Ryanodine receptor RyR1-mediated elevation of Ca 2+ concentration is required for the late stage of myogenic differentiation and fusion

Background Cytosolic Ca 2+ plays vital roles in myogenesis and muscle development. As a major Ca 2+ release channel of endoplasmic reticulum (ER), ryanodine receptor 1 (RyR1) key mutations are main causes of severe congenital myopathies. The role of RyR1 in myogenic differentiation has attracted intense research interest but remains unclear. Results In the present study, both RyR1-knockdown myoblasts and CRISPR/Cas9-based RyR1-knockout myoblasts were employed to explore the role of RyR1 in myogenic differentiation, myotube formation as well as the potential mechanism of RyR1-related myopathies. We observed that RyR1 expression was dramatically increased during the late stage of myogenic differentiation, accompanied by significantly elevated cytoplasmic Ca 2+ concentration. Inhibition of RyR1 by siRNA-mediated knockdown or chemical inhibitor, dantrolene, significantly reduced cytosolic Ca 2+ and blocked multinucleated myotube formation. The elevation of cytoplasmic Ca 2+ concentration can effectively relieve myogenic differentiation stagnation by RyR1 inhibition, demonstrating that RyR1 modulates myogenic differentiation via regulation of Ca 2+ release channel. However, RyR1-knockout-induced Ca 2+ leakage led to the severe ER stress and excessive unfolded protein response, and drove myoblasts into apoptosis. Conclusions Therefore, we concluded that Ca 2+ release mediated by dramatic increase in RyR1 expression is required for the late stage of myogenic differentiation and fusion. This study contributes to a novel understanding of the role of RyR1 in myogenic differentiation and related congenital myopathies, and provides a potential target for regulation of muscle characteristics and meat quality.