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Brain Pathology (Zurich, Switzerland) Sep 2020Altered autophagy accompanied by abnormal autophagic (rimmed) vacuoles detectable by light and electron microscopy is a common denominator of many familial and sporadic...
Altered autophagy accompanied by abnormal autophagic (rimmed) vacuoles detectable by light and electron microscopy is a common denominator of many familial and sporadic non-inflammatory muscle diseases. Even in the era of next generation sequencing (NGS), late-onset vacuolar myopathies remain a diagnostic challenge. We identified 32 adult vacuolar myopathy patients from 30 unrelated families, studied their clinical, histopathological and ultrastructural characteristics and performed genetic testing in index patients and relatives using Sanger sequencing and NGS including whole exome sequencing (WES). We established a molecular genetic diagnosis in 17 patients. Pathogenic mutations were found in genes typically linked to vacuolar myopathy (GNE, LDB3/ZASP, MYOT, DES and GAA), but also in genes not regularly associated with severely altered autophagy (FKRP, DYSF, CAV3, COL6A2, GYG1 and TRIM32) and in the digenic facioscapulohumeral muscular dystrophy 2. Characteristic histopathological features including distinct patterns of myofibrillar disarray and evidence of exocytosis proved to be helpful to distinguish causes of vacuolar myopathies. Biopsy validated the pathogenicity of the novel mutations p.(Phe55*) and p.(Arg216*) in GYG1 and of the p.(Leu156Pro) TRIM32 mutation combined with compound heterozygous deletion of exon 2 of TRIM32 and expanded the phenotype of Ala93Thr-caveolinopathy and of limb-girdle muscular dystrophy 2i caused by FKRP mutation. In 15 patients no causal variants were detected by Sanger sequencing and NGS panel analysis. In 12 of these cases, WES was performed, but did not yield any definite mutation or likely candidate gene. In one of these patients with a family history of muscle weakness, the vacuolar myopathy was eventually linked to chloroquine therapy. Our study illustrates the wide phenotypic and genotypic heterogeneity of vacuolar myopathies and validates the role of histopathology in assessing the pathogenicity of novel mutations detected by NGS. In a sizable portion of vacuolar myopathy cases, it remains to be shown whether the cause is hereditary or degenerative.
Topics: Adult; Diagnosis, Differential; Female; Genetic Testing; High-Throughput Nucleotide Sequencing; Humans; Lysosomal Storage Diseases; Male; Middle Aged; Muscular Diseases; Mutation; Phenotype; Exome Sequencing
PubMed: 32419263
DOI: 10.1111/bpa.12864 -
Journal of Neuromuscular Diseases 2017Myofibrillar myopathies (MFMs) are muscular disorders involving proteins that play a role in the structure, maintenance processes and protein quality control mechanisms... (Review)
Review
Myofibrillar myopathies (MFMs) are muscular disorders involving proteins that play a role in the structure, maintenance processes and protein quality control mechanisms closely related to the Z-disc in the muscular fibers. MFMs share common histological characteristics including progressive disorganization of the interfibrillar network and protein aggregation. Currently no treatment is available. In this review, we describe first clinical symptoms associated with mutations of the six genes (DES, CRYAB, MYOT, ZASP, FLNC and BAG3) primary involved in MFM and defining the origin of this pathology. As mechanisms determining the aetiology of the disease remain unclear yet, several research teams have developed animal models from invertebrates to mammalians species. Thus we describe here these different models that often recapitulate human clinical symptoms. Therefore they are very useful for deeper studies to understand early molecular and progressive mechanisms determining the pathology. Finally in the last part, we emphasize on the potential therapeutic approaches for MFM that could be conducted in the future. In conclusion, this review offers a link from patients to future therapy through the use of MFMs animal models.
Topics: Animals; Disease Models, Animal; Drosophila; Humans; Mice; Muscle, Skeletal; Mutation; Myopathies, Structural, Congenital; Oryzias
PubMed: 28269794
DOI: 10.3233/JND-160203 -
Biochimica Et Biophysica Acta Jan 2016αB-crystallin, once thought to be a lenticular protein, is ubiquitous and has critical roles in several cellular processes that are modulated by phosphorylation. Serine... (Review)
Review
BACKGROUND
αB-crystallin, once thought to be a lenticular protein, is ubiquitous and has critical roles in several cellular processes that are modulated by phosphorylation. Serine residues 19, 45 and 59 of αB-crystallin undergo phosphorylation. Phosphorylation of S45 is mediated by p44/42 MAP kinase, whereas S59 phosphorylation is mediated by MAPKAP kinase-2. Pathway involved in S19 phosphorylation is not known.
