bluuebunny/crossref_metadata_2025 huggingface dataset:
A comparative proteomic study of sera in paediatric systemic lupus erythematosus patients and in healthy controls using MALDI-TOF-TOF and LC MS–A pilot study
Authors: Rana Anita , Minz Ranjana W , Aggarwal Ritu , Sharma Sadhna , Pasricha Neelam , Anand Shashi , Singh Surjit
Published: August 2012

Background

Paediatric systemic lupus erythematosus (pSLE) exhibits an aggressive clinical phenotype with severe complications and overall poor prognosis. The aim of this study was to analyse differential expression of low molecular weight (LMW) serum protein molecules of pSLE patients with active disease in comparison to sera of healthy age matched controls. Further, some of the differential expressed spots were characterised and identified by Matrix Assisted Laser Desorption Ionization Time of Flight Mass Spectrometry (MALDI-TOF-MS) and liquid chromatography (LC-MS).

Methods

2D-PAGE was performed using pooled sera of active pSLE and age matched healthy controls. Gels were silver-stained and differentially expressed protein spots were detected by automated image master platinum 2D software. 79 ± 17 protein spots were detected for control gels and 78 ± 17 protein spots for patient gels. Of these eleven protein spots were selected randomly and characterized by MALDI-TOF MS (five protein spots) and LC MS (six protein spots) techniques.

Results

Out of the 11 protein spots, 5 protein spots were significantly upregulated viz., leiomodin 2 (LMOD2); epidermal cytokeratin 2; immunoglobulin kappa light chain variable region; keratin 1 and transthyretin (TTR). Three protein spots were significantly down regulated e.g., apolipoprotein A1 (APOA1); chain B human complement component C3c; campath antibody antigen complex. Two protein spots (complement component C3; retinol binding protein (RBP) were found to be expressed only in disease and one protein spot cyclohydrolase 2 was only expressed in controls.

Conclusions

We conclude that 2-D maps of patients with active pSLE and controls differ significantly. In this pilot study, using proteomic approach we have identified differential expressed proteins (of LMW) e.g., RBP, LMOD 2, TTR, Component C3c Chain B and APO A1. However, in future, further studies need to confirm the physiological and pathological role of these proteins in similar cohorts of pSLE.
Gd(III)-DOTA-modified sonosensitive liposomes for ultrasound-triggered release and MR imaging
Authors: Jung Suk Hyun , Na Kyunga , Lee Seul A , Cho Sun Hang , Seong Hasoo , Shin Byung Cheol
Published: August 2012

Ultrasound-sensitive (sonosensitive) liposomes for tumor targeting have been studied in order to increase the antitumor efficacy of drugs and decrease the associated severe side effects. Liposomal contrast agents having Gd(III) are known as a nano-contrast agent system for the efficient and selective delivery of contrast agents into pathological sites. The objective of this study was to prepare Gd(III)-DOTA-modified sonosensitive liposomes (GdSL), which could deliver a model drug, doxorubicin (DOX), to a specific site and, at the same time, be capable of magnetic resonance (MR) imaging. The GdSL was prepared using synthesized Gd(III)-DOTA-1,2-distearoyl-sn-glycero-3-phosphoethanolamine lipid. Sonosensitivity of GdSL to 20-kHz ultrasound induced 33% to 40% of DOX release. The relaxivities (r
1) of GdSL were 6.6 to 7.8 mM−1 s−1, which were higher than that of MR-bester®. Intracellular uptake properties of GdSL were evaluated according to the intensity of ultrasound. Intracellular uptake of DOX for ultrasound-triggered GdSL was higher than that for non-ultrasound-triggered GdSL. The results of our study suggest that the paramagnetic and sonosensitive liposomes, GdSL, may provide a versatile platform for molecular imaging and targeted drug delivery.
Highly conductive vertically aligned molybdenum nanowalls and their field emission property
Authors: Shen Yan , Deng Shaozhi , Zhang Yu , Liu Fei , Chen Jun , Xu Ningsheng
Published: August 2012

We report that vertically aligned molybdenum (Mo) nanowalls can grow on various substrates by simple thermal vapor deposition. Individual nanowalls have a typical thickness of about 50 nm and very good conductivity with a typical average value of about 1.97 × 104 Ω−1 cm−1, i.e., only an order of magnitude less than the value of bulk Mo. The formation process is characterized in detail, and it is found that Mo nanowalls grow from nanorods through nanotrees. The atomic arrangement, lattice mismatch relationship, and competition growth are all believed to contribute to the growth mechanism. The field emission performance is attractive, typically with a very low fluctuation of about approximately 1.18% at a high current density level of 10 mA/cm2, and a sustainably stable very large current density of approximately 57.5 mA/cm2 was recorded. These indicate that the Mo nanowall is a potential candidate as a cold cathode for application in vacuum electron devices, which demand both a high current and high current density.
Crystallization of amorphous silicon thin films deposited by PECVD on nickel-metalized porous silicon
Authors: Ben Slama Sonia , Hajji Messaoud , Ezzaouia Hatem
Published: August 2012

