Induced pluripotent stem cells (iPSCs) are flourishing in the investigation of cell reprogramming. However, we still know little about the sequential molecular mechanism during somatic cell reprogramming (SCR). Here, we first observed rapid generation of colonies whereas mouse embryonic fibroblasts (MEFs) were induced by OCT4, SOX2, KLF4 (OSK), and vitamin C for 7 days. The colony's global transcriptional profiles were analyzed using Affymetrix microarray. Microarray data confirmed that SCR was a process in which transcriptome got reversed and pluripotent genes expressed de novo. There were many changes, especially substantial growth expression of epigenetic factors, on transcriptome during the transition from Day 7 to iPSCs indicating that this period may provide 'flexibility' genome structure, chromatin remodeling, and epigenetic modifications to rebind to the transcriptional factors. Several biological processes such as viral immune response, apoptosis, cell fate specification, and cell communication were mainly involved before Day 7 whereas cell cycle, DNA methylation, and histone modification were mainly involved after Day 7. Furthermore, it was suggested that p53 signaling contributed to the transition 'hyperdynamic plastic' cell state and assembled cell niche for SCR, and small molecular compounds useful for chromatin remodeling can enhance iPSCs by exciting epigenetic modification rather than the exogenous expression of more TFs vectors.
The development of induced pluripotent stem cells (iPSCs) has enabled study of the mechanisms underlying cellular reprogramming. Here, we have studied the dynamic distribution of H2A.Z during induced reprogramming with chromatin immunoprecipitation deep sequencing (ChIP-Seq). We found that H2A.Z tended to accumulate around transcription start site (TSS) and incorporate in genes with a high transcriptional activity. GO analysis with H2A.Z incorporated genes indicated that most genes are involved in chromatin assembly or disassembly and chromatin modification both in MEF and Day 7 samples, not in iPSCs. Furthermore, we detected the highest level of incorporation of H2A.Z around TSS in Day 7 samples compared to MEFs and iPSCs. GO analysis with only incorporated genes in Day 7 also displayed the function of chromatin remodeling. So, we speculate H2A.Z may be responsible for chromatin remodeling to enhance the access of transcription factors to genes important for pluripotency. This study therefore provides a deeper understanding of the mechanisms underlying induced reprogramming.
ABSTRACT. The developmental dynamics of DNA methylation events have been well studied. Active demethylation of the paternal genome occurs in the zygote, passive demethylation occurs during cleavage stages, and de novo methylation occurs by the blastocyst stage. It is believed that the paternal genome has lower levels of methylation during early development than the maternal genome. However, in this study, we provide direct and indirect evidence of genome-wide de novo DNA methylation of the paternal genome after the first cell cycle in mouse embryos. Although very little methylation was detected within the male pronucleus in zygotes, an intense methylation signal was clearly visible within the androgenetic 2-cell embryos. Moreover, the DNA methylation level of the paternal genome in the post-zygotic metaphase embryos was similar to that of the maternal genome. Using indirect immunofluorescence with an antibody to methylated lysine 9 in histone H3, we provided new evidence to support the concept of spatial compartmentalization of parental genomes in 2-cell mouse embryos. Nevertheless, the transient segregation of parental genomes was not observed by determining the DNA methylation distribution in De novo DNA methylation in 2-cell mouse embryos the 2-cell embryos even though DNA methylation asymmetry between the maternal and paternal pronucleus existed in the 1-cell stage. The disappearance of separate immunofluorescence signals of 5-methyl cytosine in the 2-cell embryos might be attributed to the de novo methylation of the paternal genome during the first mitotic cycle.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.