SMN promotes mitochondrial metabolic maturation during myogenesis by regulating the MYOD-miRNA axis.

Abstract

Spinal muscular atrophy (SMA) is a congenital neuromuscular disease caused by the mutation or deletion of survival motor neuron 1 (SMN1) gene. Although the primary cause of progressive muscle atrophy in SMA has classically been considered the degeneration of motor neurons, recent studies have indicated a skeletal muscle-specific pathological phenotype such as impaired mitochondrial function and enhanced cell death. Here we found that the downregulation of SMN causes mitochondrial dysfunction and subsequent cell death in in vitro models of skeletal myogenesis with both a murine C2C12 cell line and human induced pluripotent stem cells. During myogenesis, SMN binds to the genome upstream of the transcriptional start sites of MYOD1 and microRNA (miR)-1 and -206. Accordingly, the loss of SMN downregulates these miRs, whereas supplementation of the miRs recovers the mitochondrial function, cell survival and myotube formation of SMN-deficient C2C12, indicating the SMN-miR axis is essential for myogenic metabolic maturation. Additionally, introduction of the miRs into ex vivo muscle stem cells derived from {Delta}7-SMA mice caused myotube formation and muscle contraction. In conclusion, our data revealed novel transcriptional roles of SMN during myogenesis, providing an alternative muscle-oriented therapeutic strategy for SMA patients. HighlightsO_LIReduced SMN causes mitochondrial dysregulation in myogenic cells. C_LIO_LIReduced SMN downregulates miR-1 and miR-206 expression in myogenic cells. C_LIO_LISMN protein binds to the genome upstream of MYOD1, miR-1 and miR-206. C_LIO_LImiR-1 and miR-206 are sufficient to improve skeletal muscle function in an SMA model. C_LI