Epigenetic control of mouse Oct-4 gene expression in embryonic stem cells and trophoblast stem cells.
ABSTRACT The first cell differentiation event in mammalian embryogenesis segregates inner cell mass lineage from the trophectoderm at the blastocyst stage. Oct-4, a member of the POU family of transcription factors, is necessary for the pluripotency of the inner cell mass lineage. Embryonic stem (ES) cells, which contribute to all of embryonic lineages, express the Oct-4 gene. Trophoblast stem (TS) cells, which have the ability to differentiate into trophoblast lineage in vitro, never contribute to embryonic proper tissues in chimeras and differentiate only into trophoblastic cells in the placenta. Expression of the Oct-4 gene was undetectable and severely repressed in trophoblastic lineage, including the stem cells. We found that the culture of TS cells with 5-aza-2'-deoxycytidine or trichostatin A caused the activation of the Oct-4 gene. Analysis of the DNA methylation status of mouse Oct-4 gene upstream region revealed that Oct-4 enhancer/promoter region was hypomethylated in ES cells but hypermethylated in TS cells. Furthermore, in vitro methylation suppressed Oct-4 enhancer/promoter activity in reporter assay. In the placenta of Dnmt1(n/n) mutant mice, most of the CpGs in the enhancer/promoter region were unmethylated, and Oct-4 gene expression was aberrantly detected. Chromatin immunoprecipitation assay revealed that Oct-4 enhancer/promoter region was hyperacetylated in ES cells compared with TS cells, thus demonstrating that DNA methylation status is closely linked to the chromatin structure of the Oct-4 gene. Here we propose that the epigenetic mechanism, consisting of DNA methylation and chromatin remodeling, underlies the developmental stage- and cell type-specific mechanism of Oct-4 gene expression.
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ABSTRACT: There are many published studies about the epigenetic effects of the prenatal and infant periods on health outcomes. However, there is very little knowledge regarding the effects of the intrapartum period (labor and birth) on health and epigenetic remodeling. Although the intrapartum period is relatively short compared to the complete perinatal period, there is emerging evidence that this time frame may be a critical formative phase for the human genome. Given the debates from the National Institutes of Health and World Health Organization regarding routine childbirth procedures, it is essential to establish the state of the science concerning normal intrapartum epigenetic physiology. EPIIC (Epigenetic Impact of Childbirth) is an international, interdisciplinary research collaboration with expertise in the fields of genetics, physiology, developmental biology, epidemiology, medicine, midwifery, and nursing. We hypothesize that events during the intrapartum period - specifically the use of synthetic oxytocin, antibiotics, and cesarean section - affect the epigenetic remodeling processes and subsequent health of the mother and offspring. The rationale for this hypothesis is based on recent evidence and current best practice.Medical Hypotheses 02/2013; · 1.05 Impact Factor
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ABSTRACT: BACKGROUND: Tissues and their component cells have unique DNA methylation profiles comprising DNA methylation patterns of tissue-dependent and differentially methylated regions (T-DMRs). Previous studies reported that DNA methylation plays crucial roles in cell differentiation and development. Here, we investigated the genome-wide DNA methylation profiles of mouse neural progenitors derived from different developmental stages using HpyCH4IV, a methylation-sensitive restriction enzyme that recognizes ACGT residues, which are uniformly distributed across the genome. RESULTS: Using a microarray-based genome-wide DNA methylation analysis system focusing on 8.5-kb regions around transcription start sites (TSSs), we analyzed the DNA methylation profiles of mouse neurospheres derived from telencephalons at embryonic days 11.5 (E11.5NSph) and 14.5 (E14.5NSph) and the adult brain (AdBr). We identified T-DMRs with different DNA methylation statuses between E11.5NSph and E14.5NSph at genes involved in neural development and/or associated with neurological disorders in humans, such as Dclk1, Nrcam, Nfia, and Ntng1. These T-DMRs were located not only within 2 kb but also distal (several kbs) from the TSSs, and those hypomethylated in E11.5NSph tended to be in CpG island (CGI-) associated genes. Most T-DMRs that were hypomethylated in neurospheres were also hypomethylated in the AdBr. Interestingly, among the T-DMRs hypomethylated in the progenitors, there were T-DMRs that were hypermethylated in the AdBr. Although certain genes, including Ntng1, had hypermethylated T-DMRs 5[prime] upstream, we identified hypomethylated T-DMRs in the AdBr, 3[prime] downstream from their TSSs. This observation could explain why Ntng1 was highly expressed in the AdBr despite upstream hypermethylation. CONCLUSION: Mouse adult brain DNA methylation and gene expression profiles could be attributed to developmental dynamics of T-DMRs in neural-related genes.BMC Genomics 02/2013; 14(1):82. · 4.40 Impact Factor
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ABSTRACT: DNA methylation is reprogrammed during early embryogenesis by active and passive mechanisms in advance of the first differentiation event producing the embryonic and extraembryonic lineage cells which contribute to the future embryo proper and to the placenta respectively. Embryonic lineage cells re-acquire a highly methylated genome dependent on the DNA methyltransferases (DNMTs) Dnmt3a and Dnmt3b that are required for de novo methylation. By contrast, extraembryonic lineage cells remain globally hypomethylated but the mechanisms that underlie this hypomethylation remain unknown. We have employed an inducible system that supports differentiation between these two lineages and recapitulates the DNA methylation asymmetry generated in vivo. We find that in vitro down-regulation of Oct3/4 in ES cells recapitulates the decline in global DNA methylation associated with trophoblast. The de novo DNMTs Dnmt3a2 and Dnmt3b are down-regulated during trophoblast differentiation. Dnmt1, which is responsible for maintenance methylation, is expressed comparably in embryonic and trophoblast lineages, however importantly in trophoblast giant cells Dnmt1fails to be attracted to replication foci, thus allowing loss of DNA methylation while implicating a passive demethylation mechanism. Interestingly, Dnmt1 localization was restored by exogenous Np95/Uhrf1, a Dnmt1 chaperone required for Dnmt1-targeting to replication foci, yet DNA methylation levels remained low. Over-expression of de novo DNMTs also failed to increase DNA methylation in target sequences. We propose that induced trophoblast cells may have a mechanism to resist genome-wide increases of DNA methylation, thus reinforcing the genome-wide epigenetic distinctions between the embryonic and extraembryonic lineages in the mouse. This resistance may be based on transcription factors or on global differences in chromatin structure.PLoS ONE 01/2013; 8(6):e68846. · 3.73 Impact Factor