The role of alternative splicing in non-muscle aspects of Duchenne muscular dystrophy.
Published: 2006
Language: eng
Number of pages: 161
ISBN-13: 9780494219379
Description: Duchenne Muscular Dystrophy (DMD) is an X-linked recessive disorder associated primarily with progressive skeletal muscle degeneration. In skeletal muscle the DMD gene product, dystrophin, is thought be responsible for maintaining membrane integrity, but the role of dystrophin outside of skeletal muscle is not clear. Individuals afflicted with DMD may display a number of secondary phenotypes, including an abnormal electroretinogram (ERG), cognitive deficiencies and profuse intraoperative bleeding. Determining the role of dystrophin in these systems is complicated by the existance of multiple DMD promoter and splice isoforms. The primary aim of the work presented here is to define the role of the dystrophin associated protein complex in these non-muscle phenotypes and to explore the functional significance of the associated exon 78 alternative splicing.The primary dystrophin protein isoform thought to contribute to the ERG in mice is Dp71. Chapter III of this work describes a regulatory region of the DMD gene that acts as a functional promoter for Dp71, designated Dp71 pro. Mice expressing GFP under control of Dp71 pro illustrate that this region is functionally similar to the endogenous Dp71 promoter.By expanding the composition of the dystrophin associated protein complex, and defining the role of the individual dystrophin splice isoforms, this work provides insight into a molecular basis for the abnormal retina physiology in patients lacking dystrophin.The electroretinogram of DMD patients is commonly marked by a significantly reduced b-wave. The two channel proteins, AQP4 and Kir4.1, are ideally suited to play a fundamental role in the generation of the ERG b-wave, and results presented here in Chapter II demonstrate that both are profoundly mislocalized in the retina of dystrophin null mice. Further, these results indicate that alpha-syntrophin likely recruits the Kir4.1 channel into the dystrophin complex in the retina.Dp71pro is used in the generation of the mdx-71D mouse model, which expresses a single dystrophin isoform, Dp71-DCT. Examination of this mouse reveals that the Dp71-DCT protein is correctly localized in the retina, and can restore the targetted localization of dystrophin associated proteins. Furthermore, mdx-71D mice display significant restoration of the ERG, demonstrating functional competence of the Dp71-DCT dystrophin isoform in this system.Finally, platelets derived from a dystrophin null mouse model were examined for the adhesion defects postulated to be responsible for the intraoperative bleeding diathesis phenotype of DMD patients. No such abnormality was observed in an assay designed to closely mimic physiological conditions.
Notes: Source: Dissertation Abstracts International, Volume: 68-01, Section: B, page: 0067.

Thesis (Ph.D.)--University of Toronto, 2006.

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