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There are more than 10,000 individual rare diseases and most are without therapy. Personalized genetic therapy represents one promising approach for their treatment. We present a road map for individualized treatment of an ultra-rare disease by establishing a gene replacement therapy developed for a single patient with hereditary spastic paraplegia type 50 (SPG50). Through a multicenter collaboration, an adeno-associated virus-based gene therapy product carrying the AP4M1 gene was created and successfully administered intrathecally to a 4-year-old patient within 3 years of diagnosis as part of a single-patient phase 1 trial. Primary endpoints were safety and tolerability, and secondary endpoints evaluated efficacy. At 12 months after dosing, the therapy was well tolerated. No serious adverse events were observed, with minor events, including transient neutropenia and Clostridioides difficile gastroenteritis, experienced but resolved. Preliminary efficacy measures suggest a stabilization of the disease course. Longer follow-up is needed to confirm the safety and provide additional insights on the efficacy of the therapy. Overall, this report supports the safety of gene therapy for SPG50 and provides insights into precision therapy development for rare diseases. Clinical trial registration: NCT06069687 .

Cytoplasmic and nuclear iron-sulfur (Fe-S) enzymes that are essential for genome maintenance and replication depend on the cytoplasmic Fe-S assembly (CIA) machinery for cluster acquisition. The core of the CIA machinery consists of a complex of CIAO1, MMS19 and FAM96B. The physiological consequences of loss of function in the components of the CIA pathway have thus far remained uncharacterized. Our study revealed that patients with biallelic loss of function in CIAO1 developed proximal and axial muscle weakness, fluctuating creatine kinase elevation, and respiratory insufficiency. In addition, they presented with CNS symptoms including learning difficulties and neurobehavioral comorbidities, along with iron deposition in deep brain nuclei, mild normocytic to macrocytic anemia, and gastrointestinal symptoms. Mutational analysis revealed reduced stability of the variants compared with WT CIAO1. Functional assays demonstrated failure of the variants identified in patients to recruit Fe-S recipient proteins, resulting in compromised activities of DNA helicases, polymerases, and repair enzymes that rely on the CIA complex to acquire their Fe-S cofactors. Lentivirus-mediated restoration of CIAO1 expression reversed all patient-derived cellular abnormalities. Our study identifies CIAO1 as a human disease gene and provides insights into the broader implications of the cytosolic Fe-S assembly pathway in human health and disease., Introduction Iron-sulfur (Fe-S) clusters are ancient and evolutionarily conserved prosthetic groups with unique chemical properties that enable the proteins that contain them (Fe-S proteins) to function in several essential cellular [...]

Proline substitutions within the coiled-coil rod region of the [beta]-myosin gene (MYH7) are the predominant mutations causing Laing distal myopathy (MPD1), an autosomal dominant disorder characterized by progressive weakness of distal/proximal muscles. We report that the MDP1 mutation R1500P, studied in what we believe to be the first mouse model for the disease, adversely affected myosin motor activity despite being in the structural rod domain that directs thick filament assembly. Contractility experiments carried out on isolated mutant muscles, myofibrils, and myofibers identified muscle fatigue and weakness phenotypes, an increased rate of actin- myosin detachment, and a conformational shift of the myosin heads toward the more reactive disordered relaxed (DRX) state, causing hypercontractility and greater ATP consumption. Similarly, molecular analysis of muscle biopsies from patients with MPD1 revealed a significant increase in sarcomeric DRX content, as observed in a subset of myosin motor domain mutations causing hypertrophic cardiomyopathy. Finally, oral administration of MYK-581, a small molecule that decreases the population of heads in the DRX configuration, significantly improved the limited running capacity of the R1500P-transgenic mice and corrected the increased DRX state of the myofibrils from patients. These studies provide evidence of the molecular pathogenesis of proline rod mutations and lay the groundwork for the therapeutic advancement of myosin modulators., Introduction Laing distal myopathy, also called myopathy distal type 1 (MPD1), is an autosomal dominant disease with variable onset and phenotypic severity. Typically, MPD1 begins with weakness of the anterior [...]

