High-throughput sequencing of sequentially reprogrammed iPS cells reveals key epigenetic modifications correlated with reduced pluripotency of iPS cells [MeDIP-seq]
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ABSTRACT: Full pluripotency of induced pluripotent stem (iPS) cells has been determined as viable all-iPS mice can be generated through tetraploid complementation. Subsequently, activation of imprinted Dlk-Dio3 gene cluster has been suggested to correlate with the pluripotency of iPS cells1. However, evidence from recent studies has demonstrated that loss of imprinting at the Dlk-Dio3 locus did not correlate strictly with the reduced pluripotency of iPS cells. Therefore, it becomes indispensable to exploit other reliable molecular markers for evaluating the quality of iPS cells accurately. In the present study, we successfully utilize the sequential reprogramming approach and produce all-iPS mice to six generations using iPS cell lines derived from different cell lineages which contain the same proviral integration in the genome. By comparing the global gene expression and epigenetic modifications of both “tetra-on” and corresponding “tetra-off” iPS cell lines established from either mesenchymal or hematopoietic lineages through deep sequencing analysis of mRNA expression, small RNA profiling, histone modifications (H3K4m2, H3K4me3 and H3K27me3) and DNA methylation, very few differences are detected among all the iPS cell lines investigated. However, we find that two imprinted genes, disruption of which correlate with the reduced pluripotency of iPS cells. Therefore, our data not only provide the first demonstration that producing of all-iPS mice to six generations is feasible, but reveal that two imprinted regions can be served as pluripotency markers of iPS cells Examination of DNA methylation in 13 cell types
Project description:We performed 5hmC/5mC DNA Immunoprecipitation followed high-throughput sequencing using the cell sample along the whole TSKM secondary reprogramming system. The TSKM 0D is the fibroblasts deried from TSKM-iPS mouse as the starting cells of the reprogramming.The intermediate cells is 3-days induced cells which are refered as TSKM 3D cells, and the final reprogrammed cells is the iPS cells with full pluripotency driven from this secondary system. We compared the profiling of 5-hydroxymethylcytosine and 5-methylcytosine modifications in these different cell lines. We found that: a widespread accompanying increase of 5hmC and 5mC at TSS and ES-active regulation regions followed by 5mC-5hmC pattern switch. Taking the advantage of the newly established TSKM secondary reprogramming system, the epigenetic remodeling and regulation mechanisms can be further investigated to advance our understanding of the epigenetic barriers and decipher the dynamic mechanism in somatic cell reprogramming. Examination of 5-hydroxymethylcytosine/5-methylcytosine modifications in a Tet1-mediated secondary reprogramming system
Project description:Full pluripotency of induced pluripotent stem (iPS) cells has been determined as viable all-iPS mice can be generated through tetraploid complementation. Subsequently, activation of imprinted Dlk-Dio3 gene cluster has been suggested to correlate with the pluripotency of iPS cells1. However, evidence from recent studies has demonstrated that loss of imprinting at the Dlk-Dio3 locus did not correlate strictly with the reduced pluripotency of iPS cells. Therefore, it becomes indispensable to exploit other reliable molecular markers for evaluating the quality of iPS cells accurately. In the present study, we successfully utilize the sequential reprogramming approach and produce all-iPS mice to six generations using iPS cell lines derived from different cell lineages which contain the same proviral integration in the genome. By comparing the global gene expression and epigenetic modifications of both “tetra-on” and corresponding “tetra-off” iPS cell lines established from either mesenchymal or hematopoietic lineages through deep sequencing analysis of mRNA expression, small RNA profiling, histone modifications (H3K4m2, H3K4me3 and H3K27me3) and DNA methylation, very few differences are detected among all the iPS cell lines investigated. However, we find that two imprinted genes, disruption of which correlate with the reduced pluripotency of iPS cells. Therefore, our data not only provide the first demonstration that producing of all-iPS mice to six generations is feasible, but reveal that two imprinted regions can be served as pluripotency markers of iPS cells Examination of 3 different histone modifications in 13 cell types
Project description:TRIM24 and TRIM33 interact to form a corepressor complex that suppresses murine hepatocellular carcinoma (HCC). TRIM24 and TRIM33 cooperatively repress retinoic acid receptor dependent activity of VL30 retro-transposons in hepatocytes in vivo. In TRIM24 knockout hepatocytes, VL30 long terminal repeats (LTRs) generate enhancer (e)RNAs and act as surrogate promoter and enhancer elements deregulating expression of neighbouring genes. We show that a VL30 LTR-derived eRNA is essential to activate the lipocalin 13 gene in hepatocytes in vivo. A further consequence of VL30 de-repression is the accumulation of retro-transcribed VL30 DNA in the cytoplasm of TRIM24-mutant hepatocytes and activation of the viral defence/interferon response. VL30 activation therefore modulates gene expression via the enhancer activity of the LTRs and by activation of the interferon response. Both of these processes are genetically linked to HCC development suggesting that VL30 repression by TRIM24 plays an important role in tumour suppression. RNA profiles in liver of wild type (WT) and Trim24-/- mice by deep sequencing using Illumina GAIIx.
