Circular RNA circMYL1 Inhibit Proliferation and Promote Differentiation of Myoblasts by Sponging miR-2400

Circular RNAs (circRNAs) are a class of endogenous non-coding RNAs (ncRNAs) involved in regulating skeletal muscle development by sponging miRNAs. In this study, we found that the circMYL1 expression was down-regulated during myoblast proliferation, while gradually up-regulated in myoblast differentiation. The potential role of circMYL1 was identified in the proliferation of bovine myoblast through mRNA and protein expression of proliferation marker genes (PCNA, CyclinD1, and CDK2), cell counting kit-8 assay, flow cytometry analysis, and 5-ethynyl 2'-deoxyuridine (EdU) assay. Analysis of the expression of differentiation marker genes (MyoD, MyoG, and MYH2) and immunofluorescence of Myosin heavy chain (MyHC) was used to assess cell differentiation. The proliferation analysis revealed that circMYL1 inhibited the proliferation of bovine primary myoblast. Furthermore, the differentiation analysis demonstrated that circMYL1 promoted the differentiation of bovine primary myoblast. The luciferase screening and RNA immunoprecipitation (RIP) assays found that circMYL1 could have interaction with miR-2400. Additionally, we demonstrated that miR-2400 promoted proliferation and inhibited differentiation of bovine primary myoblast, while circMYL1 may eliminate the effects of miR-2400, as showed by rescue experiments. Together, our results revealed that a novel circular RNA of circMYL1 could inhibit proliferation and promote differentiation of myoblast by sponging miR-2400.