Improved efficacy of FKRP AAV gene therapy by combination with ribitol treatment for LGMD2I.

Mutations in the fukutin-related protein (FKRP) gene cause dystroglycanopathy, with disease severity ranging from mild LGMD2I to severe congenital muscular dystrophy. Recently, considerable progress has been made in developing experimental therapies, with adeno-associated virus (AAV) gene therapy and ribitol treatment demonstrating significant therapeutic effect. However, each treatment has its strengths and weaknesses. AAV gene therapy can achieve normal levels of transgene expression, but it requires high doses, with toxicity concerns and variable distribution. Ribitol relies on residual FKRP function and restores limited levels of matriglycan. We hypothesized that these two treatments can work synergistically to offer an optimized therapy with efficacy and safety unmatched by each treatment alone. The most effective treatment is the combination of high-dose (5e-13 vg/kg) AAV-FKRP with ribitol, whereas low dose (1e-13 vg/kg) AAV-FKRP combined with ribitol showed a 22.6% increase in positive matriglycan fibers and the greater improvement in pathology when compared to low-dose AAV-FKRP alone. Together, our results support the potential benefits of combining ribitol with AAV gene therapy for treating FKRP-related muscular dystrophy. The fact that ribitol is a metabolite in nature and has already been tested in animal models and clinical trials in humans without severe side effects provides a safety profile for it to be trialed in combination with AAV gene therapy.

Pharmacological Treatments and Therapeutic Targets in Muscle Dystrophies Generated by Alterations in Dystrophin-Associated Proteins.

Muscular dystrophies (MDs) are a heterogeneous group of diseases of genetic origin characterized by progressive skeletal muscle degeneration and weakness. There are several types of MDs, varying in terms of age of onset, severity, and pattern of the affected muscles. However, all of them worsen over time, and many patients will eventually lose their ability to walk. In addition to skeletal muscle effects, patients with MDs may present cardiac and respiratory disorders, generating complications that could lead to death. Interdisciplinary management is required to improve the surveillance and quality of life of patients with an MD. At present, pharmacological therapy is only available for Duchene muscular dystrophy (DMD)-the most common type of MD-and is mainly based on the use of corticosteroids. Other MDs caused by alterations in dystrophin-associated proteins (DAPs) are less frequent but represent an important group within these diseases. Pharmacological alternatives with clinical potential in patients with MDs and other proteins associated with dystrophin have been scarcely explored. This review focuses on drugs and molecules that have shown beneficial effects, mainly in experimental models involving alterations in DAPs. The mechanisms associated with the effects leading to promising results regarding the recovery or maintenance of muscle strength and reduction in fibrosis in the less-common MDs (i.e., with respect to DMD) are explored, and other therapeutic targets that could contribute to maintaining the homeostasis of muscle fibers, involving different pathways, such as calcium regulation, hypertrophy, and maintenance of satellite cell function, are also examined. It is possible that some of the drugs explored here could be used to affordably improve the muscular function of patients until a definitive treatment for MDs is developed.

Clinical spectrum and genetic variations of LMNA-related muscular dystrophies in a large cohort of Chinese patients.

