The fusion of myoblasts is a crucial stage in the growth and development of skeletal muscle. Myomaker is an important myoblast fusion factor that plays a crucial role in regulating myoblast fusion. However, the function of Myomaker in economic fish during posthatching has been poorly studied. In this study, we found that the expression of Myomaker in the fast muscle of Chinese perch (Siniperca chuatsi) was higher than that in other tissues. To determine the function of Myomaker in fast muscle, Myomaker-siRNA was used to knockdown Myomaker in Chinese perch and the effect on muscle growth was determined. The results showed that the growth of Chinese perch was significantly decreased in the Myomaker-siRNA group. Furthermore, both the diameter of muscle fibers and the number of nuclei in single muscle fibers were significantly reduced in the Myomaker-siRNA group, whereas there was no significant difference in the number of BrdU-positive cells (proliferating cells) between the control and the Myomaker-siRNA groups. Together, these findings indicate that Myomaker may regulate growth of fast muscle in Chinese perch juveniles by promoting myoblast fusion rather than proliferation.

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.