SCOPE OF REVIEW
The review highlights the role of phosphorylation in (i) oligomeric structure, stability and chaperone activity, (ii) cellular processes such as apoptosis, myogenic differentiation, cell cycle regulation and angiogenesis, and (iii) aging, stress, cardiomyopathy-causing αB-crystallin mutants, and in other diseases.
MAJOR CONCLUSIONS
Depending on the context and extent of phosphorylation, αB-crystallin seems to confer beneficial or deleterious effects. Phosphorylation alters structure, stability, size distribution and dynamics of the oligomeric assembly, thus modulating chaperone activity and various cellular processes. Phosphorylated αB-crystallin has a tendency to partition to the cytoskeleton and hence to the insoluble fraction. Low levels of phosphorylation appear to be protective, while hyperphosphorylation has negative implications. Mutations in αB-crystallin, such as R120G, Q151X and 464delCT, associated with inherited myofibrillar myopathy lead to hyperphosphorylation and intracellular inclusions. An ongoing study in our laboratory with phosphorylation-mimicking mutants indicates that phosphorylation of R120GαB-crystallin increases its propensity to aggregate.
GENERAL SIGNIFICANCE
Phosphorylation of αB-crystallin has dual role that manifests either beneficial or deleterious consequences depending on the extent of phosphorylation and interaction with cytoskeleton. Considering that disease-causing mutants of αB-crystallin are hyperphosphorylated, moderation of phosphorylation may be a useful strategy in disease management. This article is part of a Special Issue entitled Crystallin Biochemistry in Health and Disease.
Topics: Aging; Animals; Cardiomyopathies; Crystallins; Humans; Models, Biological; Muscular Diseases; Phosphorylation; Stress, Physiological; Structure-Activity Relationship
PubMed: 26415747
DOI: 10.1016/j.bbagen.2015.09.017 -
Neuromuscular Disorders : NMD Jul 2010Myofibrillar myopathies are a heterogeneous group of neuromuscular disorders characterized by disintegration of myofibrils. The inheritance pattern is commonly autosomal...
Myofibrillar myopathies are a heterogeneous group of neuromuscular disorders characterized by disintegration of myofibrils. The inheritance pattern is commonly autosomal dominant, but there has been a striking absence of secondary cases noted in a BAG3-associated subtype. We studied three families with BAG3 p.Pro209Leu mutation showing a severe phenotype of myofibrillar myopathy and axonal neuropathy with giant axons. In one family, transmission to a pair of siblings has occurred from their asymptomatic father who showed somatic mosaicism. In two other families, neither of the parents was affected or showed detectable level of somatic mosaicism. These observations suggest that the BAG3 variant of myofibrillar myopathy may result from a spontaneous mutation at an early point of embryonic development and that transmission from a mosaic parent may occur more than once. The study underlines the importance of parental evaluation as it may have implications for genetic counseling.
Topics: Actin Cytoskeleton; Adaptor Proteins, Signal Transducing; Adolescent; Adult; Apoptosis Regulatory Proteins; Child; DNA Mutational Analysis; Family Health; Female; Genotype; Humans; Leucine; Male; Microscopy, Electron, Scanning; Muscular Diseases; Mutation; Phenotype; Proline; Sural Nerve; Young Adult
PubMed: 20605452
DOI: 10.1016/j.nmd.2010.05.004 -
International Journal of Molecular... Jul 2023Myofibrillar myopathies (MFMs) are a group of hereditary neuromuscular disorders sharing common histological features, such as myofibrillar derangement, Z-disk...
Myofibrillar myopathies (MFMs) are a group of hereditary neuromuscular disorders sharing common histological features, such as myofibrillar derangement, Z-disk disintegration, and the accumulation of degradation products into protein aggregates. They are caused by mutations in several genes that encode either structural proteins or molecular chaperones. Nevertheless, the mechanisms by which mutated genes result in protein aggregation are still unknown. To unveil the role of myotilin and αB-crystallin in the pathogenesis of MFM, we injected zebrafish fertilized eggs at the one-cell stage with expression plasmids harboring cDNA sequences of human wildtype or mutated (p.Ser95Ile) and human wildtype or mutated (p.Gly154Ser). We evaluated the effects on fish survival, motor behavior, muscle structure and development. We found that transgenic zebrafish showed morphological defects that were more severe in those overexpressing mutant genes. which developed a myopathic phenotype consistent with that of human myofibrillar myopathy, including the formation of protein aggregates. Results indicate that pathogenic mutations in myotilin and αB-crystallin genes associated with MFM cause a structural and functional impairment of the skeletal muscle in zebrafish, thereby making this non-mammalian organism a powerful model to dissect disease pathogenesis and find possible druggable targets.