Porous silicon layers were elaborated by electrochemical etching of heavily doped p-type silicon substrates. Metallization of porous silicon was carried out by immersion of substrates in diluted aqueous solution of nickel. Amorphous silicon thin films were deposited by plasma-enhanced chemical vapor deposition on metalized porous layers. Deposited amorphous thin films were crystallized under vacuum at 750°C. Obtained results from structural, optical, and electrical characterizations show that thermal annealing of amorphous silicon deposited on Ni-metalized porous silicon leads to an enhancement in the crystalline quality and physical properties of the silicon thin films. The improvement in the quality of the film is due to the crystallization of the amorphous film during annealing. This simple and easy method can be used to produce silicon thin films with high quality suitable for thin film solar cell applications.
Development of a modified Respiration Activity Monitoring System for accurate and highly resolved measurement of respiration activity in shake flask fermentations
Authors: Hansen Sven , Hariskos Ioanna , Luchterhand Bettina , Büchs Jochen
Published: August 2012

Background

The Respiration Activity Monitoring System (RAMOS) is an established device to measure on-line the oxygen transfer rate (OTR), thereby, yielding relevant information about metabolic activities of microorganisms and cells during shake flask fermentations. For very fast-growing microbes, however, the RAMOS technique provides too few data points for the OTR. Thus, this current study presents a new model based evaluation method for generating much more data points to enhance the information content and the precision of OTR measurements.

Results

In cultivations with E.coli BL21 pRSET eYFP-IL6, short diauxic and even triauxic metabolic activities were detected with much more detail compared to the conventional evaluation method. The decline of the OTR during the stop phases during oxygen limitations, which occur when the inlet and outlet valves of the RAMOS flask were closed for calibrating the oxygen sensor, were also detected. These declines reflected a reduced oxygen transfer due to the stop phases. In contrast to the conventional calculation method the new method was almost independent from the number of stop phases chosen in the experiments.

Conclusions

This new model based evaluation method unveils new peaks of metabolic activity which otherwise would not have been resolved by the conventional RAMOS evaluation method. The new method yields substantially more OTR data points, thereby, enhancing the information content and the precision of the OTR measurements. Furthermore, oxygen limitations can be detected by a decrease of the OTR during the stop phases.
Atorvastatin inhibits osteoclastogenesis by decreasing the expression of RANKL in the synoviocytes of rheumatoid arthritis
Authors: Kim Jeong Yeon , Lee Eun Young , Lee Eun Bong , Lee Yun Jong , Yoo Hyun Jung , Choi Jiyong , Song Yeong Wook
Published: August 2012

Introduction

Statins, hydroxymethylglutaryl-coenzyme A reductase inhibitors, have been reported to have antiinflammatory and/or immunomodulatory effects and prophylactic and therapeutic effects in collagen-induced arthritis, an experimental model of rheumatoid arthritis (RA). The authors undertook to determine the effect of atorvastatin on the expressions of osteoprotegerin (OPG) and receptor activator of nuclear factor κB ligand (RANKL) in RA fibroblast-like synoviocytes (FLSs), to identify the mechanisms responsible for these effects, and to determine whether the statin inhibits osteoclastogenesis.

Methods

FLSs isolated from five RA patients were cultured in the presence of 20 ng/ml of tumor necrosis factor-α (TNF-α) with or without atorvastatin. RANKL expressions were assayed with Western blotting and enzyme-linked immunosorbent assay. RANKL, RANK, and OPG expression were assayed with reverse transcription-polymerase chain reaction (RT-PCR). Osteoclast formation was assayed by counting cells after staining for tartrate-resistant acid phosphatase in cocultures of peripheral blood mononuclear cells (PBMCs) and RA FLSs.

Results

Atorvastatin inhibited the expression of RANKL in RA FLSs in a dose-dependent manner, and the suppression of RANKL was prevented by mevalonate. However, OPG expression was not affected by atorvastatin in RA FLSs, and atorvastatin did not affect RANK expression in CD14+ cells. Conversely, atorvastatin suppressed TNF-α-induced p38 phosphorylation in RA FLSs and significantly reduced TRAP-positive multinucleated osteoclast formation in the coculture of PBMCs and RA FLSs.

Conclusion

These results suggest that atorvastatin inhibits osteoclastogenesis and bone destruction in RA patients.
Early systemic sclerosis: short-term disease evolution and factors predicting the development of new manifestations of organ involvement
Authors: Valentini Gabriele , Vettori Serena , Cuomo Giovanna , Iudici Michele , D'Abrosca Virginia , Capocotta Domenico , Del Genio Gianmattia , Santoriello Carlo , Cozzolino Domenico
Published: August 2012

Introduction

We investigated early systemic sclerosis (SSc) (that is, Raynaud's phenomenon with SSc marker autoantibodies and/or typical capillaroscopic findings and no manifestations other than puffy fingers or arthritis) versus undifferentiated connective tissue disease (UCTD) to identify predictors of short-term disease evolution.

Methods

Thirty-nine early SSc and 37 UCTD patients were investigated. At baseline, all patients underwent clinical evaluation, B-mode echocardiography, lung function tests and esophageal manometry to detect preclinical alterations of internal organs, and were re-assessed every year. Twenty-one early SSc and 24 UCTD patients, and 25 controls were also investigated for serum endothelial, T-cell and fibroblast activation markers.