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease that affects motor neurons. Mutations in the SPTLC1 subunit of serine palmitoyltransferase (SPT), which catalyzes the first step in the de novo synthesis of sphingolipids (SLs), cause childhood-onset ALS. SPTLC1-ALS variants map to a transmembrane domain that interacts with ORMDL proteins, negative regulators of SPT activity. We show that ORMDL binding to the holoenzyme complex is impaired in cells expressing pathogenic SPTLC1-ALS alleles, resulting in increased SL synthesis and a distinct lipid signature. C-terminal SPTLC1 variants cause peripheral hereditary sensory and autonomic neuropathy type 1 (HSAN1) due to the synthesis of 1-deoxysphingolipids (1-deoxySLs) that form when SPT metabolizes L-alanine instead of L-serine. Limiting L-serine availability in SPTLC1-ALS-expressing cells increased 1-deoxySL and shifted the SL profile from an ALS to an HSAN1-like signature. This effect was corroborated in an SPTLC1-ALS pedigree in which the index patient uniquely presented with an HSAN1 phenotype, increased 1-deoxySL levels, and an L-serine deficiency. These data demonstrate how pathogenic variants in different domains of SPTLC1 give rise to distinct clinical presentations that are nonetheless modifiable by substrate availability., Introduction Amyotrophic lateral sclerosis (ALS) is a progressive, neurodegenerative disease of the lower and upper motor neurons characterized by severe muscle wasting, eventually leading to paralysis and death (1, 2). [...]

Troponin C (TnC) is a critical regulator of skeletal muscle contraction; it binds [Ca2.sup.+] to activate muscle contraction. Surprisingly, the gene encoding fast skeletal TnC (TNNC2) has not yet been implicated in muscle disease. Here, we report 2 families with pathogenic variants in TNNC2. Patients present with a distinct, dominantly inherited congenital muscle disease. Molecular dynamics simulations suggested that the pathomechanisms by which the variants cause muscle disease include disruption of the binding sites for [Ca2.sup.+] and for troponin I. In line with these findings, physiological studies in myofibers isolated from patients' biopsies revealed a markedly reduced force response of the sarcomeres to [[Ca2.sup.+]]. This pathomechanism was further confirmed in experiments in which contractile dysfunction was evoked by replacing TnC in myofibers from healthy control subjects with recombinant, mutant TnC. Conversely, the contractile dysfunction of myofibers from patients was repaired by replacing endogenous, mutant TnC with recombinant, wild-type TnC. Finally, we tested the therapeutic potential of the fast skeletal muscle troponin activator tirasemtiv in patients' myofibers and showed that the contractile dysfunction was repaired. Thus, our data reveal that pathogenic variants in TNNC2 cause congenital muscle disease, and they provide therapeutic angles to repair muscle contractility., Introduction Skeletal muscle cells (myofibers) are densely packed with myofibrils, which consist of repeating structural units named sarcomeres (Figure 1A). Sarcomeres, the contractile units of muscle, are composed of thick [...]

Exon skipping uses antisense oligonucleotides as a treatment for genetic diseases. The antisense oligonucleotides used for exon skipping are designed to bypass premature stop codons in the target RNA and restore reading frame disruption. Exon skipping is currently being tested in humans with dystrophin gene mutations who have Duchenne muscular dystrophy. For Duchenne muscular dystrophy, the rationale for exon skipping derived from observations in patients with naturally occurring dystrophin gene mutations that generated internally deleted but partially functional dystrophin proteins. We have now expanded the potential for exon skipping by testing whether an internal, in-frame truncation of a transmembrane protein γ-sarcoglycan is functional. We generated an internally truncated γ- sarcoglycan protein that we have termed Mini-Gamma by deleting a large portion of the extracellular domain. Mini-Gamma provided functional and pathological benefits to correct the loss of γ-sarcoglycan in a Drosophila model, in heterologous cell expression studies, and in transgenic mice lacking γ-sarcoglycan. We generated a cellular model of human muscle disease and showed that multiple exon skipping could be induced in RNA that encodes a mutant human γ-sarcoglycan. Since Mini-Gamma represents removal of 4 of the 7 coding exons in γ-sarcoglycan, this approach provides a viable strategy to treat the majority of patients with γ-sarcoglycan gene mutations., Introduction Mutations that disrupt the dystrophin glycoprotein complex (DGC) cause muscular dystrophy (1-3). Dystrophin and its associated proteins localize to the muscle plasma membrane, acting as a linker between the [...]

