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:5-hydroxymethylcytosine (5hmC), converted from 5-methylcytosine (5mC) by Tet enzymes, has recently drawn attention as the ‘sixth base’ of DNA since it is considered to be an intermediate of the demethylation pathway. Nonetheless, it remains to be addressed how 5hmC is linked to the development of human imprinting disorders. In this regard, conventional bisulfite (BS) treatment is unable to differentiate 5hmC from 5mC. It is thus hypothesized that BS conversion-derived ‘hypermethylation’ at imprinting control regions (ICRs), which may cause human imprinting disorders, would in fact be attributable to excessively increased levels of 5hmC as well as 5mC. To test this hypothesis, we applied the newly developed oxidative BS (oxBS) treatment to detect 5hmC in blood samples from Kagami-Ogata syndrome (KOS14) patients caused by perturbed expression of clustered imprinted genes on 14q32.2 resulting from the hypermethylation of ICRs at this locus, IG-DMR and MEG3-DMR. oxBS with pyrosequencing and cloning-based sequencing revealed that there were few amounts of 5hmC at the hypermethylated IG-DMR in blood samples from KOS14 patients. oxBS with genome-wide methylation array analysis demonstrated that global levels of 5hmC were very low with similar distribution patterns in blood samples from KOS14 patients and normal controls. We also confirmed the presence of a large amount of 5hmC in the brain sample from a normal control. 5hmC is not a major component in abnormally hypermethylated ICRs or at a global level, at least in blood from KOS14 patients. As the brain sample contained a large amount of 5hmC, the neural tissues of KOS14 patients are promising candidates for analysis in elucidating the role of 5hmC in the neurodevelopmental context. We generated illumina 450k DNA methylation data for BS or oxBS converted samples of three KOS14 blood samples, one control pooled blood sample and one control brain sample with two technical replicates for each sample.

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.

Dataset Information

Variation in 5-hydroxymethylcytosine (5hmC) across human cortex and cerebellum

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