Base Resolution Analysis of 5-Hydroxymethylcytosine in the Mammalian Genome
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ABSTRACT:
ORGANISM(S): Homo sapiens
SUBMITTER: Gary Hon
PROVIDER: E-GEOD-36173 | biostudies-arrayexpress |
REPOSITORIES: biostudies-arrayexpress
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Project description:Cytosine methylation of DNA is an evolutionarily conserved mechanism from plants to animals with crucial roles in gene regulation. However, the variation between methylomes of normal tissues is largely unexplored. To better understand the epigenetic variation of a normal individual, we profiled DNA methylation using whole genome bisulfite sequencing in 17 tissues isolated from an individual mouse. We observed a unique distribution of CpG methylation for each tissue, which cluster based on cell lineage. Global analysis identified only one-eighth of the genome as tissue-specifically methylated. Remarkably, the vast majority of these regions exhibit hallmarks of cis-regulatory activity. Our results also reveal a novel class of dormant enhancers in adult tissues which retain an epigenetic memory of regulatory elements active during development. Together, these results expand the repertoire of regulatory information encoded within the methylome, and suggest mapping it as an alternative method to identify cell-type specific regulatory elements. whole genome bisulfite sequencing of mouse adult tissue
2013-09-01 | E-GEOD-42836 | biostudies-arrayexpress
Project description:In mammals, cytosine methylation (5mC) is widely distributed throughout the genome but is notably depleted from active promoters and enhancers. While the role of DNA methylation in promoter silencing has been well documented, the function of this epigenetic mark at enhancers remains unclear. Recent experiments have demonstrated that enhancers are enriched for 5-hydroxymethylcytosine (5hmC), an oxidization product of the Tet family of 5mC dioxygenases and an intermediate of DNA demethylation. These results support the involvement of Tet proteins in the regulation of dynamic DNA methylation at enhancers. By mapping DNA methylation and hydroxymethylation at base resolution, we find that deletion of Tet2 causes extensive loss of 5hmC at enhancers, accompanied by enhancer hypermethylation, reduction of enhancer activity, and delayed gene induction in the early steps of differentiation. Our results reveal that DNA demethylation modulates enhancer activity, and its disruption influences the timing of transcriptome reprogramming during cellular differentiation. We performed traditional bisulfite sequencing, TAB-Seq, RNA-Seq, and ChIP-Seq for 6 histone modifications in two biological replicates of wild-type, Tet1-/-, and Tet2-/- mouse ES cells. We also performed RNA-Seq analysis during a timecourse of differentiation to neural progenitor cells.
2014-09-25 | E-GEOD-48519 | biostudies-arrayexpress
Project description:During mammalian development DNA methylation patterns need to be reset in primordial germ cells (PGC) and preimplantation embryos. However, many retro-transposons and imprinted genes are resistant to such global epigenetic reprogramming via hitherto undefined mechanisms. Here, we report that some of these sequences are immune to widespread erasure of DNA methylation in the mouse embryonic stem cells (mESCs) lacking de novo DNA methyltransferases. Persistence of DNA methylation at these loci in mESCs depends on the histone H3K9 methyltransferase Setdb1, as deletion of Setdb1 results in reduction of H3K9me3 and DNA methylation levels concomitant with an increase in 5-hydroxymethylation (5hmC). In addition, depletion of H3K9 methyltransferase G9a leads to genome-wide reduction of DNA methylation but to a lesser extent at the above sequences. Taken together, these data reveal that Setdb1 ensures the fidelity of DNA methylation at specific loci in mESCs, which may reflect mechanisms functioning in vivo during key developmental stages. Examination of genome-wide DNA methylation status in 2 cell types.
2014-06-03 | E-GEOD-47893 | biostudies-arrayexpress
Project description:During mammalian development DNA methylation patterns need to be reset in primordial germ cells (PGC) and preimplantation embryos. However, many retro-transposons and imprinted genes are resistant to such global epigenetic reprogramming via hitherto undefined mechanisms. Here, we report that some of these sequences are immune to widespread erasure of DNA methylation in the mouse embryonic stem cells (mESCs) lacking de novo DNA methyltransferases. Persistence of DNA methylation at these loci in mESCs depends on the histone H3K9 methyltransferase Setdb1, as deletion of Setdb1 results in reduction of H3K9me3 and DNA methylation levels concomitant with an increase in 5-hydroxymethylation (5hmC). In addition, depletion of H3K9 methyltransferase G9a leads to genome-wide reduction of DNA methylation but to a lesser extent at the above sequences. Taken together, these data reveal that Setdb1 ensures the fidelity of DNA methylation at specific loci in mESCs, which may reflect mechanisms functioning in vivo during key developmental stages. Examination of genome-wide DNA methylation status in 3 cell types.
