ABSTRACT: DNA methylation and histone modifications influence gene activities in a variety of mammalian cells. We report here the large scale mapping of DNA methylation patterns at proximal promoter regions in mouse embryonic stem cells (mESCs). A majority of methylated genes represent cell differentiation-associated genes that are repressed in mESCs. In contrast, unmethylated genes include many housekeeping and pluripotency genes such as STAT3 and Oct4/Nanog/Sox2, which are essential for ESC self-renewal. By comparing methylation patterns to the binding domains of Oct4/Nanog, Polycomb proteins, and histone H3 lysine (K) 4/27 trimethylation on gene promoters, we found that promoter DNA methylation is frequently the only epigenetic marker associated with a subset of silenced genes in mESCs that do not possess H3 K4/K27 trimethylation marks and are free from the binding of Polycomb proteins and the Oct4/Nanog transcription factors. Gene expression profiling of demethylated mESCs showed that a majority of up-regulated genes, including a subset of X-linked genes and many development genes, represent a distinct population of genes that are neither targeted by Polycomb and Oct4/Nanog, nor carry H3 K4/K27 trimethylation marks. Our data suggest that promoter methylation patterns in mESCs represent a unique epigenetic program that complements other regulatory mechanisms to allow the expression of pluripotency genes, but represses a subset of genes that will only be activated in specific cell lineages upon cell differentiation. Keywords: DNA Methylation, methylated DNA immunoprecipitation
Project description:Mefs were transduced with Oct4 , Sox2, Klf4 and c-myc to induce pluripotency. The histone H3 K4 and H3 K27 trimethylation status was compared genome wide in ES cells, MEFs, and induced pluripotent cells (iPS). Keywords: ChIP-Chip
Project description:Polycomb Repressive Complexes PRC1 and PRC2 play a crucial role in silencing lineage-specific genes during early embryogenesis. To provide new insights in polycomb biology, we profiled the proximal interactome (proxeome) of the catalytic subunits RNF2 (PRC1) and EZH2 (PRC2) in mouse embryonic stem cells (mESCs). This revealed >100 proteins proximal to PRC2 and PRC1, which mainly comprise transcription factors, transcriptional regulators and RNA binding proteins. Interestingly, the EZH2 proxeome included both PRC complexes, while the RNF2 proxeome only identified PRC1 subunits. More than half of the PRC2 proximal proteins are shared with PRC1, revealing the molecular constitution of polycomb chromatin domains. We identified several pluripotency-associated transcription factors, including NANOG, for which we confirmed genomic co-localisation with PRC2. Upon PRC2 disruption, NANOG redistributes to specific sites containing its DNA binding motif. Finally, we compared PRC2 proximal interactomes between naïve mESCs, serum-cultured mESCs and embryoid bodies, altogether providing a comprehensive resource in different cellular contexts that may help to further decipher Polycomb biology.
Project description:Polycomb Repressive Complexes PRC1 and PRC2 play a crucial role in silencing lineage-specific genes during early embryogenesis. To provide new insights in polycomb biology, we profiled the proximal interactome (proxeome) of the catalytic subunits RNF2 (PRC1) and EZH2 (PRC2) in mouse embryonic stem cells (mESCs). This revealed >100 proteins proximal to PRC2 and PRC1, which mainly comprise transcription factors, transcriptional regulators and RNA binding proteins. Interestingly, the EZH2 proxeome included both PRC complexes, while the RNF2 proxeome only identified PRC1 subunits. More than half of the PRC2 proximal proteins are shared with PRC1, revealing the molecular constitution of polycomb chromatin domains. We identified several pluripotency-associated transcription factors, including NANOG, for which we confirmed genomic co-localisation with PRC2. Upon PRC2 disruption, NANOG redistributes to specific sites containing its DNA binding motif. Finally, we compared PRC2 proximal interactomes between naïve mESCs, serum-cultured mESCs and embryoid bodies, altogether providing a comprehensive resource in different cellular contexts that may help to further decipher Polycomb biology.
