Circular PPP1R13B RNA Promotes Chicken Skeletal Muscle Satellite Cell Proliferation and Differentiation via Targeting miR-9-5p

SIMPLE SUMMARY: The skeletal muscle of livestock is the main resource of proteins for human beings. Understanding the molecular mechanisms regulating the growth and development of skeletal muscle is important in breeding high yield quality muscle animals. In this study, we evaluated the expression of a novel circular RNA circPPP1R13B in fast muscle growing broilers and slow muscle growing layers, and the results showed that circular RNA circPPP1R13B was highly expressed in fast muscle growing broilers compared to the slow muscle growing layers. It was also revealed in this study that circPPP1R13B promote the proliferation and differentiation of chicken skeletal muscle satellite cells via targeting miR-9-5p. Therefore, the results obtained in this study indicate that circPPP1R13B may be a regulatory factor for promoting skeletal muscle growth and development in broilers, and possibly as a potential target for molecular breeding. ABSTRACT: Skeletal muscle plays important roles in animal locomotion, metabolism, and meat production in farm animals. Current studies showed that non-coding RNAs, especially the circular RNA (circRNA) play an indispensable role in skeletal muscle development. Our previous study revealed that several differentially expressed circRNAs among fast muscle growing broilers (FMGB) and slow muscle growing layers (SMGL) may regulate muscle development in the chicken. In this study, a novel differentially expressed circPPP1R13B was identified. Molecular mechanism analysis indicated that circPPP1R13B targets miR-9-5p and negatively regulates the expression of miR-9-5p, which was previously reported to be an inhibitor of skeletal muscle development. In addition, circPPP1R13B positively regulated the expression of miR-9-5p target gene insulin like growth factor 2 mRNA binding protein 3 (IGF2BP3) and further activated the downstream insulin like growth factors (IGF)/phosphatidylinositol 3-kinase (PI3K)/AKT serine/threonine kinase (AKT) signaling pathway. The results also showed that the knockdown of circPPP1R13B inhibits chicken skeletal muscle satellite cells (SMSCs) proliferation and differentiation, and the overexpression of circPPP1R13B promotes the proliferation and differentiation of chicken SMSCs. Furthermore, the overexpression of circPPP1R13B could block the inhibitory effect of miR-9-5p on chicken SMSC proliferation and differentiation. In summary, our results suggested that circPPP1R13B promotes chicken SMSC proliferation and differentiation by targeting miR-9-5p and activating IGF/PI3K/AKT signaling pathway.