Lipid Deposition and Progesterone Synthesis Are Increased by miR-181b-5p through RAP1B/ERK1/2 Pathway in Chicken Granulosa Cells

Steroid hormones secreted by granulosa cells are essentialformaintaining normal development of chicken follicles. Our previoussequencing data indicated that miR-181b-5p and RAS-related protein1B (RAP1B) appeared to function in chicken granulosacells, which was further explored in this study. The results suggestedthat miR-181b-5p facilitated the aggregation of lipid droplets andthe synthesis of progesterone. In contrast, RAP1B astricted lipid deposition and progesterone secretion. Cotransfectionof the RAP1B overexpression vector with miR-181b-5pmimic eliminated the promoting effect of miR-181b-5p. Dual-luciferasereporter assay confirmed that miR-181b-5p bound directly to the 3 & PRIME;untranslated region (3 & PRIME; UTR) of RAP1B. Wealso found that miR-181b-5p and RAP1B reduced andenhanced the phosphorylation levels of extracellular signal-regulatedkinases 1 and 2 (ERK1/2), respectively. The application of ERK1/2activators and inhibitors demonstrated that ERK1/2 is a negative regulatorof lipid deposition and progesterone synthesis. In conclusion, werevealed that miR-181b-5p accelerated lipid deposition and progesteronesynthesis through the RAP1B/ERK1/2 pathway in chicken granulosa cells.miR-181b-5p and RAP1B may serve as new biomarkersin breeding to improve chicken reproductive performance and preventovary-related diseases.