Tet1 as a Negative Regulator of Somatic Cell Reprogramming
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ABSTRACT: Tet1 is a hydroxylase known for its role in the conversion of 5-methylcytosines (5mC) to 5-hydroxymethylcytosines (5hmC) involved in the possible active demethylation process and gene expression regulation1-5.M-BM- As somatic cell reprogramming involves the re-activation of pluripotency genes and the silencing of somatic ones6, it remains unclear whether Tet1 plays a positive or negative role in the reprogramming process. Here we show that Tet1 deficiency enhances reprogramming and its overexpression impairs reprogramming. Mechanistically, we demonstrated that Tet1 represses the early obligatory process of mesenchymal to epithelial transition (MET) during reprogramming7,8. Thus, our findings not only define a negative role for Tet1 in somatic cell reprogramming, but also suggest that the Tet enzymes regulate cell fate through distinctive mechanisms. Examination of genome DNA hmC modifications in 2 conditions: individually overexpressed Tet1CD or Tet2CD during MEF reprogramming; Examination of mRNA levels in five different conditions: individually overexpressed DR or Tet1CD or Tet1CDmut or Tet2CD or Tet2CDmut, during MEF reprogrammig.
Project description:Tet1 is a hydroxylase known for its role in the conversion of 5-methylcytosines (5mC) to 5-hydroxymethylcytosines (5hmC) involved in the possible active demethylation process and gene expression regulation. As somatic cell reprogramming involves the re-activation of pluripotency genes and the silencing of somatic ones, it remains unclear the role of Tet1 in the reprogramming process. Here, we performed RNAseq for WT and knocking down Tet1 in two pre-iPSCs cell lines, pre2-2 and pre3. Using two pre-iPSCs cell lines: pre2-2 and pre3, cultured by mES medium(+lif), transfected siCtrl/siTet1 siRNA or non-treatment, then, after 16h, the medium were replaced by mES(+lif) medium plus Vc(50ug/ml), total RNA was extracted after another 32h later for RNAseq.
Project description:The somatic cell fate can be converted to tumor or pluripotent ones by ectopic expression of transcription factors in vitro and in vivo. Many oncogenic transcription factors are known to mediate both fates as they share similar proliferative and metabolic properties. Paradoxically, we found c-Jun as the first oncogene that appears to specify a somatic fate, oppose the pluripotent one and impede reprogramming. We performed a series of high through out sequencing to understand the way cJun works. To understand how c-Jun drives mESCs differentiating, we obtained c-Jun TetOn mESCs, and performed RNAseq 36h later with dox inducing or not . To understand why c-Jun blocks reprogramming while c-JunDN and Jdp2 can replace Oct4, we overexpressed these factors with KSM during reprogramming and performed RNAseq 3 Days after virus transfection. Moreover, to extend understand how these factors regulate gene expression, we also overexpressed these factors in MEF and performed RNAseq. Further more, to understand how cJun regulates cell fates and gene expression, we overexpressed c-Jun in mouse ESC and performed ChIP-seq. Also, we performed c-JunDN ChIP-seq during somatic cells reprogramming on day 3, to explore the binding sites of c-JunDN.
