miR-99a-5p Regulates the Proliferation and Differentiation of Skeletal Muscle Satellite Cells by Targeting MTMR3 in Chicken.

Noncoding RNAs, especially microRNAs (miRNAs), have been reported to play important roles during skeletal muscle development and regeneration. Our previous sequencing data revealed that miR-99a-5p is one of the most abundant miRNAs in chicken breast muscle. The purpose of this study was to reveal the regulatory mechanism of miR-99a-5p in the proliferation and differentiation of chicken skeletal muscle satellite cells (SMSCs). Through the investigation of cell proliferation activity, cell cycle progression, and 5-ethynyl-29-deoxyuridine (EdU) assay, we found that miR-99a-5p can significantly promote the proliferation of SMSCs. Moreover, we found that miR-99a-5p can inhibit myotube formation by decreasing the expression of muscle cell differentiation marker genes. After miR-99a-5p target gene scanning, we confirmed that miR-99a-5p directly targets the 3' untranslated region (UTR) of myotubularin-related protein 3 (MTMR3) and regulates its expression level during chicken SMSC proliferation and differentiation. We also explored the role of MTMR3 in muscle development and found that its knockdown significantly facilitates the proliferation but represses the differentiation of SMSCs, which is opposite to the effects of miR-99a-5p. Overall, we demonstrated that miR-99a-5p regulates the proliferation and differentiation of SMSCs by targeting MTMR3.