Project description:The TET proteins TET1, TET2 and TET3 constitute a new family of dioxygenases that utilize molecular oxygen and the cofactors Fe(II) and 2-oxoglutarate to convert 5-methylcytosine (5mC) to 5-hydroxy-methylcytosine (5hmC) and further oxidation products in DNA1-5. Here we show that Tet1 and Tet2 have distinct roles in regulating 5hmC deposition and gene expression in mouse embryonic stem cells (mESC). Tet1 depletion in mESC primarily diminishes 5hmC levels at transcription start sites (TSS), whereas Tet2 depletion is mostly associated with decreased 5hmC in gene bodies relative to TSS. 5hmC is enriched at exon start and end sites, especially in exons that are highly expressed, and is significantly decreased upon Tet2 knockdown at the boundaries of high-expressed exons that are selectively regulated by Tet2. In differentiating murine B cells, Tet2 deficiency is associated with selective exon exclusion in the gene encoding the transmembrane phosphatase CD45. Tet2 depletion is associated with increased 5hmC and decreased 5mC at promoters/ TSS regions, possibly because of the redundant activity of Tet1. Together, these data indicate a complex interplay between Tet1 and Tet2 in mESC, and show that loss-of-function of a single TET protein does not necessarily lead to loss of 5hmC and a corresponding gain of 5mC, as generally assumed. The relation between Tet2 loss-of-function and selective changes in exon expression could potentially explain the frequent occurrence of both TET2 loss-of-function mutations and mutations in proteins involved in pre-mRNA splicing in myeloid malignancies in humans. Gene and exon expression analysis in mESC, Tet1 knockdown mESC, and Tet2 knockdown mESC by RNA-sequencing. Mapping of 5-hydroxymethylcytosine in mESC, Tet1 knockdown mESC, and Tet2 knockdown mESC by anti-CMS-seq. Mapping of methylcytosine in mESC, and Tet2 kd mESC by MeDIP-seq.
Project description:The TET proteins TET1, TET2 and TET3 constitute a new family of dioxygenases that utilize molecular oxygen and the cofactors Fe(II) and 2-oxoglutarate to convert 5-methylcytosine (5mC) to 5-hydroxy-methylcytosine (5hmC) and further oxidation products in DNA1-5. Here we show that Tet1 and Tet2 have distinct roles in regulating 5hmC deposition and gene expression in mouse embryonic stem cells (mESC). Tet1 depletion in mESC primarily diminishes 5hmC levels at transcription start sites (TSS), whereas Tet2 depletion is mostly associated with decreased 5hmC in gene bodies relative to TSS. 5hmC is enriched at exon start and end sites, especially in exons that are highly expressed, and is significantly decreased upon Tet2 knockdown at the boundaries of high-expressed exons that are selectively regulated by Tet2. In differentiating murine B cells, Tet2 deficiency is associated with selective exon exclusion in the gene encoding the transmembrane phosphatase CD45. Tet2 depletion is associated with increased 5hmC and decreased 5mC at promoters/ TSS regions, possibly because of the redundant activity of Tet1. Together, these data indicate a complex interplay between Tet1 and Tet2 in mESC, and show that loss-of-function of a single TET protein does not necessarily lead to loss of 5hmC and a corresponding gain of 5mC, as generally assumed. The relation between Tet2 loss-of-function and selective changes in exon expression could potentially explain the frequent occurrence of both TET2 loss-of-function mutations and mutations in proteins involved in pre-mRNA splicing in myeloid malignancies in humans. Gene and exon expression analysis in mESC, Tet1 knockdown mESC, and Tet2 knockdown mESC by RNA-sequencing. Mapping of 5-hydroxymethylcytosine in mESC, Tet1 knockdown mESC, and Tet2 knockdown mESC by anti-CMS-seq. Mapping of methylcytosine in mESC, and Tet2 kd mESC by MeDIP-seq.
