muscular dystrophies,
it is critical to understand the predictive value of specific clinical
endpoints as surrogate markers of disease progression and treatment
outcomes. Such means to carefully monitor disease progression over the
short time periods required for clinical trials are vitally needed for
all muscular dystrophies, and may be even more important in assessing
therapeutics in presymptomatic and symptomatic cases of adult
dystrophies with insidious onset and slow course (e.g.,
facioscapulohumeral and oculopharyngeal muscular dystrophies). The
coordination of data collection efforts (e.g., ensuring collection of
common data elements to facilitate comparison of results from different
trials) will be instrumental in meeting this goal.

-   *Research Objective 3:* Determine the sensitivity of clinical
    endpoints to changes in disease severity (Medium Term; Low Risk).

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-   *Research Objective 4:* Determine the magnitude of changes in
    endpoints which are clinically meaningful to patients and family
    members (Medium Term; Low Risk).

While previous clinical trials and natural history studies in muscular
dystrophy have focused on impairment measures such as strength and
functional testing (including timed testing), there is a need to include
a broader range of clinically meaningful measures of function,
participation, quality of life, and burden of disease. Data obtained
from natural history studies and clinical trials should be used to
determine the sensitivity of the various endpoints to changes in
clinical severity. In addition, the magnitude of changes in endpoint
measures that are clinically meaningful to patients and their families
should be determined.

-   *Research Objective 5:* Study the interrelationship of clinical
    endpoints for specific muscular dystrophies (Long Term; Low Risk).

It is not known how clinical endpoints relevant to individual muscular
dystrophies relate to one another. For example: what change in strength
will lead to a clinically meaningful change in gait or prolongation of
ambulation? What change in functional status will significantly impact
quality of life? Once varied clinical endpoint data are collected
longitudinally, these measures should be correlated with one another.
This will allow for the determination of shorter term, clinical
surrogate markers that can be used in clinical trials. For example,
walking speed or distance a subject can walk may correlate highly with
time to permanent reliance on a wheelchair. An intervention that can
increase walking speed or distance traveled would presumably also
prolong the time to wheelchair reliance. In addition, the study of the
interrelationship of clinical endpoints will not only help identify
which endpoints are the most clinically meaningful to patients and
family members, but also provide information regarding the predictive
value of specific endpoints. Assessment of the predictive value of
surrogate markers may be a valuable goal for chronic corticosteroid
clinical trials in muscular dystrophy.

-   *Research Objective 6:* Develop standardized data collection
    approaches nationally using clinically meaningful, readily
    obtainable parameters; develop a minimum data set for national data
    gathering efforts (Medium Term; Intermediate Risk).

The Centers for Disease Control and Prevention has an ongoing effort to
standardize data collection within the States participating in the
Duchenne muscular dystrophy surveillance system. A standardized data
collection approach that can be implemented nationally needs to be
developed to facilitate the evaluation of treatment efficacy and
prevention of secondary conditions. As more information is gathered
concerning the interrelationship between clinical endpoints, the
predictive value of endpoints, and the significance of endpoints to
patients and family members, it should be possible to streamline data
collection efforts with a focus on clinically meaningful and readily
obtainable parameters. This will facilitate the development and
implementation of a minimum data set for national data gathering
efforts.

**Consensus Guidelines for the Clinical Management of the Muscular
Dystrophies**

> .

Despite improved management of the disease, there remains a great deal
of variability in the nature and quality of care provided to persons
with muscular dystrophies. There is limited evidence to demonstrate the
benefit of much of the care. Evidence in the form of anecdotal or
retrospective clinical studies, clinical practice parameters, and/or
consensus of experts regarding best practice has been developed
regarding the use of corticosteroids and respiratory care. Additional
consensus from clinical experts needs to be derived regarding such
issues as diagnostic approaches, orthopedic management of limb and spine
deformities, exercise, nutrition management, cardiac management,
psychological, behavioral and educational approaches. Such
recommendations need to be disseminated to physicians, other providers,
affected persons, and their families to promote effective care.

-   *Research Objective 7:* Develop consensus guidelines for clinical
    management using Duchenne muscular dystrophy as a model (Short Term;
    Low Risk).

-   *Research Objective 8:* Develop consensus guidelines for the
    clinical management of other muscular dystrophies (Medium Term; Low
    Risk).

The Centers for Disease Control and Prevention has a project underway to
develop consensus guidelines for the clinical management of Duchenne
muscular dystrophy based on evidence and expert opinion. It is
recognized that there have been limitations with regard to the quantity
and quality of clinical research related to muscular dystrophies. While
the levels of scientific evidence may not be sufficient to justify
clinical practice parameters, there may still be great value in
determining the state of the science and developing consensus guidelines
from experts, based on their review of the literature and clinical
experience. A model process for the development of consensus guidelines
could be developed initially for Duchenne muscular dystrophy given the
widely available clinical literature for review. Key issues for
development of consensus guidelines include identification of leadership
for the process, participation of a range of professional organizations
(e.g., neurology, pediatrics, and cardiology), and identification of
mechanisms for dissemination of consensus guidelines. This model process
could then be applied to other muscular dystrophies.

**Benefits and Risks of Exercise and Physical Activity**

Little scientific investigation has been conducted on the effect of
resistive strength training and aerobic exercise in individuals with
muscular dystrophies. Largely uncontrolled and nonrandomized studies of
persons with neuromuscular disorders have focused on the adaptations to
strengthening exercise training, the responses to cardiopulmonary
exercise testing and adaptations to aerobic exercise training, the role
of de-conditioning on the responses to exercise testing and training
effect, and the role of muscle fatigue and endurance in limiting
physical activity. A recent analysis of the Cochrane Neuromuscular
Disease Group registry and other databases suggested that moderate
intensity exercise in myotonic dystrophy and facioscapulohumeral
muscular dystrophy appears not to do harm, however, there is
insufficient evidence to establish that it is beneficial.

-   *Research Objective 9:* Determine the benefits and risks of varied
    exercise approaches in muscular dystrophies and develop
    scientifically based recommendations concerning optimal exercise,
    physical activity, and recreation (Medium Term; Intermediate Risk).

More comprehensive multi-center studies that examine the effect of
exercise on homogeneous groups of individuals with muscular dystrophies
that have been randomized to a treatment group or a control group are
needed. Investigation should match for disease, age, gender, presence of
concomitant diseases, severity of weakness, and physical activity level
(sedentary or active). Because the individual diseases are rare and
generalizations regarding the exercise response for one disease may not
be applicable to another, single-subject designs may be beneficial.
These studies should include comprehensive measurements of the muscular
system, sensory and motor system, cardiopulmonary system, bone and
connective tissue, hormonal responses, neural and endocrine system
responses to exercise using the same subject pool. Studies should also
focus on a comprehensive battery of longitudinal measurements of small
populations as opposed to cross sectional comparisons in order to better
understand the characteristics and progression of the diseases as well
as the stable elements with varying levels of physical activities.
Finally, as therapeutic development proceeds, it will be important to
understand the effects that the interaction of a mildly effective
therapy with the resulting increased ability to exercise has upon the
progression of muscular dystrophy.

**Understanding and Managing the Secondary Consequences of Muscular
Dystrophy**

Muscular dystrophies may lead to a variety of secondary health
conditions that may negatively effect function, self-reported quality of
life, and increase the burden of disease. Secondary conditions seen
during the progression of the various muscular dystrophies may include,
pulmonary complications, orthopedic deformities, reduced bone mineral
content, swallowing dysfunction, impaired GI motility, cardiac
de-conditioning from sedentary activity, obesity, metabolic syndrome,
cognitive impairments, depression, pain, etc. Other secondary conditions
may be frequently seen in myotonic dystrophy, such as endocrinopathies,
hypersomnolence/ sleep disorders, and ophthalmologic problems. Early
detection and availability of therapeutic options for secondary
conditions will become even more important as primary disease management
strategies improve.

-   *Research Objective 10:* Assess the prevalence of secondary
    conditions in muscular dystrophy using existing longitudinal data
    collection efforts (Short Term; Low Risk).

The Centers for Disease Control and Prevention currently supports the
Muscular Dystrophy Surveillance Tracking and Research Network (MD
STARnet), which collects longitudinal data on patients with Duchenne
muscular dystrophy in five states. These data will provide information
on the prevalence of secondary conditions among patients with Duchenne
muscular dystrophy.

-   *Research Objective 11:* Assess the natural history of secondary
    conditions in muscular dystrophy using existing longitudinal data
    collection efforts (Medium Term; Low Risk).

Research should focus on determining the prevalence of secondary
conditions in relation to specific disease, age, and disease severity.
Elucidating the natural history of the progression of these secondary
conditions will allow for the study of prevention and management
strategies. This type of data is currently being collected on patients
with Duchenne muscular dystrophy in Centers for Disease Control and
Prevention's MD STARnet program. CDC also funds a national survey data
collection effort to collect retrospective data on early natural history
of Duchenne muscular dystrophy.

-   *Research Objective 12:* Assess the effectiveness of clinical
    management approaches to prevent and treat secondary conditions
    using existing multicenter collaborative networks and clinically
    meaningful outcomes (Medium Term; Intermediate Risk).

Some of these analyses will be available for Duchenne muscular dystrophy
via CDC's MD STARnet program. Clinical management strategies for many of
these secondary conditions have not been subjected to rigorous
prospective research designs that will yield higher levels of scientific
evidence. The organization of multicenter collaborative networks for the
conduct of clinical drug trials presents an opportunity for the
prospective multicenter study of the effectiveness of clinical
management approaches to treat secondary conditions. Examples might
include the management of reduced bone mineral content, noninvasive
mechanical ventilation, surgical management of spine deformity,
management of lower extremity deformities, etc.

-   *Research Objective 13:* Define the neuropsychological and
    neurobehavioral profiles that impact on quality of life and
    caregiver burden and identify useful interventions (Medium Term;
    Intermediate Risk).

