RBM24 Regulates Adult Skeletal Muscle Regeneration By Modulating Alternative Splicing

The adult skeletal muscle can self-repair efficiently following mechanical or pathological damage due to its remarkable regenerative capacity.However,regulatory mechanisms underlying muscle regeneration are complicated and have not been fully elucidated.Alternative splicing(AS)is a major mechanism responsible for posttranscriptional regulation and extensively occurs in various biological processes and diseases.Particularly,many aberrant AS events have been identified in patients with muscular dystrophy which is accompanied by abnormal muscle regeneration.However,little is known about the correlation between AS and muscle regeneration.It has been reported that RNA binding motif protein 24(RBM24),a tissue-specific splicing factor,is involved in embryo myogenesis,while the role of Rbm24 in adult myogenesis(also called muscle regeneration)is poorly understood.To clarify the function of Rbm24 in adult skeletal muscle,we constructed Rbm24 conditional knockout mice and satellite cell-specific knockout mice.Rbm24 knockout mice displayed abnormal regeneration 4 months after tamoxifen treatment.Using a CTX-induced injury model,we showed that loss of RBM24 in skeletal muscle results in myogenic fusion and differentiation defects and significantly delays muscle regeneration.Besides,satellite cell-specific Rbm24 knockout mice recapitulated the defects in regeneration seen in the global Rbm24 knockout mice.Moreover,using RNA-Seq,we found that RBM24 regulates a complex network of AS events involved in multiple biological processes,including myogenesis,muscle regeneration and muscle hypertrophy.We further demonstrated that RBM24 regulates AS of Mef2d,Naca,Rock2 and Lrrfip1 which are essential for myogenic differentiation and muscle regeneration.Importantly,AS rescue experiments in RBM24-knockdown C2C12 cell line confirmed that RBM24 regulates myogenic differentiation in part by modulating AS.The present study systematically investigates the role of RBM24 in adult skeletal muscle regeneration and contributes to a better understanding of the effects of AS on muscle regeneration,providing further insights into diagnosis and treatment of muscular dystrophy which is usually accompanied with abnormal regeneration and dysregulated alternative splicing.