Results

At baseline, 48.7% of early SSc and 37.8% of UCTD patients had at least one preclinical functional alteration (P > 0.05). Ninety-two percent of early SSc patients developed manifestations consistent with definite SSc (that is, skin sclerosis, digital ulcers/scars, two or more teleangectasias, clinically visible nailfold capillaries, cutaneous calcinosis, X-ray bibasilar lung fibrosis, X-ray esophageal dysmotility, ECG signs of myocardial fibrosis and laboratory signs of renal crisis) within five years versus 17.1% of UCTD patients (X
2
= 12.26; P = 0.0005). Avascular areas (HR = 4.39 95% CI 1.18 to 16.3; P = 0.02), increased levels of soluble IL-2 receptor alpha (HR = 4.39; 95% CI 1.03 to 18.6; P = 0.03), and of procollagen III aminopropeptide predicted disease evolution (HR = 4.55; 95% CI 1.18 to 17; P = 0.04).

Conclusion

Most early SSc but only a few UCTD patients progress to definite SSc within a short-term follow-up. Measurement of circulating markers of T-cell and fibroblast activation might serve to identify early SSc patients who are more likely to develop features of definite SSc.
Early menopause and severity of rheumatoid arthritis in women older than 45 years
Authors: Pikwer Mitra , Nilsson Jan-Åke , Bergström Ulf , Jacobsson Lennart TH , Turesson Carl
Published: August 2012

Introduction

We aimed to investigate whether recognized hormonal predictors of rheumatoid arthritis (RA) also influence the severity of RA.

Methods

One hundred thirty-four incident RA cases identified by four different local and national registers, who had participated in a community-based health survey between 1991 and 1996, were included. By a retrospective structured review of the medical records, information on the use of disease-modifying antirheumatic drugs (DMARDs), erosions on radiographs, rheumatoid factor (RF) status, and disability measured by using the health assessment questionnaire (HAQ) were collected. The variables were added to the SPSS TwoStep Cluster Analysis to reveal natural groupings of RA severity. Known hormonal predictors analyzed were breastfeeding history, history of oral contraceptive (OC) use, and menopausal age.

Results

The mean age at RA diagnosis was 63.4 years; 72% were RF positive, and 28% had received biological treatment. Three clusters were identified, one with severe RA, one with mild/moderate RF-positive RA, and one with mild/moderate RF-negative RA. A significant difference (P = 0.005) was found in the distribution of clusters between patients with a history of early menopause compared with those with menopause after 45 years, with a higher proportion with mild/moderate RF-negative RA in the early-menopause subset. No major difference in severity of the disease was noted depending on OC use or history of breastfeeding.

Conclusions

Early menopause was associated with a milder form of RA. Hormonal changes may influence pathways that are distinct from those leading to severe, progressive disease.
Mannitol increases renal blood flow and maintains filtration fraction and oxygenation in postoperative acute kidney injury: a prospective interventional study
Authors: Bragadottir Gudrun , Redfors Bengt , Ricksten Sven-Erik
Published: August 2012

Introduction

Acute kidney injury (AKI), which is a major complication after cardiovascular surgery, is associated with significant morbidity and mortality. Diuretic agents are frequently used to improve urine output and to facilitate fluid management in these patients. Mannitol, an osmotic diuretic, is used in the perioperative setting in the belief that it exerts reno-protective properties. In a recent study on uncomplicated postcardiac-surgery patients with normal renal function, mannitol increased glomerular filtration rate (GFR), possibly by a deswelling effect on tubular cells. Furthermore, experimental studies have previously shown that renal ischemia causes an endothelial cell injury and dysfunction followed by endothelial cell edema. We studied the effects of mannitol on renal blood flow (RBF), glomerular filtration rate (GFR), renal oxygen consumption (RVO2), and extraction (RO2Ex) in early, ischemic AKI after cardiac surgery.

Methods

Eleven patients with AKI were studied during propofol sedation and mechanical ventilation 2 to 6 days after complicated cardiac surgery. All patients had severe heart failure treated with one (100%) or two (73%) inotropic agents and intraaortic balloon pump (36%). Systemic hemodynamics were measured with a pulmonary artery catheter. RBF and renal filtration fraction (FF) were measured by the renal vein thermo-dilution technique and by renal extraction of chromium-51-ethylenediaminetetraacetic acid (51Cr-EDTA), respectively. GFR was calculated as the product of FF and renal plasma flow RBF × (1-hematocrit). RVO2 and RO2Ex were calculated from arterial and renal vein blood samples according to standard formulae. After control measurements, a bolus dose of mannitol, 225 mg/kg, was given, followed by an infusion at a rate of 75 mg/kg/h for two 30-minute periods.

Results

Mannitol did not affect cardiac index or cardiac filling pressures. Mannitol increased urine flow by 61% (P < 0.001). This was accompanied by a 12% increase in RBF (P < 0.05) and a 13% decrease in renal vascular resistance (P < 0.05). Mannitol increased the RBF/cardiac output (CO) relation (P = 0.040). Mannitol caused no significant changes in RO2Ext or renal FF.