Some forms of muscular dystrophy include specific neuropsychological and
neurobehavioral profiles as one component of the disease. Specific
impairments include learning disorders, difficulty coping with disease,
stress/depression, and problems with behavior, interpersonal
relationships, and community participation. The degree to which
cognitive impairments may be progressive in specific forms of muscular
dystrophy has not been fully determined, although recent progress in
Duchenne muscular dystrophy is fueling studies of the other muscular
dystrophies. Neuropsychological and neurobehavioral consequences
represent a significant need in the adult muscular dystrophies as well.
Because of the severity of central nervous system symptoms in myotonic
dystrophy, an important clinical objective is to define the neurologic,
neuropsychological, and neurobehavioral consequences of the two types of
myotonic dystrophy. Finally, there is a need to develop strategies to
help unaffected children cope with the stress of a parent who has
muscular dystrophy and to help unaffected siblings cope with affected
siblings. Research also needs to assess coping strategies and level of
functioning in caregivers and identify means to ease their burdens
emotionally, financially, and socially. Secondly, we need to assess
interventions that may be helpful for ameliorating the learning
difficulties and examine interventions known to be effective in
similarly presenting disorders such as dyslexia.

**Patient and Family Education and Social Participation in the Community
and Physician Training**

A high priority for patients and families with muscular dystrophy is
access to current information related to both clinical management and
potential therapeutic options for specific conditions. As individuals
with muscular dystrophy enter school and subsequently move into
occupations, school systems and vocational training need to be
adequately staffed and equipped. Greater opportunities for education,
vocation, recreation, and community integration should reduce the social
isolation frequently seen in persons with more severe muscular
dystrophies. Surveys of the adult muscular dystrophies show that
decreasing social isolation ranks high among priorities for improving
quality of life. We need to assess ways to decrease social isolation and
increase acceptance into the community for individuals and families
affected. Existing educational and training programs with potential
applicability need to be utilized and adapted for individuals with
muscular dystrophy. The breadth and depth of physician training in both
management of and working with patients with muscular dystrophies has an
important influence upon patient quality of life.

-   *Research Objective 14:* Establish annual educational conferences
    for patients and families focused on specific muscular dystrophies
    (Short Term; Low Risk).

Educational conferences will have the greatest value when they are
focused on specific muscular dystrophies. These conferences should bring
together persons affected with muscular dystrophies, family members,
different private advocacy groups, government organizations, clinicians,
and basic science researchers with a common purpose in mind. Thus, these
conferences will not only serve an educational purpose, but will have
the additional benefit of promoting further cooperation and fostering
collaboration among these diverse stakeholders. A successful approach
for such a national conference has been developed for spinal muscular
atrophy. In addition, national family conferences are currently held
that focus on Duchenne and facioscapulohumeral muscular dystrophy.
Future approaches to conference planning can build on recent successes
at the national and regional level. Interactions among patient support
groups should be facilitated to allow sharing of strategies and
successes from patient conferences, so that successful conferences could
be organized in the near future for Duchenne and Becker muscular
dystrophy, facioscapulohumeral muscular dystrophy, myotonic dystrophy,
and limb girdle muscular dystrophy.

-   *Research Objective 15:* Identify strategies to improve patient
    integration into educational systems (Short Term; Low Risk).

Information regarding rare diseases should be made available to school
systems to assist in the provision of appropriate educational services
in the least restrictive environment. Appropriate educational
information and information concerning rights and responsibilities
should be provided to parents so they are able to navigate the system to
help their child obtain services. Without the proper assistance, tools
and guidance, many children will not obtain appropriate education
services or succeed. A systemic program to assess the effectiveness of
the 'No Child Left Behind' and the 'Individuals with Disabilities
Education Act' is a research need. Research on the effectiveness of
Individualized Education Plan service delivery should integrate the
resources and expertise of local public schools and the rehabilitation
system. Efforts for educational integration into college and graduate
programs also need to be undertaken for adult individuals with muscular
dystrophy.

-   *Research Objective 16:* Identify strategies to improve vocational
    outcomes and reduce social isolation (Medium Term; Intermediate
    Risk).

Vocational Rehabilitation services facilitate the transition from school
or training programs to work and community living for youth and adults
with significant disabilities. Successful employment outcomes and higher
earnings are related to a positive relationship between the consumer and
the vocational rehabilitation counselor.

-   *Research Objective 17:* Develop strategies to improve physician
    effectiveness in communicating with and managing the care of
    patients with muscular dystrophy (Short Term; Low Risk).

There is a clear need for increased neuromuscular disease emphasis in
neurology training programs. A new subspeciality fellowship in
neuromuscular disorders has the potential to improve the care of
patients with muscular dystrophy. Beyond this, efforts should be made to
address the general education of neurologists and primary care
physicians in best practices for diagnosis and management of the
muscular dystrophies and to advance their knowledge of Federal and
advocacy group resources that can reduce the burden of disease in this
patient group. The medical professional organizations and specific
disease organizations represent potential sources for development of
educational strategies.

**D. Matrix of Research Objectives in Living with Muscular Dystrophy**

+-----------+------------------+------------------+------------------+
|           | **Short Term**   | **Medium Term**  | **Long term**    |
|           |                  |                  |                  |
|           | **(0-3 years)**  | **(4-6 years)**  | **(7-10 years)** |
+-----------+------------------+------------------+------------------+
| **High    |                  |                  |                  |
| Risk**    |                  |                  |                  |
+-----------+------------------+------------------+------------------+
| **Int     |                  | -   Develop      |                  |
| ermediate |                  |     standardized |                  |
| Risk**    |                  |     data         |                  |
|           |                  |     collection   |                  |
|           |                  |     approaches   |                  |
|           |                  |     nationally   |                  |
|           |                  |     using        |                  |
|           |                  |     clinically   |                  |
|           |                  |     meaningful,  |                  |
|           |                  |     readily      |                  |
|           |                  |     obtainable   |                  |
|           |                  |     parameters;  |                  |
|           |                  |     develop a    |                  |
|           |                  |     minimum data |                  |
|           |                  |     set for      |                  |
|           |                  |     national     |                  |
|           |                  |     data         |                  |
|           |                  |     gathering    |                  |
|           |                  |     efforts      |                  |
|           |                  |                  |                  |
|           |                  | -   Determine    |                  |
|           |                  |     the benefits |                  |
|           |                  |     and risks of |                  |
|           |                  |     varied       |                  |
|           |                  |     exercise     |                  |
|           |                  |     approaches   |                  |
|           |                  |     in muscular  |                  |
|           |                  |     dystrophies  |                  |
|           |                  |     and develop  |                  |
|           |                  |                  |                  |
|           |                  |   scientifically |                  |
|           |                  |     based        |                  |
|           |                  |                  |                  |
|           |                  |  recommendations |                  |
|           |                  |     concerning   |                  |
|           |                  |     optimal      |                  |
|           |                  |     exercise,    |                  |
|           |                  |     physical     |                  |
|           |                  |     activity,    |                  |
|           |                  |     and          |                  |
|           |                  |     recreation   |                  |
|           |                  |                  |                  |
|           |                  | -   Assess the   |                  |
|           |                  |                  |                  |
|           |                  |    effectiveness |                  |
|           |                  |     of clinical  |                  |
|           |                  |     management   |                  |
|           |                  |     approaches   |                  |
|           |                  |     to prevent   |                  |
|           |                  |     and treat    |                  |
|           |                  |     secondary    |                  |
|           |                  |     conditions   |                  |
|           |                  |     using        |                  |
|           |                  |     existing     |                  |
|           |                  |     multi-center |                  |
|           |                  |                  |                  |
|           |                  |    collaborative |                  |
|           |                  |     networks and |                  |
|           |                  |     clinically   |                  |
|           |                  |     meaningful   |                  |
|           |                  |     outcomes     |                  |
|           |                  |                  |                  |
|           |                  | -   Define the   |                  |
|           |                  |     ne           |                  |
|           |                  | uropsychological |                  |
|           |                  |     and          |                  |
|           |                  |                  |                  |
|           |                  |  neurobehavioral |                  |
|           |                  |     profiles     |                  |
|           |                  |     that impact  |                  |
|           |                  |     on quality   |                  |
|           |                  |     of life and  |                  |
|           |                  |     caregiver    |                  |
|           |                  |     burden and   |                  |
|           |                  |     identify     |                  |
|           |                  |     useful       |                  |
|           |                  |                  |                  |
|           |                  |    interventions |                  |
|           |                  |                  |                  |
|           |                  | -   Identify     |                  |
|           |                  |     strategies   |                  |
|           |                  |     to improve   |                  |
|           |                  |     vocational   |                  |
|           |                  |     outcomes and |                  |
|           |                  |     reduce       |                  |
|           |                  |     social       |                  |
|           |                  |     isolation    |                  |
+-----------+------------------+------------------+------------------+
| **Low     | -   Identify and | -   Develop      | -   Study the    |
| Risk**    |     evaluate the |                  |     i            |
|           |     quality of   | disease-specific | nterrelationship |
|           |     life and     |     quality of   |     of clinical  |
|           |     burden of    |     life and     |     endpoints    |
|           |     disease      |     burden of    |     for specific |
|           |     measurement  |     disease      |     muscular     |
|           |     tools that   |     measures     |     dystrophies  |
|           |     are          |     where gaps   |                  |
|           |     currently    |     in existing  |                  |
|           |     available    |     measures are |                  |
|           |                  |     found        |                  |
|           | -   Develop      |                  |                  |
|           |     consensus    | -   Determine    |                  |
|           |     guidelines   |     the          |                  |
|           |     for clinical |     sensitivity  |                  |
|           |     management   |     of clinical  |                  |
|           |     using        |     endpoints to |                  |
|           |     Duchenne     |     changes in   |                  |
|           |     muscular     |     disease      |                  |
|           |     dystrophy as |     severity     |                  |
|           |     a model      |                  |                  |
|           |                  | -   Determine    |                  |
|           | -   Assess the   |     the          |                  |
|           |     prevalence   |     magnitude of |                  |
|           |     of secondary |     changes in   |                  |
|           |     conditions   |     endpoints    |                  |
|           |     in muscular  |     which are    |                  |
|           |     dystrophy    |     clinically   |                  |
|           |     using        |     meaningful   |                  |
|           |     existing     |     to patients  |                  |
|           |     longitudinal |     and family   |                  |
|           |     data         |     members      |                  |
|           |     collection   |                  |                  |
|           |     efforts      | -   Develop      |                  |
|           |                  |     consensus    |                  |
|           | -   Establish    |     guidelines   |                  |
|           |     annual       |     for the      |                  |
|           |     educational  |     clinical     |                  |
|           |     conferences  |     management   |                  |
|           |     for patients |     of other     |                  |
|           |     and families |     muscular     |                  |
|           |     focused on   |     dystrophies  |                  |
|           |     specific     |                  |                  |
|           |     muscular     | -   Assess the   |                  |
|           |     dystrophies  |     natural      |                  |
|           |                  |     history of   |                  |
|           | -   Identify     |     secondary    |                  |
|           |     strategies   |     conditions   |                  |
|           |     to improve   |     in muscular  |                  |
|           |     patient      |     dystrophy    |                  |
|           |     integration  |     using        |                  |
|           |     into         |     existing     |                  |
|           |     educational  |     longitudinal |                  |
|           |     systems      |     data         |                  |
|           |                  |     collection   |                  |
|           | -   Develop      |     efforts      |                  |
|           |     strategies   |                  |                  |
|           |     to improve   |                  |                  |
|           |     physician    |                  |                  |
|           |                  |                  |                  |
|           |    effectiveness |                  |                  |
|           |     in           |                  |                  |
|           |                  |                  |                  |
|           |    communicating |                  |                  |
|           |     with and     |                  |                  |
|           |     managing the |                  |                  |
|           |     care of      |                  |                  |
|           |     patients     |                  |                  |
|           |     with         |                  |                  |
|           |     muscular     |                  |                  |
|           |     dystrophy    |                  |                  |
+-----------+------------------+------------------+------------------+