Biallelic pathogenic variants in the genes encoding the dolichol‐phosphate mannose synthase subunits (DPM) which produce mannosyl donors for glycosylphosphatidylinositols, N‐glycan and protein O‐ and C‐mannosylation, are rare causes of congenital disorders of glycosylation. Pathogenic variants in DPM1 and DPM2 are associated with muscle–eye–brain (MEB) disease, whereas DPM3 variants have mostly been reported in patients with isolated muscle disease—dystroglycanopathy. Thus far, only one affected individual with compound heterozygous DPM3 variants presenting with myopathy, mild intellectual disability, seizures, and nonspecific white matter abnormalities (WMA) around the lateral ventricles has been described. Here we present five affected individuals from four unrelated families with global developmental delay/intellectual disability ranging from mild to severe, microcephaly, seizures, WMA, muscle weakness and variable cardiomyopathy. Exome sequencing of the probands revealed an ultra‐rare homozygous pathogenic missense DPM3 variant NM_018973.4:c.221A>G, p.(Tyr74Cys) which segregated with the phenotype in all families. Haplotype analysis indicated that the variant arose independently in three families. Functional analysis did not reveal any alteration in the N‐glycosylation pathway caused by the variant; however, this does not exclude its pathogenicity in the function of the DPM complex and related cellular pathways. This report provides supporting evidence that, besides DPM1 and DPM2, defects in DPM3 can also lead to a muscle and brain phenotype. [ABSTRACT FROM AUTHOR]

Ehlers Danlos syndrome musculocontractural type (mcEDS) is a rare hereditary connective tissue disorder caused by biallelic pathogenic variants in the CHST14 or dermatan sulfate (DS) epimerase genes resulting in defective DS biosynthesis. It is characterized by congenital malformations and contractures, distinctive facial features and multisystemic fragility-related complications. To date, less than 100 patients with mcEDS have been reported. Vascular complications remain the major morbidity and may lead to mortality in the affected individuals. In this clinical report, we report on a currently 12-year-old boy with a novel homozygous CHST14 variant who presented with typical mcEDS symptoms and subsequently developed a life-threatening subcutaneous skull hematoma following a minor trauma, which required intensive care unit admission and surgical drainage along with several blood transfusions. This case expands the clinical and genetic spectrum of CHST14-related mcEDS which is essential for providing accurate prognosis, management and genetic counseling. [ABSTRACT FROM AUTHOR]

Regulators of skeletal muscle mass are of interest, given the morbidity and mortality of muscle atrophy and myopathy. Four-and-a-half LIM protein 1 (FHL1) is mutated in several human myopathies, including reducing-body myopathy (RBM). The normal function of FHL1 in muscle and how it causes myopathy remains unknown. We find that FHL1 transgenic expression in mouse skeletal muscle promotes hypertrophy and an oxidative fiber-type switch, leading to increased whole-body strength and fatigue resistance. Additionally, FHL1 overexpression enhances myoblast fusion, resulting in hypertrophic myotubes in C2C12 cells, (a phenotype rescued by calcineurin inhibition). In FHL1 -RBM C2C12 cells, there are no hypertrophic myotubes. FHL1 binds with the calcineurinregulated transcription factor NFATc1 (nuclear factor of activated T cells, cytoplasmic, calcineurin-dependent 1), enhancing NFATc1 transcriptional activity. Mutant RBM-FHL1 forms aggregate bodies in C2C12 cells, sequestering NFATc1 and resulting in reduced NFAT nuclear translocation and transcriptional activity. NFATc1 also colocalizes with mutant FHL1 to reducing bodies in RBM-afflicted skeletal muscle. Therefore, via NFATc1 signaling regulation, FHL1 appears to modulate muscle mass and strength enhancement.