BACKGROUND: LMNA-related muscular dystrophy is caused by mutations in LMNA gene. We aimed to identify genetic variations and clinical features in a large cohort of Chinese patients with LMNA mutations in an attempt to establish genotype-phenotype correlation. METHODS: The clinical presentations of patients with LMNA-related muscular dystrophy were recorded using retrospective and prospective cohort study. LMNA mutation analysis was performed by Sanger sequencing or next-generation sequencing. Mosaicism was detected by personal genome machine amplicon deep sequencing for mosaicism. RESULTS: Eighty-four patients were identified to harbour LMNA mutations. Forty-one of those were diagnosed with LMNA-related congenital muscular dystrophy (L-CMD), 32 with Emery-Dreifuss muscular dystrophy (EDMD) and 11 with limb-girdle muscular dystrophy type 1B (LGMD1B). We identified 21 novel and 29 known LMNA mutations. Two frequent mutations were identified: c.745C>T and c.1357C>T. A correlation between the location of mutation and the clinical phenotype was observed: mutations affecting the head and coil 2A domains mainly occurred in L-CMD, while the coil 2B and Ig-like domains mainly related to EDMD and LGMD1B. We found somatic mosaicism in one parent of four probands. Muscle biopsies revealed 11 of 20 biopsied L-CMD exhibited inflammatory changes, and muscle cell ultrastructure showed abnormal nuclear morphology. CONCLUSIONS: Our detailed clinical and genetic analysis of 84 patients with LMNA-related muscular dystrophy expands clinical spectrum and broadens genetic variations caused by LMNA mutations. We identified 21 novel and 29 known LMNA mutations and found two frequent mutations. A correlation between the location of mutation and the clinical severity was observed. Preliminary data suggested that low-dose corticosteroid treatment may be effective.

A new patient-derived iPSC model for dystroglycanopathies validates a compound that increases glycosylation of α-dystroglycan.

Dystroglycan, an extracellular matrix receptor, has essential functions in various tissues. Loss of α-dystroglycan-laminin interaction due to defective glycosylation of α-dystroglycan underlies a group of congenital muscular dystrophies often associated with brain malformations, referred to as dystroglycanopathies. The lack of isogenic human dystroglycanopathy cell models has limited our ability to test potential drugs in a human- and neural-specific context. Here, we generated induced pluripotent stem cells (iPSCs) from a severe dystroglycanopathy patient with homozygous FKRP (fukutin-related protein gene) mutation. We showed that CRISPR/Cas9-mediated gene correction of FKRP restored glycosylation of α-dystroglycan in iPSC-derived cortical neurons, whereas targeted gene mutation of FKRP in wild-type cells disrupted this glycosylation. In parallel, we screened 31,954 small molecule compounds using a mouse myoblast line for increased glycosylation of α-dystroglycan. Using human FKRP-iPSC-derived neural cells for hit validation, we demonstrated that compound 4-(4-bromophenyl)-6-ethylsulfanyl-2-oxo-3,4-dihydro-1H-pyridine-5-carbonitrile (4BPPNit) significantly augmented glycosylation of α-dystroglycan, in part through upregulation of LARGE1 glycosyltransferase gene expression. Together, isogenic human iPSC-derived cells represent a valuable platform for facilitating dystroglycanopathy drug discovery and therapeutic development.

The elusive promise of myostatin inhibition for muscular dystrophy.

PURPOSE OF REVIEW: Recent terminations of clinical trials of myostatin inhibitors in muscular dystrophy have raised questions about the predictiveness of mouse models for this therapeutic strategy. RECENT FINDINGS: A variety of myostatin inhibitors have been developed for preclinical and clinical studies. These inhibitors have ameliorated the phenotype of many but not all mouse models of muscular dystrophy. However, randomized double-blinded placebo controlled trials in both pediatric and adult muscular dystrophies have, as of yet, not demonstrated functional improvement. SUMMARY: The present article will review the preclinical promise of myostatin inhibitors, the clinical trial experience to date of these inhibitors in muscular dystrophy, and the potential reasons for the lack of observed translation.

Epilepsy in LAMA2-related muscular dystrophy: An electro-clinico-radiological characterization.

