A Unique Developmental Pattern of Oct-3/4DNA Methylation Is Controlled by a cis-demodification Element

Abstract

Oct-3/4 is the earliest expressed transcription factor that is known to be crucial in murine pre-implantation development. In this report we asked whether methylation participates in controlling changes in Oct-3/4 expression and thus may play an important role in controlling normal embryogenesis. We show that the Oct-3/4 gene is unmethylated from the blastula stage but undergoes de novo methylation at 6.5 days post-coitum and remains modified in all adult somatic tissues analyzed. Oct-3/4 remains unmethylated in 6.25 days post-coitum epiblast cells when other genes, such as apoAI, undergo de novo methylation. We show that methylation of the Oct-3/4 promoter sequence strongly compromises its ability to direct efficient transcription. Moreover, DNA methylation inhibits basal transcription of the endogenous Oct-3/4 gene in vivo. We found that the Oct-3/4 gene harbors a cis-specific demodification element that includes the proximal enhancer sequence. This element leads to demethylation in embryonal carcinoma cells when the sequence is initially methylated and protects the local region from de novo methylation in post-implantation embryos. These results indicate that in the embryo protection from de novo methylation is not a unique feature of imprinted or housekeeping genes that carry a CpG island, but is also applicable to tissue-specific genes expressed during early stages of embryogenesis. Methylation of Oct-3/4 may be analogous to methylation of CpG islands on the inactive X chromosome that also occurs at later stages of development.

Epigenetic regulation of gene expression in porcine epiblast, hypoblast, trophectoderm and epiblast-derived neural progenitor cells

“…In mouse, Oct4 is unmethylated and robustly expressed in both ESCs and embryonic carcinoma cells, whereas the gene is hypermethylated and repressed in somatic cells. 26,27 Similarly, as shown in our study, OCT4 was hypermethylated and repressed in porcine blood, representing somatic, differentiated tissue and hypomethylated and highly expressed in porcine epiblast and…”

“…In the bovine in vitro-produced morula, the DNA methylation levels of the OCT4, NANOG and SOX2 promoters are hypomethylated. 25 In mouse ESCs and trophoblast stem cells (TSCs), the DNA methylation level on distinct promoter sequences directly regulates the expression level of Oct4, 26,27 and Nanog. 28 Hence, the promoters are hypomethylated in pluripotent cells, where the transcription factors are highly expressed, and become hypermethylated in differentiated/somatic cells, where the factors are silenced.…”

Epigenetics and the plasticity of differentiation in normal and cancer stem cells

“…However, CpG islands that control gene expression remain unmethylated at this stage, and their de novo methylation and gene silencing occur postimplantation. This mechanism is responsible for silencing the self-renewal gene Oct4 (Gidekel and Bergman, 2002) and the genes on the inactive X chromosome in females in postimplantation embryos (Lock et al, 1987).…”

Epigenetic changes in early life and future risk of obesity

“…87 Lineage-specific methylation of tissue-specific genes occurs throughout prenatal development and early postnatal life and determines developmental fates of differentiating cells. For example, Oct-4 is permanently silenced by hypermethylation around E6.5 in the mouse, 88 whereas HoxA5 and HoxB5 are not methylated and silenced until early postnatal life. 89 In contrast, phosphoenolpyruvate carboxykinase and d-crystallin-2 are methylated in early embryos, but undergo progressive demethylation during development.…”