**Research Infrastructure Needs for Muscular Dystrophy**

**A. Introduction**

Research infrastructure transcends the other topics addressed by the
MDCC Scientific Working Group, in that it denotes those resources that
can facilitate the accomplishment of many of the other Research
Objectives identified throughout this report. The Research
Infrastructure Needs for Muscular Dystrophy subgroup independently
examined the resources that would be necessary to accomplish the
Research Objectives identified by each of the four other subgroups.

Historically, there are a number of examples where shared infrastructure
and research resources facilitated a major advance in the muscular
dystrophy research field. For instance, the efforts of dozens of
research laboratories were carefully coordinated for the identification
of the Duchenne muscular dystrophy gene, dystrophin. In this case, the
research community freely exchanged clones, antibodies, samples, and
testing methods in order to accelerate linkage analysis, positional
cloning, and functional characterization of dystrophin. However, there
are also examples where infrastructure for muscular dystrophy research
has been underserved, both in terms of emphasis and funding. This is
particularly true for clinical trials where the existence of clinical
trial networks and research cores might have greatly facilitated the
undertaking of clinical trials over the past 20 years.

Structured clinical trial networks facilitate more rapid initiation of
trials by having validated endpoint measures, adequate infrastructure,
sufficient patient availability, and disease-specific clinical trial
expertise already in place. It would seem imperative to have operational
clinical trial networks to test potential therapeutics as they emerge,
particularly for Duchenne muscular dystrophy where we know a fair amount
about the mechanism of disease. From 1985-1990---before the molecular
basis of the disease process was determined---seven clinical trials in
Duchenne muscular dystrophy, involving 396 Duchenne muscular dystrophy
patients, were published, with many from the Muscular Dystrophy
Association-funded Clinical Investigation of Duchenne Dystrophy (CIDD)
network. The identification of the dystrophin gene and protein in 1987
resulted in an enormous advance in our knowledge of the disease
mechanisms (hundreds of publications over a few years); however, these
advances in knowledge did not correspond to an increase in the number of
clinical trials in Duchenne muscular dystrophy. From 1991-2005, only
eight trials in Duchenne muscular dystrophy, involving 122 patients,
were reported, highlighting the need for infrastructure to run and
manage new trials. Recently, several academic and pharmaceutical
industry translational studies and clinical trials have started,
exploiting the accumulated mechanistic knowledge in muscular dystrophy
to explore multiple therapeutic strategies.

To address the great needs in infrastructure for muscular dystrophy
basic and translational research and clinical trials, there has been a
recent focus on shared research resources, including the creation of
Scientific Research Resource Cores within the Senator Paul D. Wellstone
Collaborative Research Centers, as well as the funding of clinical trial
networks, mouse drug screening cores, high-throughput drug screening
facilities, and centralized antibody production and distribution
facilities.

While efforts in the USA have led to important advances in understanding
the mechanisms of muscular dystrophy, recent European efforts have
focused on research infrastructure, with variable success in formation
of tissue and cell banks, organization of focused meetings by the
European Alliance of Muscular Dystrophy Associations, and other efforts.
It is essential that international coordination occur to maximize the
utilization of scare resources and ensure that unnecessary overlap is
avoided.

**B. Currently Available Research Resources**

**Resources for Mechanistic Studies**

Infrastructure resources that help support basic research on the causes
and pathophysiology of the muscular dystrophies were considered to
encompass three distinct areas: patient sample repositories, animal
models, and antibody repositories.

 

*Patient sample repositories:* DNA, cell, and tissue repositories are
important, since multiple disease genes remain unknown for several
muscular dystrophy phenotypes (including the mutated genes in a
substantial percentage of limb girdle muscular dystrophy patients) and
linkage/cloning studies require critical mass of familial genetic
information that can be best facilitated by DNA repositories and the
disease mechanisms that are identified in animal models require
validation in human tissues that can be aided by human cell/tissue
repositories.

The Italian Telethon network, the EuroBioBank, and the National
Institute of Neuroscience (Kodiara, Japan) maintain tissue repositories
that include the muscular dystrophies. Patient samples also are
available at several large referral sites in the USA (e.g., the
Universities of Rochester and Iowa and Children's National Medical
Center). Biological specimen banking is also planned as part of CDC's MD
STARnet program. These tissues provide an important resource for
validating mechanistic data obtained in animal studies. An extensive
library of biopsy specimens from neuromuscular disease patients also
exists at the Institute for Neuromuscular Research
(<http://www.inmr.com.au/>), at the University of Sydney.

Several public access DNA mutation databases contain data relevant for
mechanistic studies in the muscular dystrophies, including but not
restricted to: (a) Leiden University Medical Center
(<http://www.dmd.nl/> ), (b) the Human Gene Mutation Database
(<http://www.hgmd.cf.ac.uk/hgmd0.html>), and (c) the Utah Genome Depot
(<http://www.genome.utah.edu/>). Also, gene expression profiling
databases (e.g., <http://pepr.cnmcresearch.org/home.do>) can provide
researchers with broad-based information on pathogenic mechanisms in
muscular dystrophy. Data from numerous animal and human muscular
dystrophy studies are also publicly available for mining in the National
Institutes of Health Gene Expression Omnibus database
(<http://www.ncbi.nlm.nih.gov/geo/>).

*Mouse and dog models:* The absence or adequate access to appropriate
animal models of muscular dystrophy is a potential obstacle to progress
in understanding the mechanisms and pathogenesis of these diseases.
Jackson Laboratory represents a substantial resource for germ-free,
inbred mouse strains, including models for several neuromuscular
diseases. While only those strains that are requested on a somewhat
regular basis are maintained as breeding colonies with rapid
availability, other strains are warehoused as frozen embryos, but access
to these is not possible on a short-term basis. While many of the less
frequently used strains can be obtained from research labs, supplies
from these sources are inconsistent and can prove problematic in terms
of acceptance by the requesting institution as germ free (i.e., often
requiring re-derivation).

There is no animal model that perfectly mirrors human muscular
dystrophy. The mouse models serve an important role in early therapeutic
development, but dog models better reflect both disease severity and the
immunological problems that are associated with several therapeutic
development strategies. While dystrophic dog colonies are important for
pre-clinical translational projects in therapeutic development, only
limited numbers of animals are available from existing sources. To help
remedy problems in investigator access to dog models, the Senator Paul
D. Wellstone Collaborative Research Centers have a joint initiative to
expand breeding colonies in the USA. A modern dystrophic dog facility at
the National Institutes of Neuroscience (Kodaira, Japan) has a model
that has not been fully explored in the USA and may represent an
important, underused resource. Available dog models include the Golden
Retriever (CXMD; a naturally occurring mutation that has been bred),
German Shorthair Pointer (a dystrophin knockout), Welsh Corgis (a
naturally occurring mutation that has been bred), and beagle (CXMDJ;
artificially inseminated with frozen-thawed spermatozoa derived from an
affected golden retriever). Careful comparisons of these models have not
yet been done.

Muscle functional testing core facilities, for both mouse and dog, are
essential to mechanistic and therapeutic development studies in the
muscular dystrophies. Facilities at the University of Pennsylvania and
Children's National Medical Center have developed expertise for these
studies. Broader utilization of these core facilities may standardize
the data that are obtained in mechanistic and therapeutic development
studies.

*Antibody repositories:* Specific antibodies for proteins that exhibit
primary or secondary involvement in the muscular dystrophies are
essential for tissue- or cell-based mechanistic studies, patient
diagnosis, and in helping evaluation of the efficacy of novel therapies.
Most of the important antibodies are available on an ad hoc basis from
the original research laboratories. As is the case for the existing
animal models, access to antibodies from individual research labs can be
highly variable. A specific source of many muscle disease-related
antibodies is the North East Wales Institute
(<http://www.rjah.nhs.uk/cind/morrisge/mabs.htm>), which houses about
300 mouse monoclonal antibodies, about half of which directly relate to
study of the muscular dystrophies, including exon-specific dystrophin
antibodies and antibodies for Emery-Dreifuss muscular dystrophy and
myotonic dystrophy. The Developmental Studies Hybridoma Bank
(<http://www.uiowa.edu/~dshbwww/>), at the University of Iowa, also is a
significant, inexpensive, and rapid source of antibodies to proteins
relevant to neuromuscular disease. The National Institutes of Health
also supports a mouse monoclonal production facility for nervous
system-related antibodies that will undertake development of antibodies
for many proteins pertinent to muscular dystrophy (NeuroMab Hybridoma
Facility, University of California at Davis;
<http://www.neuromab.org/>).

**Resources for Diagnosis and Screening and Therapeutic Development**

Prior to 1987, the classification of the muscular dystrophies was solely
based on clinical characteristics, including the pattern of inheritance,
pattern of weakness, evidence of multisystemic involvement, and
histological features. After identification of the dystrophin mutations
that are responsible for Duchenne and Becker muscular dystrophies, the
standards of diagnosis and classification began to shift to requiring
refined genetic testing. Subsequent identification of genetic mutations
for myotonic dystrophy, facioscapulohumeral dystrophy, oculopharyngeal
muscular dystrophy, Emery-Dreifuss muscular dystrophy, and multiple
forms of congenital and limb-girdle muscular dystrophy have further
refined the diagnostic capabilities for these diseases. With this
knowledge, the view of the muscular dystrophies began to shift toward
molecular- and biochemical-based perspectives.

