In female mammals, the abnormal apoptosis of ovarian granulosa cells (GCs) impairs follicular development and causes reproductive dysfunction. Many studies have indicated that the FGFR1 gene of the PI3K signaling pathway and the p65 subunit of the transcription factor NF-κB may regulate the proliferation and apoptosis of GCs involved in follicular development. However, little is known about whether p65 regulates the transcription of FGFR1, as well as the biological effects of p65 and FGFR1 on the survival of GCs and follicular development. In porcine follicles and GCs, we found that p65 and FGFR1 were exclusively expressed in the GCs of follicles, and the mRNA and protein levels of p65 and FGFR1 significantly increased from small to large follicles. Both p65 and FGFR1 were found to activate the PI3K signaling pathway, and the expressions of proliferation markers (PCNA and MKI67) and the anti-apoptotic gene BCL2 were significantly increased by p65 and FGFR1. Furthermore, both p65 and FGFR1 were observed to promote cell proliferation and inhibit the cell apoptosis of GCs, and p65 was confirmed to bind at the −348/−338 region of FGFR1 to positively regulate its transcription. Moreover, p65 was further found to enhance the pro-proliferation and anti-apoptotic effects of FGFR1. Taken together, p65 may target the −348/−338 region of FGFR1, promote the transcription of FGFR1, and enhance the pro-proliferation effect and anti-apoptotic effect of FGFR1 to facilitate the growth of follicles. This study will provide useful information for further investigations on the p65-mediated-FGFR1 signaling pathway during folliculogenesis in mammals.

Previous studies have strongly recommended that KISS-1 metastasis suppressor (KISS1) plays an essential gatekeeper of the initiation of reproductive maturation in mammals. However, KISS1 has been recently reported to highly express in ovarian granulosa cells (GCs). But the biological functionalities of KISS1 on cell apoptosis, cell cycle, and synthesis of estradiol-17β (E2) have not been explored in GCs. In this study, using porcine GCs as a cellular model, the overexpression plasmid of KISS1 was built to explore the biological effects of KISS1 on the PI3K signaling pathway, estrogen signaling pathway, cell apoptosis, cell cycle, and E2 secretion. We found that mRNA of KISS1 highly expressed in the ovary and significantly increased from immature to mature follicles in gilts. Overexpression of KISS1 could significantly increase the mRNA expression of PIK3CG, PIK3C1, and PDK1, and significantly decreased the mRNA levels of FOXO3, TSC2, and BAD of PI3K signaling pathway. Furthermore, results of the flow cytometry showed that overexpression of KISS1 significantly inhibited the apoptosis of GCs and decreased the percentage of GCs at G0/G1 phase of the cell cycle. Additionally, overexpression of KISS1 could increase the mRNA levels of Star, CYP17, 3B-HSD, 17B-HSD of estrogen synthesis signaling pathway, significantly increase the concentration of E2 in the supernatant of the cultured GCs, and up-regulate the mRNA expression levels of ESR1 and ESR2. These results suggested that KISS1 might suppress cell apoptosis through activating the PI3K signaling pathway and stimulate synthesis of E2 via boosting the estrogen synthesis signaling pathway. This study would be of great interests for exploring the biological functionalities of KISS1 in the folliculogenesis and sex steroid production of the ovaries in mammals.

Previous studies suggest that signal transducer and activator of transcription 3 (STAT3) and CCAAT/enhancer binding protein beta (C/EBPβ) play an essential role in ovarian granulosa cells (GCs) for mammalian follicular development. Several C/EBPβ putative binding sites were previously predicted on the STAT3 promoter in mammals. However, the molecular regulation of C/EBPβ on STAT3 and their effects on cell proliferation and apoptosis remain virtually unexplored in GCs. Using porcine GCs as a model, the 5′-deletion, luciferase report assay, mutation, chromatin immunoprecipitation, Annexin-V/PI staining and EdU assays were applied to investigate the molecular mechanism for C/EBPβ regulating the expression of STAT3 and their effects on the cell proliferation and apoptosis ability. We found that over and interfering with the expression of C/EBPβ significantly increased and decreased the messenger RNA (mRNA) and protein levels of STAT3, respectively. The dual luciferase reporter assay showed that C/EBPβ directly bound at −1397/−1387 of STAT3 to positively regulate the mRNA and protein expressions of STAT3. Both C/EBPβ and STAT3 were observed to inhibit cell apoptosis and promote cell proliferation. Furthermore, C/EBPβ might enhance the antiapoptotic and pro-proliferative effects of STAT3. These results would be of great insight in further exploring the molecular mechanism of C/EBPβ and STAT3 on the function of GCs and the development of ovarian follicles in mammals.

