The Removal of H3K27me3 Promoted SLPI Transcription and Pubertal Initiation in Pigs

Pubertal initiation critically determines reproductive performance in female pigs. Histone H3 lysine 27 trimethylation (H3K27me3) has been implicated in ovarian development. However, its genome-wide regulatory landscape during the pubertal transition remains unexplored. Here, we obtained transcriptomes of GCs treated with the pharmacological H3K27me3 agonist GSK-J4 or H3K27me3 inhibitor EPZ005687. We found that H3K27me3 substantially remodels the transcriptomic landscape of porcine GCs, with differentially expressed genes significantly enriched in pathways governing cell proliferation and apoptosis. Mechanistically, H3K27me3 suppressed GC proliferation by downregulating the expression of PCNA and promoting apoptosis through upregulation of CASP3, thereby delaying pubertal initiation. Furthermore, genome-wide ChIP-seq analysis on porcine ovaries from pre-pubertal and in-pubertal gilts revealed higher H3K27me3 enrichment around transcription start sites in the In-puberty stage than in the Pre-puberty stage. Genes with promoters exhibiting reduced H3K27me3 occupancy during the pubertal transition were enriched in pathways related to sex differentiation and serine-type endopeptidase inhibitor activity. Notably, secretory leukocyte peptidase inhibitor (SLPI) was identified by ChIP-qPCR as a direct target repressed by H3K27me3. Functional validation demonstrated that SLPI promoted GC proliferation and inhibited GC apoptosis in vitro. Intraperitoneal injection of LV-Slpi or sh-Slpi into C57BL/6J mice showed that Slpi accelerated pubertal initiation of mice in vivo. Collectively, our findings confirmed that developmental stage-specific loss of H3K27me3 at the SLPI promoter derepressed SLPI transcription, which in turn promoted porcine GC proliferation, suppressed apoptosis, and facilitated pubertal initiation in mice. These results provided valuable insights into the epigenetic regulation of pubertal initiation in mammals.