Identification of the responsible genetic changes has been critical both
in defining the pathophysiological bases of the different forms of
muscular dystrophy, and in permitting accurate diagnoses in clinical
practice. Many conditions that were initially clinically defined to be
distinct disorders have subsequently been shown to arise from common
genetic causes, thus demonstrating the value of genetic testing. Only by
use of genetic testing can the epigenetic and environmental
contributions to disease phenotypes be resolved, which, in turn, might
lead to the identification of novel treatment modalities.

Interpretable evaluation of therapeutic approaches depends upon the
availability of sufficient numbers of accurately defined subjects.
Clearly, determination of the genetic abnormality in subjects, or
characterization of the clinical phenotype at the molecular level by
determining abnormalities of gene product, are of immediate value in
development of meaningful clinical trials. The increasing availability
of accurate genetic testing for most forms of muscular dystrophy thus
has set the stage for more powerful and informative clinic trials. The
emergence of disease registries, such as the National Registry of
Myotonic Dystrophy and Facioscapulohumeral Muscular Dystrophy Patients
and Family Members (University of Rochester;
<http://www.urmc.rochester.edu/nihregistry/>), and epidemiological
studies, such as the Muscular Dystrophy Surveillance Tracking and
Research Network (MD STARnet;
<http://www.cdc.gov/ncbddd/duchenne/mdstarnet.htm>), provide an
important infrastructure for supporting refinement of diagnostic and
screening mechanisms and providing adequate numbers of molecularly
characterized patients for clinical trials.

Many methods are used for clinical and research diagnostic testing and
molecular characterization. Clinical tests are available to assess the
gene product at the protein level, with immunohistochemistry or
immunofluorescence being the standard of care for all muscle biopsy
laboratories, and Western analysis or specialized immunostaining of some
proteins available as clinical tests at specialized laboratories.
Research laboratories also offer specialized testing of gene products at
the protein or RNA level for further characterization of individual
subjects. Genetic testing available for clinical use includes linkage
analyses or mutation analyses by several different methods (e.g.,
PCR-based assays, entire gene sequencing, or Southern analyses)
depending on the features of the gene and the type of mutation being
investigated. Important advances in the tools necessary for precise and
reproducible diagnosis of the muscular dystrophies are described in the
chapter on Diagnosis and Screening in Muscular Dystrophy.

GeneTests (<http://www.genetests.org/>) is a publicly funded medical
genetics information resource website that provides current,
authoritative information on genetic testing and its use in diagnosis,
management, and genetic counseling. The diagnostic tests that are
currently available for muscular dystrophy are included in this
database. There has been a proliferation of laboratories that offer
genetic tests for certain forms of muscular dystrophy, most notably
Duchenne (available from at least 26 labs) and myotonic dystrophy type 1
(DM1, available from at least 25 labs). Prenatal, presymptomatic, and
diagnostic testing for facioscapulohumeral muscular dystrophy is
available for chromosome 4-linked families through a number of academic
and commercial laboratories. Genetic testing for the GCG trinucleotide
repeat expansion in the PABPN1 gene that are responsible for
oculopharyngeal muscular dystrophy is available from both commercial and
academic labs (at least 8 labs). Other forms of muscular dystrophy are
still principally diagnosed by immunostaining of muscle biopsies, with
little availability of genetic testing (e.g., most forms of limb girdle
and congenital muscular dystrophy). An open issue in this area relates
to questions of the comparability of test results between diagnostic
laboratories, and, by extension, the diagnostic frequency of the
muscular dystrophies. An important aspect of testing that is hard to
quantify is the degree of counseling or interpretation that is provided
to help clinicians and patients understand the full meaning of their
test results.

[The Cooperative International Neuromuscular Research
Group](http://www.cnmcresearch.org/cinrg/index.asp) (CINRG) is an
international clinical trial network for studies in Duchenne/Becker
muscular dystrophy. CINRG's major efforts have been been screening and
testing FDA-approved drugs for efficacy in Duchenne muscular dystrophy.
The Muscle Study Group (University of Rochester), a consortium of
investigators interested in facilitating clinical trials in the
neuromuscular disorders, also serves to coordinate clinical trials in
neuromuscular disease, providing access to a considerable expertise in
such studies and a data coordination center and statistical unit.

The strengths of the existing infrastructure for diagnosis and treatment
of muscular dystrophy thus include:

-   Diagnostic methods are now available for most forms of muscular
    dystrophy

-   Diagnostic testing has become increasingly affordable and accessible
    so that a majority of muscular dystrophy patients can be accurately
    identified.

-   Reliable testing of carriers is increasingly available for many
    forms of muscular dystrophy, allowing accurate genetic counseling

-   Pre-natal or pre-implantation testing is increasingly available,
    allowing refined approaches to family planning

-   Muscular dystrophy research laboratories have remained connected in
    many instances to the diagnostic laboratories, increasing the
    accuracy of information for clinicians in interpretation of results

-   Patient registries and clinical networks are starting to emerge that
    can facilitate the conduct of clinical trials in muscular dystrophy.

**Resources for Reducing the Clinical Burden of Disease**

*Rehabilitation research.* The resources to pursue rehabilitation
research and to investigate the spectrum of medical problems that are
associated with the different types of muscular dystrophy are very
limited. These limitations cloud the vision of the scope and type of
resources necessary to accelerate research in these important areas.
Rehabilitation resources can provide key preventive strategies for
muscular dystrophy-associated medical problems. The National Institute
on Disability and Rehabilitation Research (NIDRR) provides leadership
and support for a comprehensive program of research related to the
rehabilitation of individuals with disabilities, including those with
muscular dystrophy. Existing infrastructure resources for rehabilitation
research include the NIDRR-funded Rehabilitation Research Training
Center in Neuromuscular Diseases at University of California at Davis.
NIDRR also supports studies of pain, assessment of quality of life, and
the effects of a community-based exercise program in neuromuscular
diseases.

*Quality of life.* The opportunity to develop resources to study quality
of life and clinical burden of disease in the muscular dystrophies is
tremendous. Patients and family members are eager to pursue studies and
develop the needed capabilities. To date, however, few investigations
have occurred to establish the optimal instruments to measure quality of
life in the muscular dystrophies, and with the growing interest in
patient-reported outcomes research and in pre-emptive health care, the
time is at hand to accelerate and enhance research in this area.

The National Institutes of Health sponsored a two-day workshop on the
"Burden of Muscle Disease" in January 2005 to review the present status
of research and the available databases and test instruments to assess
quality of life and burden of disease in patients with the different
types of muscular dystrophy. Additional efforts to improve the quality
of life of these patients include a NIDRR-funded study, to evaluate
instruments to assess quality of life in patients with muscular
dystrophies. In addition, collaborative studies between CINRG, the
University of California at Davis research group, and the University of
Utah Dystrophin Project include instruments to assess quality of life in
patients with Duchenne muscular dystrophy.

An additional study has tested instruments to measure quality of life in
caregivers and family members affected by Duchenne muscular dystrophy.
Finally, the Muscular Dystrophy Association has funded validation
studies of the "Individualized Neuromuscular Quality of Life (INQoL)
measure"---an instrument for adults with muscular dystrophy---that was
developed by researchers in the United Kingdom.

*Cognitive changes in muscular dystrophy.* Cognitive involvement and
other central nervous system dysfunction have been demonstrated in
several of the muscular dystrophies. Cognitive, behavioral, and other
alterations of central nervous system function occur in particularly in
Duchenne muscular dystrophy and myotonic muscular dystrophy (DM1 and
DM2), but our understanding of the pathophysiologic mechanisms, the
impact of their deficits on learning, employment, coping with disease,
and interpersonal relationships is severely limited. There are few
well-established instruments to measure cognitive alterations in the
muscular dystrophies and a paucity of researchers investigating these
problems. For example, only a modest number of investigations of
hypersomnia have occurred in myotonic dystrophy (DM1) and yet patients
rate this symptom as one of the most disabling, especially as it relates
to employment and meeting responsibilities in caring for children. The
National Institutes of Health has funded studies of cognitive/genetic
aspects and of spirituality of children with Duchenne muscular
dystrophy. Opportunities abound to develop infrastructure and research
studies in this area.

**Resource Centers for Muscular Dystrophy**

The National Institutes of Health has established six Senator Paul D.
Wellstone Muscular Dystrophy Cooperative Research Centers, in order to
accelerate basic and clinical research on muscular dystrophy. These
Centers are located at the Children's National Medical Center,
University of Iowa, University of Pennsylvania, University of
Pittsburgh, University of Rochester, and the University of Washington.
The goals of the Centers are to promote side-by-side basic,
translational, and clinical research, to provide resources that can be
used by the national muscle biology and neuromuscular research
communities, and to provide training and advice about muscle diseases
for researchers and physicians who provide initial diagnosis and
treatment, including rehabilitation, care for cognitive and behavioral
concerns, and therapy for other system complications. Taken together,
the Centers constitute a cohesive program, operating under the
guidelines for National Institutes of Health cooperative agreements in
order to maximize collaborative utilization of the unique resources in
infrastructure, expertise, and clinical recruitment that are available
in the Centers.

# Resources for Education and Training

The National Institutes of Health and other funding agencies are aware
of the dearth of clinical investigators and the need to increase the
number and scope of individuals pursuing translational research as well
as basic and clinical research in muscular dystrophy. Despite having a
spectrum of training opportunities for medical and graduate students,
fellows, and more established researchers the number of new
investigators is lagging behind the need and opportunities.

The challenge has been to recruit and train new investigators to pursue
research related to the muscular dystrophies and to educate patients and
health care providers about opportunities for research and about the
current standards of care for each of the different muscular
dystrophies. Several initiatives in education and training have been
issued by Federal agencies and patient advocacy groups. For training and
research career development, the National Institutes of Health have
developed Senator Paul D. Wellstone Muscular Dystrophy Collaborative
Research Center fellowships (NOT-AR-05-001), Mentored Clinical
Investigator Career Development Awards in Muscle Disease Research (K08
and K23; PA-05-051), Ruth L. Kirschstein National Research Service
Awards for Postdoctoral Fellowships in Muscle Disease Research (F32;
PA-05-052), and Academic Research Enhancement awards (R15; PA-03-053).
The NIH also has established Loan Repayment Programs in the areas of
Clinical Research, Pediatric Research, Health Disparities Research, and
Clinical Research for Disadvantaged Background Individuals.

