Effects of demethylase KDM4B on the biological characteristics and function of yak cumulus cells in vitro

The present study aims to investigate the expression and function of lysine-specific demethylase 4B (KDM4B) in yak cumulus cells (CCs) in order to reveal the mechanisms by which KDM4B regulates biological characteristics and function of CCs. The cellular location of KDM4B and the methylation pattern of H3K9 were detected using immunofluorescence (IF) staining in CCs. The mRNA expression levels of apoptosis-related genes (BCL-2, HAX1 and BAX) and genes related to the estrogen pathway (ESR2, CYP17 and 3B-HSD) were estimated by qRT-PCR after knockdown of KDM4B expression by siRNA in yak CCs. Then, a proliferation assay, Annexin V-FITC staining, and ELISA were utilized to explore the effects of KDM4B silencing on CCs proliferation, apoptosis, and estrogen (E2) secretion, respectively. The results showed that KDM4B is located in the nuclei of yak CCs and is distributed in a dotted pattern. Knockdown KDM4B induced a decrease in cell proliferation, an increase in apoptotic rate and a reduction in the levels of E2 secretion of CCs. Additionally, the methylation patterns of H3K9me2 and H3K9me3 were significantly increased in CCs transfected with KDM4B siRNA-1 (P