Conclusions

Mannitol treatment of postoperative AKI induces a renal vasodilation and redistributes systemic blood flow to the kidneys. Mannitol does not affect filtration fraction or renal oxygenation, suggestive of balanced increases in perfusion/filtration and oxygen demand/supply.
Genome-wide distribution of 5-formylcytosine in embryonic stem cells is associated with transcription and depends on thymine DNA glycosylase
Authors: Raiber Eun-Ang , Beraldi Dario , Ficz Gabriella , Burgess Heather E , Branco Miguel R , Murat Pierre , Oxley David , Booth Michael J , Reik Wolf , Balasubramanian Shankar
Published: August 2012

Background

Methylation of cytosine in DNA (5mC) is an important epigenetic mark that is involved in the regulation of genome function. During early embryonic development in mammals, the methylation landscape is dynamically reprogrammed in part through active demethylation. Recent advances have identified key players involved in active demethylation pathways, including oxidation of 5mC to 5-hydroxymethylcytosine (5hmC) and 5-formylcytosine (5fC) by the TET enzymes, and excision of 5fC by the base excision repair enzyme thymine DNA glycosylase (TDG). Here, we provide the first genome-wide map of 5fC in mouse embryonic stem (ES) cells and evaluate potential roles for 5fC in differentiation.

Results

Our method exploits the unique reactivity of 5fC for pulldown and high-throughput sequencing. Genome-wide mapping revealed 5fC enrichment in CpG islands (CGIs) of promoters and exons. CGI promoters in which 5fC was relatively more enriched than 5mC or 5hmC corresponded to transcriptionally active genes. Accordingly, 5fC-rich promoters had elevated H3K4me3 levels, associated with active transcription, and were frequently bound by RNA polymerase II. TDG down-regulation led to 5fC accumulation in CGIs in ES cells, which correlates with increased methylation in these genomic regions during differentiation of ES cells in wild-type and TDG knockout contexts.

Conclusions

Collectively, our data suggest that 5fC plays a role in epigenetic reprogramming within specific genomic regions, which is controlled in part by TDG-mediated excision. Notably, 5fC excision in ES cells is necessary for the correct establishment of CGI methylation patterns during differentiation and hence for appropriate patterns of gene expression during development.
Migration from 3D irregular surfaces: A prestack time migration approach
Authors: Zhang Jianfeng , Xu Jincheng , Zhang Hao
Published: August 2012

We have developed a modified 3D prestack time migration (PSTM) scheme that can handle rugged topography as well as high near-surface velocities in land seismic imaging. The proposed topography PSTM can be applied to seismic data recorded on a 3D irregular surface without static corrections. Two effective velocity parameters were found to describe wave propagation through inhomogeneous media above and below a chosen datum. As a result, wave propagation phenomena in the complex near surface, such as near-vertical incidences through a weathering layer and raypaths bending away from vertical in the presence of high near-surface velocities, are correctly considered. The two effective velocity parameters can be estimated by flattening events in imaging gathers. Hence, it is not necessary to have detailed knowledge of the near-surface velocity model and velocity field below the datum when applying topography PSTM. We integrated residual static corrections into topography PSTM. This eliminated the distortions along the events better than conventional residual static corrections, which are usually applied before migration. The computational cost of the topography PSTM was only slightly higher than that of conventional PSTM due to the use of a table-driven algorithm. Three-dimensional synthetic and field data sets were used to test the proposed topography PSTM. High-quality imaging results were obtained.
Bacteria without Borders: Communicable Disease Politics in Europe
Authors: Greer Scott L. , Mätzke Margitta
Published: August 2012

Communicable disease control might be one of the oldest and most important functions of the modern state, but it receives very little attention today. This article introduces a special issue on the Europeanization of communicable disease control politics in Europe. The Europeanization of communicable disease control is a case of both European integration and communicable disease politics. We first analyze the problems and tensions in communicable disease control as a problem of overlapping interprofessional, interorganizational, intergovernmental, and international tensions. We then present the European Union, a new and understudied actor in communicable disease politics, sketching the theoretical background for Europeanization of the field and introducing the articles in the special issue.
Mapping Communicable Disease Control in the European Union
Authors: Elliott Heather A. , Jones David K. , Greer Scott L.
Published: August 2012

Understanding both the current performance of communicable disease control in Europe and the scale of the differences among systems is crucial to understanding its present performance and possible Europeanization. We attempt to identify the structure of authority in communicable disease control in each European Union (EU) member state. The primary sources of information were the competent bodies list posted on the European Centre for Disease Prevention and Control website and the Health in Transition reports produced by the European Observatory on Health Systems and Policies. Three key patterns emerge to answer the question of who does what. First, the landscape is full and crowded, with many actors involved. Second, the landscape is highly fragmented, with many organizations performing overlapping functions in each country. Third, regional patterns describe which types of organizations are assigned which functions. These full, fragmented, and regionally disparate systems show no signs of constituting a shared model. As a result, if there is an EU model of communicable disease control today, it is at most an aspiration.
Variation Matters: Epidemiological Surveillance in Europe
Authors: Reintjes Ralf
Published: August 2012

Communicable diseases do not respect national boundaries and are important challenges to health internationally. This article aims to support the improvement and integration of surveillance systems in Europe and beyond by drawing on research comparing national systems. Definitions and concepts of epidemiological surveillance are described as a continuous systematic process that observes and reflects the real situation in society not only within but also across political boundaries. Outbreaks that affect more than one country show that a systematic comparative analysis of surveillance systems in Europe can help improve disease control. National surveillance systems from six European Union countries and from a later comparison of twenty-six European countries are examined. An effective surveillance system can provide information for action and act as a monitoring body for health authorities. Nevertheless, many European surveillance systems still require improvement in the interests of public health.
The Role of Networks in the European Union Public Health Experience
Authors: Jacobson Peter D.
Published: August 2012