Project description:Maintenance of stem-cell identity requires proper regulation of enhancer activity. Both transcription factors OCT4/SOX2/NANOG and histone methyltransferase complexes MLL/SET1 were shown to regulate enhancer activity, but how they are regulated in embryonic stem cells (ESCs) remains further studies. Here, we report a transcription factor BACH1, who which directly interacts with OCT4/SOX2/NANOG (OSN) and MLL/SET1 methyltransferase complexes and maintains pluripotency in mouse ESCs (mESCs). BTB domain and bZIP domain of BACH1 are required for these interactions and pluripotency maintenance. Loss of BACH1 reduced the interaction between NANOG and MLL1/SET1 complexes, and decreased their occupancy on chromatin, and further decreased H3 lysine 4 trimethylation (H3K4me3) level on gene promoters and (super-) enhancers, leading to decreased enhancer activity and transcription activity, especially on stemness-related genes. Moreover, BACH1 recruited NANOG through chromatin looping and regulated remote NANOG binding, fine-tuning enhancer-promoter activity and gene expression. Collectively, these observations suggest that BACH1 maintains pluripotency in ESCs by recruiting NANOG and MLL/SET1 complexes to chromatin and maintaining the trimethylated state of H3K4 and enhancer-promoter activity, especially on stemness-related genes.
Project description:Bivalent histone domains have been proposed to contribute to pluripotency in embryonic stem cells, suggesting an epigenetic mechanism may regulate stem cell behavior in general. Here we compare histone modifications in two other stem cells derived from the blastocyst. We show that extraembryonic stem cells have little repressive lysine 27 trimethylation and few bivalent domains. Thus, bivalent domains are not a common mechanism for maintaining the undifferentiated state in blastocyst-derived stem cells and alternative mechanisms must mediate transcriptional repression in extraembryonic cells. We show that lysine 9 trimethylation, but not DNA methylation, is likely to fulfill this role. Intriguingly, although we do detect bivalent domains in pluripotent cells in the early mouse embryo, the epigenetic status of extraembryonic cells does not entirely reflect their in vitro stem cell counterparts. Therefore, differences in epigenetic regulation between lineage progenitors in vivo and in vitro may arise during selection for self-renewal in vitro. Expression profiles [GSM388878-GSM388881] of three different stem cells (R1 embryonic stem cells, trophoblast stem cells, extraembryonic endoderm stem cells) were generated for comparison to CHIP-seq data [GSM392044-GSM392055] of the same three stem cell lines to observe correlations with Histone 3 K4 and K27 trimethylation patterns. CHIP-seq details: R1 embryonic stem cells, trophoblast stem cells or extraembryonic endoderm stem cells were grown, lysed and chromatin purified. The chromatin was immunoprecipitated for either histone 3 K4 trimethylation or histone 3 K27 trimethylation and the immunoprecipitate was subjected to purification and high-throughput Illumina-based sequencing.
Project description:Multipotential naïve CD4+ T cells differentiate into distinct lineages including Th1, Th2, Th17, and inducible T regulatory (iTreg) cells. The remarkable diversity of CD4+ T cells begs the question whether the observed changes reflect terminal differentiation with heritable epigenetic modifications or plasticity in T cell responses. We generated genome-wide histone H3 lysine 4 (H3K4) and lysine 27 (H3K27) trimethylation maps in naïve, Th1, Th2, Th17, iTreg, and natural (n)Treg cells. We find that while modifications of signature cytokine genes (Ifng, Il4, and Il17) partially conform to the expectation of lineage commitment, critical transcription factors such as Tbx21 exhibit a broad spectrum of epigenetic states, consistent with our demonstration of T-bet and IFN-γ induction in nTreg cells. Our data suggest an epigenetic mechanism underlying the specificity and plasticity of effector and regulatory T cells and also provide a framework for understanding complexity of CD4+ T helper cell differentiation. genome-wide analysis of histone H3 K4 and K27 trimethylation in different sub-lineages of mouse CD4+ T cells. (12 samples in total)
Project description:Polycomb repression of gene expression is critical for development, with a pivotal role for trimethylation of lysine 27 of histone H3 (H3K27me3) deposited by Polycomb Repressive Complex 2 (PRC2). While the function and regulation of PRC2 have been extensively studied, the mechanism(s) by which it is recruited to specific genomic targets has remained largely elusive, in particular in vertebrates. Here we identify the PRC2-associated protein Mtf2 as a novel DNA methylation-sensitive PRC2 recruiter in mouse embryonic stem cells (mESCs). Mtf2 directly binds to DNA and is essential for recruitment of PRC2 both in vitro and in vivo. Genome-wide recruitment of the PRC2 catalytic subunit Ezh2 to genomic targets is drastically impaired in Mtf2 knock-out mESCs, resulting in largely reduced H3K27me3 deposition. Mtf2 selectively binds regions with high density of closely spaced unmethylated CpG-containing motifs with a locally unwound helical structure. This binding is dependent on one of the Mtf2 PHD domains, a protein domain shared among Pcl homologs, and an Mtf2-specific domain. The sequences bound by Mtf2 are enriched in PRC2-repressed CpG island-containing targets in zebrafish, Xenopus, mouse and human, suggesting that Mtf2-mediated PRC2 recruitment to unmethylated genomic regions is conserved among vertebrates.
