Calponin 3 Regulates Myoblast Proliferation and Differentiation Through Actin Cytoskeleton Remodeling and YAP1-Mediated Signaling in Myoblasts

Calponin 3 (CNN3) is an actin-binding protein that modulates actin cytoskeleton dynamics, which are vital processes for maintaining skeletal muscle homeostasis. Although the function of CNN3 in actin dynamics has been established, its biological significance in myogenic differentiation of pro-genitor cells remains largely unexplored. This study investigates the role of CNN3 in myogenic differentiation and its impact on actin cytoskeletal dynamics and mechanosensitive signaling in C2C12 myoblasts. CNN3 knockdown led to a marked increase in F-actin accumulation, which promoted the nuclear translocation of YAP1, a mechanosensitive transcriptional coactivator re-quired for response to mechanical cues that drive cell proliferation. CNN3 depletion enhanced myoblast proliferation and increased the expressions of YAP1 target genes involved in cell cycle progression, including PCNA, cyclin B1, and cyclin D1. Flow cytometry revealed that CNN3-deficient cells displayed higher S and G2/M phase fractions, which concurred with elevated proliferation rates. Furthermore, CNN3 knockdown impaired myogenic differentiation, as evi-denced by reduced levels of MyoD, MyoG, and MyHC, key markers of myogenic commitment and maturation, and immunocytochemistry showed myotube formation was diminished in CNN3-suppressed cells, which was supported by lower differentiation and fusion indices. These findings suggest that CNN3 is essential for myogenic differentiation and that it functions by regu-lating actin remodeling and YAP1 signaling to direct progenitor cells toward proliferation rather than differentiation. This study demonstrates CNN3 as a critical factor in skeletal myogenesis and a potential therapeutic target in muscle-wasting conditions.