Expression and regulation of Noggin4 gene in chicken ovarian follicles and its role in the proliferation and differentiation of granulosa cells

As a member of Noggin family, Noggin4 is reported to play an important role in the formation of head structure during the embryo development of Xenopus laevis and chicken. We previously detected an increase of Noggin4 transcript in the granulosa cells of chicken hierarchal follicles (Post-GCs) compared to pre-hierarchal follicles (Pre-GCs) by ONT transcriptome sequencing. To further clarify the role of Noggin4 in chicken follicle selection, in this study, we investigated its expression, regulation and function in follicles and granulosa cells. The mRNA expression of chicken Noggin4 exhibited dynamic changes during follicle development. It was significantly higher in the small yellow follicles than in the small white, F6, F5 and F4 follicles, and also increased in Post-GCs than in Pre-GCs. The Noggin4 mRNA could be stimulated by follicle stimulating hormone (FSH) and bone morphogenetic protein 4 (BMP4) in both Pre-GCs and Post-GCs. However, the estrogen and progesterone could exert opposing transcriptional regulations on Noggin 4 mRNA in both Pre- and Post-GCs. In chicken Post-GCs, knockdown of Noggin4 by siRNA reduced the mRNA expression of steroidogenic acute regulatory protein (STAR), cytochrome P450 family 11 subfamily A member 1 (CYP11A1), but increased that of Wnt family member 4 (Wnt4), while overexpression of Noggin4 significantly decreased the mRNA expression of Wnt4 but had no marked effects on that of STAR and CYP11A1. Moreover, Noggin4 significantly decreased the mRNA expression of BMP4 in both Pre-GCs and Post-GCs. Overexpression of Noggin4 inhibited the proliferation of both Pre-GCs and Post-GCs. These data collectively suggest an important role of Noggin4 in chicken follicle selection, especially on the proliferation of granulosa cells.