The Department of Education has funded the National Institute on
Disability and Rehabilitation (NIDRR) Research Fellowship awards to
support research on rehabilitation of individuals with disabilities.
NIDRR also supports the National Center for Dissemination of Disability
Research, which has sponsored the program, "Rehabilitation Science for
Basic Scientists and Engineers", to increase the number of Ph.D.
engineers and basic scientists trained to perform research to solve
problems of individuals with disabilities.

The Centers for Disease Control and Prevention also has initiated
programs to fund educational and outreach activities in muscular
dystrophy. In cooperation with CDC, Parent Project Muscular Dystrophy
will conduct outreach activities targeted toward individuals who know
people with muscular dystrophy (such as teachers and fellow students of
children with Duchenne muscular dystrophy) and the general public. The
Genetic Alliance will coordinate a CDC-funded resource center on Single
Gene Disorders, and will conduct provider education activities, and
disseminate resources to families, providers and the general public on
Duchenne muscular dystrophy.

In addition to its regular conference grant program (R13), the NIH has
initiated a targeted program to support small, focused conferences
coordinated through the Senator Paul D. Wellstone Muscular Dystrophy
Collaborative Research Centers (Support for Muscular Dystrophy Workshops
and Research Conferences; NOT-AR-05-008). The Office of Rare Diseases
also provides important support for conferences, including many related
to the muscular dystrophies.

Several patient advocacy groups provide important information for
patients with muscular dystrophy and their families. These include the
Facioscapulohumeral Society (<http://www.fshsociety.org/>), the
International Myotonic Dystrophy Organization
(<http://www.myotonicdystrophy.org/>), the Muscular Dystrophy
Association (<http://www.mdausa.org/>), the Muscular Dystrophy Family
Foundation (<http://www.mdff.org/>), and the Parent Project Muscular
Dystrophy
([http://www.parentprojectmd.org](http://www.parentprojectmd.org/)).
Many of these offer a variety of educational and support materials,
including websites, brochures, fact sheets, and newsletters. In
addition, many of these organizations fund research conferences, patient
support groups, and educational projects, as well as grants to
individual muscular dystrophy students, fellows, and established
investigators.

**Resources for Muscular Dystrophy in Europe**

International cooperation and coordination is essential to achieving the
goal of timely detection, diagnosis, treatment, and prevention of the
muscular dystrophies. An understanding of the research strategies used
by and the resources available in the European community will help
ensure optimal utilization of resources.

*Current funding streams for muscular dystrophy research in Europe.* The
European national funding bodies, like those in the USA, focus upon
funding high-quality science, with only limited funding earmarked for
neuromuscular diseases. The neuromuscular disease patient advocacy
groups have major national differences in how much funds are generated
and on the spending patterns for research and care. Scandinavian patient
advocacy groups, for example, invest almost exclusively in social
interventions. By contrast, the Association Française contre les
Myopathies (AFM; France;
[www.afm-france.org](http://www.afm-france.org/)) and Telethon (Italy;
<http://www.telethon.it/english/index.asp>) are major advocacy groups
with significant research budgets. Both organizations utilize
peer-review systems to evaluate and fund responsive research projects
and research infrastructure projects, including coordinated
interdisciplinary research facilities (e.g., Genethon;
<http://www.genethon.fr/php/index_us.php>), Neuromuscular Research
Center in Paris, and Telethon Institute of Genetics and Medicine (TIGEM;
<http://www.tigem.it/Introduction.htm>). AFM supports research in labs
outside of France, while Telethon supports predominantly Italian
scientists within Italy, with some support for Italian scientists
working abroad who plan to return to Italy. Other charities (e.g.,
Muscular Dystrophy Campaign in the United Kingdom) have mixed
expenditures on care and research and a very small budget.

European Union research funding is limited to expenditures on specific
requests for applications. The European Union has funded specific
research projects in muscular dystrophy (e.g., congenital muscular
dystrophy, Bethlem muscular dystrophy, and Emery-Dreifuss muscular
dystrophy) but, until recently (see below, *Addressing fragmentation in
European translational research*), no strategic funding plan has existed
for neuromuscular disease research.

*The European Neuromuscular Centre (ENMC).* The ENMC was established in
1989 through the support of the neuromuscular patient advocacy groups in
Austria, Denmark, France, Germany, Italy, The Netherlands, Switzerland,
the United Kingdom, and Spain. The aim of the ENMC is to foster research
collaborations in neuromuscular disease. Its major activity has been
support of research workshops: 137 workshops have been supported to
date, involving over 1,100 participants from 30 countries. The workshops
are investigator-initiated, small and tightly focused (typically \<
20-25 participants). Lay reports are published immediately on the ENMC
website and full meeting reports subsequently published in
*Neuromuscular Disorders*. Small grants may also be awarded by ENMC.

The initial focus of the ENMC workshops was on collaborations leading to
establishment of diagnostic criteria, disease gene identification, and
genotype-phenotype studies. In the last few years, the ENMC has also
invested in a clinical trials unit. The aims of the clinical trials unit
are to promote the publication of Cochrane Reviews in Neuromuscular
Diseases and facilitate the development of clinical trial applications
where these are considered necessary. Focus of funding is upon initial
stages of trial development, rather than being a trial management group
per se. ENMC initial clinical trial priorities in muscular dystrophy
were to investigate the use of steroids and the prophylactic treatment
for cardiomyopathy in Duchenne muscular dystrophy.

*National neuromuscular networks and service structures.* Efforts have
been made in various European countries to develop networks of
clinicians and researchers interested in neuromuscular diseases. As with
the national advocacy groups these efforts have taken different
directions and have different emphases in different countries. In
Germany, the opportunity to obtain Federal funding for networks
addressing rare diseases allowed the development of MD-NET, which
provides a national service and research structure and encompasses
diagnostics, clinical services, research laboratories and a clinical
trials unit. In Scandinavia, there is a well-developed network that
focuses on generation of standards of assessment and reference documents
for management of various neuromuscular diseases. In the United Kingdom,
the Muscular Dystrophy Campaign has invested in a pediatric audit group
for Duchenne muscular dystrophy (the North Star project), which is
working on standardization of assessment and audit of practice
standards. In Italy and France, the Telethon (with Unione Italiana Lotta
alla Distrofia Muscolare, the patient organization for muscular
dystrophy) and AFM are making similar efforts, and there are networks
also in Belgium, the Netherlands, and Spain.

Provision of diagnostic services for the muscular dystrophies by Federal
agencies is variable across Europe. In the United Kingdom, the
Department of Health funds a national service that includes limb girdle
muscular dystrophy and congenital muscular dystrophy. MD-NET in Germany
provides a comprehensive network of diagnostic services.

*Addressing fragmentation in European translational research.* The
European Union has focused upon infrastructure for translational
research in neuromuscular disease in a recent request for applications.
Specifically, networks of excellence were solicited to "aim at sharing
expertise between basic and clinical academics and industrial partners
in order to develop technological and methodological tools with a view
to accelerate the elaboration of new therapies for rare neuromuscular
diseases." These networks of excellence are designed to address
fragmentation in specific research areas by integrating partners to work
together on an indefinite basis, by providing funding for activities
that address integration, but not the research per se. There is
substantial emphasis upon infrastructure, including the development of
tools, including animal models, databases, biobanks, well defined
patient cohorts, and methods for efficacy assessment.

One application for support by the network of excellence focuses upon
muscular dystrophy (TREAT-NMD) and exemplifies the current European
Union strategy. This application proposes the establishment of a
European Neuromuscular Institute committed to deliver innovative
treatments for rare neuromuscular diseases from laboratory development
to clinical practice. Bringing together the top researchers, clinicians,
and industry researchers in Europe, this application addresses the
fragmentation currently hindering the progress of promising therapies by
establishing a common road map for their assessment, from cellular and
animal models to clinical outcome measures. Cutting edge treatments
currently under development for the muscular dystrophies will be
specifically targeted in this process, while future developments will
also benefit from the durable infrastructure of the Institute, which
will include patient registries and biobanks. A further role of the
Institute will be in the education of clinicians and researchers,
thereby ensuring a long term leading position for European research in
the muscular dystrophy field.

Specifically, the European Neuromuscular Institute proposal provides
for: (a) acquisition of preclinical evidence for efficacy of candidate
therapeutics (coordinate and develop assessment methodologies and
screening techniques in different animal models and cell systems), (b)
support for production and toxicology (large scale support for
production of clinical grade material for clinical trials including
toxicology), (c) developing and evaluating methods for systemic delivery
in humans (including commercial collaborations), (d) defining the
patient population (establish, coordinate, and harmonize patient
registries, databases, and biobanks in order to create a unified
resource for the definition of patient cohorts and biological material),
(e) harmonizing the patient population (focus on standards of care,
including all aspects of multidisciplinary management with the aim to
harmonize approaches to management so that defined patient groups are
managed similarly, and gold standards established for testing against in
future clinical trials), (f) defining outcome measures (elaborating
clinical assessment tools), (g) running trials (supporting protocol
design, regulatory and statistical support, liaison with orphan drugs
and European Union clinical trials authorities), (h) applying the tools
(coordinate program integration and bring innovative therapies for
muscular dystrophies), and (i) addressing ethics and communications
issues (address the ethical and safety dimension for the development of
therapies, as well as the need for a clear strategy of communication to
lay and scientific audiences of the work of the network).

**C. Needed Research Resources**

**Preclinical Research Infrastructure**

-   *Research Objective 1:* Facilitate research (discovery, validation,
    and dissemination) of the biochemical pathways involved in muscular
    dystrophy (Medium Term; Intermediate Risk).

Several of the muscular dystrophies are in a relatively unique position
of having substantial biochemical pathway data already known, and many
of the downstream consequences of biochemical defects in these pathways
are evident.  Facilitation of studies by collaborative teams of
biochemists, molecular geneticists, and bioinformaticians are encouraged
to develop public resources that assemble all domain knowledge of
biochemical pathways in the muscular dystrophies. The emphasis should be
on characterization of key pathway components, with particular attention
to muscle-specific members of ubiquitous pathways. The subgroup
considered this as part of a larger-vision "road map" for the muscular
dystrophies that could not only advance mechanistic understanding of the
muscular dystrophies, but also identify viable drug targets.

