Novel insights into the regulation of NF2/SWH signaling in granulosa cells of prehierarchical follicle development in hen ovary

The tumor suppressor gene NF2 (Neurofibromatosis type 2) is involved in critical biological processes, including organ-size control, cell proliferation, differentiation, apoptosis, and cancer development by activating the SWH signaling pathway (also named Hippo pathway) in humans and Drosophila. However, the exact roles and molecular regulatory mechanisms of NF2 in chicken granulosa cells (GCs) proliferation, differentiation, apoptosis, and steroidogenesis are required for ovarian follicle growth, prehierarchical follicular development, and follicular selection remain poorly understood. This study demonstrated that the NF2 mRNA was expressed in various-sized prehierarchical follicles (PFs) and GCs. NF2 protein was localized in the GC cytoplasm and predominantly expressed in the undifferentiated GCs and oocytes of the PFs. Here, the effects of NF2 on the proliferation, differentiation, apoptosis, and mitochondrial function of GCs were detected. NF2 regulates GC proliferation, differentiation, and apoptosis via SWH signaling pathway downstream transcriptional co-activator YAP1 in vitro. Additionally, NF2/SWH significantly increased the phosphorylation level of p38 via transcriptional co-activator YAP1. To explore the role of the p38 signaling pathway in the process of NF2/SWH-induced apoptosis in GCs, an activator of p38 (U46619) was added to the si-NF2 treatment, and inhibitor of p38 (SB203580) added to the si-NF2 treatment. We found that NF2/SWH signaling pathway promoted GC apoptosis by affecting the function of GC mitochondria via p38 signaling via SWH signaling pathway downstream transcriptional co-activator YAP1. In conclusion, these results demonstrated that NF2/SWH inhibited proliferation, and differentiation of GCs via SWH signaling pathway downstream transcriptional co-activator YAP1, and promoted apoptosis of GCs by p38 MAPK signaling and mitochondrial function in chicken via SWH signaling downstream transcriptional co-activator YAP1.