Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Charting a dynamic DNA methylation landscape of the human genome

ABSTRACT: DNA methylation is a defining feature of mammalian cellular identity and is essential for normal development. Most cell types, except germ cells and pre-implantation embryos, display relatively stable DNA methylation patterns, with 70-80% of all CpGs being methylated. Despite recent advances we still have a too limited understanding of when, where and how many CpGs participate in genomic regulation. Here we report the in depth analysis of 42 whole genome bisulfite sequencing (WGBS) data sets across 30 diverse human cell and tissue types. We observe dynamic regulation for only 21.8% of autosomal CpGs within a normal developmental context, a majority of which are distal to transcription start sites. These dynamic CpGs co-localize with gene regulatory elements, particularly enhancers and transcription factor binding sites (TFBS), which allow identification of key lineage specific regulators. In addition, differentially methylated regions (DMRs) often harbor SNPs associated with cell type related diseases as determined by GWAS. The results also highlight the general inefficiency of WGBS as 70-80% of the sequencing reads across these data sets provided little or no relevant information regarding CpG methylation. To further demonstrate the utility of our DMR set, we use it to classify unknown samples and identify representative signature regions that recapitulate major DNA methylation dynamics. In summary, although in theory every CpG can change its methylation state, our results confirm that only a fraction does so as part of coordinated regulatory programs. Therefore our selected DMRs can serve as a starting point to help guide novel, more effective reduced representation approaches to capture the most informative fraction of CpGs as well as further pinpoint putative regulatory elements. Analysis of 42 human WGBS libraries comprising 30 distinct primary cell lines, tissues, in vitro derived cell types and cell lines. BiSeq raw sequencing reads were aligned using maq in bisulfite mode (Li et al. 2008) or bsmap 2.7 (Xi et al. 2009) against human genome version hg19/GRCh37, discarding duplicate reads. DNA methylation calling was performed based on an extended custom software pipeline published previously for RRBS (Gu et al., 2010). The bed files contain all seen CpGs within the given library. The number of methylated reads/number of total reads is listed in the score column. This study includes a re-analysis of Samples from the NIH Roadmap Epigenomics Mapping Consortium (REMC; GSE16256, GSE17312), Hodges et al. 2011 (GSE31971), Molaro et al. 2011 (GSE30340), and Xi et al. 2013. WARNING: This submission is incomplete pending further deposits of raw data files from Meissner via EDACC.

ORGANISM(S): Homo sapiens

SUBMITTER: Michael Ziller

PROVIDER: E-GEOD-46644 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Charting a dynamic DNA methylation landscape of the human genome.

Ziller Michael J MJ Gu Hongcang H Müller Fabian F Donaghey Julie J Tsai Linus T-Y LT Kohlbacher Oliver O De Jager Philip L PL Rosen Evan D ED Bennett David A DA Bernstein Bradley E BE Gnirke Andreas A Meissner Alexander A

Nature 20130807 7463

DNA methylation is a defining feature of mammalian cellular identity and is essential for normal development. Most cell types, except germ cells and pre-implantation embryos, display relatively stable DNA methylation patterns, with 70-80% of all CpGs being methylated. Despite recent advances, we still have a limited understanding of when, where and how many CpGs participate in genomic regulation. Here we report the in-depth analysis of 42 whole-genome bisulphite sequencing data sets across 30 di ...[more]

PMID: 23925113

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Project description:DNA methylation appears to play an essential mechanistic role in the pathogenesis of ALL, thereby potentiate its use as a biomarker for diagnosis and prognosis (Milani, Lundmark et al. 2010; Geng, Brennan et al. 2012; Sandoval, Heyn et al. 2013), and even a potential target of novel therapeutic approaches in ALL. In present study, we collected blood specimens for 4 pairs of monozygotic twins (MZ) and 1 pair of dizygotic twin (DZ) that are discordant for ALL. We sought to comprehensively assess the magnitude of genetic and epigenetic differences between ALL-affected and unaffected twins. we conducted whole genome and whole methylome sequencing on these five pairs of ALL-discordant twins. We also examined both the MZ and DZ twins using whole-genome bisulfite sequencing (WGBS). At first, the methylation differences across the genome were addressed globally by Circos software. And then tried to characterize the co-twin methylation divergence in specific genomic regions between ALL-discordant twin pairs. These patterns of dynamic co-twin methylation changes in these discordant ALL samples were generally consistent among MZ and DZ twins, indicating similarities of methylation abnormalities. As a result, 780, 566, 309, 293 and 2110 DMRs were identified, with a similar distribution pattern across different genomic elements among the five twin pairs.Then we annotate whether these DMRs were located in regulatory elements and identification of genes with recurring methylation alterations in a cohort of ALL patients. We collected blood specimens from 4 pairs of MZ twins and 1 pair of DZ twin that are discordant for ALL. At first, the methylation differences across the genome were addressed globally by Circos software. And then tried to characterize the co-twin methylation divergence in specific genomic regions and differentially methylated gene regions (DMRs) were identified between ALL-discordant twin pairs. Then we annotate whether these DMRs were located in regulatory elements and identification of genes with recurring methylation alterations in a cohort of ALL patients.