-   *Research Objective 2:* Establish standardized endpoints for
    preclinical trials in both mouse models, and the dog model, and
    ensure that facilities are available that enable testing of drugs
    and other therapeutic approaches (Long Term; Low Risk).

Animal trials should be designed with validated and standardized
endpoints, such that the Food and Drug Administration would subsequently
view the data as robust when considering Investigational New Drug
applications for human clinical trials. Functional endpoints with
significance for the target patient populations (i.e., reducing the
clinical burden of disease) are most appropriate as they have the
greatest likelihood of influencing clinical practice.

-   *Research Objective 3:* Create a mechanism to maintain mouse models
    of muscular dystrophy at approved vendors in a live state, available
    for easy and rapid importation into academic colonies (Medium Term;
    Low Risk).

Mouse models are essential for mechanistic studies and translational
research, particularly for medium-throughput screening and efficacy
testing of potential therapeutics.  For any new drug that shows promise,
extensive mouse model testing bolsters Investigational New Drug
applications to the Food and Drug Administration.  Despite the
importance of mouse models, it can be difficult to determine how to
obtain certain models; moreover there are few, if any, standard methods
of testing mice and few facilities exist with standardized protocols to
test drugs or other therapeutic approaches in mouse models.  Existing
strains and places to obtain animals or breeding pairs, and sites for
functionally testing both disease progression and therapeutic efficacy,
should be surveyed and tracked on an accessible website. The adequacy of
existing facilities should be evaluated to ensure that they are
sufficient to meet demands.

-   *Research Objective 4:* Develop optimized models for mechanistic
    studies of specific muscular dystrophies, including models
    appropriate for therapeutic development screens (Medium Term; High
    Risk).

Efforts should be undertaken to develop mouse models for those muscular
dystrophies for which such models do not currently exist, and to improve
the existing mouse models for Duchenne muscular dystrophy. Expansion of
animal testing capabilities for screening and evaluating therapeutic
agents is also an important goal to facilitate the preclinical testing
of novel agents. While animal-based testing cannot truly be
high-throughput, efforts to generate strategies to allow meaningful
indicators of therapeutic response in large numbers of animals in
parallel should be encouraged. These initial screens can then be
augmented with subsequent, detailed evaluations to probe mode of action
and impact on pathogenesis.

-   *Research Objective 5:* Encourage the development of cell-based
    assays that target aspects of pathogenesis and pathophysiology in
    the muscular dystrophies, to enable high throughput drug screening
    (Medium Term; High Risk).

There is desperate need to develop new therapeutics for the muscular
dystrophies. Two types of therapeutic interventions can be imagined. The
first is correction of the disease in instances where there is simply a
missing protein. This has been the major focus of the field, and
currently is envisioned with either viral gene therapy or cell-based
therapy. Such approaches face major technical hurdles before
implementation, and therefore are long-term goals for the field. For a
number of diseases that result from more complicated mechanisms than a
mutation in a single gene (e.g., facioscapulohumeral muscular dystrophy
and myotonic dystrophy), such approaches may or may not be applicable.
For these cases, as well as for developing approaches with a broad
impact on a number of muscular dystrophies, there is need for a second
type of therapeutic development. Namely, efforts need to be directed
toward discovering agents (especially small molecules, RNAi, or shRNA)
that can be easily delivered and that will target and slow aspects of
the muscle pathogenesis in various forms of muscular dystrophy.

Even with candidate small molecule therapeutics in hand, there are
substantial barriers to translation of animal studies to clinical
trials, including adequate funding sources for medicinal chemistry
facilities and personnel to provide chemical optimization, synthesis and
characterization of small molecules based on the compounds with activity
in animal models, lack of in-vitro assays to do high- or low-throughput
studies of compounds and a less than optimal animal model for more
advanced testing. In the clinical arena, there are well established
clinical trial networks with very accurate and well defined strength and
functional outcome measures where these drugs could be easily tested in
a Phase II setting. These networks are also characterizing disease
specific quality of life instruments and more advanced functional
outcome measures to use in Phase II trials. In all cases, increasing
industry involvement is essential, especially for the intermediate
efforts (medicinal chemistry) and large Phase III trials for moving the
therapies forward and ultimately into clinical practice.

A major obstacle to high-throughput screening is the inability of
cultured cells from either humans or animals with muscular dystrophy to
recapitulate the disease phenotype. While there are clearly instances,
such as immune involvement, which cannot be mimicked in culture systems,
it should be possible to develop models of cellular injury that would
allow meaningful high-throughput screens.

Finally, there is a real need to increase industry involvement in the
development of therapeutics for all forms of muscular dystrophy. Over
the past five years, the first interest on the part of industry in the
development of therapeutics for muscular dystrophy has emerged. There
are at least two models for industry involvement in a rare disease such
as muscular dystrophy. In one model, a drug may have wide application
within the human population, as well as the possibility of affecting one
or more of the muscular dystrophies. In this case, the orphan disease
status of the muscular dystrophy, combined with the rapid progression of
the disease, creates a fast track to approval of the therapy. Thus, even
a large pharmaceutical company may become interested in an orphan
disease. In the other model of therapies directed solely at one or more
muscular dystrophies, the niche market, orphan disease status and lack
of interest on the part of large pharmaceutical companies, make muscular
dystrophy attractive for therapeutic development by small biotechnology
companies. Nonetheless, increased industry involvement should be
encouraged by specific funding programs that target therapeutic
development for the muscular dystrophies. These programs should be
designed to support all phases of therapeutic development and early
phases of clinical trials. There should also be specific programs to
promote increased academic-industry partnerships.

**Clinical Research and Trial Infrastructure**

-   *Research Objective 6:* Establish a focus panel for molecular
    diagnostics of the muscular dystrophies, with the charge of
    developing consensus standards and approaches for molecular testing,
    screening, interpretation of results, and genetic counseling (Long
    Term; Low Risk).

A major challenge of this focus panel will be to identify methods by
which such consensus standards can be delivered homogeneously throughout
the United States. The Ataxia Diagnostics Group is a potential model for
this effort.

Consensus on testing for Duchenne muscular dystrophy. Currently, many
patients are diagnosed by either immunostaining of muscle biopsy or
deletion testing, but the identification of point mutations or
duplications is not uniform. Complete genetic characterization is
becoming increasingly important for numerous reasons. First of all,
accurate genetic counseling and availability for treatment is dependent
upon an accurate genetic diagnosis. In addition, the prescription of
effective treatments could quite possibly be tailored to specific
genetic causes, a complete genetic characterization is increasingly
important for all patients.

Consensus protocol for limb girdle muscular dystrophies. Currently, limb
girdle muscular dystrophy is often diagnosed clinically with
non-specific biopsy results and variable immunostaining
characterization. Recently, available genetic screens for many common
mutations have been helpful in better defining some patients, but
complete genetic testing of all patients is unavailable and
unaffordable. It would be useful to provide a protocol to assist
clinicians as well as muscle biopsy directors with the task of
characterizing apparent limb girdle muscular dystrophy patients. This
would be invaluable in improving the frequency and accuracy of
diagnosis.

Consensus protocol for facioscapulohumeral muscular dystrophy. The last
several years have seen a much improved diagnostic protocol for
facioscapulohumeral muscular dystrophy. Because of the complexity of the
algorithm and mechanics of testing, there is a need for improved
documentation, training, and education for professionals (physicians,
neurologists, genetic counselors) on interpretation of genetic testing
for facioscapulohumeral muscular dystrophy.

Improved education and interpretation of results. Many clinicians order
testing indiscriminately, thereby increasing the cost of testing without
increasing the yield. To the extent possible, generation of protocols or
algorithms that focus and streamline testing would improve the diagnosis
and decrease cost. Development of a publicly accessible website, or use
of existing websites, to host this type of information would be valuable
to practicing clinicians. Web-based information to assist clinicians in
interpretation of results is also needed, and possibly access to
individuals knowledgeable about the current status of testing in the
various forms of muscular dystrophy.

Standardization of testing between laboratories. Many laboratories are
offering comparable testing, without a mechanism for standardization of
test results. An organization of diagnostic laboratories that
facilitated development of consensus standards and approaches would
improve reliability of testing, improve the diagnostic infrastructure,
and would be an important adjunct to ongoing and upcoming clinical
trials and research.

Improved prenatal, pre-implantation and carrier testing. One important
means of reducing the number of affected muscular dystrophy patients is
through accurate and meaningful genetic counseling. Effective counseling
is dependent upon the availability of testing for genetic status at
multiple levels, including parental, embryonic and fetal. This dictates
a high level of testing accuracy, but also clinically focused
laboratories that can provide reliable information quickly.

-   *Research Objective 7:* Identify, develop, and encourage the use of
    standardized instruments to measure quality of life, cognitive, and
    central nervous system function using existing databases, and
    potentially develop new common element databases to extend research
    capabilities (Medium Term; Intermediate Risk).

A consensus should be reached on the identity of currently available
quality of life instruments that are validated and appropriate for use
in assessing muscular dystrophy patients and unaffected family members
(including children---infants to teenagers---with Duchenne muscular
dystrophy, limb girdle muscular dystrophy, myotonic muscular dystrophy,
and facioscapulohumeral muscular dystrophy at different stages of
handicap, as well as adults with these disorders). Steps should be taken
to develop and validate new instruments and facilitate the training of
those administering these new instruments. This process will require
cooperation and collaboration between different disciplines and between
different agencies within Federal and State governments as well as with
private organizations.

Individual investigator-initiated and collaborative research efforts
should be directed toward assessment of existing instruments with the
capacity to evaluate cognitive and behavioral function in muscular
dystrophy patient populations. This assessment is needed in order to
determine the type and extent of infrastructure that will be required to
reach long-term goals. Data mining/analysis of those test instruments
being utilized in currently studied patient populations should be used
to identify additional infrastructure needs. These databases include
National Institutes of Health- and Muscular Dystrophy Association-funded
clinical investigations of the different muscular dystrophies (e.g.,
National Registry of Myotonic Dystrophy and Facioscapulohumeral Muscular
Dystrophy Patients and Family Members, CINRG-University of California at
Davis study, the Utah Dystrophin Project, and the Ohio State University
limb girdle muscular dystrophy natural history study), Centers for
Disease Control and Prevention-funded studies of Duchenne/Becker
muscular dystrophy (MD STARnet), and the neuromuscular clinical patient
populations affiliated with the National Institutes of Health-supported
Senator Paul D. Wellstone Muscular Dystrophy Cooperative Research
Centers.

