Topalovic V, Schwirtlich M, Stevanovic M, Mojsin M
Institute of Molecular Genetics and Genetic Engineering, University of Belgrade, Belgrade, Serbia.
Biochemistry (Mosc). 2017 Jun;82(6):715-722. doi: 10.1134/S0006297917060086.
Transcription factors OCT4 and NANOG are main constituents of a functional network that controls proliferation and pluripotency maintenance of stem cells as well as early lineage decisions. We investigated expression profiles of OCT4 and NANOG during the early phases of neural differentiation using NT2/D1 cells induced by retinoic acid as an in vitro model system of human neurogenesis. We demonstrated decrease in OCT4 and NANOG mRNA and protein levels following exposure to retinoic acid. Next, by employing chromatin immunoprecipitation, we investigated profiles of selected H3 and H2B histone marks deposited on the promoters of the OCT4 and NANOG genes. We found decline in H3K4me3, H2BK5ac, and H2BK120ac on both promoters, which paralleled the decrease in OCT4 and NANOG expression. Moreover, we found that the H2BK16ac mark is differentially enriched on these two promoters, pointing to differences in epigenetic regulation of OCT4 and NANOG gene expression. Finally, based on our data, we suggest that the early response of pluripotency genes OCT4 and NANOG to the differentiation-inducing stimuli is mediated by dynamic changes in chromatin marks, while DNA methylation is acquired in the later stages of neurogenesis.
转录因子OCT4和NANOG是一个功能网络的主要组成部分，该网络控制干细胞的增殖和多能性维持以及早期谱系决定。我们使用视黄酸诱导的NT2/D1细胞作为人类神经发生的体外模型系统，研究了神经分化早期阶段OCT4和NANOG的表达谱。我们证明了暴露于视黄酸后OCT4和NANOG的mRNA和蛋白质水平降低。接下来，通过染色质免疫沉淀，我们研究了沉积在OCT4和NANOG基因启动子上的选定H3和H2B组蛋白标记的谱。我们发现两个启动子上的H3K4me3、H2BK5ac和H2BK120ac均下降，这与OCT4和NANOG表达的降低平行。此外，我们发现H2BK16ac标记在这两个启动子上的富集存在差异，这表明OCT4和NANOG基因表达的表观遗传调控存在差异。最后，基于我们的数据，我们认为多能性基因OCT4和NANOG对分化诱导刺激的早期反应是由染色质标记的动态变化介导的，而DNA甲基化是在神经发生的后期获得的。
