Chi-miR-487b-3p Inhibits Goat Myoblast Proliferation and Differentiation by Targeting IRS1 through the IRS1/PI3K/Akt Signaling Pathway.

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MicroRNAs (miRNAs) are endogenously expressed small noncoding RNAs and play critical roles in the regulation of post-transcriptional gene expression. Our previous study uncovered that chi-miR-487b-3p is widespread in different goat tissues, which is significantly higher in muscle, especially in lamb. Here, we demonstrate the role of chi-miR-487b-3p as a myogenic miRNA that regulates skeletal muscle development. chi-miR-487b-3p overexpression was demonstrated to significantly inhibit goat myoblast proliferation and differentiation, whereas chi-miR-487b-3p inhibition resulted in the opposite effects. Next, chi-miR-487b-3p was predicted to target the 3′UTR of insulin receptor substrate 1 (IRS1) gene by Target-Scan and miRDB. The results of dual-luciferase assay, RT-qPCR, and western blot all confirmed that IRS1 might be a direct target of chi-miR-487b-3p as its expression was negatively regulated by chi-miR-487b-3p. siRNA silencing of IRS1 further demonstrated significant inhibition on goat myoblast proliferation and differentiation, confirming the effect of IRS1 downregulation by chi-miR-487b-3p in myogenesis. In addition, chi-miR-487b-3p knockout goat myoblast clones were generated using CRISPR/Cas9 technology, and we further illustrated that chi-miR-487b-3p regulates goat myoblast growth through the PI3K/Akt signaling pathway by targeting IRS1. Collectively, our work demonstrated that chi-miR-487b-3p is a potent inhibitor of skeletal myogenesis and provided new insights into the mechanisms of miRNA on the regulation of goat growth.