Improving our understanding of how the public health system should be organized is important, because the system's organizational structure makes a significant difference to the public's health. How the system is structured influences a practitioner's ability to respond and the system's capacity to adapt to changing circumstances. In view of the scarce resources society is willing to expend for public health, it is essential to have a structure in place that most appropriately and efficiently allocates those resources. The articles in this issue offer considerable insight from a European context, that deserves attention from US public health practitioners, advocates, and policy makers.
The Europeanization of Public Health: How Does It Work? The Seminal Role of the AIDS Case
Authors: Steffen Monika
Published: August 2012

This article analyzes the path that led the European Union from a somewhat accidental involvement in fighting AIDS to a new and sustainable policy of communicable disease control. It responds to three main questions: Why did an unexpected case lead to the organization of a new sustainable policy? How was this achieved despite national competency over the given policy sector? How did the new policy succeed in covering the enlarged EU? The explanation combines political factors and public health issues. European integration and eastern enlargement made transborder disease management a political necessity. Treaties gave legitimacy to EU policy, while the AIDS matrix furnished the practical procedures: networking, data harmonization, peer-conducted policy coaching, and participation. This pattern of public health management is compatible with national competency, and it is consistent with the democratic values the EU promotes throughout and beyond the enlarged EU. From a theoretical point of view, these patterns of activities constitute the empirically grounded content of the much used but less defined concept of cognitive Europeanization.
The Governance of Disease Control in Europe
Authors: Fox Daniel M.
Published: August 2012

The eight articles on the governance of communicable disease control in Europe in this issue contribute information and insight to the literature on health politics, policy, and law. Each is a carefully researched and well-argued analysis of a subject on which its authors are experts. The set will be useful to scholars of comparative health policy as well as to specialists in European affairs. The articles also illustrate two methodological issues in conducting research on the governance of health policy. The first is that how researchers define governance influences what evidence they acquire and how they evaluate it. The second is that governance affects how diseases are conceptualized in order to make and implement policy.
Celf1 regulation of dmrt2a is required for somite symmetry and left-right patterning during zebrafish development
Authors: Matsui Takaaki , Sasaki Akihiro , Akazawa Naoko , Otani Hifumi , Bessho Yasumasa
Published: August 2012

RNA-binding proteins (RBPs) bind to numerous and diverse mRNAs to control gene expression post-transcriptionally, although the in vivo functions of specific RBP-mRNA interactions remain largely unknown. Here, we show that an RBP named Cugbp, Elav-like family member 1 (Celf1) controls expression of a gene named doublesex and mab-3 related transcription factor 2a (dmrt2a), which is essential for somite symmetry and left-right patterning during zebrafish development. Celf1 promotes dmrt2a mRNA decay by binding to UGU repeats in the 3′UTR of dmrt2a mRNA such that celf1 overexpression reduces the amount of dmrt2a mRNA, leading to asymmetric somitogenesis and laterality defects. Furthermore, blocking the Celf1-dmrt2a mRNA interaction by a target protector morpholino alleviates failures in somite symmetry and left-right patterning that are caused by celf1 overexpression. Our results therefore demonstrate that Celf1-dependent fine-tuning of dmrt2a expression is essential for generating bilateral symmetry of somites and left-right asymmetric patterning during zebrafish development.
Immature hematopoietic stem cells undergo maturation in the fetal liver
Authors: Kieusseian Aurelie , de la Grange Philippe Brunet , Burlen-Defranoux Odile , Godin Isabelle , Cumano Ana
Published: August 2012

Hematopoietic stem cells (HSCs), which are defined by their capacity to reconstitute adult conventional mice, are first found in the dorsal aorta after 10.5 days post coitus (dpc) and in the fetal liver at 11 dpc. However, lympho-myeloid hematopoietic progenitors are detected in the dorsal aorta from 9 dpc, raising the issue of their role in establishing adult hematopoiesis. Here, we show that these progenitors are endowed with long-term reconstitution capacity, but only engraft natural killer (NK)-deficient Rag2γc–/– mice. This novel population, called here immature HSCs, evolves in culture with thrombopoietin and stromal cells, into HSCs, defined by acquisition of CD45 and MHC-1 expression and by the capacity to reconstitute NK-competent mice. This evolution occurs during ontogeny, as early colonization of fetal liver by immature HSCs precedes that of HSCs. Moreover, organ culture experiments show that immature HSCs acquire, in this environment, the features of HSCs.
Antagonistic cross-regulation between Wnt and Hedgehog signalling pathways controls post-embryonic retinal proliferation
Authors: Borday Caroline , Cabochette Pauline , Parain Karine , Mazurier Nicolas , Janssens Sylvie , Tran Hong Thi , Sekkali Belaïd , Bronchain Odile , Vleminckx Kris , Locker Morgane , Perron Muriel
Published: August 2012

Continuous neurogenesis in the adult nervous system requires a delicate balance between proliferation and differentiation. Although Wnt/β-catenin and Hedgehog signalling pathways are thought to share a mitogenic function in adult neural stem/progenitor cells, it remains unclear how they interact in this process. Adult amphibians produce retinal neurons from a pool of neural stem cells localised in the ciliary marginal zone (CMZ). Surprisingly, we found that perturbations of the Wnt and Hedgehog pathways result in opposite proliferative outcomes of neural stem/progenitor cells in the CMZ. Additionally, our study revealed that Wnt and Hedgehog morphogens are produced in mutually exclusive territories of the post-embryonic retina. Using genetic and pharmacological tools, we found that the Wnt and Hedgehog pathways exhibit reciprocal inhibition. Our data suggest that Sfrp-1 and Gli3 contribute to this negative cross-regulation. Altogether, our results reveal an unexpected antagonistic interplay of Wnt and Hedgehog signals that may tightly regulate the extent of neural stem/progenitor cell proliferation in the Xenopus retina.
Motoneuronal Sema3C is essential for setting stereotyped motor tract positioning in limb-derived chemotropic semaphorins
Authors: Sanyas Isabelle , Bozon Muriel , Moret Frédéric , Castellani Valérie
Published: August 2012

