IGF2 Activates the PI3K-AKT Signaling Pathway to Promote Proliferation of Duck Ovarian Granulosa Cells

To elucidate the specific role and mechanism of IGF2 (a strongly selected gene in egg-production traits identified in our previous genome resequencing of Chinese Jinding ducks) in duck ovaries, this study investigated the expression and distribution of IGF2, assessed its impact on the proliferation of duck ovarian granulosa cells (GC), and elucidated the underlying regulatory mechanisms.The expression of IGF2 mRNA in the ovary was significantly higher than in all other tissues (P<0.05),being 5.69 times that in the liver the tissue with the second-highest expression.Its protein was mainly located in GC, oocyte cytoplasm and vascular endothelium of duck follicles.In vitro experiments demonstrated that IGF2 enhanced the proliferation of duck GC.Further mechanistic analysis showed that IGF2 promoted the phosphorylation of PI3K and AKT, as well as the expression of downstream CCND3 gene, a cell cycle regulation gene.These findings suggested that IGF2 regulated duck GC proliferation through the PI3K/AKT/CCND3 pathway, thereby affecting the laying traits of ducks.These results revealed a regulatory role of IGF2 in duck follicular development via the PI3K-AKT pathway and extended the existing understanding of IGF2 function in ducks.