ChIP-seq analyses of human periodontal ligament fibroblasts (PDLF) transfected with siRNA for PPARg

Periodontal ligament is soft connective tissue between alveolar bone and cementum, the surface hard tissue of tooth. Periodontal ligament fibroblasts (PDLF) actively express osteo/cementogenic genes, which contribute in periodontal tissue homeostasis. However, the key factors by which PDLF retain such osteo/cementogenic abilities has not been clarified yet. Here, we find PPARg is expressed in vivo periodontal ligament tissue and its distribution pattern is highly correlated with the alkaline phosphate enzymatic activity. Knockdown of PPARg drastically deprives PDLF of osteo/cementogenic abilities in vitro. In contrast, PPARg agonists enhance it. PPARg is required for maintaining acetylation status of H3K9 and H3K27, active chromatin marks, and the supplementation of acetyl-coA, the donor of histone acetylation, is able to restore PPARg knockdown-induced decreased osteo/cementogenic abilities in PDLF. RNA-seq and ChIP-seq combined analyses identify 4 osteogenic transcripts, RUNX2, SULF2, RCAN2, and RGMA, in the PPARg-dependent active chromatin region marked by H3K27ac. Furthermore, the RUNX2 binding sites are selectively enriched in the PPARg-dependent active chromatin region. Together, these findings identify PPARg is the key transcriptional factor of PDLF to retain osteo/cementogenic abilities and reveal that global H3K27ac modification involves in the comprehensive osteo/cementogenic transcriptional alteration mediated by PPARg. Overall design: Comparison of the H3K27ac peaks between control siRNA- and si-PPARg-transfected PDLF.