Project description:This data was generated by ENCODE. If you have questions about the data, contact the submitting laboratory directly (). If you have questions about the Genome Browser track associated with this data, contact ENCODE (mailto:genome@soe.ucsc.edu). This track was produced as part of the ENCODE project. It reports the percentage of DNA molecules that exhibit cytosine methylation. In general, DNA methylation within a gene's promoter is associated with gene silencing, and DNA methylation within the exons and introns of a gene is associated with gene expression. Proper regulation of DNA methylation is essential during development and aberrant DNA methylation is a hallmark of cancer. DNA methylation status was assayed with Whole Genome Bisulfite Sequencing (WGBS). Genomic DNA was sheared by sonication, end-repaired and then ligated to methylated sequencing adapters. The library fragments were treated with sodium bisulfite and amplified by PCR to convert every unmethylated cytosine to a thymine while leaving methylated cytosines intact. The sequenced fragments were aligned to a bisulfite-converted reference genome. For each assayed cytosine, the number of sequencing reads covering that C and the percentage of those reads that were methylated were reported. For data usage terms and conditions, please refer to http://www.genome.gov/27528022 and http://www.genome.gov/Pages/Research/ENCODE/ENCODEDataReleasePolicyFinal2008.pdf DNA methylation at cytosines across the genome was assayed with Whole Genome Bisulfite Sequencing (WGBS). WGBS was performed on cell lines grown by ENCODE production groups. WGBS was carried out by the Myers production group at the HudsonAlpha Institute for Biotechnology. Isolation of Genomic DNA: Genomic DNA was isolated from each cell line using the QIAGEN DNeasy Blood & Tissue Kit according to the instructions provided by the manufacturer. DNA concentrations for each genomic DNA preparation were determined using fluorescent DNA-binding dye and a fluorometer (Invitrogen Quant-iT dsDNA High Sensitivity Kit and Qubit Fluorometer). Typically, 2 µg of genomic DNA is used to make WGBS libraries. WGBS Library Construction and Sequencing: WGBS library construction started with sonication of genomic DNA on a Covaris S2 instrument. Sheared ends were then repaired and blunted with DNA polymerase I, T4 DNA polymerase and T4 polynucleotide kinase in the presence of dATP, dGTP and dTTP. After end repair, Klenow exo- DNA Polymerase was used to add an adenosine as a 3' overhang. Next, a methylated version of the Illumina paired-end adapters was ligated onto the DNA. Adapter-ligated 400 bp genomic DNA fragments were selected using a 2% agarose SizeSelect E-gel. The selected adapter-ligated fragments were treated with sodium bisulfite using the Zymo Research EZ DNA Methylation Gold Kit, which converts unmethylated cytosines to uracils and leaves methylated cytosines unchanged. Bisulfite-treated DNA was amplified in a final PCR reaction which was optimized to uniformly amplify diverse fragment sizes and sequence contexts in the same reaction. During this final PCR reaction, uracils were copied as thymines, resulting in a thymine in the PCR products wherever an unmethylated cytosine existed in the genomic DNA. These libraries were then sequenced with an Illumina HiSeq 2000 according to the manufacturer's recommendations as paired-end 50 bp reads. Libraries were sequenced to a depth of 600 million aligned reads. Data Analysis: To analyze the sequence data, Bismark (Krueger and Andrews, 2011) was used to align sequences reads. Generally, each read went through a conversion of Cs to Ts and was then aligned to fully converted plus and minus strands of the hg19 build of the human genome. A few custom refinements were made to the Bismark program. Since these libraries were made in a directional orientation with the first read always being C-poor, we skipped unnecessary alignments to impossible orientations. We also implemented a more stringent uniqueness filter, only allowing reads that have one acceptable alignment (based on default Bowtie parameters) across both strands. Once reads were aligned, the percent methylation was calculated for each cytosine using the original sequence reads. The percent methylation and number of reads is reported for each CpG in the wgEncodeHaibMethylWgbsXXXXCpg.bigBed file and for each non CpG cytosine in the wgEncodeHaibMethylWgbsXXXXNoncpg.bigBed file.