Project description:Mature oocyte cytoplasm can reprogram somatic cell nuclei to the pluripotent state through a series of sequential events including protein exchange between the donor nucleus and ooplasm, chromatin remodeling, and pluripotency gene reactivation. Maternal factors that are responsible for this reprogramming process remain largely unidentified. Here, we demonstrate that knockdown of histone variant H3.3 in mouse oocytes results in compromised reprogramming and down-regulation of key pluripotency genes; and this compromised reprogramming both for developmental potentials and transcription of pluripotency genes can be rescued by injecting exogenous H3.3 mRNA, but not H3.2 mRNA into oocytes in somatic cell nuclear transfer (SCNT) embryos. We show that maternal H3.3, and not H3.3 in the donor nucleus, is essential for successful reprogramming of somatic cell nucleus into the pluripotent state. Furthermore, H3.3 is involved in this reprogramming process by remodeling the donor nuclear chromatin through replacement of donor nucleus-derived H3 with de novo synthesized maternal H3.3 protein. Our study shows that H3.3 is a crucial maternal factor for oocyte reprogramming and provides a practical model to directly dissect the oocyte for its reprogramming capacity. Transcriptome sequencing of 4-cell NT embryos, Luciferase 4-cell SCNT embryos, 4-cell NT embryos_H3.3KD, 4-cell NT embryos_H3.3KD+H3.3mRNA, H3.3 KD + H3.2 mRNA SCNT embryos
Project description:We performed 5hmC DNA Immunoprecipitation followed high-throughput sequencing using R1 ESCs, OT ESCs, TSKM ESCs, Day3 TSKM and OSKM induction cells. We compared the profiling of 5-hydroxymethylcytosine modifications in these different cell lines. We found that: the TSKM and OT iPSCs shared similar 5hmC modification pattern while apart from that of R1 ESCs. However the comparison based on the gene promoter (-1000/+500 of gene’s TSS) showed less differences. The TSKM 2nd induction samples were quite like each other and have shared the basic pattern with traditional OSKM 2nd sample. However comparison based on the gene promoter showed sharp increase. Moreover higher enrichment of 5hmC on the distal enhancer of Oct4 was specifically detected in Day 3 TSKM 2nd cells as well as TSKM and OT iPSCs, which might be helpful for us to study the Tet1-mediated somatic reprogramming. Examination of 5-hydroxymethylcytosine modifications in 5 different cell lines.
Project description:We performed a meta analysis of publicly available TET1, 5mC, 5hmC and genome wide bisulfite profiling data mostly from mouse embryonic stem cells (ESC). Genome wide chromatin immunoprecipitation combined with deep sequencing (ChIP-seq) has revealed binding of the TET1 protein at CpG-island (CGI) promoters and at bivalent promoters. We show that TET1 also coincides with DNAseI hypersensitive sites (HS). Presence of TET1 at these THREE locations suggests that it may play a dual role: an active role at CpG-islands and DNAseI hypersensitive sites and a repressive role at bivalent loci. In line with the presence of TET1, significant enrichment of 5hmC but not 5mC is detected at bivalent promoters and DNaseI HS. Surprisingly, 5hmC is not detected or present at very low levels at CGI promoters notwithstanding the presence of TET1 at these loci. Our meta analysis suggest that asymmetric methylation is present at CA- and CT-repeats in the genome of some human ESC. Examination of the distribution of 5-methylcytosine and 5-hydroxymethylcytosine in the genome of mouse embryonic stem cells.
Project description:Reprogramming somatic cells to induced pluripotency by Yamanaka factors is usually slow and inefficient, and is thought to be a stochastic process. We identified a privileged somatic cell state, from which acquisition of pluripotency could occur in a non-stochastic manner. Subsets of murine hematopoietic progenitors are privileged, whose progeny cells predominantly adopt the pluripotent fate with activation of endogenous Oct4 locus after 4-5 divisions in reprogramming conditions. Privileged cells display an ultrafast cell cycle of ~8 hours. In fibroblasts, a subpopulation cycling at a similar ultrafast speed is observed after 6 days of factor expression, and is increased by p53-knockdown. This ultrafast-cycling population accounts for >99% of the bulk reprogramming activity in wildtype or p53-knockdown fibroblasts. We compared the transcriptomes of the fast cycling cells with those of slower hematopoietic progenitors, bulk fibroblasts and established iPS cells. 3-5 replicates for each of the six cell types were included: 4 replicates for established iPS cells, 4 replicates for bulk mouse embryonic fibroblasts (MEF), 4 replicates for fast cycling MEF, 4 replicates for slow cycling MEF, 5 replicates for fast cycling granulocyte monocyte progenitors (GMP) and 3 replicates for slow cycling GMP.