Project description:The TET proteins TET1, TET2 and TET3 constitute a new family of dioxygenases that utilize molecular oxygen and the cofactors Fe(II) and 2-oxoglutarate to convert 5-methylcytosine (5mC) to 5-hydroxy-methylcytosine (5hmC) and further oxidation products in DNA1-5. Here we show that Tet1 and Tet2 have distinct roles in regulating 5hmC deposition and gene expression in mouse embryonic stem cells (mESC). Tet1 depletion in mESC primarily diminishes 5hmC levels at transcription start sites (TSS), whereas Tet2 depletion is mostly associated with decreased 5hmC in gene bodies relative to TSS. 5hmC is enriched at exon start and end sites, especially in exons that are highly expressed, and is significantly decreased upon Tet2 knockdown at the boundaries of high-expressed exons that are selectively regulated by Tet2. In differentiating murine B cells, Tet2 deficiency is associated with selective exon exclusion in the gene encoding the transmembrane phosphatase CD45. Tet2 depletion is associated with increased 5hmC and decreased 5mC at promoters/ TSS regions, possibly because of the redundant activity of Tet1. Together, these data indicate a complex interplay between Tet1 and Tet2 in mESC, and show that loss-of-function of a single TET protein does not necessarily lead to loss of 5hmC and a corresponding gain of 5mC, as generally assumed. The relation between Tet2 loss-of-function and selective changes in exon expression could potentially explain the frequent occurrence of both TET2 loss-of-function mutations and mutations in proteins involved in pre-mRNA splicing in myeloid malignancies in humans. Gene and exon expression analysis in mESC, Tet1 knockdown mESC, and Tet2 knockdown mESC by RNA-sequencing. Mapping of 5-hydroxymethylcytosine in mESC, Tet1 knockdown mESC, and Tet2 knockdown mESC by anti-CMS-seq. Mapping of methylcytosine in mESC, and Tet2 kd mESC by MeDIP-seq.
Project description:Tet enzymes (Tet1/2/3) convert 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC). Tet1 and Tet2 mediate 5hmC generation in mouse embryonic stem cells (ESCs) and various embryonic and adult tissues. To investigate the effects of combined deficiency of Tet1 and Tet2 on pluripotency and development, we have generated Tet1 and Tet2 double knockout (DKO) ESCs and mice. DKO ESCs were depleted of 5hmC, but remained pluripotent with subtle defects in differentiation and changes in gene expression. Double mutant embryos and chimeras exhibited mid-gestation defects and postnatal DKO mice displayed partially penetrant neonatal lethality and stochastic perturbation of imprinting. Viable DKO animals developed normally to adulthood but had reduced 5hmC level, increased 5mC level and lacked 5hmC in germ cells. Nevertheless, DKO mice of both sexes were fertile with females having smaller ovaries and reduced fertility. Our data suggest that both Tet1 and Tet2 contribute to 5hmC levels during development. Their combined loss does not block differentiation and embryogenesis, but leads to partially penetrant embryonic and perinatal abnormalities and compromised viability. Moreover, the presence of substantial levels of 5hmC in DKO embryos and adult mice suggests a significant contribution of Tet3 in hydroxylation of 5mC during development. Methylation patterns in tissue samples from a series of wt and Tet1/Tet2 DKO embryos, neonates and adults were generated using methylated DNA immunoprecipitation with antibodies against 5mC (MeDIP) and 5hmC (hMeDIP) followed by deep sequencing.
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:PGCs undergo two distinct stages of demethylation before reaching a hypomethylated ground state at E13.5. Stage 1 occurs between E7.25- E9.5 in which PGCs experience a global loss of cytosine methylation. However, discreet loci escape this global loss of methylation and between E10.5-E13.5, stage 2 of demethylation takes place. In this stage these loci are targeted by Tet1 and Tet2 leading to the loss of the remaining methylation and resulting in the epigenetic ground state. Our data shows that Dnmt1 is responsible for maintaining the methylation of loci that escape stage 1 demethylation, and that it functions in a UHRF1 independent manner. Our data further demonstrates that when these loci lose methylation prior to stage 2 it results in early activation of the meiotic program, which leads to precocious differentiation of the germ line resulting in a decreased pool of PGCs in the embryo and subsequent infertility in adult mice.