Project description:Cytosine DNA bases can be methylated by DNA methyltransferases and subsequently oxidized by TET proteins. The resulting 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC), and 5-carboxylcytosine (5caC) are considered demethylation intermediates as well as stable epigenetic marks. To dissect the contribution of these cytosine modifying enzymes, we generated combinations of Tet knockout (KO) embryonic stem cells (ESCs) and systematically measured protein and DNA modification levels at the transition from naive to primed pluripotency. Whereas the increase of genomic 5-methylcytosine (5mC) levels during exit from pluripotency correlated with an upregulation of the de novo DNA methyltransferases DNMT3A and DNMT3B, the subsequent oxidation steps turned out to be far more complex. The strong increase of oxidized cytosine bases (5hmC, 5fC, and 5caC) was accompanied by a drop in TET2 levels, yet the analysis of KO cells suggested that TET2 is responsible for most 5fC formation. The comparison of modified cytosine and enzyme levels in Tet KO cells revealed distinct and differentiation-dependent contributions of TET1 and TET2 to 5hmC and 5fC formation arguing against a processive mechanism of 5mC oxidation. The apparent independent steps of 5hmC and 5fC formation suggest yet to be identified mechanisms regulating TET activity and may constitute another layer of epigenetic regulation.
Project description:Regulation of chondrogenic differentiation by DNA demethylation is little understood. The ten-eleven-translocation (TET) proteins oxidize methylated cytosines (5mC) to 5hmC, 5fC and 5caC eventually leading to DNA demethylation. However, 5hmC is stable and can potentially act as an epigenetic mark as well. Here, we report that global changes in 5hmC mark chondrogenic differentiation.
Project description:Regulation of chondrogenic differentiation by DNA demethylation is little understood. The ten-eleven-translocation (TET) proteins oxidize methylated cytosines (5mC) to 5hmC, 5fC and 5caC eventually leading to DNA demethylation. However, 5hmC is stable and can potentially act as an epigenetic mark as well. In this study, we report that global changes in 5hmC mark chondrogenic differentiation.
Project description:Principal neurons in the mammalian brain exit cell cycle and execute a complex and prolonged differentiation program that continues into early adult life. Although high levels of 5-hydroxymethylcytosine (5hmC) accumulate in neurons, it is not known whether 5hmC can serve as an intermediate in DNA demethylation in postmitotic neurons. Here we report high resolution mapping of DNA methylation and hydroxymethylation, chromatin accessibility, and activating and repressive histone marks in developing postmitotic Purkinje cells (PCs). Our data reveal new relationships between PC transcriptional and epigenetic programs, and identify a class of late expressed genes that lose both 5mC and 5hmC during terminal differentiation. Deletion of the 5hmC writers Tet1, Tet2, and Tet3 from postmitotic Purkinje cells prevents loss of 5mC and 5hmC in regulatory domains and gene bodies and hinders transcriptional and epigenetic developmental transitions, resulting in hyper-excitability and increased susceptibility to excitotoxic drugs. Our data demonstrate that Tet-mediated active DNA demethylation occurs in vivo, and that acquisition of the precise molecular and electrophysiological properties of adult PCs requires continued oxidation of 5mC to 5hmC during the final phases of differentiation.
Project description:Enhancers are developmentally-controlled transcriptional regulatory regions whose activities are modulated through histone modifications or histone variant deposition. Here, we show by genome-wide mapping that the newly discovered DNA modification 5-hydroxymethylcytosine (5hmC) is dynamically associated with transcription factor binding to distal regulatory sites during neural differentiation of mouse P19 cells as well as during adipocyte differentiation of mouse 3T3-L1 cells. Functional annotation reveals that regions gaining 5hmC are associated with genes expressed either in neural tissues when P19 cells undergo neural differentiation or in adipose tissue when 3T3-L1 cells undergo adipocyte differentiation. Furthermore, distal regions gaining 5hmC together with H3K4me2 and H3K27ac in P19 cells behave as differentiation-dependent transcriptional enhancers. Identified regions are enriched in motifs for transcription factors regulating specific cell fates like Meis1 in P19 cells and PPARgamma in 3T3-L1 cells. Accordingly, a fraction of hydroxymethylated Meis1 sites were associated with a dynamic engagement of the 5mC hydroxylase Tet1. In addition, kinetic studies of cytosine hydroxymethylation of selected enhancers indicated that DNA hydroxymethylation is an early event of enhancer activation. Hence, acquisition of 5hmC in cell-specific distal regulatory regions may represent a major event of enhancer progression toward an active state and participate in selective activation of tissue-specific genes A 6-chip study aiming to characterize regulated genes in P19.6 mouse embryonal carcinoma cells following 48 hours treatment with 1M-BM-5M all-trans retinoic acid. RNAs were prepared from three independent triplicate experiments.