Reducing body myopathy (RBM) is a rare disorder causing progressive muscular weakness characterized by aggresome-like inclusions in the myofibrils. Identification of genes responsible for RBM by traditional genetic approaches has been impossible due to the frequently sporadic occurrence in affected patients and small family sizes. As an alternative approach to gene identification, we used laser microdissection of intracytoplasmic inclusions identified in patient muscle biopsies, followed by nanoflow liquid chromatography--tandem mass spectrometry and proteomic analysis. The most prominent component of the inclusions was the Xq26.3-encoded four and a half LIM domain 1 (FHL1) protein, expressed predominantly in skeletal but also in cardiac muscle. Mutational analysis identified 4 FHL1 mutations in 2 sporadic unrelated females and in 2 families with severely affected boys and less-affected mothers. Transfection of kidney COS-7 and skeletal muscle C2C12 cells with mutant FHL1 induced the formation of aggresome-like inclusions that incorporated both mutant and wild-type FHL1 and trapped other proteins in a dominant-negative manner. Thus, a novel laser microdissection/proteomics approach has helped identify both inherited and de novo mutations in FHL1, thereby defining a new X-linked protein aggregation disorder of muscle., Introduction Reducing body myopathy (RBM) is a rare muscle disorder causing progressive muscular weakness and characteristic intracytoplasmic inclusions in myofibers, first described more than 30 years ago (1). Clinical presentations [...]

Contractile myocytes provide a test of the hypothesis that cells sense their mechanical as well as molecular microenvironment, altering expression, organization, and/or morphology accordingly. Here, myoblasts were cultured on collagen strips attached to glass or polymer gels of varied elasticity. Subsequent fusion into myotubes occurs independent of substrate flexibility. However, myosin/actin striations emerge later only on gels with stiffness typical of normal muscle (passive Young's modulus, E ~ 12 kPa). On glass and much softer or stiffer gels, including gels emulating stiff dystrophic muscle, cells do not striate. In addition, myotubes grown on top of a compliant bottom layer of glass-attached myotubes (but not softer fibroblasts) will striate, whereas the bottom cells will only assemble stress fibers and vinculin-rich adhesions. Unlike sarcomere formation, adhesion strength increases monotonically versus substrate stiffness with strongest adhesion on glass. These findings have major implications for in vivo introduction of stem cells into diseased or damaged striated muscle of altered mechanical composition.

Byline: Ayush Dagvadorj (1), Montse Olive (2), Jean-Andoni Urtizberea (3), Martin Halle (4), Alexey Shatunov (1), Carsten Bonnemann (5), Kye-Yoon Park (1), Hans H. Goebel (6), Isidro Ferrer (2), Patrick Vicart (7), Marinos C. Dalakas (1), Lev G. Goldfarb (1) Keywords: cardiomyopathy; skeletal myopathy; desmin gene; de novo mutation Abstract: Abstract. Desminopathy is a familial or sporadic cardiac and skeletal muscular dystrophy associated with mutations in desmin. We have previously characterized a de novo desmin R406W mutation in a patient of European origin with early onset muscle weakness in the lower extremities and atrioventricular conduction block requiring a permanent pacemaker. The disease relentlessly progressed resulting in severe incapacity within 5 years after onset. We have now identified three other patients with early onset rapidly progressive cardiac and skeletal myopathy caused by this same desmin R406W mutation. The mutation was present in each studied patient, but not in their parents or other unaffected family members, indicating that the mutation in all four cases was generated de novo. The patients' mutationcarrying chromosomes showed no similarity, suggesting that the R406W mutation has occurred independently. These observations strongly confirm that the de novo R406W desmin mutation is the genetic basis for early-onset cardiac and skeletal myopathy in patients with sporadic disease and indicate that desmin position 406 is a hot spot for spontaneous mutations. The high pathogenic potential of this mutation can be explained by its location in the highly conserved YRKLLEGEE motif at the C-terminal end of the 2B helix that has a critical role in the process of desmin filament assembly. Author Affiliation: (1) National Institute of Neurological Disorders and Stroke, National Institutes of Health Bldg 10, Room 4B37, 10 Center Dr., MSC 1361, Bethesda, Maryland, 20892-1361, USA (2) Institut de Neuropatologia Ciutat Sanitaria i Universitaria de Bellvitge, Hospitalet de Llobregat, Barcelona, Spain (3) Hopital Raymond Poincare, 92380, Garches, France (4) Medizinische Klinik, Georg-August-Universitaet, 37075, Goettingen, Germany (5) Division of Neurology, The Children's Hospital of Philadelphia, Philadelphia, PA, 19104, US (6) Department of Neuropathology, Johannes Gutenberg-University, Medical Center, Langenbeckstrasse 1, 55131, Mainz, Germany (7) Laboratoire Cytosquelette et Developpement, UMR CNRS 7000 Faculte de Medecine Pitie-Salpetriere, 105 Bd de l'Hopital, 75013, Paris, France Article History: Registration Date: 01/01/2004 Received Date: 05/03/2003 Accepted Date: 18/09/2003