Project description:The nuclear receptor HNF4A regulates embryonic and post-natal hepatocyte gene expression. Using hepatocyte-specific inactivation in mice, we show that the TAF4 subunit of TFIID acts as a cofactor for HNF4A in vivo and that HNF4A interacts directly with the TAF4-TAF12 heterodimer in vitro. In vivo, TAF4 is required to maintain HNF4A-directed embryonic gene expression at post-natal stages and for HNF4A-directed activation of post-natal gene expression. TAF4 promotes HNF4A occupancy of functional cis-regulatory elements located adjacent to the transcription start sites of post-natal expressed genes and for pre-initiation complex formation required for their expression. Promoter-proximal HNF4A-TFIID interactions are therefore required for pre-initiation complex formation and stable HNF4A occupancy of regulatory elements as two concomitant mutually dependent processes. RNA profiles in wild-type and Taf4-/- livers by deep sequencing
Project description:Myc is a master transcription factor that has been demonstrated to be required for embryonic stem cell (ESC) pluripotency, self-renewal, and inhibition of differentiation. Although recent works identified several Myc-targets in ESC the list of Myc binding sites is largely incomplete due to the low sensitivity and specificity of the antibodies available so far. To systematically identify Myc binding sites in mouse ESCs here we used a stringent streptavidin based genome-wide chromatin immunoprecipitation (ChIP-Seq) of a biotin-tagged Myc (Bio-Myc) as well as a ChIP-Seq of the Myc partner Max. This analysis identified 4273 Myc binding sites of which more than 85% co-occupied by Max, overlap with H3K4me3 positive promoters and active enhancers of transcriptional regulators, chromatin modifiers, and genes involved in stem cell self-renewing. The new sites identified were validated experimentally. This study provides a new Myc and Max binding reference in mouse ESCs. ChIP-seq of bio-Myc and Max in E14 and respective controls; Bio-Myc ChIP-seq was performed in a stable clone of E14 mouse embryonic stem cell expressing Biotin-tagged Myc; Mock, Max and IgG were performed in parental wt E14 mESC.
Project description:5-hydroxymethylcytosine (5hmC) is a recently discovered epigenetic modification that is lost in human cancers. Formation of 5hmC is catalysed by the Ten eleven translocation (TET) proteins that mediate the sequential oxidation of 5-methylcytosine (5mC) to 5hmC, leading to eventual DNA demethylation. Several mechanisms can lead to loss of 5hmC in cancers, including mutations in IDH or TET2 genes. However, little is known about the role of TET proteins and 5hmC in adult cells. Here, we report that TET1 downmodulation is required to permit adult cells to proliferate. TET1 is rapidly downmodulated in proliferating primary cells and in regenerating liver. TET1 silencing accelerates cell cycle progression while its constitutive expression inhibits cell growth. TET1 is a negative regulator of cell proliferation and it is regulated during development in tissue specific manner. These findings enlarge our knowledge on how one epigenetic modification such as the DNA hydroxymethylation mediated by TET1 is a key player on the control of cell proliferation. Examination of 5hmC in MEF at passage 0 and at passage 5.
Project description:The de novo DNA methyltransferase 3-like (Dnmt3L) is a catalytically inactive DNA methylase that has been previously shown to cooperate with Dnmt3a and Dnmt3b to methylate DNA. Dnmt3L is highly expressed in mouse embryonic stem cells (ESC) but its function in these cells is unknown. We here report that Dnmt3L is required for the differentiation of ESC into primordial germ cells (PGC) through activation of the homeotic gene Rhox5. By genome-wide analysis we found that Dnmt3L is a positive regulator of methylation at gene bodies of housekeeping genes and a negative regulator of methylation at promoters of bivalent genes. We demonstrate that Dnmt3L interacts with the Polycomb PRC2 complex in competition with the DNA methyl transferases Dnmt3a and Dnmt3b to maintain low the methylation level at H3H27me3 regions. Thus in ESC, Dnmt3L counteracts the activity of de novo DNA methylases to keep low the level of DNA methylation at developmental gene promoters. Examination of 5mC in shGFP and shDnmt3L ESC by MeDIP-Seq
Project description:Recent studies have analyzed the distribution and role of 5-hydroxymethylcytosin (5hmC) in Embryonic Stem Cells (ESC). However, DNA hydroxymethylation occurs also in differentiated cells and it is significantly deregulated in cancer. Here we mapped 5hmC genome-wide profile in pluripotent ES cells in comparison to embryonic and adult differentiated cells. Comparative analysis of 5hmC genomic distribution with respect to gene expression reveals that 5hmC is enriched on the gene body of genes expressed at medium/high level and on TSS of genes not expressed or expressed at low level independently from the cell type. ESC showed a significant enrichment of DNA hydroxymethylation in active enhancers and bivalent promoters with respect to more differentiated cells as well as preferential association of Tet1 and 5hmC with promoter bound by Polycomb Repressive Complex 2 (PRC2). Furthermore, we show that in ESC PRC2 interacts with Tet1 and it is required for Tet1 recruitment to the chromatin and 5hmC deposition at developmental genes. Examination of 5hmC in ESC, MEF, Brain, Liver, shGFP ESC, and shSuz12ESC, and examination of expression in shGFP ESC and shSuz12ESC.