Long-read single-molecule maps of the functional methylome.

We report on the development of a methylation analysis workflow for optical detection of fluorescent methylation profiles along chromosomal DNA molecules. In combination with Bionano Genomics genome mapping technology, these profiles provide a hybrid genetic/epigenetic genome-wide map composed of DNA molecules spanning hundreds of kilobase pairs. The method provides kilobase pair-scale genomic methylation patterns comparable to whole-genome bisulfite sequencing (WGBS) along genes and regulatory elements. These long single-molecule reads allow for methylation variation calling and analysis of large structural aberrations such as pathogenic macrosatellite arrays not accessible to single-cell second-generation sequencing. The method is applied here to study facioscapulohumeral muscular dystrophy (FSHD), simultaneously recording the haplotype, copy number, and methylation status of the disease-associated, highly repetitive locus on Chromosome 4q.

Mss51 deletion increases endurance and ameliorates histopathology in the mdx mouse model of Duchenne muscular dystrophy.

Mitochondrial derangement is an important contributor to the pathophysiology of muscular dystrophies and may be among the earliest cellular deficits. We have previously shown that disruption of Mss51, a mammalian skeletal muscle protein that localizes to the mitochondria, results in enhanced muscle oxygen consumption rate, increased endurance capacity, and improved limb muscle strength in mice with wildtype background. Here, we investigate whether Mss51 deletion in the mdx murine model of Duchenne muscular dystrophy (mdx-Mss51 KO) counteracts the muscle pathology and mitochondrial irregularities observed in mdx mice. We found that mdx-Mss51 KO mice had increased myofiber oxygen consumption rates and an amelioration of muscle histopathology compared to mdx counterparts. This corresponded with greater treadmill endurance and less percent fatigue in muscle physiology, but no improvement in forelimb grip strength or limb muscle force production. These findings suggest that although Mss51 deletion ameliorates the skeletal muscle mitochondrial respiration defects in mdx and improves fatigue resistance in vivo, the lack of improvement in force production suggests that this target alone may be insufficient for a therapeutic effect.

Home-based gait analysis as an exploratory endpoint during a multicenter phase 1 trial in limb girdle muscular dystrophy type R2 and facioscapulohumeral muscular dystrophy.

INTRODUCTION/AIMS: Limb girdle muscular dystrophy type 2B (LGMDR2) and facioscapulohumeral muscular dystrophy (FSHD) are genetic muscular dystrophies with an increasing number of potential therapeutic approaches. The aim of this study is to report the data of exploratory digital outcomes extracted from wearable magneto-inertial sensors used in a non-controlled environment for ambulant patients with FSHD and LGMDR2 in a short-term, multicenter clinical study. METHODS: Digital outcomes (stride length, stride speed, and walk parameters in a non-controlled environment) were used as exploratory outcomes in the open-label study ATYR1940-C-004 in ambulant patients during the 3 mo of ATYR1940 treatment and 1 mo of follow-up. Activity and gait variables were calculated from the data recorded in 30-day sub-periods using the sensors. For each sub-period, activity and gait parameters were compared between FSHD and LGMDR2 patients. Change from baseline over the 4-mo study period was assessed. RESULTS: Ten patients (5 FSHD, 5 LGMDR2) were ambulant and compliant for analysis. Gait parameters, but not activity variables, were significantly lower in LGMDR2 compared to FSHD patients at baseline. Longitudinal analyses showed a slight but significant decrease in stride speed at month 4 for all subjects. Activity variables such as total number of strides per day were highly variable from month to month in individual patients, and no visit effects were found for this variable. DISCUSSION: The present study suggests that home-recorded stride speed constitutes a precise and sensitive outcome in ambulant patients with FSHD and LGMDR2.

Quantitative muscle analysis in facioscapulohumeral muscular dystrophy using whole-body fat-referenced MRI: Protocol development, multicenter feasibility, and repeatability.

