CircCCDC91 regulates chicken skeletal muscle development by sponging miR-15 family via activating IGF1-PI3K/AKT signaling pathway

Circular RNAs (circRNAs) has been reported in various tissues of animals and associated with multiple biological processes. From our previous sequencing data, we found a novel circRNA, circCCDC91 which was generated from exon 2 to 8 of the CCDC91 gene. We observed that circCCDC91 was differentially expressed in the chicken breast muscle among 4 different embryonic developmental time points (embryonic day 10 [E10], E13, E16, and E19). Therefore, we assumed that circCCDC91 have a potential function in chicken skeletal muscle development. In this study, we firstly verify the annular structure and expression pattern of circCCDC91, and further investigate on whether circCCDC91 could promote chicken skeletal development. Mechanistically, circCCDC91 could absorb miR-15a, miR-15b-5p, and miR-15c-5p to modulate the expression of Insulin receptor substrate1 (IRS1), as well as activate insulin-1ike growth factor 1-phosphatidylinositol 3-kinase/AKT (IGF1-PI3K/AKT) signaling pathway. In addition, circCCDC91 could rescue skeletal muscle atrophy by activating IGF1-PI3K/AKT pathway. Taken together, the findings in this study revealed that the newly identified circCCDC91 promotes myoblasts proliferation and differentiation, and alleviates skeletal muscle atrophy by directly binding to miR-15 family via activating IGF1-PI3K/AKT signaling pathway in chicken.