OBJECTIVE: To delineate the epileptic phenotype of LAMA2-related muscular dystrophy (MD) and correlate it with the neuroradiological and muscle biopsy findings, as well as the functional motor phenotype. METHODS: Clinical, electrophysiological, neuroradiological, and histopathological data of 25 patients with diagnosis of LAMA2-related MD were analyzed. RESULTS: Epilepsy occurred in 36% of patients with LAMA2-related MD. Mean age at first seizure was 8 years. The most common presenting seizure type was focal-onset seizures with or without impaired awareness. Visual aura and autonomic signs, including vomiting, were frequently reported. Despite a certain degree of variability, bilateral occipital or temporo-occipital epileptiform abnormalities were by far the most commonly observed. Refractory epilepsy was found in 75% of these patients. Epilepsy in LAMA2-related MD was significantly more prevalent in those patients in whom the cortical malformations were more extensive. In contrast, the occurrence of epilepsy was not found to be associated with the patients' motor ability, the size of their white matter abnormalities, or the amount of residual merosin expressed on muscle. SIGNIFICANCE: The epileptic phenotype of LAMA2-related MD is characterized by focal seizures with prominent visual and autonomic features associated with EEG abnormalities that predominate in the posterior quadrants. A consistent correlation between epileptic phenotype and neuroimaging was identified, suggesting that the extension of the polymicrogyria may serve as a predictor of epilepsy occurrence.

Skin damage in a patient with lipid storage myopathy with a novel ETFDH mutation responsive to riboflavin.

Background: Recessive mutations in ETFDH gene have been associated with Multiple Acyl-CoA dehydrogenase deficiency (MADD). The late-onset MADD is often muscle involved, presenting with lipid storage myopathy (LSM). The symptoms of LSM were heterogeneous and definite diagnosis of this disease depends on the pathology and gene test.Methods: Neurological examination, muscle biopsy, and MRI examinations were performed in a patient with a novel missense ETFDH mutation.Results: We describe a patient with lipid storage myopathy complicated with skin damage. In addition, the next generation revealed a novel missense mutation (c.970G > T, p.Val324Leu) in exon 8, which was predicted to be a disease-causing mutation by Mutation-taster, and destroy the function of the protein by Sift.Conclusion: These findings expand the known mutational spectrum of ETFDH and phenotype of MADD.

Cytidine Diphosphate-Ribitol Analysis for Diagnostics and Treatment Monitoring of Cytidine Diphosphate-l-Ribitol Pyrophosphorylase A Muscular Dystrophy.

BACKGROUND: Many muscular dystrophies currently remain untreatable. Recently, dietary ribitol has been suggested as a treatment for cytidine diphosphate (CDP)-l-ribitol pyrophosphorylase A (CRPPA, ISPD), fukutin (FKTN), and fukutin-related protein (FKRP) myopathy, by raising CDP-ribitol concentrations. Thus, to facilitate fast diagnosis, treatment development, and treatment monitoring, sensitive detection of CDP-ribitol is required. METHODS: An LC-MS method was optimized for CDP-ribitol in human and mice cells and tissues. RESULTS: CDP-ribitol, the product of CRPPA, was detected in all major human and mouse tissues. Moreover, CDP-ribitol concentrations were reduced in fibroblasts and skeletal muscle biopsies from patients with CRPPA myopathy, showing that CDP-ribitol could serve as a diagnostic marker to identify patients with CRPPA with severe Walker-Warburg syndrome and mild limb-girdle muscular dystrophy (LGMD) phenotypes. A screen for potentially therapeutic monosaccharides revealed that ribose, in addition to ribitol, restored CDP-ribitol concentrations and the associated O-glycosylation defect of α-dystroglycan. As the effect occurred in a mutation-dependent manner, we established a CDP-ribitol blood test to facilitate diagnosis and predict individualized treatment response. Ex vivo incubation of blood cells with ribose or ribitol restored CDP-ribitol concentrations in a patient with CRPPA LGMD. CONCLUSIONS: Sensitive detection of CDP-ribitol with LC-MS allows fast diagnosis of patients with severe and mild CRPPA myopathy. Ribose offers a readily testable dietary therapy for CRPPA myopathy, with possible applicability for patients with FKRP and FKTN myopathy. Evaluation of CDP-ribitol in blood is a promising tool for the evaluation and monitoring of dietary therapies for CRPPA myopathy in a patient-specific manner.

Membrane Stabilization by Modified Steroid Offers a Potential Therapy for Muscular Dystrophy Due to Dysferlin Deficit.