In female mammals, the initiation of puberty, coupling with the dramatically morphological changes in ovaries, indicates the sexual and follicular maturation. Previous studies have suggested that the disrupted DNA methylation results in the delayed puberty. However, to date, the changes in ovarian methylomes during pubertal transition have not been investigated. In this study, using gilts as a pubertal model, the genome-wide DNA methylation were profiled to explore their dynamics during pubertal transition across Pre-, In- and Post-puberty. During pubertal transition, the follicles underwent maturation and luteinization, coupled with the significant changes in the mRNA expression of DNMT1 and DNMT3a. DNA methylation levels of In-puberty were higher than that of Pre- and Post-puberty at the locations of genes and CpG islands (CGIs). Analysis of the DNA methylation changes identified 12,313, 20,960 and 17,694 differentially methylated CpGs (DMCs) for the comparisons of Pre- vs. In-, In vs. Post-, and Pre- vs. Post-puberty, respectively. Moreover, the CGIs, upstream and exonic regions showed a significant underrepresentation of DMCs, but the CGI shores, CGI shelves, intronic, downstream and intergenic regions showed a significant overrepresentation of DMCs. Furthermore, biological functions of these methylation changes enriched in PI3K-Akt signaling pathway, GnRH signaling pathway, and Insulin secretion, and the mRNA expressions of several genes of these signaling pathway, including MMP2, ESR1, GSK3B, FGF21, IGF1R, and TAC3, were significantly changed across Pre-, In- and Post-puberty in ovaries. During pubertal transition in gilts, the DNA methylation changes of ovaries were likely to affect the transcription of genes related to PI3K-Akt signaling pathway, GnRH signaling pathway, and Insulin secretion. These observations can provide new insight into the epigenetic mechanism of follicular and sexual maturation during pubertal transition in mammals.

Journal of Animal Science and Technology (JAST) is a peer-reviewed, open access journal publishing original research, review articles and notes in all fields of animal science. Topics covered by the journal include: genetics and breeding, physiology, nutrition of monogastric animals, nutrition of ruminants, animal products (milk, meat, eggs and their by-products) and their processing, grasslands and roughages, livestock environment, animal biotechnology, animal behavior and welfare.

Background The biological structure and function of mammalian ovaries undergo important developmental changes during pre- puberty. Posttranslational modified histones dynamically regulate ovarian development, which also can respond to the onset of puberty with heritable changes in gene expression that are associated with nucleosome modifications. This research used chromatin immunoprecipitation followed by sequencing (ChIP-seq) technology and bioinformatic analysis to confirm the histone-DNA interaction in pre-puberty ovarian follicles (PreOV) and in-puberty ovarian follicles (InOV). Then, employed qRT-PCR, and cell proliferation and apoptosis testing to further investigate the function of H3K4me3and H3K27me3 in gene transcription and cell growth. Results With the onset of puberty, ChIP-Seq found 946 higher- enrichment and 916 lower- enrichment genes were significantly differentially modified with H3K4me3, while 1954 higher- enrichment and 882 lower- enrichment genes were significantly differentially modified with H3K27me3 in InOV vs. PreOV. Then interestingly, 88 significantly genes were associated with significantly differentially H3K4me3-enriched, H3K4me3-delepted, H3K27me3-enriched, and H3K27me3-delepted modifications, which also were related to female gemmate development pathway, bone mineralization and fatty acid transport, including FOXO3, RUNX1, NOBOX, DMRT1, MYC, LEPTIN, ACVR2, and BMPR1B. Furthermore, compare medium-sized antral with Graff follicles, FOXO3, RUNX1 and BMPR1B were low expressed in medium-sized antral follicles, while NOBOX and LEPTIN were low expressed in Graff follicles. Finally, H3K4me3 exhibited to promote proliferation and anti-apoptosis, whereas H3K27me3 was more to inhibited proliferation and induced cell apoptosis in porcine granulosa cells (pGCs). Conclusions The genome-wide modified profile of H3K4me3 and H3K27me3 showed that H3K27me3 modification was more active than H3K4me3 modification during the onset of puberty in porcine ovaries. H3K4me3 and H3K27me3 acted as activator and repressor to regulate gene transcription that are related to porcine puberty initiation process. Genes including FOXO3, BMPR1B, LEPTIN, RUNX1, involved in networks of female gamete generation pathway associating with ovarian follicle development, ovulation, ovulation cycle process and female gonad development, which showed the further direction to investigate the function of H3K4me3/H3K27me3-targets in puberty initiation.