FOXO1 regulates bovine skeletal muscle cells differentiation by targeting MYH3.

The growth and development of bovine skeletal muscle and beef yield is closely intertwined. Our previous research found that forkhead box O1 (FOXO1) plays an important role in the regulation of beef muscle formation, but its specific mechanism is still unknown. In this study, we aimed to clarify the regulatory mechanism of FOXO1 in proliferation and differentiation of bovine skeletal muscle cells (BSMCs). The results showed that interfering with FOXO1 can promote proliferation and the cell G1/S phase of BSMCs by up-regulating the expression of PCNA, CDK1, CDK2, CCNA2, CCNB1, CCND1 and CCNE2. Besides, interfering with FOXO1 inhibited the apoptosis of BSMCs by up-regulating the expression of anti-apoptosis gene BCL2, while simultaneously down-regulating the expression of the pro-apoptosis genes BAD and BAX. Inversely, interfering with FOXO1 can promote the differentiation of BSMCs by up-regulating the expression of myogenic differentiation marker genes MYOD, MYOG, MYF5, MYF6 and MYHC. Furthermore, RNA-seq combined with western bolt, immunofluorescence and chromatin immunoprecipitation analysis showed that FOXO1 could regulate BSMCs differentiation process by influencing PI3K-Akt, Relaxin and TGF-beta signaling pathways, and target MYH3 for transcriptional inhibition. In conclusion, this study provides a basis for studying the role and molecular mechanism of FOXO1 in BSMCs.