The Role of Twist2 in Myoblast Proliferation, Fusion, and Its Impact on Muscle Structure During the Growth of Chinese Perch (Siniperca chuatsi).

Twist2 plays a pivotal regulatory role in the growth of skeletal muscle across various organisms. Nonetheless, the specific mechanism by which Twist2 governs skeletal muscle function in fish, particularly in the economically significant Chinese perch (Siniperca chuatsi), remains unclear. Within the muscle injury model in Chinese perch, we observed that Twist2 expression was upregulated during the repair phase of fast muscle tissue, exhibiting an expression pattern analogous to that of Pax7. Following the knockdown of Twist2 using Twist2-specific in vivo-siRNA in fast muscle tissues, the expression of myogenic regulatory factors (MRFs) and Myomaker was significantly reduced in the Twist2-siRNA-treated group compared with the control group, whereas no significant differences were observed for Pax3 and Pax7. Furthermore, the diameter of myofibers and the number of nuclei in single myofibers were reduced, and concurrently, the number of BrdU-positive cells (proliferating cells) was significantly reduced in the Twist2-siRNA-treated group. Taken together, this study demonstrates that Twist2 promotes myoblast proliferation and fusion, thereby regulating fast muscle growth in juvenile Chinese perch. These findings provide a clear direction for further exploration of molecular mechanisms underlying skeletal muscle growth in economic fish species.