Mutations of the DYSF gene leading to reduced dysferlin protein level causes limb girdle muscular dystrophy type 2B (LGMD2B). Dysferlin facilitates sarcolemmal membrane repair in healthy myofibers, thus its deficit compromises myofiber repair and leads to chronic muscle inflammation. An experimental therapeutic approach for LGMD2B is to protect damage or improve repair of myofiber sarcolemma. Here, we compared the effects of prednisolone and vamorolone (a dissociative steroid; VBP15) on dysferlin-deficient myofiber repair. Vamorolone, but not prednisolone, stabilized dysferlin-deficient muscle cell membrane and improved repair of dysferlin-deficient mouse (B6A/J) myofibers injured by focal sarcolemmal damage, eccentric contraction-induced injury or injury due to spontaneous in vivo activity. Vamorolone decreased sarcolemmal lipid mobility, increased muscle strength, and decreased late-stage myofiber loss due to adipogenic infiltration. In contrast, the conventional glucocorticoid prednisolone failed to stabilize dysferlin deficient muscle cell membrane or improve repair of dysferlinopathic patient myoblasts and mouse myofibers. Instead, prednisolone treatment increased muscle weakness and myofiber atrophy in B6A/J mice-findings that correlate with reports of prednisolone worsening symptoms of LGMD2B patients. Our findings showing improved cellular and pre-clinical efficacy of vamorolone compared to prednisolone and better safety profile of vamorolone indicates the suitability of vamorolone for clinical trials in LGMD2B.

Renin-angiotensin-aldosterone system inhibitors improve membrane stability and change gene-expression profiles in dystrophic skeletal muscles.

Angiotensin-converting enzyme inhibitors (ACEi) and mineralocorticoid receptor (MR) antagonists are FDA-approved drugs that inhibit the renin-angiotensin-aldosterone system (RAAS) and are used to treat heart failure. Combined treatment with the ACEi lisinopril and the nonspecific MR antagonist spironolactone surprisingly improves skeletal muscle, in addition to heart function and pathology in a Duchenne muscular dystrophy (DMD) mouse model. We recently demonstrated that MR is present in all limb and respiratory muscles and functions as a steroid hormone receptor in differentiated normal human skeletal muscle fibers. The goals of the current study were to begin to define cellular and molecular mechanisms mediating the skeletal muscle efficacy of RAAS inhibitor treatment. We also compared molecular changes resulting from RAAS inhibition with those resulting from the current DMD standard-of-care glucocorticoid treatment. Direct assessment of muscle membrane integrity demonstrated improvement in dystrophic mice treated with lisinopril and spironolactone compared with untreated mice. Short-term treatments of dystrophic mice with specific and nonspecific MR antagonists combined with lisinopril led to overlapping gene-expression profiles with beneficial regulation of metabolic processes and decreased inflammatory gene expression. Glucocorticoids increased apoptotic, proteolytic, and chemokine gene expression that was not changed by RAAS inhibitors in dystrophic mice. Microarray data identified potential genes that may underlie RAAS inhibitor treatment efficacy and the side effects of glucocorticoids. Direct effects of RAAS inhibitors on membrane integrity also contribute to improved pathology of dystrophic muscles. Together, these data will inform clinical development of MR antagonists for treating skeletal muscles in DMD.

[Skeletal muscle stem cell.]

Adult skeletal muscle has its own stem cell population known as satellite cells. After muscle injury, quiescent satellite cells are activated and then proliferate and differentiate into mature skeletal muscle to ensure that muscle function is recovered. In our screen for myocyte differentiation-promoting factors, we noted markedly elevated expression of granulocyte-colony stimulating factor receptor(G-CSFR, encoded by csf3r)in the skeletal muscle developing area. Furthermore, G-CSFR was transiently expressed in regenerating myocytes of adult injured skeletal muscle, and extrinsic G-CSF supported short-term and long-term muscle regeneration in mouse model of skeletal muscle injury.