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Project description:Investigations of 5-hydroxymethylcytosine (5hmC) in biologically and clinically samples and models with low cell numbers have been hampered by the low sensitivity and reproducibility using current 5hmC mapping approaches. Here, we develop a selective 5hmC chemical labeling approach using tagmentation-based library preparation in order to profile nanogram levels of 5hmC isolated from ~1,000 cells (nano-hmC-Seal). Using this technology, we profiled the dynamics of 5hmC across different stages of mouse hematopoietic differentiation. Additionally, applying nano-hmC-Seal to the hematopoietic multipotent progenitor cells in an acute myeloid leukemia (AML) mouse model, we identified leukemia-specific, differentially hydroxymethylated regions that harbor previously reported and as-yet-unidentified functionally relevant factors. The change of 5hmC patterns in AML strongly correlates with the altered gene expression on a global scale. Together, our new approach offers a highly sensitive and robust method to study and detect DNA methylation dynamics from in vivo model and clinical samples. Selective 5hmC chemical labeling approach using tagmentation-based library preparation in order to profile nanogram levels of 5hmC isolated from ~1,000 cells
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Project description:TET proteins oxidize 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC), and 5-carboxylcytosine (5caC). 5fC and 5caC are excised by mammalian DNA glycosylase TDG, implicating 5mC oxidation in DNA demethylation. Here we show that the genomic locations of 5fC can be determined by coupling chemical reduction with biotin tagging. Genome-wide mapping of 5fC in mouse embryonic stem cells (mESCs) reveals that 5fC preferentially occurs at poised enhancers among other gene regulatory elements. Application to Tdg null mESCs further suggests that 5fC production coordinates with p300 in remodeling epigenetic states of enhancers. This process, which is not influenced by 5hmC, appears to be associated with further oxidation of 5hmC and commitment to demethylation through 5fC. Finally, we resolved 5fC at base-resolution by hydroxylamine-based protection from bisulfite-mediated deamination, thereby confirming sites of 5fC accumulation. Our results reveal roles of active 5mC/5hmC oxidation and TDG-mediated demethylation in epigenetic tuning at regulatory elements. We report here a chemical labeling method that effectively differentiates 5fC from 5mC, 5hmC, and 5caC in genomic DNA. First, we quantitatively protect endogenous 5hmC with a regular glucose using b-glucosytransferase-catalyzed 5hmC glucosylation. Then, we selectively reduce 5fC with NaBH4 to 5hmC, and chemically label the resulting 5hmC (from 5fC) with an azide-modified glucose. Biotin can be installed subsequently for specific enrichment of 5fC. Our method thereby provides an effective tool of general utility for the genomic localization of 5fC. Here we provide genome-wide profiles of 5hmC, 5fC, and p300 in Tdg fl/fl and Tdg-/- mESCs as well as a 5fC control (Non-NaBH4) and polyA RNA-Seq expression data. Genome-wide profiles of 5hmC and 5fC in mESCs differentiated to embryoid bodies are also included. We also report the development and application of a single-base resolution method for the detection of 5fC in genomic DNA by hydroylamine mediated protection of 5fC from deamination during bisulfite treatment, or 5fC Chemical Assisted Bisulfite Sequencing (fCAB-Seq). We applied this method in parallel with conventional ChIP-Methyl-Seq to H3K4me1 ChIP enriched DNA from Tdg fl/fl and Tdg-/- mice.
