miR-339-5p impairs myogenic proliferation and differentiation by repressing contractile gene programs in skeletal muscle

MicroRNAs (miRNAs) are critical regulators of skeletal muscle development and adaptation, orchestrating the balance between proliferation, differentiation, and tissue repair. Here, we identify miR-339-5p as a previously unrecognized, conserved regulator of skeletal muscle remodeling. Transcriptomic analysis from human, mouse, and rat studies revealed that miR-339-5p is consistently upregulated in skeletal muscle under conditions of stress or injury and declines during myogenic differentiation in vitro. Gain-of-function experiments demonstrated that miR-339-5p overexpression impairs expression of genes associated with myogenic differentiation and promotes expression of proliferative markers in both primary human myotubes and mouse C2C12 cells. Transcriptomic profiling confirmed widespread repression of pathways involved in cytoskeletal organization, myofibrillar assembly, and mitochondrial function. In vivo, electroporation-mediated overexpression of miR-339-5p in mouse tibialis anterior altered regeneration-associated gene expression and increased the number of immature fibers, therefore modulating tissue remodeling during post-injury growth. Integrated analyses combining target prediction algorithms, differentiation-associated correlations, and overexpression datasets identified seven conserved high-confidence miR-339-5p targets, among which the autophagy-associated phosphatase MTMR3 emerged as the most consistently regulated candidate. Collectively, our data demonstrate that miR-339-5p functions as a conserved inhibitor of myogenic progression, linking injury-induced stress responses to delayed differentiation and altered muscle remodeling. These findings establish miR-339-5p as a potential therapeutic target in conditions characterized by impaired muscle regeneration or dysregulated tissue remodeling.