Laminin-111 improves muscle repair in a mouse model of merosin-deficient congenital muscular dystrophy.

Merosin-deficient congenital muscular dystrophy type 1A (MDC1A) is a severe and fatal muscle-wasting disease with no cure. MDC1A patients and the dy(W-/-) mouse model exhibit severe muscle weakness, demyelinating neuropathy, failed muscle regeneration and premature death. We have recently shown that laminin-111, a form of laminin found in embryonic skeletal muscle, can substitute for the loss of laminin-211/221 and prevent muscle disease progression in the dy(W-/-) mouse model. What is unclear from these studies is whether laminin-111 can restore failed regeneration to laminin-α2-deficient muscle. To investigate the potential of laminin-111 protein therapy to improve muscle regeneration, laminin-111 or phosphate-buffered saline-treated laminin-α2-deficient muscle was damaged with cardiotoxin and muscle regeneration quantified. Our results show laminin-111 treatment promoted an increase in myofiber size and number, and an increased expression of α7ß1 integrin, Pax7, myogenin and embryonic myosin heavy chain, indicating a restoration of the muscle regenerative program. Together, our results show laminin-111 restores muscle regeneration to laminin-α2-deficient muscle and further supports laminin-111 protein as a therapy for the treatment of MDC1A.

NIM811, a cyclophilin inhibitor without immunosuppressive activity, is beneficial in collagen VI congenital muscular dystrophy models.

Ullrich congenital muscular dystrophy (UCMD) and Bethlem myopathy (BM) are inherited muscle diseases due to mutations in the genes encoding the extracellular matrix protein collagen (Col) VI. Opening of the cyclosporin A-sensitive mitochondrial permeability transition pore (PTP) is a causative event in disease pathogenesis, and a potential target for therapy. Here, we have tested the effect of N-methyl-4-isoleucine-cyclosporin (NIM811), a non-immunosuppressive cyclophilin inhibitor, in a zebrafish model of ColVI myopathy obtained by deletion of the N-terminal region of the ColVI α1 triple helical domain, a common mutation of UCMD. Treatment with antisense morpholino sequences targeting col6a1 exon 9 at the 1-4 cell stage (within 1 h post fertilization, hpf) caused severe ultrastructural and motor abnormalities as assessed by electron and fluorescence microscopy, birefringence, spontaneous coiling events and touch-evoked responses measured at 24-48 hpf. Structural and functional abnormalities were largely prevented when NIM811--which proved significantly more effective than cyclosporin A--was administered at 21 hpf, while FK506 was ineffective. Beneficial effects of NIM811 were also detected (i) in primary muscle-derived cell cultures from UCMD and BM patients, where the typical mitochondrial alterations and depolarizing response to rotenone and oligomycin were significantly reduced; and (ii) in the Col6a1(-/-) myopathic mouse model, where apoptosis was prevented and muscle strength was increased. Since the PTP of zebrafish shares its key regulatory features with the mammalian pore, our results suggest that early treatment with NIM811 should be tested as a potential therapy for UCMD and BM.

In vivo treatment with the NF-κB inhibitor ursodeoxycholic acid (UDCA) improves tension development in the isolated mdx costal diaphragm.

INTRODUCTION: Previous experiments have indicated that in vivo administration of ursodeoxycholic acid (UDCA) inhibits nuclear NF-κB activation and has beneficial effects on the structure and function of dystrophic (mdx) muscle. We examined the effect of UDCA on tension development in dystrophic muscle. METHODS: Isometric tension development was examined in costal diaphragms that were freshly isolated from vehicle and UDCA treated mdx mice. Percent recovery scores were obtained by directly comparing these measurements to those obtained from age-matched nondystrophic mice. RESULTS: Vehicle treated mdx mice exhibited significantly reduced optimal muscle lengths (lo ) and specific twitch and tetanic tensions compared with age-matched nondystrophic mice. UDCA treated preparations exhibited significantly improved tension development with a 33% recovery score. CONCLUSIONS: Because UDCA is used in treating certain clinical disorders, these results provide a rationale for human clinical trials using this and related drugs for treatment of Duchenne and related muscular dystrophies.

