title: Myosin Storage Myopathy in C. elegans and Human Cultured Muscle Cells.
abstract: Myosin storage myopathy is a protein aggregate myopathy associated with the characteristic subsarcolemmal accumulation of myosin heavy chain in muscle fibers. Despite similar histological findings, the clinical severity and age of onset are highly variable, ranging from no weakness to severe impairment of ambulation, and usually childhood-onset to onset later in life. Mutations located in the distal end of the tail of slow/ß-cardiac myosin heavy chain are associated with myosin storage myopathy. Four missense mutations (L1793P, R1845W, E1883K and H1901L), two of which have been reported in several unrelated families, are located within or closed to the assembly competence domain. This location is critical for the proper assembly of sarcomeric myosin rod filaments. To assess the mechanisms leading to protein aggregation in myosin storage myopathy and to evaluate the impact of these mutations on myosin assembly and muscle function, we expressed mutated myosin proteins in cultured human muscle cells and in the nematode Caenorhabditis elegans. While L1793P mutant myosin protein efficiently incorporated into the sarcomeric thick filaments, R1845W and H1901L mutants were prone to formation of myosin aggregates without assembly into striated sarcomeric thick filaments in cultured muscle cells. In C. elegans, mutant alleles of the myosin heavy chain gene unc-54 corresponding to R1845W, E1883K and H1901L, were as effective as the wild-type myosin gene in rescuing the null mutant worms, indicating that they retain functionality. Taken together, our results suggest that the basis for the pathogenic effect of the R1845W and H1901L mutations are primarily structural rather than functional. Further analyses are needed to identify the primary trigger for the histological changes seen in muscle biopsies of patients with L1793P and E1883K mutations.
authors.affiliation: Department of Pathology, University of Gothenburg, Sahlgrenska University Hospital, Gothenburg, Sweden.
authors.forename: Martin
authors.initials: M
authors.lastname: Dahl-Halvarsson
authors.affiliation: Department of Pathology, University of Gothenburg, Sahlgrenska University Hospital, Gothenburg, Sweden.
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Pokrzywa
authors.affiliation: Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Manish
authors.initials: M
authors.lastname: Rauthan
authors.affiliation: Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Marc
authors.initials: M
authors.lastname: Pilon
authors.affiliation: School of Health and Education, Div Biomedicine and Public Health, University of Skovde, Skovde, Sweden.
authors.forename: Homa
authors.identifier: http://orcid.org/0000-0001-8854-5213
authors.initials: H
authors.lastname: Tajsharghi
mesh_terms: D008841:Actin Cytoskeleton / Q000235:genetics / Q000378:metabolism; D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000096:biosynthesis / Q000235:genetics*; D006801:Humans; D032342:Muscle Cells / Q000378:metabolism / Q000473:pathology; D018485:Muscle Fibers, Skeletal / Q000378:metabolism / Q000473:pathology; D009135:Muscular Diseases / Q000151:congenital* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D009154:Mutation; D018995:Myosin Heavy Chains / Q000096:biosynthesis / Q000235:genetics*; D009218:Myosins / Q000096:biosynthesis / Q000235:genetics*; D066263:Protein Aggregation, Pathological / Q000235:genetics*; D012518:Sarcomeres / Q000235:genetics / Q000378:metabolism; D020389:Muscular Dystrophy, Emery-Dreifuss
chemical_list: D029742:Caenorhabditis elegans Proteins; C000621828:UNC-54 protein, C elegans; D018995:Myosin Heavy Chains; D009218:Myosins