Severe childhood autosomal recessive muscular dystrophy (SCARMD) is a progressive muscle-wasting disorder common in North Africa that segregates with microsatellite markers at chromosome 13ql2. Here, it is shown that a mutation in the gene encoding the 35-kilodalton dystrophin-associated glycoprotein, y-sarcoglycan, is likely to be the primary genetic defect in this disorder. The human y-sarcoglycan gene was mapped to chromosome 13ql2, and deletions that alter its reading frame were identified in three families and one of four sporadic cases of SCARMD. These mutations not only affect y-sarcoglycan but also disrupt the integrity of the entire sarcoglycan complex., The muscular dystrophies are genetically heterogeneous (1). X-linked recessive muscular dystrophy, or Duchenne muscular dystrophy (DMD), is the most common form and arises from mutations in the dystrophin gene (2). [...]

Context.--There is no current standard among myopathologists for reporting muscle biopsy findings. The National Institute of Neurological Disorders and Stroke has recently launched a common data element (CDE) project to standardize neuromuscular data collected in clinical reports and to facilitate their use in research. Objective.--To develop a more-uniform, prospective reporting tool for muscle biopsies, incorporating the elements identified by the CDE project, in an effort to improve reporting and educational resources. Design.--The variation in current biopsy reporting practice was evaluated through a study of 51 muscle biopsy reports from self-reported diagnoses of genetically confirmed or undiagnosed muscle disease from the Congenital Muscle Disease International Registry. Two reviewers independently extracted data from deidentified reports and entered them into the revised CDE format to identify what was missing and whether or not information provided on the revised CDE report (complete/incomplete) could be successfully interpreted by a neuropathologist. Results.--Analysis of the data highlighted showed (1) inconsistent reporting of key clinical features from referring physicians, and (2) considerable variability in the reporting of pertinent positive and negative histologic findings by pathologists. Conclusions.--We propose a format for muscle-biopsy reporting that includes the elements in the CDE checklist and a brief narrative comment that interprets the data in support of a final interpretation. Such a format standardizes cataloging of pathologic findings across the spectrum of muscle diseases and serves emerging clinical care and research needs with the expansion of genetic-testing therapeutic trials. (Arch Pathol Lab Med. 2016; 140:51-65; doi: 10.5858/arpa.2014-0453-OA), The muscle biopsy is an essential, and frequently used, diagnostic tool in the evaluation of pediatric and adult neuromuscular disorders, but its usefulness may be limited by poor communication from [...]

The majority of patients with spinal muscular atrophy (SMA) identified to date harbor a biallelic exonic deletion of SMN1. However, there have been reports of SMA‐like disorders that are independent of SMN1, including those due to pathogenic variants in the glycyl‐tRNA synthetase gene (GARS1). We report three unrelated patients with de novo variants in GARS1 that are associated with infantile‐onset SMA (iSMA). Patients were ascertained during inpatient hospital evaluations for complications of neuropathy. Evaluations were completed as indicated for clinical care and management and informed consent for publication was obtained. One newly identified, disease‐associated GARS1 variant, identified in two out of three patients, was analyzed by functional studies in yeast complementation assays. Genomic analyses by exome and/or gene panel and SMN1 copy number analysis of three patients identified two previously undescribed de novo missense variants in GARS1 and excluded SMN1 as the causative gene. Functional studies in yeast revealed that one of the de novoGARS1 variants results in a loss‐of‐function effect, consistent with other pathogenic GARS1 alleles. In sum, the patients' clinical presentation, assessments of previously identified GARS1 variants and functional assays in yeast suggest that the GARS1 variants described here cause iSMA. GARS1 variants have been previously associated with Charcot–Marie–Tooth disease (CMT2D) and distal SMA type V (dSMAV). Our findings expand the allelic heterogeneity of GARS‐associated disease and support that severe early‐onset SMA can be caused by variants in this gene. Distinguishing the SMA phenotype caused by SMN1 variants from that due to pathogenic variants in other genes such as GARS1 significantly alters approaches to treatment. [ABSTRACT FROM AUTHOR]

