Genome-wide single base resolution profiling of 5-methyl and 5-hydroxymethylcytosine in glioblastoma
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ABSTRACT: Through parallel processing of genomic DNA with bisulfite and oxidative bisulfite treatments on Illumina 450K arrays we resolved both 5mC and 5hmC in glioblastoma tissues. We developed and applied a novel technique for estimating 5mC, 5hmC, and unmethylated proportions from array data to glioblastoma tissues and compare with normal brain tissue. Genomic distribution of 5hmC was associated with features of transcription despite the glioblastoma genome being relatively depleted of 5hmC. When integrating 5mC and 5hmC data using a Gaussian finite mixture model approach, we observed significant associations between 5hmC levels and gene-sets involved in immune and RNA regulatory processes. We also observed an enrichment of 5hmC in introns, enhancer regions, and genes that are actively transcribed in glioblastomas from TCGA. Significant differences in patient survival were observed among classes of 5hmC obtained from a recursively partitioned mixture model. Glioblastoma dervied (n=30) DNA was subjected to tandem bisulfite and oxidative bisulfite conversion with an input of 4ug per sample using the TrueMethyl® kit v.1.1 (Cambridge Epigenetix) protocol optimized for Illumina HumanMethylation450 arrays.
Project description:5-hydroxymethylcytosine (5hmC), an oxidized derivative of 5-methylcytosine (5mC), has been implicated as an important epigenetic regulator of mammalian development. Current procedures use cost-prohibitive DNA sequencing methods to discriminate 5hmC from 5mC, limiting their accessibility to the scientific community. Here we report a method that combines TET-assisted bisulfite conversion with Illumina 450K DNA methylation arrays for a low-cost high-throughput approach that distinguishes 5hmC and 5mC signals. Implementing this approach, termed TAB-array, we assessed DNA methylation dynamics in the differentiation of human pluripotent stem cells into cardiovascular and neural progenitors. With the ability to discriminate 5mC and 5hmC, we found a much larger number of dynamically methylated genomic regions implicated in the development of these lineages than we could detect by 5mC analysis alone. The increased resolution and accuracy afforded by this approach provides a powerful means to investigate the distinct contributions of 5mC and 5hmC in human development and disease. We generated illumina 450k DNA methylation data for a total of 9 sample groups with two biological replicates for each group. Data for 4/9 groups were generated from glucosylated and bisulfite converted DNA, from human induced plurupotent stem cells (hIPSCs), differentiated cardiovascular progenitors (CVPs), differentiated neural progenitors (NPCs), and fibroblasts. Data for the next 4/9 groups were generated from glucosylated, TET-oxidized and bisulfite converted DNA, from and included replicates of hIPSCs, CVPs, NPCs, and fibroblasts. Data for the last group was generated from standard bisulfite converted DNA (not glucosylated) from fibroblasts.
Project description:Aberrant DNA methylation is common in cancer. To associate DNA methylation with gene function, we performed RNAseq upon tumor tissue and matched normal tissues of two ccRCC (clear cell renal cell carcinoma) patients. To quantify 5mC and 5hmC level in each CG site at genome-wide level, we performed BS-seq and TAB-seq upon tumor tissue and matched normal tissues of two ccRCC (clear cell renal cell carcinoma) patients, respectively. mRNA profiles of tumor and matched normal tissues from two ccRCC patients were generated by deep sequencing, using Hiseq 2000. Single-nucleotide-resolution, whole-genome, 5mC and 5hmC profiles of tumor and matched normal tissues from two ccRCC (clear cell renal cell carcinoma) patients were generated by deep sequencing, using Hiseq 2000.
Project description:Glioblastoma (GBM) is a fatal disease with a poor prognosis, whose aetiology involves profound molecular alterations. Given the limited progress made in recent years, research into new therapeutic avenues may improve the treatment of GBM patients. In this work, we have characterised the epigenomic landscape of patient-derived glioblastoma stem cells in the context of a proneural GBM subtype (U31117). We performed a systematic knockdown of each of the TET proteins (TET1, TET2 and TET3) and explored the consequences of their deletion at the level of DNA methylation (5mC) and hydroxymethylation (5hmC). Global 5hmC levels were then restored using a low dose of ascorbic acid, and the epigenetic landscape of all these conditions was examined using high-content DNA methylation microarrays (Illumina MethylationEPIC Beadchip platform).
