We ascertained a nuclear family in which three of four siblings were affected with an unclassified autosomal recessive myopathy characterized by severe weakness, respiratory impairment, scoliosis, joint contractures, and an unusual combination of dystrophic and myopathic features on muscle biopsy. Whole genome sequence from one affected subject was filtered using linkage data and variant databases. A single gene, MEGF10, contained nonsynonymous mutations that cosegregated with the phenotype. Affected subjects were compound heterozygous for missense mutations c.976T>C (p.C326R) and c.2320T>C (p.C774R). Screening the MEGF10 open reading frame in 190 patients with genetically unexplained myopathies revealed a heterozygous mutation, c.211C>T (p.R71W), in one additional subject with a similar clinical and histological presentation as the discovery family. All three mutations were absent from at least 645 genotyped unaffected control subjects. MEGF10 contains 17 atypical epidermal growth factor-like domains, each of which contains eight cysteine residues that likely form disulfide bonds. Both the p.C326R and p.C774R mutations alter one of these residues, which are completely conserved in vertebrates. Previous work showed that murine Megf10 is required for preserving the undifferentiated, proliferative potential of satellite cells, myogenic precursors that regenerate skeletal muscle in response to injury or disease. Here, knockdown of megf10 in zebrafish by four different morpholinos resulted in abnormal phenotypes including unhatched eggs, curved tails, impaired motility, and disorganized muscle tissue, corroborating the pathogenicity of the human mutations. Our data establish the importance of MEGF10 in human skeletal muscle and suggest satellite cell dysfunction as a novel myopathic mechanism.
Bibliographical noteFunding Information:
The authors thank the patients and their families for their participation in this study, as well as Hal Schneider, Laura Moody, Susan Kim, Sachiko Kajino, Kanako Goto, and Yukiko Hayashi for technical assistance, Michael Lawlor and Pankaj Agrawal for helpful discussions, Fedik Rahimov for critical reading of the manuscript, and Timothy Yu and Christopher Walsh for contribution of control genome sequence data. This work was supported by NIH K08 NS048180 (PBK), the Genise Goldenson Fund (PBK), a Children's Hospital Boston Pilot Grant (PBK), Muscular Dystrophy Association Research Grants 186796 (PBK) and 201302 (AHB), the Bernard F. and Alva B. Gimbel Foundation (LMK), NIH R01 AR044345 (AHB), the Lee and Penny Anderson Family Foundation (AHB), and the Professor-Dr.-Adolf-Schmidtmann-Stiftung (FD). Microarray genotyping and Sanger DNA sequencing experiments were performed in the Molecular Genetics Core Facility at Children's Hospital Boston, supported by NIH P30 HD18655 through the Intellectual and Developmental Disabilities Research Center and NIH P50 NS40828 through the Neuromuscular Disease Project. Electron microscopy was performed at the Harvard Medical School EM Core Facility with the assistance of Maria Ericsson, Louise Trakimas, and Elizabeth Benecchi.
- Cleft palate
- Congenital myopathy
- Linkage analysis
- Satellite cells
- Whole genome sequencing