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- Title
Two novel MYH7 proline substitutions cause Laing Distal Myopathy-like phenotypes with variable expressivity and neck extensor contracture.
- Authors
Feinstein-Linial, Miora; Buvoli, Massimo; Buvoli, Ada; Sadeh, Menachem; Dabby, Ron; Straussberg, Rachel; Shelef, Ilan; Dayan, Daniel; Leinwand, Leslie Anne; Birk, Ohad S.
- Abstract
Background: Human skeletal muscles express three major myosin heavy chain (MyHC) isoforms: MyHCIIx (MYH1) in fast type 2B muscle fibers, MyHCIIa (MYH2) in fast type 2A fibers and MyHCI/β-cardiac MyHC (MYH7) in slow type I skeletal fibers and cardiac ventricles. In line with its expression pattern, MYH7 mutations have been reported in association with hypertrophic or dilated cardiomyopathy, skeletal myopathies or a combination of both. We analyzed the clinical and molecular phenotype of two unrelated families of Jewish Moroccan ancestry that presented with apparently autosomal dominant inheritance of progressive Laing-like distal myopathy with non-specific myopathic changes, but uncommon marked contractures and wasting of the neck extensors. Methods: Clinical phenotyping, whole exome sequencing and restriction analysis, generation of mutants followed by cell culture transfection and imaging. Results: Using whole exome sequencing we identified in both families two novel heterozygous proline substitutions located in exon 31 of MYH7 within its rod domain: c.4309G>C (p.Ala1437Pro) and c.4301G>C (p.Arg1434Pro). Here we show that the phenotype caused by these mutations includes marked cervical muscle contracture, and report that the severity of the phenotype varies significantly, to the extent of non-penetrance in one of the families. Finally, we provide evidence that both proline substitutions impair myosin self-assembly in non-muscle cells transfected with β-myosin constructs carrying the mutations, but do not prevent incorporation of the mutant molecules into the sarcomere. Conclusions: This study expands our clinical and molecular knowledge of MYH7 rod mutations causing skeletal myopathies, and underscores the importance of discussing disease penetrance during genetic counseling.
- Subjects
PROLINE metabolism; NECK muscles; PHENOTYPES; GENETIC mutation; MYOSIN; HYPERTROPHIC cardiomyopathy; EXTENSOR muscles; WOUNDS &; injuries
- Publication
BMC Medical Genetics, 2016, Vol 17, p1
- ISSN
1471-2350
- Publication type
Article
- DOI
10.1186/s12881-016-0315-1