Existing instruments with the capacity to assess
cognitive/neurobehavioral/other central nervous system functions (e.g.,
sleep and neuroendocrine regulation) should be identified and evaluated
as potential tools for studies of patients with the muscular
dystrophies. Such tools should take into account children---infants to
teenagers---with Duchenne muscular dystrophy, limb girdle muscular
dystrophy, myotonic muscular dystrophy (DM1), and facioscapulohumeral
muscular dystrophy at different stages of handicap as well as adults
with these disorders. Research should be initiated to develop and
validate new instruments and facilitate the training of those
administering them for cognitive and behavioral assessment. This process
will require cooperation and collaboration between different disciplines
and between different agencies within Federal and State governments as
well as with private organizations.

It is vital to develop research infrastructure (e.g., patient database
networks) to nurture investigations of specific groups of patients with
muscular dystrophy with higher risk of cognitive and central nervous
system dysfunction (Duchenne muscular dystrophy; congenital muscular
dystrophy; congenital myotonic dystrophy; and adult onset myotonic
dystrophy, including both DM1 and DM2).

-   *Research Objective 8:* Monitor, coordinate, and communicate the
    rehabilitation and educational assessment activities of the various
    Federal agencies, voluntary, and patient advocacy groups (Long Term;
    Low Risk).

Additional research designed to identify the high priority
rehabilitation needs of patients with the different forms of muscular
dystrophy (at critical stages in each) is necessary as a pre-requisite
to determine the need for additional resources and infrastructure to
investigate rehabilitation care and treatment of associated medical
problems. Mining of currently available databases, prospective studies
using existing and new patient databases, studies using patient reported
outcomes of care of associated medical problems (PROMIS network), and
studies that include partnerships with large patient populations, such
as, the muscular dystrophy clinics, National Institutes of Health- and
Muscular Dystrophy Association-funded clinical investigations of the
different muscular dystrophies, Centers for Disease Control and
Prevention-funded studies of Duchenne/Becker muscular dystrophy, and the
neuromuscular clinical patient populations affiliated with the National
Institutes of Health-supported Senator Paul D. Wellstone Muscular
Dystrophy Cooperative Research Centers are all examples of approaches to
identify the need for additional resources and infrastructure. Patients,
health care providers, social services, health care economists,
government agencies, and private industry, as well as researchers, are
groups that should be encouraged to apply for and obtain grants or other
funding for these studies. Compatible computer networking is needed to
accomplish these investigations.

Studies should identify the highest priority medical problems that occur
in the different types of muscular dystrophy and create training,
funding, and research opportunities for individual grants and for
partnering with various Government and non-government groups to pursue
studies to evaluate and treat the associated medical problems. The
evaluation of problems that occur at specific stages of each of the
muscular dystrophies will be a necessary part of achieving this goal.

**Communication and Education**

-   *Research Objective 9:* Design and implement a web site that
    provides information and links to all existing resources in both the
    USA and internationally (Short Term; Low Risk).

Collaborative team approaches are becoming necessary in order to
translate basic mechanistic findings into novel disease treatments and
to ensure the coordinated management of what are frequently multi-system
diseases. As these interdisciplinary efforts in the muscular dystrophies
expand, one key rate-limiting factor, access to a variety of types of
information, can be eliminated rather easily through the establishment
of web-based catalogs of available resources. Genetic Alliance's
CDC-sponsored resource center will provide an organized portal for
resources related to Duchenne muscular dystrophy in the United States.

Both formal and informal tissue/cell line repositories exist for
muscular dystrophy patients, but these are difficult to find, and it is
even more difficult to determine what can be obtained from each. 
Efforts to develop a catalog of resources available from known or
potential patient repositories should include a brief description of the
resource, the procedures for access to samples, any fee structure, and
any requirements for acknowledgement or co-authorship.

Gene mutation databases are essential to studies of disease mechanisms,
development of diagnostic/screening tools, and initiation of molecular
therapy-based clinical trials. The mutation database at Leiden
University Medical Center (<http://www.dmd.nl/>) is among the most
developed mutation databases in any disease.  Other muscular dystrophy
mutation databases are listed in the chapter on Diagnosis and Screening
in Muscular Dystrophy. The mRNA expression profiling databases and
public access tools for neuromuscular disease from Children's National
Medical Center are highly evolved.   However, both proteomics and
development of sophisticated biochemical pathway tools have lagged
behind similar efforts in other disease systems.  Both bioinformatics as
applied to biochemical pathway information (e.g. Ingenuity Inc type
interfaces), and proteomics efforts, need to be encouraged and fostered
in the muscular dystrophies.

Antibodies are important research tools, and are now used extensively
for molecular diagnostics.  Dr. Glenn Morris has created an impressive
battery of muscular dystrophy-relevant monoclonal antibodies, and has
received funding from the Muscular Dystrophy Association TRAC committee
to distribute these at cost.  Antibodies from Dr. Morris, and other
laboratories willing to provide aliquots, should be listed on a web
site. Muscular dystrophy-relevant antibodies, including protocols for
receiving aliquots, the size aliquots that can/will be sent, and any
costs associated with these should be listed as well.

-   *Research Objective 10:* Establish a USA equivalent of the European
    Neuromuscular Centre's disease focus meetings to link to and
    communicate with European and other international networks or groups
    (Short Term; Low Risk).

Small, focused research meetings, with a clear agenda and requirement
for specific outcomes, can be invaluable in establishing collaborations,
reaching consensus, and moving a field forward. The standard for the
muscular dystrophy field has been the European Neuromuscular Centre's
continuing series of meetings that has had proceedings published in the
journal *Neuromuscular Disorders*. A complementary series should be
established in the USA, focusing on the muscular dystrophies and with
similar participant numbers and deliverables. USA---European
partnerships should be encouraged; a means for USA investigator
participation in the European Neuromuscular Centre's meetings, and
corresponding European investigator participation in USA meetings,
should also be provided.

-   *Research Objective 11:* Increase the number and scientific breadth
    of basic scientists and clinicians involved in translational
    research in the muscular dystrophies (Long Term; Intermediate Risk).

While substantial progress has been made in the mechanistic
understanding of many types of muscular dystrophy, few of these findings
have translated into potential therapies for the disease. Frequently,
academic investigators lack the expertise to undertake the steps
necessary for therapeutic development up to Food and Drug Administration
approval of an Investigational New Drug application. Training and
research support vehicles should be put into place to ensure that major
mechanistic discoveries are fully evaluated to determine potential
therapeutic targets. Due to the nature of translational research, there
is also a significant need to increase the breadth of disciplines from
which these researchers are coming to include, developmental biology,
systems physiology, the range of medical specialties (neurology,
cardiology, pulmonology, orthopedics, ophthalmology, and rehabilitation
medicine), nursing, social work, and psychology.

-   *Research Objective 12:* Provide a publicly accessible listing of
    available training grants and resources so that opportunities for
    physicians and scientists are transparent (Short Term; Low Risk).

There remains a vital need to train and recruit new clinical and basic
scientists to pursue research in the muscular dystrophies. Efforts
should be made to enhance the visibility and availability of information
about existing opportunities for training and education of research
fellows. To improve the multi-disciplinary approach to the muscular
dystrophies, there should be a broadening of the base of disciplines
receiving training to include not only the medical and basic biological
sciences but also the social sciences and medical economics. To this
end, new fellowship opportunities should be created in nursing, physical
therapy/occupational therapy, social work, clinical psychology,
epidemiology, and health care management/economics in order to
facilitate research in areas such as: living with muscular dystrophy,
measuring/reducing the clinical burden of muscular dystrophy, and
identifying optimal endpoints for disease manifestations of muscular
dystrophy. These new grant opportunities and approaches should be
developed using existing infrastructure, such as the Senator Paul D.
Wellstone Muscular Dystrophy Collaborative Research Center Network, the
Muscular Dystrophy Association-initiated PROD network, and the Centers
for Disease Control and Prevention MD STARnet project, to enhance the
education of patients and care providers on the subject of the muscular
dystrophies. It is imperative to provide funding for grants,
conferences, and communications networks that will help establish
guidelines for care of patients with different forms of muscular
dystrophy. This should include the establishment of networks of clinical
centers, research groups, patient groups, professional societies, and
other stakeholders (Government and private foundations) to maximize the
use of existing resources and create optimal platforms for communication
through computers and other means.

-   *Research Objective 13:* Stimulate international collaborations and
    infrastructure sharing to ensure that opportunities are exploited
    and resources are used to maximum advantage, particularly in cases
    of novel opportunity or for the rare and/or understudied muscular
    dystrophies (Short Term; Intermediate Risk).

There is a critical need for better understanding of the mechanisms of
some of the under-studied muscular dystrophies. This current deficiency
in knowledge can have various causes; the most important ones being a
complex etiology and low prevalence. In both situations the critical
mass to swiftly proceed is lacking due to insufficient local
multidisciplinary expertise, access to material etc. Pooling of
scientific and patient resources is an attractive and cost-effective
solution. Collaborations and sharing of resources among the
international research groups focusing on these diseases will maximize
the opportunities for discovery and will accelerate the accumulation of
knowledge necessary for the development of effective treatment
strategies.

