Project description:Tissue and their component cells have unique DNA methylation profiles comprising DNA methylation patterns of tissue-dependent and differentially methylated regions (T-DMRs). T-DMRs are found throughout the genome and influence tissue-specific gene expression. DNA methylation profile of T-DMRs underlies the network of tissue- and developmental stage-specific transcription factors and their targets. The adult brain consists of various kinds of cells that sequentially appear as neurons, astrocytes, and oligodendrocytes from late gestation through the neonatal period. Distinctive neural progenitor cells (NPCs) that exhibit different differentiation poteintials to neurons to glial cells are generated during mid-to-late gestation. To explore DNA methylation profiles of mouse NPCs, we compared neurospheres derived from telencephalons at embryonic day 11.5 (E11.5NSph) and 14.5 (E14.5NSph) by T-DMR profiling with restriction tag-mediated amplification (D-REAM) combined with Affymetrix GeneChip Mouse Promoter 1.0R Array. We used HpyCH4IV, a methylation-sensitive restriction enzyme that recognizes ACGT residues. Because these are uniformly distributed across the genome, it enables less biased analysis. By comparing D-REAM data between E11.5NSph and E14.5NSph, we identified genes with T-DMRs including those involved in neural develpment and/or associated with neurological disorders in humans. The present study elucidates the underlying dynamics of the DNA methylation profile of T-DMRs during neural development, including insights into developmental stage-specific hypomethylation of T-DMRs around TSSs.
Project description:To gain genome wide information on the association of EZH2 with promoter regions in HeLa cells, DamID experiments and subsequent analysis by promoter arrays (Affymetrix GeneChip Human Promoter 1.0R ) were performed. The DamID method uses fusions of the bacterial Dam DNA methylase and the protein of interest, to direct the enzymatic activity to the protein’s genomic binding sites, where the DNA is methylated. Methylated DNA is then extracted, enriched and further analysed by microarray. EZH2 is the enzymatic subunit of the Polycomb Repressive Complex 2, which deposits the H3K27me3 mark on chromatin. This mark is associated with low gene expression, either in polycomb repressed regions or, in combination with methylation of H3K4, at poised promoters. An EZH2-T416A mutant (EZH2-mTP5) fails to bind to NIPP1, a factor implied in the regulation of PRC2 binding to a subset of target regions. To obtain a genome wide picture of differential binding of EZH2-WT and the EZH2-mTP5 mutant to promoter regions, the mutant was subjected to DamID/microanalysis as well. DamID of EZH2-WT (2 replicates) and EZH2-mTP5(T416A)(2 replicates) vs. control (Dam without fused protein)(4 samples)
Project description:Embryogenesis is tightly regulated by multiple levels of epigenetic systems such as DNA methylation, histone modification, and chromatin remodeling. DNA methylation patterns are erased in primordial germ cells and in the interval immediately following fertilization. Subsequent reprogramming occurs by de novo methylation and demethylation. Variance of DNA methylation patterns between different cell types is not well understood. Here, using methylated DNA immunoprecipitation and tiling array technology, we have comprehensively analysed DNA methylation patterns at proximal promoter regions in mouse embryonic stem (ES) cells, ES cell-derived early germ layers (ectoderm, endoderm and mesoderm) and four adult tissues (brain, liver, skeletal muscle and sperm). Most of the methylated regions in the three germ layers and in the three adult somatic tissues are shared in common. This commonly methylated gene set is enriched in germ cell associated genes that are generally transcriptionally inactive in somatic cells. We also compared DNA methylation patterns with global mapping of histone H3 lysine 4/27 trimethylation, and found that gain of DNA methylation correlates with loss of histone H3 lysine 4 trimethylation. Taken together, our findings indicate that differentiation from ES cells to the three germ layers is accompanied by an increase in the number of commonly methylated DNA regions and that these tissue-specific alterations are present for only a small number of genes. Our findings indicate that DNA methylation at the proximal promoter regions of commonly methylated genes act as an irreversible mark which fixes somatic lineage by repressing transcription of germ cell specific genes. Using the MeDIP on chip protocol, we immunoprecipitated methylated DNA from R1 ES cell, SK7 cell, as well as SK7 derived-Ectoderm, - Endoderm, -Paraxial mesoderm, brain, liver, skeletal muscle, and sperm, and hybridized to a genome tiling array. The three germ layer lineages from ES cells were confirmed by the expression of specific marker genes in each germ layer (see related expression analysis).
Project description:The NuA4 histone acetyltransferase (HAT) complex is required for gene specific regulation, cell cycle progression, and DNA repair. Dissection of the 13-subunit complex reveals that the Eaf7 subunit bridges Eaf5 with Eaf3, a H3K36me3-binding chromodomain protein, and this Eaf5/7/3 trimer is anchored to NuA4 through Eaf5. This subcomplex represents a functional module as deletions of these genes create similar phenotypes and a large portion of the trimer exists in a native form outside the NuA4 complex. Gene-specific and genome-wide location analyses indicate that the Eaf5/7/3 trimer correlates with transcription activity and is enriched over the coding region. In agreement with a role in transcription elongation, the Eaf5/7/3 trimer interacts with phosphorylated RNA polymerase II and helps its progression. In addition, loss of Eaf5/7/3 partially suppresses intragenic cryptic transcription arising in set2 mutant cells, suggesting a role in nucleosome destabilization. Such a function is supported by genetic interactions with the FACT histone chaperone. On the other hand, loss of the trimer leads to an increase of replication-independent histone exchange over the coding region of transcribed genes. Taken together, these results lead to a model where Eaf5/7/3 associates with elongating polymerase and is involved in the disassembly of nucleosomes in front of the polymerase, but also in their recycling in its wake.