title: Developmental MYH3 Myopathy Associated with Expression of Mutant Protein and Reduced Expression Levels of Embryonic MyHC.
abstract: OBJECTIVE
  An essential role for embryonic MyHC in foetal development has been found from its association with distal arthrogryposis syndromes, a heterogeneous group of disorders characterised by congenital contractions. The latter probably result from severe myopathy during foetal development. Lack of embryonic muscle biopsy material and suitable animal models has hindered study of the pathomechanisms linking mutations in MYH3 to prenatal myopathy.
  
  
  RESULTS
  We determined the pathomechanisms of developmental myopathy caused by recurrent p.Thr178Ile MYH3 heterozygosity, using patient-derived skeletal muscle cells in culture as an experimental disease model to emulate early embryonic development. These cultured cells were processed for discrimination and quantitative analysis of mutant and wild-type MYH3 alleles and MyHC transcripts, real-time RT-qPCR, sequence analysis, immunofluorescence microscopy, immunoblot, and proteomic assessments. Involvement of the ubiquitin proteasome system was investigated in patients with p.Thr178Ile mutations in MYH3 and MYH2. We found equal overall expression of mutant and wild-type MyHC mRNAs and proteins. Compared to the controls, however, expression of embryonic MyHC transcripts and proteins was reduced whereas expression of myosin-specific E3 ubiquitin ligase (MuRF1) was increased. We also found delayed myofibrillogenesis and atrophic myotubes but structured sarcomeres.
  
  
  CONCLUSIONS
  In conclusion, this study suggests that developmental p.Thr178Ile MYH3 myopathy is associated with a combined pathomechanism of insufficient dosage of functional embryonic MyHC and production of mutant protein.
authors.affiliation: Department of Clinical and Medical Genetics, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Pokrzywa
authors.affiliation: Department of Clinical and Medical Genetics, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Michaela
authors.initials: M
authors.lastname: Norum
authors.affiliation: Proteomic Core Facility, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: Lengqvist
authors.affiliation: Department of Clinical and Medical Genetics, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Mehrnaz
authors.initials: M
authors.lastname: Ghobadpour
authors.affiliation: Department of Pathology, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Saba
authors.initials: S
authors.lastname: Abdul-Hussein
authors.affiliation: Department of Pathology, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Ali-Reza
authors.initials: AR
authors.lastname: Moslemi
authors.affiliation: Department of Clinical and Medical Genetics, University of Gothenburg, Gothenburg, Sweden.|Department of Pathology, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.|Systems Biology Research Centre, School of Biomedicine, University of Skövde, Skövde, Sweden.
authors.forename: Homa
authors.initials: H
authors.lastname: Tajsharghi
mesh_terms: D002454:Cell Differentiation / Q000235:genetics; D003598:Cytoskeletal Proteins / Q000235:genetics* / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D007223:Infant; D024510:Muscle Development / Q000235:genetics; D018485:Muscle Fibers, Skeletal / Q000473:pathology; D009124:Muscle Proteins / Q000378:metabolism; D009135:Muscular Diseases / Q000196:embryology* / Q000235:genetics* / Q000473:pathology / Q000503:physiopathology; D050505:Mutant Proteins / Q000235:genetics*; D018995:Myosin Heavy Chains / Q000235:genetics*; D020033:Protein Isoforms / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012518:Sarcomeres / Q000378:metabolism; D014158:Transcription, Genetic; D000070584:Tripartite Motif Proteins; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism
chemical_list: D003598:Cytoskeletal Proteins; C510594:MYH3 polypeptide, human; D009124:Muscle Proteins; D050505:Mutant Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger; D000070584:Tripartite Motif Proteins; C440908:TRIM63 protein, human; D044767:Ubiquitin-Protein Ligases; D018995:Myosin Heavy Chains