**D. Matrix of Research Objectives in research infrastructure needs for
muscular dystrophy**

+-----------+------------------+------------------+------------------+
|           | **Short Term**   | **Medium Term**  | **Long term**    |
|           |                  |                  |                  |
|           | **(0-3 years)**  | **(4-6 years)**  | **(7-10 years)** |
+-----------+------------------+------------------+------------------+
| **High    |                  | -   Develop      |                  |
| Risk**    |                  |     optimized    |                  |
|           |                  |     models for   |                  |
|           |                  |     mechanistic  |                  |
|           |                  |     studies of   |                  |
|           |                  |     specific     |                  |
|           |                  |     muscular     |                  |
|           |                  |     dystrophies, |                  |
|           |                  |     including    |                  |
|           |                  |     models       |                  |
|           |                  |     appropriate  |                  |
|           |                  |     for          |                  |
|           |                  |     therapeutic  |                  |
|           |                  |     development  |                  |
|           |                  |     screens      |                  |
|           |                  |                  |                  |
|           |                  | -   Encourage    |                  |
|           |                  |     the          |                  |
|           |                  |     development  |                  |
|           |                  |     of           |                  |
|           |                  |     cell-based   |                  |
|           |                  |     assays that  |                  |
|           |                  |     target       |                  |
|           |                  |     aspects of   |                  |
|           |                  |     pathogenesis |                  |
|           |                  |     and          |                  |
|           |                  |                  |                  |
|           |                  |  pathophysiology |                  |
|           |                  |     in the       |                  |
|           |                  |     muscular     |                  |
|           |                  |     dystrophies, |                  |
|           |                  |     to enable    |                  |
|           |                  |     high         |                  |
|           |                  |     throughput   |                  |
|           |                  |     drug         |                  |
|           |                  |     screening    |                  |
+-----------+------------------+------------------+------------------+
| **Int     | -   Stimulate    | Facilitate       | -   Increase the |
| ermediate |                  | research         |     number and   |
| Risk**    |    international | (discovery,      |     scientific   |
|           |                  | validation, and  |     breadth of   |
|           |   collaborations | dissemination)   |     basic        |
|           |     and          | of the           |     scientists   |
|           |                  | biochemical      |     and          |
|           |   infrastructure | pathways         |     clinicians   |
|           |     sharing to   | involved in      |     involved in  |
|           |     ensure that  | muscular         |                  |
|           |                  | dystrophy        |    translational |
|           |    opportunities |                  |     research in  |
|           |     are          | -   Identify,    |     the muscular |
|           |     exploited    |     develop, and |     dystrophies  |
|           |     and          |     encourage    |                  |
|           |     resources    |     the use of   |                  |
|           |     are used to  |     standardized |                  |
|           |     maximum      |     instruments  |                  |
|           |     advantage,   |     to measure   |                  |
|           |     particularly |     quality of   |                  |
|           |     in cases of  |     life,        |                  |
|           |     novel        |     cognitive,   |                  |
|           |     opportunity  |     and central  |                  |
|           |     or for the   |     nervous      |                  |
|           |     rare and/or  |     system       |                  |
|           |     understudied |     function     |                  |
|           |     muscular     |     using        |                  |
|           |     dystrophies  |     existing     |                  |
|           |                  |     databases    |                  |
|           |                  |     and          |                  |
|           |                  |     potentially  |                  |
|           |                  |     develop new  |                  |
|           |                  |     common       |                  |
|           |                  |     element      |                  |
|           |                  |     databases to |                  |
|           |                  |     extend       |                  |
|           |                  |     research     |                  |
|           |                  |     capabilities |                  |
+-----------+------------------+------------------+------------------+
| **Low     | -   Design and   | -   Create a     | -   Establish    |
| Risk**    |     implement a  |     mechanism to |     standardized |
|           |     web site     |     maintain     |     endpoints    |
|           |     that         |     mouse models |     for          |
|           |     provides     |     of muscular  |     preclinical  |
|           |     information  |     dystrophy at |     trials in    |
|           |     and links to |     approved     |     both mouse   |
|           |     all existing |     vendors in a |     models, and  |
|           |     resources in |     live state,  |     the dog      |
|           |     both the USA |     available    |     model, and   |
|           |     and          |     for easy and |     ensure that  |
|           |                  |     rapid        |     facilities   |
|           |  internationally |     importation  |     are          |
|           |                  |     into         |     available    |
|           | -   Establish a  |     academic     |     that enable  |
|           |     USA          |     colonies     |     testing of   |
|           |     equivalent   |                  |     drugs and    |
|           |     of the       |                  |     other        |
|           |     European     |                  |     therapeutic  |
|           |                  |                  |     approaches   |
|           |    Neuromuscular |                  |                  |
|           |     Centre's     |                  | -   Establish a  |
|           |     disease      |                  |     focus panel  |
|           |     focus        |                  |     for          |
|           |     meetings to  |                  |     molecular    |
|           |     link to and  |                  |     diagnostics  |
|           |     communicate  |                  |     of the       |
|           |     with         |                  |     muscular     |
|           |     European and |                  |     dystrophies, |
|           |     other        |                  |     with the     |
|           |                  |                  |     charge of    |
|           |    international |                  |     developing   |
|           |     networks or  |                  |     consensus    |
|           |     groups       |                  |     standards    |
|           |                  |                  |     and          |
|           | -   Provide a    |                  |     approaches   |
|           |     publicly     |                  |     for          |
|           |     accessible   |                  |     molecular    |
|           |     listing of   |                  |     testing,     |
|           |     available    |                  |     screening,   |
|           |     training     |                  |                  |
|           |     grants and   |                  |   interpretation |
|           |     resources so |                  |     of results,  |
|           |     that         |                  |     and genetic  |
|           |                  |                  |     counseling   |
|           |    opportunities |                  |                  |
|           |     for          |                  | -   Monitor,     |
|           |     physicians   |                  |     coordinate,  |
|           |     and          |                  |     and          |
|           |     scientists   |                  |     communicate  |
|           |     are          |                  |     the          |
|           |     transparent  |                  |                  |
|           |                  |                  |   rehabilitation |
|           |                  |                  |     and          |
|           |                  |                  |     educational  |
|           |                  |                  |     assessment   |
|           |                  |                  |     activities   |
|           |                  |                  |     of the       |
|           |                  |                  |     various      |
|           |                  |                  |     Federal      |
|           |                  |                  |     agencies,    |
|           |                  |                  |     voluntary,   |
|           |                  |                  |     and patient  |
|           |                  |                  |     advocacy     |
|           |                  |                  |     groups       |
+-----------+------------------+------------------+------------------+

**action plan Implementation, Tracking, and Assessment**

The Action Plan for the Muscular Dystrophies was developed with
significant input from the leading researchers and clinicians in the
field, and subsequently reviewed and approved by the MDCC. The goal was
to identify Research Objectives that have the greatest priority and
potential for success in reducing the clinical burden of disease. This
Action Plan should not be perceived as a final, static document, but
instead as an initial set of goals that will be implemented, tracked,
and periodically re-assessed to ensure the best possible coordination of
resources from the public and private sectors for detecting, diagnosing,
treating, and preventing the muscular dystrophies.

**A. Plan Implementation**

The Action Plan for the Muscular Dystrophies was developed by the MDCC
SWG and the MDCC as a resource document for the entire muscular
dystrophy research and education community. The Research Objectives
identified here touch upon all aspects of the muscular dystrophies, from
identification of pathogenic mechanisms to clinical management of
patients with these diseases. While the NIH has played a leading role in
the basic science discoveries that will help drive therapeutic
development, given the mission of, and expertise and resources present
at, the Federal agencies that are represented on the MDCC, many aspects
of the Action Plan are most appropriately addressed by agencies besides
the NIH. In addition, many of the activities that will be initiated as a
result of the Action Plan will be facilitated by the leadership of the
muscular dystrophy patient advocacy groups, particularly given their
wide access to, and deep understanding of, the muscular dystrophy
patient and family community. Indeed, many Federal agencies and advocacy
organizations are already engaged in the types of activities that were
identified as priorities by the MDCC SWG. Future activities may include
the continuation and/or expansion of existing efforts, as well as the
development of new initiatives by MDCC member agencies and
organizations.

Many of the activities that will emerge from the Research Objectives
identified in the Action Plan will be, by necessity, collaborative in
nature. Because of the breadth of available knowledge and research
tools, the multi-system complexity of disease mechanisms, and the need
for rapidly translating basic findings into effective therapies, the
research teams of the future must be comprised of multidisciplinary,
interactive groups. Similarly, due to the scope of the emerging
opportunities in the muscular dystrophies, and the financial resources
that these require, there is also a real need for active collaborations
between the agencies and organizations that invest in the research. The
MDCC should play an important role in identifying and implementing
collaborations among the various Federal agencies and facilitating
collaborations between public agencies and voluntary patient advocacy
groups in order to ensure the continuation of breakthroughs in reducing
the clinical burden of muscular dystrophy. Working through its partners
on the MDCC, the NIH will encourage and facilitate collaborative
activities where they represent the best approach to achieving specific
Research Objectives.

The Action Plan for the Muscular Dystrophies will also serve as a basis
for communicating scientific priorities to the research community. Since
its content reflects the expertise of the scientific leaders in the
field, the Action Plan itself may serve as a stimulus for the design of
basic and clinical research grant applications. The Action Plan will be
publicized and made available on the MDCC website, and shared with
students and postdoctoral fellows working in the muscular dystrophy
field, current and prospective grantees, and members of the appropriate
Federal advisory committees and initial review groups.

Taken together, success in achieving the Research Objectives of the
Action Plan for the Muscular Dystrophies will require coordination among
the public agencies and private organizations that comprise the MDCC to
ensure efficient use of scarce manpower and fiscal resources and
avoidance of unnecessary duplication of efforts.

**B. Plan Tracking**

The NIH, together with its partner agencies and organizations in the
MDCC, will ensure that progress relevant to this Action Plan is tracked
and made publicly available. Future accomplishments and initiatives by
all MDCC member agencies and organizations relative to the Action Plan
will be tracked by means of the MDCC public website
(<http://www.ninds.nih.gov/find_people/groups/mdcc/index.htm>). A record
of key publications, conferences and workshops, and initiatives that are
relevant to specific Research Objectives will be maintained on the MDCC
website as well. This ensures that progress in achieving the Research
Objectives of the Action Plan can be viewed by Governmental officials,
advocacy groups, physicians, basic and clinical researchers, care
providers, and patients and their families. MDCC members will present
annual reports on activities relative to the Action Plan at the
regularly scheduled MDCC meetings.

**C. Plan Assessment**

The Action Plan for the Muscular Dystrophies is not meant to be a static
document, but rather a snapshot at this point in time of the judgment of
leading investigators in the field as to where current application of
effort and resources can best address the most compelling opportunities.
The Action Plan will require active tracking and assessment if it is to
serve the purpose of stimulating research in the field and guiding
activities of the MDCC. The 76 Research Objectives identified in the
Action Plan will be used as guideposts for assessing progress and the
Action Plan will be periodically reviewed and revised. Any revisions to
the Action Plan will be included in the MDCC biennial report to
Congress, as required in the MD-CARE Act. As appropriate, the MDCC may
reconvene a scientific working group to assist in Action Plan assessment
and revision. Reporting on progress made toward the Research Objectives
will occur at future MDCC meetings and will be tracked on the MDCC
website, providing a public record of progress toward the goal of
improving the detection, diagnosis, treatment, and prevention of the
muscular dystrophies.