INTRODUCTION/AIMS: Functional performance tests are the gold standard to assess disease progression and treatment effects in neuromuscular disorders. These tests can be confounded by motivation, pain, fatigue, and learning effects, increasing variability and decreasing sensitivity to disease progression, limiting efficacy assessment in clinical trials with small sample sizes. We aimed to develop and validate a quantitative and objective method to measure skeletal muscle volume and fat content based on whole-body fat-referenced magnetic resonance imaging (MRI) for use in multisite clinical trials. METHODS: Subjects aged 18 to 65 years, genetically confirmed facioscapulohumeral muscular dystrophy 1 (FSHD1), clinical severity 2 to 4 (Ricci's scale, range 0-5), were enrolled at six sites and imaged twice 4-12 weeks apart with T1-weighted two-point Dixon MRI covering the torso and upper and lower extremities. Thirty-six muscles were volumetrically segmented using semi-automatic multi-atlas-based segmentation. Muscle fat fraction (MFF), muscle fat infiltration (MFI), and lean muscle volume (LMV) were quantified for each muscle using fat-referenced quantification. RESULTS: Seventeen patients (mean age ± SD, 49.4 years ±13.02; 12 men) were enrolled. Within-patient SD ranged from 1.00% to 3.51% for MFF and 0.40% to 1.48% for MFI in individual muscles. For LMV, coefficients of variation ranged from 2.7% to 11.7%. For the composite score average of all muscles, observed SDs were 0.70% and 0.32% for MFF and MFI, respectively; composite LMV coefficient of variation was 2.0%. DISCUSSION: We developed and validated a method for measuring skeletal muscle volume and fat content for use in multisite clinical trials of neuromuscular disorders.

Randomized phase 2 study of ACE-083, a muscle-promoting agent, in facioscapulohumeral muscular dystrophy.

INTRODUCTION/AIMS: Facioscapulohumeral muscular dystrophy (FSHD) is a slowly progressive muscular dystrophy without approved therapies. In this study we evaluated whether locally acting ACE-083 could safely increase muscle volume and improve functional outcomes in adults with FSHD. METHODS: Participants were at least 18 years old and had FSHD1/FSHD2. Part 1 was open label, ascending dose, assessing safety and tolerability (primary objective). Part 2 was randomized, double-blind for 6 months, evaluating ACE-083240 mg/muscle vs placebo injected bilaterally every 3 weeks in the biceps brachii (BB) or tibialis anterior (TA) muscles, followed by 6 months of open label. Magnetic resonance imaging measures included total muscle volume (TMV; primary objective), fat fraction (FF), and contractile muscle volume (CMV). Functional measures included 6-minute walk test, 10-meter walk/run, and 4-stair climb (TA group), and performance of upper limb midlevel/elbow score (BB group). Strength, patient-reported outcomes (PROs), and safety were also evaluated. RESULTS: Parts 1 and 2 enrolled 37 and 58 participants, respectively. Among 55 participants evaluable in Part 2, the least-squares mean (90% confidence interval, analysis of covariance) treatment difference for TMV was 16.4% (9.8%-23.0%) in the BB group (P < .0001) and 9.5% (3.2%-15.9%) in the TA group (P = .01). CMV increased significantly in the BB and TA groups and FF decreased in the TA group. There were no consistent improvements in functional or PRO measures in either group. The most common adverse events were mild or moderate injection-site reactions. DISCUSSION: Significant increases in TMV with ACE-083 vs placebo did not result in consistent functional or PRO improvements with up to 12 months of treatment.

Safety, tolerability, and pharmacokinetics of casimersen in patients with Duchenne muscular dystrophy amenable to exon 45 skipping: A randomized, double-blind, placebo-controlled, dose-titration trial.