Project description:Cytosine base modifications 5-methylcytosine (5mC), 5-hydroxymethylcytosine (5hmC) and 5-formylcytosine (5fC) are present in mammalian DNA. Here, reduced bisulfite sequencing is developed for quantitatively sequencing 5fC at single-base resolution. This method is then applied with oxidative bisulfite sequencing to gain a map of 5mC, 5hmC and 5fC in mouse embryonic stem cells. 12 samples, reduced representation bisulphite treatment: 4 replicates each for bisulphite (BS), oxidative BS (oxBS) and reduced BS (redBS) for the detection of 5mC, 5hmC and 5fC. Mouse (strain B6C) embryonic stem cells.
Project description:TET1/2/3 are methylcytosine dioxygenases regulating cytosine hydroxymethylation in the genome. Tet1 and Tet2 are abundantly expressed in HSC/HPCs and implicated in the pathogenesis of hematological malignancies. Tet2-deletion in mice causes myeloid malignancies, while Tet1-null mice develop B-cell lymphoma after an extended period of latency. Interestingly, TET1 and TET2 were often concomitantly down-regulated in acute B-lymphocytic leukemia. Here, we investigated the overlapping and non-redundant functions of Tet1/Tet2 in HSC maintenance and development of hematological malignancies using Tet1/2 double knockout (DKO) mice. DKO and Tet2-/- HSC/HPCs had overlapping and unique 5hmC and 5mC profiles and behaved differently. DKO mice exhibited strikingly decreased incidence and delayed onset of myeloid malignancies compared to Tet2-/- mice and in contrast developed lethal B-cell malignancies. Transcriptome analysis of DKO tumors revealed expression changes in many genes dysregulated in human B-cell malignancies, such as LMO2, BCL6 and MYC. These results highlight the critical roles of TET1 or TET2 individually and their cross-talks in the pathogenesis of hematological malignancies. Given the role of Tet proteins in 5mC oxidation, we employed a previously established chemical labeling and affinity purification method coupled with high-throughput sequencing (hMe-Seal) to profile the genome-wide distribution of 5hmC, as well as methylated DNA immunoprecipitation (MeDIP) coupled with high-throughput sequencing (MeDIP-seq) to profile 5mC using BM LK cells purified from young WT, Tet2-/- and DKO mice (6-10 wks old).
Project description:DNA hydroxymethylation is frequently lost in glioblastoma. We hypothesized that reduced 5hmC levels might be related to the impaired expression of TET proteins in brain tumors. In this study we performed a genome-wide methylation analysis of LN229 cells stably transfected with scramble or TET3 overexpressing vectors. TET3 overexpression partially restored the genome-wide patterns of 5hmC characteristic of control brain samples in glioblastoma cell lines.
Project description:Through parallel processing of genomic DNA with bisulfite and oxidative bisulfite treatments on Illumina 450K arrays we resolved both 5mC and 5hmC in glioblastoma tissues. We developed and applied a novel technique for estimating 5mC, 5hmC, and unmethylated proportions from array data to glioblastoma tissues and compare with normal brain tissue. Genomic distribution of 5hmC was associated with features of transcription despite the glioblastoma genome being relatively depleted of 5hmC. When integrating 5mC and 5hmC data using a Gaussian finite mixture model approach, we observed significant associations between 5hmC levels and gene-sets involved in immune and RNA regulatory processes. We also observed an enrichment of 5hmC in introns, enhancer regions, and genes that are actively transcribed in glioblastomas from TCGA. Significant differences in patient survival were observed among classes of 5hmC obtained from a recursively partitioned mixture model.