The wiring of neuronal circuits requires complex mechanisms to guide axon subsets to their specific target with high precision. To overcome the limited number of guidance cues, modulation of axon responsiveness is crucial for specifying accurate trajectories. We report here a novel mechanism by which ligand/receptor co-expression in neurons modulates the integration of other guidance cues by the growth cone. Class 3 semaphorins (Sema3 semaphorins) are chemotropic guidance cues for various neuronal projections, among which are spinal motor axons navigating towards their peripheral target muscles. Intriguingly, Sema3 proteins are dynamically expressed, forming a code in motoneuron subpopulations, whereas their receptors, the neuropilins, are expressed in most of them. Targeted gain- and loss-of-function approaches in the chick neural tube were performed to enable selective manipulation of Sema3C expression in motoneurons. We show that motoneuronal Sema3C regulates the shared Sema3 neuropilin receptors Nrp1 and Nrp2 levels in opposite ways at the growth cone surface. This sets the respective responsiveness to exogenous Nrp1- and Nrp2-dependent Sema3A, Sema3F and Sema3C repellents. Moreover, in vivo analysis revealed a context where this modulation is essential. Motor axons innervating the forelimb muscles are exposed to combined expressions of semaphorins. We show first that the positioning of spinal nerves is highly stereotyped and second that it is compromised by alteration of motoneuronal Sema3C. Thus, the role of the motoneuronal Sema3 code could be to set population-specific axon sensitivity to limb-derived chemotropic Sema3 proteins, therefore specifying stereotyped motor nerve trajectories in their target field.
Centrosome movements in vivo correlate with specific neurite formation downstream of LIM homeodomain transcription factor activity
Authors: Andersen Erica F. , Halloran Mary C.
Published: August 2012

Neurons must develop complex structure to form proper connections in the nervous system. The initiation of axons in defined locations on the cell body and their extension to synaptic targets are critical steps in neuronal morphogenesis, yet the mechanisms controlling axon formation in vivo are poorly understood. The centrosome has been implicated in multiple aspects of neuronal morphogenesis; however, its function in axon development is under debate. Conflicting results from studies of centrosome function in axonogenesis suggest that its role is context dependent and underscore the importance of studying centrosome function as neurons develop in their natural environment. Using live imaging of zebrafish Rohon-Beard (RB) sensory neurons in vivo, we discovered a spatiotemporal relationship between centrosome position and the formation of RB peripheral, but not central, axons. We tested centrosome function by laser ablation and found that centrosome disruption inhibited peripheral axon outgrowth. In addition, we show that centrosome position and motility are regulated by LIM homeodomain transcription factor activity, which is specifically required for the development of RB peripheral axons. Furthermore, we show a correlation between centrosome mislocalization and ectopic axon formation in bashful (laminin alpha 1) mutants. Thus, both intrinsic transcription factor activity and extracellular cues can influence centrosome position and axon formation in vivo. This study presents the first positive association between the centrosome and axon formation in vivo and suggests that the centrosome is important for differential neurite formation in neurons with complex axonal morphologies.
Amputation induces stem cell mobilization to sites of injury during planarian regeneration
Authors: Guedelhoefer Otto C. , Alvarado Alejandro Sánchez
Published: August 2012

How adult stem cell populations are recruited for tissue renewal and repair is a fundamental question of biology. Mobilization of stem cells out of their niches followed by correct migration and differentiation at a site of tissue turnover or injury are important requirements for proper tissue maintenance and regeneration. However, we understand little about the mechanisms that control this process, possibly because the best studied vertebrate adult stem cell systems are not readily amenable to in vivo observation. Furthermore, few clear examples of the recruitment of fully potent stem cells, compared with limited progenitors, are known. Here, we show that planarian stem cells directionally migrate to amputation sites during regeneration. We also show that during tissue homeostasis they are stationary. Our study not only uncovers the existence of specific recruitment mechanisms elicited by amputation, but also sets the stage for the systematic characterization of evolutionarily conserved stem cell regulatory processes likely to inform stem cell function and dysfunction in higher organisms, including humans.
Myocardin-like protein 2 regulates TGFβ signaling in embryonic stem cells and the developing vasculature
Authors: Li Jian , Bowens Nina , Cheng Lan , Zhu Xiaohong , Chen Mary , Hannenhalli Sridhar , Cappola Thomas P. , Parmacek Michael S.
Published: August 2012