INTRODUCTION/AIMS: Duchenne muscular dystrophy (DMD) is caused by mutations in the DMD gene resulting in the absence of dystrophin. Casimersen is a phosphorodiamidate morpholino oligomer designed to bypass frameshift DMD mutations and produce internally truncated, yet functional, dystrophin protein in patients amenable to exon 45 skipping. Our primary study objective was to evaluate safety and tolerability of casimersen; the secondary objective was to characterize the plasma pharmacokinetics. METHODS: This multicenter, phase 1/2 trial enrolled 12 participants (aged 7-21 years, who had limited ambulation or were nonambulatory) and comprised a 12-week, double-blind dose titration, then an open-label extension for up to 132 weeks. During dose titration, participants were randomized 2:1 to weekly casimersen infusions at escalating doses of 4, 10, 20, and 30 mg/kg (≥2 weeks per dose), or placebo. RESULTS: Participants received casimersen for a mean 139.6 weeks. Treatment-emergent adverse events (TEAEs) occurred in all casimersen- and placebo-treated participants and were mostly mild (over 91.4%) and unrelated to casimersen or its dose. There were no deaths, dose reductions, abnormalities in laboratory parameters or vital signs, or casimersen-related serious AEs. Casimersen plasma concentration increased with dose and declined similarly for all dose levels over 24 hours postinfusion. All pharmacokinetic parameters were similar at weeks 7 and 60. DISCUSSION: Casimersen was well tolerated in participants with DMD amenable to exon 45 skipping. Most TEAEs were mild, nonserious, and unrelated to casimersen. Plasma exposure was dose proportional with no suggestion of plasma accumulation. These results support further studies of casimersen in this population.

A phase Ib/IIa, open-label, multiple ascending-dose trial of domagrozumab in fukutin-related protein limb-girdle muscular dystrophy.

INTRODUCTION/AIMS: In this study we report the results of a phase Ib/IIa, open-label, multiple ascending-dose trial of domagrozumab, a myostatin inhibitor, in patients with fukutin-related protein (FKRP)-associated limb-girdle muscular dystrophy. METHODS: Nineteen patients were enrolled and assigned to one of three dosing arms (5, 20, or 40 mg/kg every 4 weeks). After 32 weeks of treatment, participants receiving the lowest dose were switched to the highest dose (40 mg/kg) for an additional 32 weeks. An extension study was also conducted. The primary endpoints were safety and tolerability. Secondary endpoints included muscle strength, timed function testing, pulmonary function, lean body mass, pharmacokinetics, and pharmacodynamics. As an exploratory outcome, muscle fat fractions were derived from whole-body magnetic resonance images. RESULTS: Serum concentrations of domagrozumab increased in a dose-dependent manner and modest levels of myostatin inhibition were observed in both serum and muscle tissue. The most frequently occurring adverse events were injuries secondary to falls. There were no significant between-group differences in the strength, functional, or imaging outcomes studied. DISCUSSION: We conclude that, although domagrozumab was safe in patients in limb-girdle muscular dystrophy type 2I/R9, there was no clear evidence supporting its efficacy in improving muscle strength or function.

Diabetes, metformin and cancer risk in myotonic dystrophy type I.

Myotonic dystrophy type I (DM1) is an autosomal dominant multisystem disorder characterized by myotonia and muscle weakness. Type 2 diabetes (T2D) and cancer have been shown to be part of the DM1 phenotype. Metformin, a well-established agent for the management of T2D, is thought to have cancer-preventive effects in the general population. In our study, we aimed to assess the association between T2D, metformin use and the risk of cancer in DM1 patients. We identified a cohort of 913 DM1 patients and an age-, sex- and clinic-matched cohort of 12,318 DM1-free controls from the UK Clinical Practice Research Datalink, a large primary care records database. We used Cox regression models to assess cancer risk in T2D patients who were metformin users or nonusers compared to patients without T2D. Separate analyses were conducted for DM1 patients and controls. T2D was more prevalent in DM1 than in controls (8% vs. 3%, p < 0.0001). DM1 patients with T2D, compared to those without T2D, were more likely to develop cancer (hazard ratio [HR] = 3.60, 95% confidence interval [CI] = 1.18-10.97; p = 0.02), but not if they were treated with metformin (HR = 0.43, 95% CI = 0.06-3.35; p = 0.42). Among controls, we observed no significant associations between T2D and cancer risk in either users or nonusers of Metformin (HR = 1.28, 95% CI = 0.91-1.79; p = 0.16 and HR = 1.13, 95% CI = 0.72-1.79; p = 0.59, respectively). These results show an association between T2D and cancer risk in DM1 patients and may provide new insights into the possible benefits of Metformin use in DM1.

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.

The care of patients with Duchenne, Becker, and other muscular dystrophies in the COVID-19 pandemic.

