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Received October 28, 2016; Revision received January 30, 2017
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.
KEY WORDS: OCT4, NANOG, NT2/D1 cell line, histone modifications