Project description:Recent studies have demonstrated that the Ten-eleven translocation (Tet) family proteins can enzymatically convert 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC). While 5mC has been studied extensively, little is known about the distribution and function of 5hmC. Here we present a genome-wide profile of 5hmC in mouse embryonic stem (ES) cells. A combined analysis of global 5hmC distribution and gene expression profile in wild-type and Tet1-depleted ES cells revealed suggests that 5hmC is enriched at both gene bodies of actively transcribed genes and extended promoter regions of Polycomb-repressed developmental regulators. Thus, our study reveals the first genome-wide 5hmC distribution in pluripotent stem cells and supports its dual function in regulating gene expression. Genomic DNA extracted from control (Con) or Tet1 knockdown (KD) mouse ES cells was immunoprecipitated with 5-hydroxymethylcytosine (5hmC) antibodies and analyzed by NimbleGen 2.1M mouse whole genome tiling microarrays (a 4-array set covering the entired non-repetitive portion of mouse genome). Whole cell extract (WCE) was used as input controls in IP/input experiments.
Project description:Background: Trisomy 21 causes Down syndrome (DS), but the mechanisms by which the extra chromosome leads to deficient intellectual and immune function are not well understood. Results: Here, we profile CpG methylation in DS and control cerebral and cerebellar cortex of adults and cerebrum of fetuses. We purify neuronal and non-neuronal nuclei and T-lymphocytes and find biologically relevant genes with DS-specific methylation (DS-DM) in brain cells. Some genes show brain-specific DS-DM, while others show stronger DS-DM in T cells. Both 5-methyl-cytosine and 5-hydroxy-methyl-cytosine contribute to the DS-DM. Thirty percent of genes with DS-DM in adult brain cells also show DS-DM in fetal brains, indicating early onset of these epigenetic changes, and we find early maturation of methylation patterns in DS brain and lymphocytes. Some, but not all, of the DS-DM genes show differential expression. DS-DM preferentially affected CpGs in or near specific transcription factor binding sites, implicating a mechanism involving altered transcription factor binding. Methyl-seq of brain DNA from mouse models with sub-chromosomal duplications mimicking DS reveals partial but significant overlaps with human DS-DM and shows that multiple chromosome 21 genes contribute to the downstream epigenetic effects. Conclusions: These data point to novel biological mechanisms in DS and have general implications for trans effects of chromosomal duplications and aneuploidies on epigenetic patterning. Bisulfite converted DNA from 119 samples from Down syndrome patients and controls were hybridised to the Illumina Infinium 450k Human Methylation Beadchip. In addition, we re-analyzed 6 Down syndrome and 6 control cerebellum DNA samples on the 450K BeadChips using an adaptation of the Illumina probe preparation protocol (TrueMethyl kit; Cambridge Epigenetics, CEGX), in which parallel analyses of bisulfite and oxidative bisulfite DNA for each sample allows assessment of the relative contributions of 5mC and 5hmC to net methylation.
Project description:DNA methylation at 5-position of cytosine (5mC) is one of the best studied epigenetic modifications that plays important roles in diverse biological processes. Iterative oxidation of 5mC by the Ten-eleven translocation (Tet) family of proteins generates 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC), and 5-carboxylcytosine (5caC), which can be further processed by DNA repair proteins leading to DNA demethylation. Functional characterization of the Tet proteins has been complicated by the redundancy between the three Tet proteins. Using the CRISPR/Cas9 technology, we have generated mouse embryonic stem cells (ESCs) deficient for all three Tet proteins (TKO). Whole genome bisulphite sequencing (WGBS) analysis revealed that Tet-mediated DNA demethylation mainly occurs distal enhancers as well as promoters that significantly overlap with 5hmC, 5fC and 5caC. Characterization of the Tet TKO ESCs revealed a function for Tet proteins in cell fate restriction as Tet TKO ESCs tend to adopt both primed pluripotent stem cell-like state and 2-cell embryo-like state. In addition, Tet TKO ESCs exhibit elongated telomeres. Thus, our study reveals a role of Tet proteins not only in DNA demethylation, but also in cell fate restriction and telomere maintenance. 2 samples for WGBS and 2 samples for RNA-seq