The coronavirus disease 2019 (COVID-19) pandemic has resulted in the reorganization of health-care settings affecting clinical care delivery to patients with Duchenne and Becker muscular dystrophy (DBMD) as well as other inherited muscular dystrophies. The magnitude of the impact of this public health emergency on the care of patients with DBMD is unclear as they are suspected of having an increased risk for severe manifestations of COVID-19. In this article, the authors discuss their consensus recommendations pertaining to care of these patients during the pandemic. We address issues surrounding corticosteroid and exon-skipping treatments, cardiac medications, hydroxychloroquine use, emergency/respiratory care, rehabilitation management, and the conduct of clinical trials. We highlight the importance of collaborative treatment decisions between the patient, family, and health-care provider, considering any geographic or institution-specific policies and precautions for COVID-19. We advocate for continuing multidisciplinary care for these patients using telehealth.

Longitudinal functional and imaging outcome measures in FKRP limb-girdle muscular dystrophy.

BACKGROUND: Pathogenic variants in the FKRP gene cause impaired glycosylation of α-dystroglycan in muscle, producing a limb-girdle muscular dystrophy with cardiomyopathy. Despite advances in understanding the pathophysiology of FKRP-associated myopathies, clinical research in the limb-girdle muscular dystrophies has been limited by the lack of normative biomarker data to gauge disease progression. METHODS: Participants in a phase 2 clinical trial were evaluated over a 4-month, untreated lead-in period to evaluate repeatability and to obtain normative data for timed function tests, strength tests, pulmonary function, and body composition using DEXA and whole-body MRI. Novel deep learning algorithms were used to analyze MRI scans and quantify muscle, fat, and intramuscular fat infiltration in the thighs. T-tests and signed rank tests were used to assess changes in these outcome measures. RESULTS: Nineteen participants were observed during the lead-in period for this trial. No significant changes were noted in the strength, pulmonary function, or body composition outcome measures over the 4-month observation period. One timed function measure, the 4-stair climb, showed a statistically significant difference over the observation period. Quantitative estimates of muscle, fat, and intramuscular fat infiltration from whole-body MRI corresponded significantly with DEXA estimates of body composition, strength, and timed function measures. CONCLUSIONS: We describe normative data and repeatability performance for multiple physical function measures in an adult FKRP muscular dystrophy population. Our analysis indicates that deep learning algorithms can be used to quantify healthy and dystrophic muscle seen on whole-body imaging. TRIAL REGISTRATION: This study was retrospectively registered in clinicaltrials.gov (NCT02841267) on July 22, 2016 and data supporting this study has been submitted to this registry.

AAV9 Edits Muscle Stem Cells in Normal and Dystrophic Adult Mice.

CRISPR editing of muscle stem cells (MuSCs) with adeno-associated virus serotype-9 (AAV9) holds promise for sustained gene repair therapy for muscular dystrophies. However, conflicting evidence exists on whether AAV9 transduces MuSCs. To rigorously address this question, we used a muscle graft model. The grafted muscle underwent complete necrosis before regenerating from its MuSCs. We injected AAV9.Cre into Ai14 mice. These mice express tdTomato upon Cre-mediated removal of a floxed stop codon. About 28%-47% and 24%-89% of Pax7+ MuSCs expressed tdTomato in pre-grafts and regenerated grafts (p > 0.05), respectively, suggesting AAV9 efficiently transduced MuSCs, and AAV9-edited MuSCs renewed successfully. Robust MuSC transduction was further confirmed by delivering AAV9.Cre to Pax7-ZsGreen-Ai14 mice in which Pax7+ MuSCs are genetically labeled by ZsGreen. Next, we co-injected AAV9.Cas9 and AAV9.gRNA to dystrophic mdx mice to repair the mutated dystrophin gene. CRISPR-treated and untreated muscles were grafted to immune-deficient, dystrophin-null NSG.mdx4cv mice. Grafts regenerated from CRISPR-treated muscle contained the edited genome and yielded 2.7-fold more dystrophin+ cells (p = 0.015). Importantly, increased dystrophin expression was not due to enhanced formation of revertant fibers or de novo transduction by residual CRISPR vectors in the graft. We conclude that AAV9 effectively transduces MuSCs. AAV9 CRISPR editing of MuSCs may provide enduring therapy.

