Identification and Characterization of Disease Mechanisms in MEGF10 Myopathy

Abstract

Mutations in MEGF10 have recently been found to cause a rare congenital recessive myopathy, MEGF10 myopathy / early‐onset myopathy with areflexia, respiratory distress, and dysphagia (EMARDD). MEGF10 is an orphan receptor with 17 EGF‐like domains in the extracellular region. MEGF10 has multiple tyrosine residues in its cytoplasmic region that are potential sites of tyrosine phosphorylation. We previously showed that the p.C774R mutation is more severe than the p.C326R mutation due to differential impairment of tyrosine phosphorylation primarily of Y1030. We hypothesize that MEGF10 is a positive regulator of myoblast proliferation and migration in skeletal muscles in part due to involvement in the Wnt signaling pathway, and that this mechanism is impaired in MEGF10 myopathy. siRNA knockdown of endogenous MEGF10 in C2C12 cells caused significantly reduced proliferation compared to untreated C2C12 cells. Overexpression of wild type and mutant MEGF10 in C2C12 mouse myoblasts led to increased proliferation with wild type overexpression, whereas overexpressed p.C326R MEGF10 showed normal levels of proliferation, and overexpressed p.C774R MEGF10 showed reduced proliferation. Cell migration patterns were impaired in C2C12 cells that were subjected to shRNA knockdown of MEGF10 compared to wild type C2C12 cells. Preliminary proteomics studies suggest that MEGF10 interacts with components of the Wnt signaling pathway. These data indicate that MEGF10 plays an important role in myoblast proliferation and migration, and that impairment of these mechanisms lead to human muscle disease. Further studies will explore crucial details of MEGF10 signaling in these contexts.