The molecular mechanisms that regulate and coordinate signaling between the extracellular matrix (ECM) and cells contributing to the developing vasculature are complex and poorly understood. Myocardin-like protein 2 (MKL2) is a transcriptional co-activator that in response to RhoA and cytoskeletal actin signals physically associates with serum response factor (SRF), activating a subset of SRF-regulated genes. We now report the discovery of a previously undescribed MKL2/TGFβ signaling pathway in embryonic stem (ES) cells that is required for maturation and stabilization of the embryonic vasculature. Mkl2–/– null embryos exhibit profound derangements in the tunica media of select arteries and arterial beds, which leads to aneurysmal dilation, dissection and hemorrhage. Remarkably, TGFβ expression, TGFβ signaling and TGFβ-regulated genes encoding ECM are downregulated in Mkl2–/– ES cells and the vasculature of Mkl2–/– embryos. The gene encoding TGFβ2, the predominant TGFβ isoform expressed in vascular smooth muscle cells and embryonic vasculature, is activated directly via binding of an MKL2/SRF protein complex to a conserved CArG box in the TGFβ2 promoter. Moreover, Mkl2–/– ES cells exhibit derangements in cytoskeletal organization, cell adhesion and expression of ECM that are rescued by forced expression of TGFβ2. Taken together, these data demonstrate that MKL2 regulates a conserved TGF-β signaling pathway that is required for angiogenesis and ultimately embryonic survival.
miR-92b regulates Mef2 levels through a negative-feedback circuit during Drosophila muscle development
Authors: Chen Zhimin , Liang Shanshan , Zhao Ying , Han Zhe
Published: August 2012

Mef2 is the key transcription factor for muscle development and differentiation in Drosophila. It activates hundreds of downstream target genes, including itself. Precise control of Mef2 levels is essential for muscle development as different Mef2 protein levels activate distinct sets of muscle genes, but how this is achieved remains unclear. Here, we have identified a novel heart- and muscle-specific microRNA, miR-92b, which is activated by Mef2 and subsequently downregulates Mef2 through binding to its 3′UTR, forming a negative regulatory circuit that fine-tunes the level of Mef2. Deletion of miR-92b caused abnormally high Mef2 expression, leading to muscle defects and lethality. Blocking miR-92b function using microRNA sponge techniques also increased Mef2 levels and caused muscle defects similar to those seen with the miR-92b deletion. Additionally, overexpression of miR-92b reduced Mef2 levels and caused muscle defects similar to those seen in Mef2 RNAi, and Mef2 overexpression led to reversal of these defects. Our results suggest that the negative feedback circuit between miR-92b and Mef2 efficiently maintains the stable expression of both components that is required for homeostasis during Drosophila muscle development.
A zebrafish model of congenital disorders of glycosylation with phosphomannose isomerase deficiency reveals an early opportunity for corrective mannose supplementation
Authors: Chu Jaime , Mir Alexander , Gao Ningguo , Rosa Sabrina , Monson Christopher , Sharma Vandana , Steet Richard , Freeze Hudson H. , Lehrman Mark A. , Sadler Kirsten C.
Published: August 2012

Individuals with congenital disorders of glycosylation (CDG) have recessive mutations in genes required for protein N-glycosylation, resulting in multi-systemic disease. Despite the well-characterized biochemical consequences in these individuals, the underlying cellular defects that contribute to CDG are not well understood. Synthesis of the lipid-linked oligosaccharide (LLO), which serves as the sugar donor for the N-glycosylation of secretory proteins, requires conversion of fructose-6-phosphate to mannose-6-phosphate via the phosphomannose isomerase (MPI) enzyme. Individuals who are deficient in MPI present with bleeding, diarrhea, edema, gastrointestinal bleeding and liver fibrosis. MPI-CDG patients can be treated with oral mannose supplements, which is converted to mannose-6-phosphate through a minor complementary metabolic pathway, restoring protein glycosylation and ameliorating most symptoms, although liver disease continues to progress. Because Mpi deletion in mice causes early embryonic lethality and thus is difficult to study, we used zebrafish to establish a model of MPI-CDG. We used a morpholino to block mpi mRNA translation and established a concentration that consistently yielded 13% residual Mpi enzyme activity at 4 days post-fertilization (dpf), which is within the range of MPI activity detected in fibroblasts from MPI-CDG patients. Fluorophore-assisted carbohydrate electrophoresis detected decreased LLO and N-glycans in mpi morphants. These deficiencies resulted in 50% embryonic lethality by 4 dpf. Multi-systemic abnormalities, including small eyes, dysmorphic jaws, pericardial edema, a small liver and curled tails, occurred in 82% of the surviving larvae. Importantly, these phenotypes could be rescued with mannose supplementation. Thus, parallel processes in fish and humans contribute to the phenotypes caused by Mpi depletion. Interestingly, mannose was only effective if provided prior to 24 hpf. These data provide insight into treatment efficacy and the broader molecular and developmental abnormalities that contribute to disorders associated with defective protein glycosylation.
Serotonin has early, cilia-independent roles inXenopusleft-right patterning
Authors: Vandenberg Laura N. , Lemire Joan M. , Levin Michael
Published: August 2012