Biological scaffold-mediated delivery of myostatin inhibitor promotes a regenerative immune response in an animal model of Duchenne muscular dystrophy.

Recent studies have reported that the immune system significantly mediates skeletal muscle repair and regeneration. Additionally, biological scaffolds have been shown to play a role in polarizing the immune microenvironment toward pro-myogenic outcomes. Moreover, myostatin inhibitors are known to promote muscle regeneration and ameliorate fibrosis in animal models of Duchenne muscular dystrophy (DMD), a human disease characterized by chronic muscle degeneration. Biological scaffolds and myostatin inhibition can potentially influence immune-mediated regeneration in the dystrophic environment, but have not been evaluated together. Toward this end, here we created an injectable biological scaffold composed of hyaluronic acid and processed skeletal muscle extracellular matrix. This material formed a cytocompatible hydrogel at physiological temperatures in vitro When injected subfascially above the tibialis anterior muscles of both WT and dystrophic mdx-5Cv mice, a murine model of DMD, the hydrogel spreads across the entire muscle before completely degrading at 3 weeks in vivo We found that the hydrogel is associated with CD206+ pro-regenerative macrophage polarization and elevated anti-inflammatory cytokine expression in both WT and dystrophic mice. Co-injection of both hydrogel and myostatin inhibitor significantly increased FoxP3+ regulatory T cell modulation and Foxp3 gene expression in the scaffold immune microenvironment. Finally, delivery of myostatin inhibitor with the hydrogel increased its bioactivity in vivo, and transplantation of immortalized human myoblasts with the hydrogel promoted their survival in vivo This study identifies a key role for biological scaffolds and myostatin inhibitors in modulating a pro-regenerative immune microenvironment in dystrophic muscle.

Multivoxel proton magnetic resonance spectroscopy in facioscapulohumeral muscular dystrophy.

INTRODUCTION: Facioscapulohumeral muscular dystrophy (FSHD) is a hereditary disorder that causes progressive muscle wasting. This study evaluates the use of proton magnetic resonance spectroscopy (1 H MRS) as a biomarker of muscle strength and function in FSHD. METHODS: Thirty-six individuals with FSHD and 15 healthy controls underwent multivoxel 1 H MRS of a cross-section of the mid-thigh. Concentrations of creatine, intramyocellular and extramyocellular lipids, and trimethylamine (TMA)-containing compounds in skeletal muscle were calculated. Metabolite concentrations for individuals with FSHD were compared with those of controls. The relationship between metabolite concentrations and muscle strength was also examined. RESULTS: The TMA/creatine (Cr) ratio in individuals with FSHD was reduced compared with controls. The TMA/Cr ratio in the hamstrings also showed a moderate linear correlation with muscle strength. DISCUSSION: 1 H MRS offers a potential method of detecting early muscle pathology in FSHD prior to the development of fat infiltration. Muscle Nerve 57: 958-963, 2018.

Validity of the 6 minute walk test in facioscapulohumeral muscular dystrophy.

INTRODUCTION: In preparation for future clinical trials, we determined the reliability, relationship to measures of disease severity, and consistency across sites of the 6 Minute Walk Test (6MWT) in patients with facioscapulohumeral muscular dystrophy (FSHD). METHODS: Genetically defined and clinically affected FSHD participants at 2 sites performed the 6MWT, the Timed Up and Go, and the 30 foot Go/Timed 10 meter test as measures of mobility using standard procedures. RESULTS: Eight-six participants representing the full range of severity performed the 6MWT. The mean 6MWT distance was 404.3 meters (SD 123.9), with no difference between sites. The 6MWT was reliable (n = 25; intraclass correlation coefficient = 0.99) and demonstrated moderate to strong correlations with lower extremity strength, functional outcomes, and FSHD Clinical Score. CONCLUSIONS: The 6MWT is reliable and is associated with other measures of FSHD disease severity. Future directions include assessing its sensitivity to disease progression. Muscle Nerve 55: 333-337, 2017.

Bone health in facioscapulohumeral muscular dystrophy: A cross-sectional study.