Topics: Animals; Humans; alpha-Crystallin B Chain; Crystallins; Muscle, Skeletal; Mutation; Myofibrils; Myopathies, Structural, Congenital; Protein Aggregates; Zebrafish
PubMed: 37511242
DOI: 10.3390/ijms241411483 -
International Journal of Molecular... Feb 2024Alpha-B-crystallin, a member of the small heat shock family of proteins, has been implicated in a variety of cardiomyopathies and in normal cardiac homeostasis. It is... (Review)
Review
Alpha-B-crystallin, a member of the small heat shock family of proteins, has been implicated in a variety of cardiomyopathies and in normal cardiac homeostasis. It is known to function as a molecular chaperone, particularly for desmin, but also interacts with a wide variety of additional proteins. The molecular chaperone function is also enhanced by signal-dependent phosphorylation at specific residues under stress conditions. Naturally occurring mutations in , the gene that encodes alpha-B-crystallin, have been suggested to alter ionic intermolecular interactions that affect dimerization and chaperone function. These mutations have been associated with myofibrillar myopathy, restrictive cardiomyopathy, and hypertrophic cardiomyopathy and promote pathological hypertrophy through different mechanisms such as desmin aggregation, increased reductive stress, or activation of calcineurin-NFAT signaling. This review will discuss the known mechanisms by which alpha-B-crystallin functions in cardiac homeostasis and the pathogenesis of cardiomyopathies and provide insight into potential future areas of exploration.
Topics: Humans; Desmin; Cardiomyopathies; Mutation; Cardiomyopathy, Restrictive; Molecular Chaperones
PubMed: 38474073
DOI: 10.3390/ijms25052826 -
Brain and Behavior Feb 2022Mutations in the GFPT1 gene are associated with a particular subtype of congenital myasthenia syndrome (CMS) called limb-girdle myasthenia with tubular aggregates....
INTRODUCTION
Mutations in the GFPT1 gene are associated with a particular subtype of congenital myasthenia syndrome (CMS) called limb-girdle myasthenia with tubular aggregates. However, not all patients show tubular aggregates in muscle biopsy, suggesting the diversity of myopathology should be further investigated.
METHODS
In this study, we reported two unrelated patients clinically characterized by easy fatigability, limb-girdle muscle weakness, positive decrements of repetitive stimulation, and response to pyridostigmine. The routine examinations of myopathology were conducted. The causative gene was explored by whole-exome screening. In addition, we summarized all GFPT1-related CMS patients with muscle biopsy in the literature.
RESULTS
Pathogenic biallelic GFPT1 mutations were identified in the two patients. In patient one, muscle biopsy indicated vacuolar myopathic changes and atypical pathological changes of myofibrillar myopathy characterized by desmin deposits, Z-disc disorganization, and electronic dense granulofilamentous aggregation. In patient two, muscle biopsy showed typical myopathy with tubular aggregates. Among the 51 reported GFPT1-related CMS patients with muscle biopsy, most of them showed tubular aggregates myopathy, while rimmed vacuolar myopathy, autophagic vacuolar myopathy, mitochondria-like myopathy, neurogenic myopathy, and unspecific myopathic changes were also observed in some patients. These extra-synaptic pathological changes might be associated with GFPT1-deficiency hypoglycosylation and altered function of muscle-specific glycoproteins, as well as partly responsible for the permanent muscle weakness and resistance to acetylcholinesterase inhibitor therapy.
CONCLUSIONS
Most patients with GFPT1-related CMS had tubular aggregates in the muscle biopsy, but some patients could show great diversities of the pathological change. The myopathological findings might be a biomarker to predict the prognosis of the disease.
Topics: Acetylcholinesterase; Glutamine-Fructose-6-Phosphate Transaminase (Isomerizing); Humans; Muscle Weakness; Muscle, Skeletal; Mutation; Myasthenic Syndromes, Congenital; Myopathies, Structural, Congenital
PubMed: 34978387
DOI: 10.1002/brb3.2469 -
ELife Aug 2022Dystonin (), which encodes cytoskeletal linker proteins, expresses three tissue-selective isoforms: neural DST-a, muscular DST-b, and epithelial DST-e. mutations cause...
Dystonin (), which encodes cytoskeletal linker proteins, expresses three tissue-selective isoforms: neural DST-a, muscular DST-b, and epithelial DST-e. mutations cause different disorders, including hereditary sensory and autonomic neuropathy 6 (HSAN-VI) and epidermolysis bullosa simplex; however, etiology of the muscle phenotype in -related diseases has been unclear. Because contains all of the -encoding exons, known HSAN-VI mutations could affect both DST-a and DST-b isoforms. To investigate the specific function of DST-b in striated muscles, we generated a -specific mutant mouse model harboring a nonsense mutation. mutant mice exhibited late-onset protein aggregate myopathy and cardiomyopathy without neuropathy. We observed desmin aggregation, focal myofibrillar dissolution, and mitochondrial accumulation in striated muscles, which are common characteristics of myofibrillar myopathy. We also found nuclear inclusions containing p62, ubiquitin, and SUMO proteins with nuclear envelope invaginations as a unique pathological hallmark in mutation-induced cardiomyopathy. RNA-sequencing analysis revealed changes in expression of genes responsible for cardiovascular functions. In silico analysis identified alleles with nonsense mutations in populations worldwide, suggesting that some unidentified hereditary myopathy and cardiomyopathy are caused by mutations. Here, we demonstrate that the Dst-b isoform is essential for long-term maintenance of striated muscles.
