circ_0000132 Regulates Chicken Granulosa Cell Proliferation Apoptosis and E2/P4 Synthesis via miR-206 E2F5 Signaling

This study investigates the regulatory role of circFBN1 in chicken follicular granulosa cells (GCs) and its underlying molecular mechanisms through the miR-206/E2F5 pathway. circFBN1 was found to significantly enhance GC proliferation and inhibit apoptosis, as evidenced by increased expression of proliferation-related genes (PCNA, CDK1, and CCND1) and decreased expression of apoptosis-related genes (Caspase-3). Additionally, circFBN1 overexpression promoted the secretion of estradiol (E2) and progesterone (P4) by upregulating steroidogenesis-related genes (StAR and CYP11A1). Mechanistic studies revealed that circFBN1 functions as a molecular sponge for miR-206, thereby alleviating its inhibitory effect on the target gene E2F5. Dual-luciferase reporter assays confirmed the specific binding between circFBN1 and miR-206. Overexpression of miR-206 had the opposite effects, inhibiting GC proliferation, inducing apoptosis, and reducing E2 and P4 secretion by downregulating StAR and CYP11A1. Furthermore, E2F5 was identified as a direct target of miR-206, and its knockdown significantly reduced GC proliferation, increased apoptosis, and decreased steroid hormone secretion. These findings elucidate the regulatory mechanisms of the circFBN1/miR-206/E2F5 axis in avian follicle development and provide potential molecular targets for improving poultry reproductive performance. Future research should focus on exploring the upstream regulators of this axis and its interactions with other signaling pathways.