Project description:DNA hydroxymethylation (5hmC) represents a new layer of epigenetic regulation in addition to DNA methylation (5mC). The genome-wide patterns of 5hmC distribution in many tissues and cells have recently been revealed by hydroxymethylated DNA immunoprecipitation (hMeDIP) followed by high throughput sequencing or tiling arrays. However, the DNA hydroxymethylome data generated by the conventional hMeDIP-seq method can not be used for direct quantitative comparison across different samples. In this study, we report a new quantitative hMeDIP-seq method, which uses barcode technology to label different DNA samples and performs hMeDIP-seq for multiple samples in one reaction system. Using this new method, we profiled and compared the DNA hydroxymethylomes of mouse ES cells (ESCs) and mouse ESCs-derived neural progenitor cells (NPCs). 5hmC levels around TSS in either ESCs or NPCs had negative correlation with gene expression levels，while 5hmC levels at gene body regions had different correlation with gene expression, depending on cell types. We identified differential hydroxymethylated regions (DHMRs) by comparing the 5hmC density of all 5hmC peaks between ESCs and NPCs. Many selected DHMRs (e.g., Ankrd23, Hist1h2aa, Fbxw7, and Epha2) were validated by hMeDIP-qPCR. Furthermore, we analyzed the relationship between the alteration of DNA hydroxymethylation and the gene expression change during neural differentiation, and our data suggest that both up- and down-regulated genes exhibited dramatic decrease in 5hmC during neural differentiation while the alteration of 5hmC had weak positive correlation with the changes in gene expression. Taken together, our data demonstrate that quantitative hMeDIP-seq is a powerful approach for genome-wide comparison of DNA hydroxymethylation across multiple samples. Importantly, the DHMRs between ESCs and NPCs uncovered in this study may provide clues for further investigation of the function of 5hmC in gene regulation and neural differentiation. Comparision of the genome-wide distribution of 5hmC in mouse embryonic stem cells and mouse ES-derived neural progenitor cells.

Project description:DNA hydroxymethylation (5hmC) represents a new layer of epigenetic regulation in addition to DNA methylation (5mC). The genome-wide patterns of 5hmC distribution in many tissues and cells have recently been revealed by hydroxymethylated DNA immunoprecipitation (hMeDIP) followed by high throughput sequencing or tiling arrays. However, the DNA hydroxymethylome data generated by the conventional hMeDIP-seq method can not be used for direct quantitative comparison across different samples. In this study, we report a new quantitative hMeDIP-seq method, which uses barcode technology to label different DNA samples and performs hMeDIP-seq for multiple samples in one reaction system. Using this new method, we profiled and compared the DNA hydroxymethylomes of mouse ES cells (ESCs) and mouse ESCs-derived neural progenitor cells (NPCs). 5hmC levels around TSS in either ESCs or NPCs had negative correlation with gene expression levels，while 5hmC levels at gene body regions had different correlation with gene expression, depending on cell types. We identified differential hydroxymethylated regions (DHMRs) by comparing the 5hmC density of all 5hmC peaks between ESCs and NPCs. Many selected DHMRs (e.g., Ankrd23, Hist1h2aa, Fbxw7, and Epha2) were validated by hMeDIP-qPCR. Furthermore, we analyzed the relationship between the alteration of DNA hydroxymethylation and the gene expression change during neural differentiation, and our data suggest that both up- and down-regulated genes exhibited dramatic decrease in 5hmC during neural differentiation while the alteration of 5hmC had weak positive correlation with the changes in gene expression. Taken together, our data demonstrate that quantitative hMeDIP-seq is a powerful approach for genome-wide comparison of DNA hydroxymethylation across multiple samples. Importantly, the DHMRs between ESCs and NPCs uncovered in this study may provide clues for further investigation of the function of 5hmC in gene regulation and neural differentiation.

Project description:DNA methylation at the 5-postion of cytosine (5mC) is a well-established epigenetic modification which regulates gene expression and cellular plasticity in development and disease. The ten-eleven translocation (TET) gene family is able to oxidize 5mC to 5-hydroxmethylcytosine (5hmC), providing an active mechanism for DNA demethylation, and may also provide its own regulatory function. Here we applied oxidative bisulfite sequencing to generate whole-genome DNA methylation and hydroxymethylation maps at single-base resolution in paired human liver and lung normal and cancer. We found that 5hmC is significantly enriched in CpG island (CGI) shores while depleted in CGS themselves, in particular at active genes, resulting in a 5hmC but not 5mC bimodal distribution around CGI corresponding to H3K4me1 marks. Hydroxymethylation on promoters, gene bodies, and transcription termination regions showed strong positive correlation with gene expression within and across tissues, suggesting that 5hmC is a mark of active genes and could play a role gene expression mediated by DNA demethylation. Comparative analysis of methylomes and hydroxymethylomes at differentially methylated regions (DMRs) revealed that 5hmC is significantly enriched in both tissue specific DMRs (t-DMRs) and cancer specific DMRs (c-DMRs), and 5hmC is negatively correlated with methylation changes, particularly in non-CGI associated DMRs. Analysis of differentially methylated regions (DMRs) in normal and tumor tissues revealed that gain or loss of 5hmC negatively correlated with changes in 5mC, especially on non-CGI associated DMRs, suggesting a profound role for hydroxymethylation in regulation of dynamic DNA demethylation. Together these findings indicate that changes in 5mC as well as in 5hmC and coupled to H3K4me1 correspond to differential gene expression in tissues and matching tumors, revealing an intricate gene expression regulation through interplay of methylome, hydroxymethylome, and histone modifications.

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Genome-wide alterations of DNA methylation and hydroxymethylation in uroepithelial cells revealed potential carcinogenicity of halobenzoquinone disinfection byproducts [Bisulfite-Seq]

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