EZH2 Regulates the Pluripotency of Mouse Embryonic Stem Cells by Modulating Nanog Expression Under PKC Inhibition

Polycomb repressive complex 2 (PRC2) regulates the expression of pluripotency genes in embryonic stem cells (ESCs) and suppresses multiple genes associated with development, cell fate determination, and differentiation. Mouse embryonic stem cells (mESCs) derived from protein kinase C inhibition (PKCi) exhibit self-renewal and pluripotency comparable to those ESCs captured by the classical 2iL (CHIR99021, PD0325901, and leukemia inhibitory factor) system. However, the dynamic expression pattern of PRC2 in PKCi-mESCs and its role in regulating pluripotency remain unclear. This study demonstrated that the expression level of the enhancer of zeste 2 gene (Ezh2), of which protein is the catalytic subunit of PRC2 responsible for the trimethylation of lysine 27 on nucleosome histone H3 subunit (H3K27me3), is significantly higher in PKCi-mESCs than in 2iL-mESCs. EZH2 knockdown enhances the self-renewal capacity of PKCi-mESCs, as evidenced by a significant increase in the number of undifferentiated mESCs colonies. The effect of an EZH2 reduced expression is accompanied by the upregulation of specific core pluripotency gene Nanog, along with the general downregulation of differentiational genes representing the three germ layers. Conversely, EZH2 overexpression promotes a significant differentiation of PKCi-mESCs, resulting in the downregulation of pluripotency genes, including core pluripotency genes Nanog and Sox2, as well as naïve pluripotency genes Klf4, Fgf4, and Esrrb, while with a wide upregulation of three germ layer associated genes. Importantly, Cleavage Under Targets and Tagmentation (CUT&Tag) demonstrates that EZH2 directly controls H3K27me3 enrichment at the Nanog promoter near the transcription start site. Thus, EZH2, a core subunit of PRC2, exhibits the distinct regulatory functions orchestrating mESCs at a poised state between self-renewal and differentiation under PKC inhibition. EZH2 exerts histone H3 methyltransferase activity to regulate Nanog expression as one of its key targets, thereby modulating the transcriptional regulatory network that maintains pluripotency and lineage specification in mESCs.