miR-215-5p Suppresses Proliferation/Cell-Cycle Progression and Promotes Apoptosis via Targeting CTCF in Goat Mammary Epithelial Cells

MicroRNA (miRNA) is a type of small non-coding RNA that influences various biological processes by targeting gene expression. However, the roles of microRNA in mediating ruminant mammary cell proliferation and survival remain poorly understood. This study aimed to elucidate how miR-215-5p regulates cell cycle and apoptosis-related genes in goat mammary epithelial cells (GMECs). The effects of miR-215-5p on cell cycle and apoptosis were assessed by flow cytometry. A combination of bioinformatics analysis was conducted to predict the target genes of miR-215-5p; this was followed by experimental validation using techniques such as luciferase reporter assays. The effects of CTCF, the targeting gene of miR-215-5p, on cell cycle and apoptosis were examined by qRT-PCR, Western blot and flow cytometry in GMECs. The study demonstrated that miR-215-5p induced cell-cycle arrest at the G0/G1 phase and promoted apoptosis in GMECs. Mechanistically, miR-215-5p downregulated CTCF expression by directly targeting its 3'-untranslated region (3'UTR). This miR-215-5p-mediated depletion of CTCF inhibits CDK2 and CDK6 activity, consequently downregulating genes involved in cell-cycle progression. Furthermore, the miR-215-5p/CTCF axis was found to promote apoptosis by downregulating the protein expression of Bcl-xL and upregulating the gene expression of Bax. In summary, miR-215-5p suppresses GMEC proliferation and survival through CTCF-dependent histone modifications.