Introduction: MYH7 gene mutations are related to a heterogeneous group of skeletal and cardiac myopathies.Methods: We evaluated clinical and muscle MRI changes in patients with mutations in the rod domain of MYH7, including 1 with mosaicism and 3 with novel missense mutations.Results: Patients presented in childhood with a distal and axial phenotype. Biopsy findings were variable. Half of the cases displaying some type of core pathology, including minicores and eccentric cores. Most patients demonstrated internal bands of infiltration ("inverted-collagen-VI sign") in multiple muscles, particularly the soleus, and prominent atrophy and fatty infiltration of the tongue and the paraspinal, gluteus minimus, sartorius, gracilis, tibialis anterior, and extensor digitorum longus muscles.Discussion: Muscle imaging findings in patients with axial involvement provide significant clues permitting the distinction between MYH7-related myopathies and other axial myopathies such as those related to SEPN1 and LMNA genes. Muscle Nerve 58: 224-234, 2018. [ABSTRACT FROM AUTHOR]

Background: X-linked myotubular myopathy (XLMTM) is caused by mutations in the MTM1 gene, leading to absent or dysfunctional myotubularin, respiratory failure and profound muscle weakness at birth, and early death. Objective: We report the pathologic findings of 4 deceased XLMTM patients who received investigational MTM1 gene replacement therapy. Methods: ASPIRO (NCT03199469) is an open-label, phase 1/2/3 randomized trial in which young boys with genetically confirmed XLMTM and chronic ventilator dependence received resamirigene bilparvovec (AT132), a single intravenous dose of adeno-associated viral (AAV) vector delivering human MTM1. Results: Three of 17 participants in the higher dose (3.5x1014 vg/kg) and 1 of 7 participants in the lower dose (1.3x1014 vg/kg) cohort died. All 4 deceased participants had ongoing hepatobiliary cholestasis with decompensated liver disease at death. Immediate causes of death included sepsis and gastrointestinal hemorrhage. Two serial liver biopsies obtained from 1 participant demonstrated progression to liver fibrosis over the course of ~7 months. All 4 participants had histological similarities. This progressive, cholestatic disease was associated with a previously unrecognized cholestatic tendency, exposure to AT132 with mechanism of cholestatic disease exacerbation not understood, and evidence of decreased expression of bile salt export protein (BSEP) in liver tissue. Retrospective analyses of preclinical mouse and canine XLMTM models and healthy non-human primates treated with AAV8 gene transfer did not reveal evidence of cholestatic disease. Conclusions: Deaths were attributable to AT132-triggered severe exacerbation of cholestatic liver disease; factors that would help predict this susceptibility remain under investigation while the ASPIRO study is currently on hold. aASPIRO Pathology Study Group: James J. Dowling, Benedikt Schoser, Marta Margeta, Hui Meng, Amanda M. Hopp, Laura Wozniak, A. Reghan Foley, Dimah N. Saade, David E. Kleiner, Esra Dikoglu, Christine Jones, Osorio Lopes Abath Neto, Astrid Blaschek, Eberhard Lurz, Susanna Mueller, Nitin R Wadhwani, Saeed Mohammad, Catherine A Chapin, Robyn C. Reed, Evelyn Hsu, Suyash Prasad, Salvador Rico, Michael Murtagh, Nathan Bachtell. [ABSTRACT FROM AUTHOR]