Consistent left-right (LR) patterning of the heart and viscera is a crucial part of normal embryogenesis. Because errors of laterality form a common class of birth defects, it is important to understand the molecular mechanisms and stage at which LR asymmetry is initiated. Frog embryos are a system uniquely suited to analysis of the mechanisms involved in orientation of the LR axis because of the many genetic and pharmacological tools available for use and the fate-map and accessibility of early blastomeres. Two major models exist for the origin of LR asymmetry and both implicate pre-nervous serotonergic signaling. In the first, the charged serotonin molecule is instructive for LR patterning; it is redistributed asymmetrically along the LR axis and signals intracellularly on the right side at cleavage stages. A second model suggests that serotonin is a permissive factor required to specify the dorsal region of the embryo containing chiral cilia that generate asymmetric fluid flow during neurulation, a much later process. We performed theory-neutral experiments designed to distinguish between these models. The results uniformly support a role for serotonin in the cleavage-stage embryo, long before the appearance of cilia, in ventral right blastomeres that do not contribute to the ciliated organ.
Unrepairable DNA double-strand breaks that are generated by ionising radiation determine the cell fate of normal human cells
Authors: Noda Asao , Hirai Yuko , Hamasaki Kanya , Mitani Hiroshi , Nakamura Nori , Kodama Yoshiaki
Published: August 2012

After an exposure to ionising radiation, cells can quickly repair damages to their genomes; however, a few unrepairable DNA double-strand breaks (DSBs) emerge in the nucleus in a prolonged culture and perpetuate as long as the culture continues. These DSBs may be retained forever in cells such as non-dividing ageing tissues, which are resistant to apoptosis. We show that such unrepairable DSBs, which had been advocated by the classical Target Theory as the “radiation hit”, are attributable to permanent growth arrest and premature senescence. The unrepairable DSBs build up by repeated irradiation, which accounts for an accumulated dose. Because these DSBs tend to be paired, we propose that the untethered and “torn-off” molecular structures at the broken ends of the DNA result in an alteration of chromatin structure, which protects the ends of the DNA from genomic catastrophe. Such biochemical responses are important for cell survival but may cause gradual tissue malfunction, which could lead to the late effects of radiation exposure. Thus, understanding the biology of unrepairable damages will provide new insights into the long-term effects of radiation.
Mutant p53R273H attenuates the expression of phase 2 detoxifying enzymes and promotes the survival of cells with high ROS levels
Authors: Kalo Eyal , Kogan-Sakin Ira , Solomon Hilla , Bar-Nathan Elad , Shay Moshe , Shetzer Yoav , Dekel Elya , Goldfinger Naomi , Buganim Yossi , Stambolsky Perry , Goldstein Ido , Madar Shalom , Rotter Varda
Published: August 2012

Uncontrolled accumulation of reactive oxygen species (ROS) causes oxidative stress and induces harmful effects. Both high ROS levels and p53 mutations are frequent in human cancer. Mutant p53 forms are known to actively promote malignant growth. However, no mechanistic details are known about the contribution of mutant p53 to excessive ROS in cancer cells. Herein we examined the effect of p53R273H, a commonly occurring mutated p53 form, on the expression of phase 2 ROS detoxifying enzymes, and on the ability of cells to readopt a reducing environment after exposure to oxidative stress. Our data suggest that p53R273H mutant interferes with the normal response of human cells to oxidative stress. We show here that upon oxidative stress mutant p53R273H attenuates the activation and function of NF-E2-related factor 2 (NRF2), a transcription factor that induces antioxidant response. This effect of mutant p53 is manifested by decreased expression of phase 2 detoxifying enzymes NQO1 and HO-1 and high ROS levels. These findings were observed in several human cancer cell lines highlighting the general nature of this phenomenon. The failure of p53R273H mutant-expressing cells to restore a reducing oxidative environment was accompanied by increased survival, a known consequence of mutant p53 expression. These activities are attributable to mutant p53R273H gain of function and may underlie its well-documented oncogenic nature in human cancer.
Deregulated Cdk5 Triggers Aberrant Activation of Cell Cycle Kinases and Phosphatases Inducing Neuronal Death
Authors: Chang Kuei-Hua , Vincent Fabien , Shah Kavita
Published: August 2012

Aberrant activation of cell cycle proteins is believed to play a critical role in Alzheimer's disease (AD) pathogenesis; although, the molecular mechanisms leading to their activation in diseased neurons remain elusive. The goal of this study is to investigate the mechanistic link between Cdk5 deregulation and cell cycle re-activation in Aβ1-42-induced neurotoxicity. Using a chemical genetic approach, we identified Cdc25A, Cdc25B, and Cdc25C as direct Cdk5 substrates in mouse brain lysates. We show that deregulated Cdk5 directly phosphorylates Cdc25A, Cdc25B, and Cdc25C at multiple sites, which not only increases their phosphatase activities but also facilitates their release from 14-3-3 inhibitory binding. Cdc25A, Cdc25B, and Cdc25C in turn activate Cdk1, Cdk2 and Cdk4 kinases causing neuronal death. Selective inhibition of Cdk5 abrogates Cdc25 and Cdk activations in Aβ1-42-treated neurons. Similarly, phosphorylation-resistant mutants of Cdc25 at Cdk5 sites are defective in activating Cdk1, Cdk2, and Cdk4 in Aβ1-42-treated primary cortical neurons, underlining Cdk5-mediated Cdc25 activation as a major mechanism causing Cdks activation in AD pathogenesis. These results were further confirmed in human clinical samples which displayed higher Cdc25A, Cdc25B and Cdc25C activities which were coincident with increased Cdk5 activity in AD samples, as compared to age-matched controls. Inhibition of Cdk5 confers the highest neuroprotection against Aβ1-42 toxicity, while inhibition of Cdc25 was partially neuroprotective, further emphasizing a decisive role of Cdk5 deregulation in cell cycle-driven AD neuronal death.