Project description:The Polycomb group (PcG) gene products mediate heritable silencing of developmental regulators in metazoans, participating in one of two distinct multimeric protein complexes, the Polycomb repressive complexes-1 (PRC1) and -2 (PRC2). PRC2 catalyses trimethylation of histone H3 at lysine 27 (H3K27) which in turn is thought to provide a recruitment site for PRC1. Recent studies demonstrate that mono-ubiquitylation of histone H2A at lysine 119 is important in PcG mediated silencing with the core PRC1 component Ring1A/B functioning as the E3 ligase8. PRC2 has been shown to share target genes with the core transcription network to maintain embryonic stem (ES) cells including Oct4 and Nanog. Here we identify an essential role for PRC1 in repressing developmental regulators in ES cells, and thereby in maintaining ES cell pluripotency. A significant proportion of the PRC1 target genes are also repressed by Oct4. We demonstrate that engagement of PRC1 and PRC2 at target genes is Oct4-dependent and moreover that Ring1B interacts with Oct4. Collectively these results show that PcG complexes are instrumental in Oct4-dependent repression required to maintain pluripotency of ES cells. This study provides a first functional link between a core ES cell regulator and global epigenetic regulation of the genome. Experiment Overall Design: Eed is a protein included in PRC2 (Polycomb repressor complex). Experiment Overall Design: We generated constitutive Eed KO mouse ES cells and observed gene expression using Affymetrix MOE430.2 microarray. Experiment Overall Design: These results were compared with other KO cells of PRC1 proteins (Ring1A, Ring1B) and other proteins in our study.
Project description:Natural CD4+FOXP3+ regulatory T (Treg) cells constitute a unique T-cell lineage that plays a pivotal role in maintaining immune homeostasis and immune tolerance. Recent studies provide evidence for the heterogeneity and plasticity of the Treg cell lineage. However, the fate of human Treg cells after loss of FOXP3 expression and the underlying epigenetic mechanisms remain to be fully elucidated. Here, we compared gene expression profiles and histone methylation status on two histone H3 lysine residues (H3K4me3 and H3K27me3) of expanded FOXP3+ and corresponding FOXP3-losing Treg cells. DGE assay showed that human Treg cells down-regulated Treg signature genes, whereas up-regulated a set of Th lineages-associated genes, especially for Th2, such as GATA3, GFI1 and IL13, after in vitro expansion. Furthermore, we found that reprogramming of Treg cells was associated with histone modifications, as shown by decreased abundance of permissive H3K4me3 within down-regulated Treg signature genes, such as FOXP3, CTLA4 and LRRC32 loci, although with no significant changes in H3K27me3 modification. Thus, our results indicate that human Treg cells could convert into a Th-like cells upon in vitro expansion, displaying a gene expression signature dominated by Th2 lineage associated genes, and the histone methylation might contribute to such conversion. Genome-wide analysis of histone H3 K4 and K27 trimethylation in expanded human FOXP3+ Treg cells and FOXP3-losing Treg cells
Project description:Lysine 56 acetylation in the helical core of histone H3 opens yeast chromatin and enables histone gene transcription, DNA replication, DNA repair, and prevents epigenetic silencing. While K56Ac is globally abundant in yeast and flies its presence has been uncertain in mammals. We show here using mass spectrometry and genome wide analyses that K56Ac is present in human embryonic stem cells (hESCs) overlapping strongly at active and inactive promoters with the binding of the key regulators of pluripotency NANOG, SOX2 and OCT4. This includes also the canonical histone gene promoters and those for the hESC-specific microRNAs. K56Ac then relocates to developmental genes upon cellular differentiation. Thus K56Ac state more accurately reflects the epigenetic differences between hESCs and somatic cells than other active histone marks such as H3 K4 tri-methylation and K9 acetylation. These results suggest that K56Ac is involved in the human core transcriptional network of pluripotency. Genome wide location analysis ChIP-chip was performed in two human embryonic stem cell lines (HSF1 and HSF6) and two somatic cell lines (ARPE and BJ), for each of the following histone modifications: H3 K56Ac, H3 K9Ac, H3 K4me3 and H3 K27me3.