Project description:Transfer of frozen-thawed embryos leads to sex-specific DNA hypermethylation in both human and mouse placentas. : In humans, frozen ET led to placentas with significant alterations in DNA methylation with most genes demonstrating hypermethylation compared to placentas from fresh ET (4402 CpGs; 1600 genes; p-value < 0.05 in two–tailed unpaired t tests, and a mean methylation difference > 0.05). When compared to control samples, both frozen and fresh samples showed significant differences in methylation.(Frozen vs Control: 5600 CpGs, 2775 genes; Fresh vs Control: 4096 CpGS; 1914 genes; p-value < 0.05, mean methylation difference > 0.05). Paired analysis showed similar trends, despite controlling for maternal environment. Sex specific analysis revealed that these changes were primarily driven by male placentas, as seen by a larger number of CpGs that were differentially methylated, and a larger proportion of genes with at least 2 differentially methylated CpG sites in male placentas as compared to female placentas. (Males: 15572 CpGs, 4399 genes; Females: 7441 CpGs, 3070 genes; p-value < 0.05, mean methylation difference > 0.05). In order to isolate the effects of vitrification we utilized the mouse model, controlling for the effect of the maternal hormonal milieu. In the first genome-wide profiling of DNA methylation in a mouse IVF model, we found that trends in DNA methylation differences paralleled those seen in human placentas. Using similar significance cutoffs as for human samples, and BumpHunter analysis that identifies differentially methylated regions to compensate for a lower number of samples, placentas derived from frozen embryos were predominantly hypermethylated compared to placentas after fresh ET (589 DMRs, 445 genes). Both frozen and fresh embryo transfer samples demonstrated perturbations compared to control samples (Frozen vs Control: 1787 DMRs, 1319 genes; Fresh vs Control: 1119 DMRs, 808 genes). Consistent with the sex-specific trends we observed in human placentas, differences between samples derived from frozen compared to fresh embryo transfer were driven by changes in male placentas (Males: 1069 DMRs, 798 genes; Females:14 DMRs, 11 genes) . When considering the effect of IVF as a whole, murine placentas were predominantly hypomethylated, replicating existing human genome-wide methylation data. As seen previously, IVF led to changes in placental weight, placental morphology and microvessel density in mice, but no persistent changes were seen after embryo vitrification alone. Sexually dimorphic epigenetic changes could indicate differential susceptibility of male and female embryos to IVF-associated perturbations. This observation highlights the importance of sex-specific evaluation of the incidence of adverse outcomes. Similarities between changes seen in mouse and human samples underscore the suitability of the mouse model in evaluating the effect of ART on the epigenetic landscape. This convergence is especially valuable, given limited access to human tissues and the ability to isolate specific interventions in the mouse model.

Project description:Background: Down syndrome (DS) is characterized by a genome-wide profile of differential DNA methylation that is skewed towards hypermethylation in most tissues, including brain, and includes pan-tissue differential methylation. The molecular mechanisms involve the overexpression of genes related to DNA methylation on chromosome 21. Here, we stably overexpressed the chromosome 21 gene DNA methyltransferase 3L (DNMT3L) in the human SH-SY5Y neuroblastoma cell line and assayed DNA methylation at over 26 million CpGs by whole genome bisulfite sequencing (WGBS) at three different developmental phases (undifferentiated, differentiating, and differentiated). Results: DNMT3L overexpression resulted in global CpG and CpG island hypermethylation as well as thousands of differentially methylated regions (DMRs). The DNMT3L DMRs were skewed towards hypermethylation and mapped to genes involved in neurodevelopment, cellular signaling, and gene regulation. Consensus DNMT3L DMRs showed that cell lines clustered by genotype and then differentiation phase, demonstrating sets of common genes affected across neuronal differentiation. The hypermethylated DNMT3L DMRs from all pairwise comparisons were enriched for regions of bivalent chromatin marked by H3K4me3 as well as differentially methylated sites from previous DS studies of diverse tissues. In contrast, the hypomethylated DNMT3L DMRs from all pairwise comparisons displayed a tissue-specific profile enriched for regions of heterochromatin marked by H3K9me3 during embryonic development. Conclusions: Taken together, these results support a mechanism whereby regions of bivalent chromatin that lose H3K4me3 during neuronal differentiation are targeted by excess DNMT3L and become hypermethylated. Overall, these findings demonstrate that DNMT3L overexpression during neurodevelopment recreates a facet of the genome-wide DS DNA methylation signature by targeting known genes and gene clusters that display pan-tissue differential methylation in DS.

Dataset Information

Charting a dynamic DNA methylation landscape of the human genome

Publications

Charting a dynamic DNA methylation landscape of the human genome.

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