Topics: Animals; Cardiomyopathies; Dystonin; Hereditary Sensory and Autonomic Neuropathies; Mice; Muscular Diseases; Mutation; Protein Aggregates; Protein Isoforms
PubMed: 35942699
DOI: 10.7554/eLife.78419 -
Acta Myologica : Myopathies and... Oct 2011The term myofibrillar myopathies (MFM) refers to uncommon neuromuscular disorders that pathologically are characterized by myofibrillar degeneration and ectopic...
The term myofibrillar myopathies (MFM) refers to uncommon neuromuscular disorders that pathologically are characterized by myofibrillar degeneration and ectopic expression of several proteins. MFM are partly caused by mutations in genes that encode mainly Z-disk-related proteins (desmin, alphaB-crystallin, myotilin, ZASP, filamin C and BAG3). We reviewed clinical, light and electron microscopy, immunohistochemistry, immunoblotting and genetic findings of 21 patients with MFM (15 unrelated patients and three pairs of brothers) investigated at our neuromuscular center. MFM patients begin to show symptoms at any age, from juvenile to late adult life and present a different distribution of muscle weakness. Cardiac involvement and peripheral neuropathy are common. Typical histological features include focal areas with reduction/loss of ATPase and oxidative enzyme activity, and amorphous material (eosinophilic on hematoxylin and eosin and dark blue on Engel-Gomori trichrome) in these abnormal fiber areas. Electron microscopy shows disintegration of myofibrils starting from the Z-disk and accumulation of granular and filamentous material among the myofilaments. Immunohistochemical studies demonstrate focal accumulation of desmin, alphaB-crystallin and myotilin in abnormal muscle fibers while immunoblot analysis does not highlight differences in the expression of these proteins also including ZASP protein. Therefore, unlike immunoblot, immunohistochemistry together with light and electron microscopy is a useful diagnostic tool in MFM. Finally three of our 21 patients have missense mutations in the desmin gene, two brothers carry missense mutations in the gene encoding myotilin, one has a missense mutation in alphaB-crystallin, and none harbour pathogenic variations in the genes encoding ZASP and BAG3.
Topics: Age of Onset; Cohort Studies; Contractile Proteins; Cytoskeletal Proteins; Female; Genome-Wide Association Study; Heart Diseases; Humans; Immunohistochemistry; Inheritance Patterns; Male; Microscopy, Electron; Middle Aged; Muscle Weakness; Muscular Dystrophies; Mutation; Myofibrils; Peripheral Nervous System Diseases
PubMed: 22106715
DOI: No ID Found -
Neuromuscular Disorders : NMD Aug 2011Myofibrillar myopathies (MFM) are a group of disorders associated with mutations in DES, CRYAB, MYOT, ZASP, FLNC, or BAG3 genes and characterized by disintegration of...
Myofibrillar myopathies (MFM) are a group of disorders associated with mutations in DES, CRYAB, MYOT, ZASP, FLNC, or BAG3 genes and characterized by disintegration of myofibrils and accumulation of degradation products into intracellular inclusions. We retrospectively evaluated 53 MFM patients from 35 Spanish families. Studies included neurologic exam, muscle imaging, light and electron microscopic analysis of muscle biopsy, respiratory function testing and cardiologic work-up. Search for pathogenic mutations was accomplished by sequencing of coding regions of the six genes known to cause MFM. Mutations in MYOT were the predominant cause of MFM in Spain affecting 18 of 35 families, followed by DES in 11 and ZASP in 3; in 3 families the cause of MFM remains undetermined. Comparative analysis of DES, MYOT and ZASP associated phenotypes demonstrates substantial phenotypic distinctions that should be considered in studies of disease pathogenesis, for optimization of subtype-specific treatments and management, and directing molecular analysis.
Topics: Adaptor Proteins, Signal Transducing; Adolescent; Adult; Age of Onset; Aged; Biopsy; Connectin; Cytoskeletal Proteins; Desmin; Female; Humans; LIM Domain Proteins; Magnetic Resonance Imaging; Male; Microfilament Proteins; Middle Aged; Muscle Proteins; Muscular Diseases; Mutation; Myofibrils; Phenotype; Retrospective Studies; Spain; Young Adult
PubMed: 21676617
DOI: 10.1016/j.nmd.2011.05.002