Unknown,Transcriptomics,Genomics,Proteomics

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Integrated analyses of DNA methylation and hydroxymethylation reveal tumor suppressive roles of ECM1, ATF5 and EOMES in human hepatocellular carcinoma

ABSTRACT: The newly discovered 5-hydroxymethylcytosine (5hmC) may complicate previous observations of abnormal cytosine methylation statuses used for the identification of new tumor suppressor gene candidates relevant to human hepatocarcinogenesis. The simultaneous detection of 5mC and 5hmC will stimulate the discovery of aberrantly methylated genes with increased accuracy in human hepatocellular carcinoma (HCC). Here, we performed a newly developed single-base high-throughput sequencing approach (hydroxymethylation and methylation Sensitive Tag sequencing, HMST-seq) to synchronously measure these two modifications in HCC samples. After identifying the differentially methylated and hydroxymethylated genes in HCC, we integrated the DNA copy-number alterations as determined using array-based comparative genomic hybridization (aCGH) data with gene expression to identify genes potentially silenced by promoter hypermethylation. As a result, we report a high enrichment of genes with epigenetic aberrations in cancer signaling pathways. Six genes were selected as tumor suppressor gene (TSG) candidates, among which, ECM1, ATF5 and EOMES were confirmed to have potential anti-cancer function via siRNA experiments. To fully examine 5mC and 5hmC status in HCC, we used a newly developed single-base high-throughput sequencing approach (hydroxymethylation and methylation sensitive tag sequencing, HMST-seq) to synchronously measure these two modifications in HCC samples and their adjacent non-cancerous liver tissues (non-HCCs).

ORGANISM(S): Homo sapiens

SUBMITTER: Yudong Xia

PROVIDER: E-GEOD-54141 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:5-methylcytosine (5-mC) can be oxidized to 5-hydroxymethylcytosine (5-hmC). Genome-wide profiling of 5-hmC thus far indicated 5-hmC may not only be an intermediate form of DNA demethylation but could also constitute an epigenetic mark per se. We describe a cost-effective and selective method to detect both the hydroxymethylation and methylation status of cytosines in more than 1.8 million MspI sites in the human genome. This method involves the selective glucosylation of 5-hmC residues, short-sequence tag generation and high-throughput sequencing. We tested this method by screening H9 human embryonic stem cells and their differentiated embroid body cells, and found that differential hydroxymethylation preferentially occur in bivalent genes during cellular differentiation. Especially, our results support hydroxymethylation can regulate key transcription regulators with bivalent marks through demethylation and affect cellular decision on choosing active or inactive state of these genes upon cellular differentiation. We developed a cost-effective and selective method to detect both the hydroxymethylation and methylation status of cytosines in more than 1.8 million MspI sites in the human genome. In this method, we took advantage of the differential enzymatic sensitivities of the isoschizomers MspI and HpaII. HpaII cleaves only a completely unmodified site, any modification at either cytosine blocks the cleavage, while MspI recognizes and cleaves both 5-mC and 5-hmC, but not the newly discovered 5-formylcytosine (5-fC) and 5-carboxylcytosine (5-caC). Furthermore, beta-glucosyltransferase (beta-GT) can transfer a glucose to the hydroxyl group of 5-hmC and generate beta-glucosyl-5-hydroxymethylcytosine (5-ghmC) that blocks MspI digestion. Thus, either by combining beta-GT treatment with MspI digestion or simply applying MspI/HpaII digestion, short sequence tags generated can be used for inferring hydroxymethylation or methylation status in around 1.8 million cytosine sites in the human genome. We tested this method by screening H9 human embryonic stem cells and their differentiated embroid body cells.