This study aimed to analyze the correlation between the phenotype and genotype of Chinese patients with early-onset lamin A (LMNA)-related muscular dystrophy (MD). The clinical and myopathological data of 21 Chinese pediatric patients with early-onset LMNA-related MD were collected and analyzed. LMNA gene mutation analysis was performed by direct sequencing of genomic DNA. Sublocalization of wild-type and mutant proteins were observed by immunofluorescence using cultured fibroblasts and human embryonic kidney 293 (HEK 293) cell. Seven patients were diagnosed with Emery-Dreifuss muscular dystrophy (EDMD) and 14 were diagnosed with LMNA-associated congenital muscular dystrophy (L-CMD). Four biopsy specimens from the L-CMD cases exhibited inflammatory changes. Abnormal nuclear morphology was observed with both transmission electron microscopy and lamin A/C staining. We identified 10 novel and nine known LMNA gene mutations in the 21 patients. Some mutations (c.91G>A, c.94_96delAAG, c.116A>G, c.745C>T, c.746G>A, and c.1580G>C) were well correlated with EDMD or L-CMD. LMNA-related MD has a common symptom triad of muscle weakness, joint contractures, and cardiac involvement, but the severity of symptoms and disease progression differ greatly. Inflammatory change in biopsied muscle is a characteristic of early-stage L-CMD. Phenotype–genotype analysis determines that some mutations are well correlated with LMNA-related MD. [ABSTRACT FROM AUTHOR]

Research was conducted to examine the molecular organization of sarcoglycan complex in mouse myotubes in culture. Results based on coimmunoprecipitation analyses under different stringencies indicate that alpha-sarcoglycan is loosely associated with the other sarcoglycans and that the interaction between delta- and beta-sarcoglycan is particularly strong. Findings also show that delta-sarcoglycan can be cross-linked to the dystroglycan complex.

Background: RYR1 mutations are typically associated with core myopathies and are the most common overall cause of congenital myopathy. Dominant mutations are most often associated with central core disease and malignant hyperthermia, and genotype-phenotype patterns have emerged from the study of these mutations that have contributed to the understanding of disease pathogenesis. The recent availability of genetic testing for the entire RYR1 coding sequence has led to a dramatic expansion in the identification of recessive mutations in core myopathies and other congenital myopathies. To date, no clear patterns have been identified in these recessive mutations, though no systematic examination has yet been performed. Methods: In this study, we investigated genotype-phenotype correlations in a large combined cohort of unpublished (n = 14) and previously reported (n = 92) recessive RYR1 cases. Results: Overall examination of this cohort revealed nearly 50% of cases to be non-core myopathy related. Our most significant finding was that hypomorphic mutations (mutations expected to diminish RyR1 expression) were enriched in patients with severe clinical phenotypes. We also determined that hypomorphic mutations were more likely to be encountered in non-central core myopathies. With analysis of the location of non-hypomorphic mutations, we found that missense mutations were generally enriched in the MH/CCD hotspots and specifically enriched in the selectivity filter of the channel pore. Conclusions: These results support a hypothesis that loss of protein function is a key predictive disease parameter. In addition, they suggest that decreased RyR1 expression may dictate non-core related pathology though, data on protein expression was limited and should be confirmed in a larger cohort. Lastly, the results implicate abnormal ion conductance through the channel pore in the pathogenesis in recessive core myopathies. Overall, our findings represent a comprehensive analysis of genotype-phenotype associations in recessive RYR1-myopathies. [ABSTRACT FROM AUTHOR]

The congenital muscular dystrophies (CMDs) comprise a heterogeneous group of heritable muscle disorders with often difficult to interpret muscle pathology, making them challenging to diagnose. Serial Sanger sequencing of suspected CMD genes, while the current molecular diagnostic method of choice, can be slow and expensive. A comprehensive panel test for simultaneous screening of mutations in all known CMD-associated genes would be a more effective diagnostic strategy. Thus, the CMDs are a model disorder group for development and validation of next-generation sequencing (NGS) strategies for diagnostic and clinical care applications. Using a highly multiplexed PCR-based target enrichment method (RainDance) in conjunction with NGS, we performed mutation detection in all CMD genes of 26 samples and compared the results with Sanger sequencing. The RainDance NGS panel showed great consistency in coverage depth, on-target efficiency, versatility of mutation detection, and genotype concordance with Sanger sequencing, demonstrating the test's appropriateness for clinical use. Compared to single tests, a higher diagnostic yield was observed by panel implementation. The panel's limitation is the amplification failure of select gene-specific exons which require Sanger sequencing for test completion. Successful validation and application of the CMD NGS panel to improve the diagnostic yield in a clinical laboratory was shown. [ABSTRACT FROM AUTHOR]