miR-27b-3p Was Involved in Retinoic Acid-induced Abnormal Early Myogenic Differentiation of C2C12 Cells via Targeting CaMKIIδ

Myogenic differentiation is an important stage within the multi-step process of skeletal muscle development. We previously found that excess retinoic acid (RA) could induce derangement of myofilaments in the embryonic tongue by inhibiting differentiation through Wnt5a/CaMKII delta (calcium/calmodulin-dependent protein kinase II delta) pathway. Furthermore, our recently studies indicated that excess RA can directly induce abnormal expression of series of miRNAs in embryonic tongue, including miR-27b-3p. miR-27b-3p has been reported as a regulator involved in kinds of tumors development. In addition, miR-27 was proved to negatively regulate adipogenesis. It has been indicated that miR-27b could down-regulate the expression of Pax3 and Pax7 and thus inhibits myoblast proliferation. Here, we found that the expression of miR-27b-3p increased at early stage of myogenic differentiation (differentiation day 2, D2) in RA-treated C2C12 cells, but CaMKII delta expression was reduced. Furthermore, bioinformatics analysis predicted that miR-27b-3p targets the 3'UTR of CaMKII delta. The direct interaction between of miR-27b-3p and CaMKII delta was confirmed by luciferase reporter assays. More importantly, rescue experiments indicated that CaMKII delta mediated miR-27b-3p to regulate the early differentiation defects induced by excess RA, and which was achieved mainly via Myogenin. In conclusion, excess RA disturbed the early differentiation of C2C12 cells by stimulating miR-27b-3p expression which targeted CaMKII delta, and then controlled the expression of Myogenin, those above implying new mechanism in myogenic differentiation and miR-27b-3p may act as a new biomarker for muscle disease.