Project description:DNA methylation and hydroxymethylation have been implicated in normal development and differentiation, but our knowledge about the genome-wide distribution of 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) during cellular differentiation remains limited. Using in vitro model system of gradual differentiation of human embryonic stem (hES) cells into ventral midbrain-type neural precursor (NP) cells and terminally into dopamine (DA) neurons, we explored changes in 5mC or 5hmC patterns during lineage commitment. We used three techniques, 450K DNA methylation array, MBD-seq, and hMeDIP-seq, and found combination of these methods can provide comprehensive information on the genome-wide 5mC or 5hmC patterns. We observed dramatic changes of 5mC patterns during differentiation of hES cells into NP cells. Although genome-wide 5hmC distribution was more stable than 5mC, coding exons, CpG islands and shores showed dynamic 5hmC patterns during differentiation. In addition to the role of DNA methylation as a mechanism to initiating gene silencing, we also found DNA methylation as a locking system to maintain gene silencing. More than 1,000 genes including mesoderm development related genes acquired promoter methylation during neuronal differentiation even though they were already silenced in hES cells. Finally, we found that activated genes lost 5mC in transcription start site (TSS) but acquired 5hmC around TSS and gene body during differentiation. Our findings may provide clues for elucidating the molecular mechanisms underlying lineage specific differentiation of pluripotent stem cells during human embryonic development. Examination of hMeDIP-Seq and MBD-Seq in 3 cell types (human embryonic stem, neural precursor, and dopamine neuron cells)
Project description:DNA methylation and hydroxymethylation have been implicated in normal development and differentiation, but our knowledge about the genome-wide distribution of 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) during cellular differentiation remains limited. Using in vitro model system of gradual differentiation of human embryonic stem (hES) cells into ventral midbrain-type neural precursor (NP) cells and terminally into dopamine (DA) neurons, we explored changes in 5mC or 5hmC patterns during lineage commitment. We used three techniques, 450K DNA methylation array, MBD-seq, and hMeDIP-seq, and found combination of these methods can provide comprehensive information on the genome-wide 5mC or 5hmC patterns. We observed dramatic changes of 5mC patterns during differentiation of hES cells into NP cells. Although genome-wide 5hmC distribution was more stable than 5mC, coding exons, CpG islands and shores showed dynamic 5hmC patterns during differentiation. In addition to the role of DNA methylation as a mechanism to initiating gene silencing, we also found DNA methylation as a locking system to maintain gene silencing. More than 1,000 genes including mesoderm development related genes acquired promoter methylation during neuronal differentiation even though they were already silenced in hES cells. Finally, we found that activated genes lost 5mC in transcription start site (TSS) but acquired 5hmC around TSS and gene body during differentiation. Our findings may provide clues for elucidating the molecular mechanisms underlying lineage specific differentiation of pluripotent stem cells during human embryonic development. Examination of genome-wide DNA methylation in 3 cell types (human embryonic stem, neural precursor, and dopamine neuron cells)
Project description:Differentiation is accompanied by extensive epigenomic reprogramming, leading to the repression of stemness factors and the transcriptional maintenance of activated lineage-specific genes. Here we used the mammalian Hoxa cluster of developmental genes as a model system to follow changes in DNA modification patterns during retinoic acid induced differentiation. We found the inactive cluster to be marked by defined patterns of 5-methylcytosine (5mC). Upon the induction of differentiation, the active anterior part of the cluster became increasingly enriched in 5-hydroxymethylcytosine (5hmC), following closely the colinear activation pattern of the gene array, which was paralleled by the reduction of 5mC. Depletion of the 5hmC generating dioxygenase Tet2 impaired the maintenance of Hoxa activity and partially restored 5mC levels. Our results indicate that gene specific 5mC-5hmC conversion by Tet2 is crucial for the maintenance of active chromatin states at lineage-specific loci. Examination of 5-methylcytosine (MeDIP-seq) and 5-hydroxymethylcytosine (hMeDIP-seq) at the HOXA cluster in 2 different developmental stages of a pluripotent cancer cell line.