Clinical trial network for the promotion of clinical research for rare diseases in Japan: muscular dystrophy clinical trial network.

BACKGROUND: Duchenne muscular dystrophy (DMD) is the most commonly inherited neuromuscular disease. Therapeutic agents for the treatment of rare disease, namely "orphan drugs", have recently drawn the attention of researchers and pharmaceutical companies. To ensure the successful conduction of clinical trials to evaluate novel treatments for patients with rare diseases, an appropriate infrastructure is needed. One of the effective solutions for the lack of infrastructure is to establish a network of rare diseases. METHODS: To accomplish the conduction of clinical trials in Japan, the Muscular dystrophy clinical trial network (MDCTN) was established by the clinical research group for muscular dystrophy, including the National Center of Neurology and Psychiatry, as well as national and university hospitals, all which have a long-standing history of research cooperation. RESULTS: Thirty-one medical institutions (17 national hospital organizations, 10 university hospitals, 1 national center, 2 public hospitals, and 1 private hospital) belong to this network and collaborate to facilitate clinical trials. The Care and Treatment Site Registry (CTSR) calculates and reports the proportion of patients with neuromuscular diseases in the cooperating sites. In total, there are 5,589 patients with neuromuscular diseases in Japan and the proportion of patients with each disease is as follows: DMD, 29 %; myotonic dystrophy type 1, 23 %; limb girdle muscular dystrophy, 11 %; Becker muscular dystrophy, 10 %. We work jointly to share updated health care information and standardized evaluations of clinical outcomes as well. The collaboration with the patient registry (CTSR), allows the MDCTN to recruit DMD participants with specific mutations and conditions, in a remarkably short period of time. CONCLUSION: Counting with a network that operates at a national level is important to address the corresponding national issues. Thus, our network will be able to contribute with international research activity, which can lead to an improvement of neuromuscular disease treatment in Japan.

The Role of Leukemia Inhibitory Factor Receptor Signaling in Skeletal Muscle Growth, Injury and Disease.

Cytokines are an incredibly diverse group of secreted proteins with equally diverse functions. The actions of cytokines are mediated by the unique and sometimes overlapping receptors to which the soluble ligands bind. Classified within the interleukin-6 family of cytokines are leukemia inhibitory factor (LIF), oncostatin-M (OSM), cardiotrophin-1 (CT-1) and ciliary neurotrophic factor (CNTF). These cytokines all bind to the leukemia inhibitory factor receptor (LIFR) and gp130, and in some cases an additional receptor subunit, leading to activation of downstream kinases and transcriptional activators. LIFR is expressed on a broad range of cell types and can generate pleiotropic effects. In the context of skeletal muscle physiology, these cytokines have been shown to exert effects on motor neurons, inflammatory and muscle cells. From isolated cells through to whole organisms, manipulations of LIFR signaling cytokines have a wide range of outcomes influencing muscle cell growth, myogenic differentiation, response to exercise, metabolism, neural innervation and recruitment of inflammatory cells to sites of muscle injury. This article will discuss the shared and distinct processes that LIFR cytokines regulate in a variety of experimental models with the common theme of skeletal muscle physiology.

Small molecules enhance functional O-mannosylation of Alpha-dystroglycan.