Project description:Tet1 is a hydroxylase known for its role in the conversion of 5-methylcytosines (5mC) to 5-hydroxymethylcytosines (5hmC) involved in the possible active demethylation process and gene expression regulation. As somatic cell reprogramming involves the re-activation of pluripotency genes and the silencing of somatic ones, it remains unclear the role of Tet1 in the reprogramming process. Here, we performed hMeDIP-seq and RNA-seq during somatic cells reprogramming with Tet1 over expression to invest the effect of Tet1.
Project description:This study uses whole methylome sequencing to characterize the methylomes of mouse embryonic fibroblasts (MEF's). Two conditions were analyzed, MEF cells with intact TET1/TET2 enzymes (WT) and MEF cells with TET1/TET2 knocked out (DKO). Our results identify sets of differentially methylated genes which are correlated with TET1/TET2 induced expression changes of the corresponding genes. Whole methylome analysis of M. musculus MEF cells. Two conditions were sequenced and analyzed, the first is wild type (WT), the second (DKO) corresponds to knock-out of TET1 and TET2 enzymes.
Project description:Tet1 is a hydroxylase known for its role in the conversion of 5-methylcytosines (5mC) to 5-hydroxymethylcytosines (5hmC) involved in the possible active demethylation process and gene expression regulation. As somatic cell reprogramming involves the re-activation of pluripotency genes and the silencing of somatic ones, it remains unclear the role of Tet1 in the reprogramming process. Here, we performed RNAseq for WT and knocking down Tet1 in two pre-iPSCs cell lines, pre2-2 and pre3.
Project description:The activation-induced cytidine deaminase enzyme (AID) is required in germinal center (GC) B cells for somatic hyper-mutation and class switch recombination at the immunoglobulin locus. In GC-B cells, AID is highly expressed, with inherent mutator activity that helps generate antibody diversity. However, AID may also regulate gene expression epigenetically, irrespective of mutator activity, by directly deaminating 5-methylcytosine (5mC) in concert with base excision repair glycosylases to exchange unmethylated cytosine. This pathway promotes gene demethylation, thereby removing epigenetic memory. For example, AID promotes active demethylation of the genome in primordial germ cells. However, the range and mechanism by which AID promotes pluripotency is not known. Different studies have suggested either a requirement or a lack of function for promoting pluripotency in somatic nuclei following fusion with embryonic stem cells (ESC). Here we tested directly whether AID regulates epigenetic memory, by comparing the relative ability of cells lacking AID to reprogram from a differentiated cell type to an induced pluripotent stem cell (iPSC). We show that loss of AID impacts two distinct steps of reprogramming: First, AID-null cells are transiently hyper-responsive to the reprogramming process. Second, although they initiate expression of pluripotency genes, they fail to stabilize the pluripotent state. The genome of AID-null cells remains hypermethylated in reprogramming cells, and hypermethylated genes associated with pluripotency fail to be stably up-regulated. MYC target genes are highly enriched in the set of genes hypermethylated and under-expressed in reprogramming cells lacking AID. Recent studies identified a distinctive late step of reprogramming associated with methylation status. AID appears to regulate this step to stabilize the pluripotent state, removing epigenetic memory to promote expression of secondary pluripotency network genes. Transcriptome sequencing of AID-null tail fibroblasts, wildtype tail fibroblasts, AID-null and wildtype tail fibroblasts reprogrammed for three weeks by ectopic expression of transcription factors Oct4, Sox2, KLf4 and cMyc. Methylation profiling by reduced representation bisulphite seuencing of AID-null tail fibroblasts, wildtype tail fibroblasts, AID-null and wildtype tail fibroblasts reprogrammed for three weeks and AID-null and wildtype clones after three weeks of reprogramming (Picked at two weeks)