2013-04-18 | E-GEOD-41545 | biostudies-arrayexpress
Project description:While genetic mutation is a hallmark of cancer, many cancers also acquire epigenetic alterations during tumorigenesis including aberrant DNA hypermethylation of tumor suppressors as well as changes in chromatin modifications as caused by genetic mutations of the chromatin-modifying machinery. However, the extent of epigenetic alterations in cancer cells has not been fully characterized. Here, we describe the first complete methylome maps at single nucleotide resolution of a low-passage breast cancer cell line and primary human mammary epithelial cells. We find widespread DNA hypomethylation in the cancer cell, primarily at partially methylated domains (PMDs) in normal breast cells. Unexpectedly, genes within these regions are largely silenced in cancer cells. The loss of DNA methylation in these regions is accompanied by formation of repressive chromatin, with a significant fraction displaying allelic DNA methylation where one allele is DNA methylated while the other allele is occupied by histone modifications H3K9me3 or H3K27me3. Our results show a mutually exclusive and complementary relationship between DNA methylation and H3K9me3 or H3K27me3. These results suggest that global DNA hypomethylation in breast cancer is tightly linked to the formation of repressive chromatin domains and gene silencing, thus identifying a potential epigenetic pathway for gene regulation in cancer cells and suggesting a possible new approach toward the development of cancer therapeutics. ChIP-methylC-Seq on H3K9me3, H3K27me3, and H3K36me3 in breast cancer HCC1954. 36 cycles of sequencing on Illumina platform.
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Project description:5-hydroxymethylcytosines (5hmC) is particularly abundant in mammalian brain with little-known functions. Here we present the first genome-wide and single-base-resolution maps of 5hmC and 5mC in human brain by combined application of TAB-Seq and MethylC-Seq. We report that the majority of modified cytosines are hydroxymethylated in adult human brain, a significant proportion of which are highly-hydroxymethylated with enrichment in active genic regions and distal-regulatory elements. 5hmC is more enriched in poised than active enhancers, and CpG island shores and enhancers show comparable 5hmC profiles. Notably, 5hmC spikes were identified at the 5’ splicing sites, suggesting a link between 5hmC and splicing. Additionally, we identified a transcription-correlated 5hmC bias towards to sense strand and a 5mC bias towards antisense strand of gene bodies, and a bias towards C-rich sequences surrounding the 5hmC sites. Our data imply multiple roles for 5hmC in alternative splicing and gene regulation in addition to be an intermediate of DNA demethylation in human brain. Examination of hydroxymethylomes of 1 adult and 1 fetal brain tissue of frontal lobe, as well as 1 methylome of the same adult.
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Project description:During differentiation, neurons experience a reorganization of DNA modification patterns within their genomes. However, the mechanisms underlying this developmental patterning and its role in defining the neuronaÂÂl state are currently unclear. Here, we find that the dÂÂe novo DNA methyltransferase Dnmt3a is necessary for elevated levels of 5-hydroxymethylcytosine (5hmC), a derivative of 5-methylcytosine (5mC), in olfactory sensory neurons (OSNs). Through an analysis of genome-wide 5mC and 5hmC distributions in isolated OSNs, we find that Dnmt3a-dependent 5mC and 5hmC occurs within regions of high accessibility, neural enhancers, and the transcription start sites of transcribed genes. Its loss results in the global disruption of gene expression patterns, including the upregulation of silent genes, the downregulation of mOSN-expressed genes, and the alteration of odorant-induced transcriptional responses of immediate early genes. Together, these results demonstrate that Dnmt3a is necessary to define the neuronal transcriptional state and may be broadly involved in refining expression profiles within differentiated cells. To determine the contributions of Dnmt3a to the DNA modification and transcriptional landscapes of a post-mitotic neuronal population, we performed DNA immunoprecipitation (DIP-seq) using antibodies specific for 5mC and 5hmC and rRNA-depleted transcriptional profiling (RNA-seq) coupled to high-throughput sequencing using genomic DNA or RNA from FACS-isolated mature olfactory sensory neurons (mOSNs) from main olfactory epithelium (MOE) of Dnmt3a wildtype (WT), heterozygous-null (Het), or homozygous-null (KO) 3-week old mice. Similarly, to compare this information with other epigenetic features of the MOE, we performed H3K4me1 (WT), H3K27ac (WT), and H3K27me3 (WT and KO) chromatin immunoprecipitation (ChIP)-seq and DNase I hypersensitivity assays (DNase-seq) using MOE nuclei from 3-week old mice. In addition, we assayed the influence of Dnmt3a-deficiency on the induction of odorant-responsive genes by exposing 3-week old Dnmt3a WT, Het, and KO mice to either water or a 1:1:1 mixture of amyl acetate:acetophenone:octanal for 1 hour and performed rRNA-depleted RNA-seq using RNA isolated from their MOEs.
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