Alpha-dystroglycan (α-DG), a highly glycosylated receptor for extracellular matrix proteins, plays a critical role in many biological processes. Hypoglycosylation of α-DG results in various types of muscular dystrophies and is also highly associated with progression of majority of cancers. Currently, there are no effective treatments for those devastating diseases. Enhancing functional O-mannosyl glycans (FOG) of α-DG on the cell surfaces is a potential approach to address this unmet challenge. Based on the hypothesis that the cells can up-regulate FOG of α-DG in response to certain chemical stimuli, we developed a cell-based high-throughput screening (HTS) platform for searching chemical enhancers of FOG of α-DG from a large chemical library with 364,168 compounds. Sequential validation of the hits from a primary screening campaign and chemical works led to identification of a cluster of compounds that positively modulate FOG of α-DG on various cell surfaces including patient-derived myoblasts. These compounds enhance FOG of α-DG by almost ten folds, which provide us powerful tools for O-mannosylation studies and potential starting points for the development of drug to treat dystroglycanopathy.

Chronic oral administration of Ang-(1-7) improves skeletal muscle, autonomic and locomotor phenotypes in muscular dystrophy.

Muscular dystrophies are a group of heterogeneous genetic disorders that cause progressive muscle weakness and wasting, dilated cardiomyopathy and early mortality. There are different types of muscular dystrophies with varying aetiologies but they all have a common hallmark of myofibre degeneration, atrophy and decreased mobility. Mutation in Sgcd (sarcoglycan-δ), a subunit of dystrophin glycoprotein complex, causes LGMD2F (limb girdle muscular dystrophy 2F). Previously, we have reported that Sgcd-deficient (Sgcd-/-) mice exhibit AngII (angiotensin II)-induced autonomic and skeletal muscle dysfunction at a young age, which contributes to onset of dilated cardiomyopathy and mortality at older ages. Two counter-regulatory RAS (renin-angiotensin system) pathways have been identified: deleterious actions of AngII acting on the AT1R (AngII type 1 receptor) compared with the protective actions of Ang-(1-7) [angiotensin-(1-7)] acting on the receptor Mas. We propose that the balance between the AngII/AT1R and Ang-(1-7)/Mas axes is disturbed in Sgcd-/- mice. Control C57BL/6J and Sgcd-/- mice were treated with Ang-(1-7) included in hydroxypropyl ß-cyclodextrin (in drinking water) for 8-9 weeks beginning at 3 weeks of age. Ang-(1-7) treatment restored the AngII/AT1R compared with Ang-(1-7)/Mas balance, decreased oxidative stress and fibrosis in skeletal muscle, increased locomotor activity, and prevented autonomic dysfunction without lowering blood pressure in Sgcd-/- mice. Our results suggest that correcting the early autonomic dysregulation by administering Ang-(1-7) or enhancing its endogenous production may provide a novel therapeutic approach in muscular dystrophy.

Epigenetic regulation of skeletal muscle development and differentiation.

Skeletal muscle cells have served as a paradigm for understanding mechanisms leading to cellular differentiation. Formation of skeletal muscle involves a series of steps in which cells are committed towards the myogenic lineage, undergo expansion to give rise to myoblasts that differentiate into multinucleated myotubes, and mature to form adult muscle fibers. The commitment, proliferation, and differentiation of progenitor cells involve both genetic and epigenetic changes that culminate in alterations in gene expression. Members of the Myogenic regulatory factor (MRF), as well as the Myocyte Enhancer Factor (MEF2) families control distinct steps of skeletal muscle proliferation and differentiation. In addition, -growing evidence indicates that chromatin modifying enzymes and remodeling complexes epigenetically reprogram muscle promoters at various stages that preclude or promote MRF and MEF2 activites. Among these, histone deacetylases (HDACs), histone acetyltransferases (HATs), histone methyltransferases (HMTs) and SWI/SNF complexes alter chromatin structure through post-translational modifications to impact MRF and MEF2 activities. With such new and emerging knowledge, we are beginning to develop a true molecular understanding of the mechanisms by which skeletal muscle development and differentiation is regulated. Elucidation of the mechanisms by which epigenetic regulators control myogenesis will likely provide a new foundation for the development of novel therapeutic drugs for muscle dystrophies, ageing-related regeneration defects that occur due to altered proliferation and differentiation, and other malignancies.