INTRODUCTION: Herein we provide a comprehensive overview of bone health in facioscapulohumeral muscular dystrophy (FSHD). METHODS: Ninety-four adult individuals with FSHD type 1 from 2 sites were included in this cross-sectional study. Clinical characteristics and determinants of bone health were examined. Relationships between bone mineral density (BMD), strength, and function were explored. RESULTS: Nearly a third of subjects were deficient in vitamin D3 . Mean whole-body BMD z-score was -0.7; 11% of subjects had greater than age-related reductions in whole-body BMD (z-score < -2.0). Whole-body and regional BMDs were associated with strength and function. Thirty-six percent had a history of fractures. Likelihood of fractures was reduced for those with normal whole-body BMD (odds ratio = 0.25, 95% confidence interval 0.04-0.78). DISCUSSION: A diagnosis of FSHD is not necessarily predictive of reduced BMD or increased fracture rate. Given the considerable variability of bone health in the FSHD population, strength and function can serve as predictors of BMD. Muscle Nerve 56: 1108-1113, 2017.

Morpholino-mediated Knockdown of DUX4 Toward Facioscapulohumeral Muscular Dystrophy Therapeutics.

Derepression of DUX4 in skeletal muscle has emerged as a likely cause of pathology in facioscapulohumeral muscular dystrophy (FSHD). Here we report on the use of antisense phosphorodiamidate morpholino oligonucleotides to suppress DUX4 expression and function in FSHD myotubes and xenografts. The most effective was phosphorodiamidate morpholino oligonucleotide FM10, which targets the polyadenylation signal of DUX4. FM10 had no significant cell toxicity, and RNA-seq analyses of FSHD and control myotubes revealed that FM10 down-regulated many transcriptional targets of DUX4, without overt off-target effects. Electroporation of FM10 into FSHD patient muscle xenografts in mice also down-regulated DUX4 and DUX4 targets. These findings demonstrate the potential of antisense phosphorodiamidate morpholino oligonucleotides as an FSHD therapeutic option.

In Vivo Selection Yields AAV-B1 Capsid for Central Nervous System and Muscle Gene Therapy.

Adeno-associated viral (AAV) vectors have shown promise as a platform for gene therapy of neurological disorders. Achieving global gene delivery to the central nervous system (CNS) is key for development of effective therapies for many of these diseases. Here we report the isolation of a novel CNS tropic AAV capsid, AAV-B1, after a single round of in vivo selection from an AAV capsid library. Systemic injection of AAV-B1 vector in adult mice and cat resulted in widespread gene transfer throughout the CNS with transduction of multiple neuronal subpopulations. In addition, AAV-B1 transduces muscle, ß-cells, pulmonary alveoli, and retinal vasculature at high efficiency. This vector is more efficient than AAV9 for gene delivery to mouse brain, spinal cord, muscle, pancreas, and lung. Together with reduced sensitivity to neutralization by antibodies in pooled human sera, the broad transduction profile of AAV-B1 represents an important improvement over AAV9 for CNS gene therapy.

Human skeletal muscle xenograft as a new preclinical model for muscle disorders.

Development of novel therapeutics requires good animal models of disease. Disorders for which good animal models do not exist have very few drugs in development or clinical trial. Even where there are accepted, albeit imperfect models, the leap from promising preclinical drug results to positive clinical trials commonly fails, including in disorders of skeletal muscle. The main alternative model for early drug development, tissue culture, lacks both the architecture and, usually, the metabolic fidelity of the normal tissue in vivo. Herein, we demonstrate the feasibility and validity of human to mouse xenografts as a preclinical model of myopathy. Human skeletal muscle biopsies transplanted into the anterior tibial compartment of the hindlimbs of NOD-Rag1(null) IL2rγ(null) immunodeficient host mice regenerate new vascularized and innervated myofibers from human myogenic precursor cells. The grafts exhibit contractile and calcium release behavior, characteristic of functional muscle tissue. The validity of the human graft as a model of facioscapulohumeral muscular dystrophy is demonstrated in disease biomarker studies, showing that gene expression profiles of xenografts mirror those of the fresh donor biopsies. These findings illustrate the value of a new experimental model of muscle disease, the human muscle xenograft in mice, as a feasible and valid preclinical tool to better investigate the pathogenesis of human genetic myopathies and to more accurately predict their response to novel therapeutics.