CircRNA Profiling Reveals an Abundant circBDP1 that Regulates Bovine Fat Development by Sponging miR-181b/miR-204 Targeting Sirt1/TRARG1

The proliferation and differentiation of preadipocytes is an important factor determining bovine fat development, which is closely related to the feed conversion ratio, carcass traits, and beef quality. The purpose of this study was to identify the effects of candidate circRNA and miRNA on the proliferation and differentiation of bovine preadipocytes in order to provide basic materials for molecular breeding in cattle. circRNA sequencing was performed on bovine adipocyte samples at different differentiation time points, and a total of 1830 differentially expressed circRNAs were identified. Among them, circBDP1, derived from the bovine BDP1 gene, has potential binding sites for miR-204 (known as a regulator of bovine fat development) and miR-181b, which gives us a hint that circBDP1 may regulate bovine fat development by adsorbing miR-204 and miR-181b. Here, our results revealed that circBDP1 overexpression promoted the proliferation and differentiation of bovine preadipocytes. The miRNA profile of bovine adipocytes at different differentiation time points was also analyzed using the small RNA sequencing method, and a total of 89 differentially expressed miRNAs were identified, including miR-204 and miR-181b. As expected, dual-luciferase reporter results showed that circBDP1 competitively adsorbed miR-181b and miR-204. Overexpression and interference of miR-181b in bovine preadipocytes and 3T3-L1 showed that miR-181b promoted the proliferation and differentiation of preadipocytes. Further results displayed that miR-181b and miR-204 simultaneously targeted the SIRT1 gene, and miR-204 also targeted the 3' UTR region of the TRARG1 gene. In summary, this study found that miR-181b and miR-204 were involved in fat development by targeting SIRT1 and TRARG1. The results of this study will lay a foundation for the research of fat development and beef cattle industry.