TG-interacting factor1 (Tgif1) maintains the identity of mouse ES cells by counterbalancing the expression of ES cell core factors
Ontology highlight
ABSTRACT: TG-interacting factor1 (Tgif1) is well-known as a transcriptional repressor in transforming growth factor beta (TGFβ) signaling pathway. Target mapping of ES cell core factors in mouse embryonic stem (ES) cells revealed that Tgif1 is occupied by Oct4 and Nanog. Moreover, recent interactome study of mouse gene regulatory regions showed a preferential regulation of Tgif1 by mouse ES cell specific enhancers. However, the detailed role and mode of actions of Tgif1 in stem cell maintenance and development remains elusive. We show that Tgif1 is indispensable for self-renewal and pluripotency of mouse embryonic stem (ES) cells. Aberrant expression of Tgif1 promotes differentiation of ES cells even in the presence of LIF in part by deregulation of pluripotency factors. Intriguingly, we find that Tgif1 level is a critical factor to determine specific lineage commitment in a dosage-dependent manner. We further show that Tgif1 interacts with ES cell core factors and co-localizes at their binding sites, which eventually restricts expression of ES cell core factors including Oct4, Sox2, and Nanog. Taken together, we provide new insights into the roles of Tgif1 in maintenance as well as differentiation of ES cells.
Project description:TG-interacting factor1 (Tgif1) is well-known as a transcriptional repressor in transforming growth factor beta (TGFβ) signaling pathway. Target mapping of ES core factors in mouse embryonic stem (ES) cells revealed that Tgif1 is occupied by Oct4 and Nanog. Moreover, recent interactome study of mouse gene regulatory regions showed a preferential regulation of Tgif1 by mouse ES cell specific enhancers. However, the detailed role and mode of actions of Tgif1 in stem cell maintenance and development remains elusive. We show that Tgif1 is indispensable for self-renewal and pluripotency of mouse embryonic stem (ES) cells. Aberrant expression of Tgif1 promotes differentiation of ES cells even in the presence of LIF in part by deregulation of pluripotency factors. Intriguingly, we find that Tgif1 level is a critical factor to determine specific lineage commitment in a dosage-dependent manner. We further show that Tgif1 interacts with ES cell core factors and co-localizes at their binding sites, which eventually restricts expression of ES cell core factors including Oct4, Sox2, and Nanog. Taken together, we provide new insights into the roles of Tgif1 in maintenance as well as differentiation of ES cells.
Project description:The Polycomb group (PcG) gene products mediate heritable silencing of developmental regulators in metazoans, participating in one of two distinct multimeric protein complexes, the Polycomb repressive complexes-1 (PRC1) and -2 (PRC2). PRC2 catalyses trimethylation of histone H3 at lysine 27 (H3K27) which in turn is thought to provide a recruitment site for PRC1. Recent studies demonstrate that mono-ubiquitylation of histone H2A at lysine 119 is important in PcG mediated silencing with the core PRC1 component Ring1A/B functioning as the E3 ligase8. PRC2 has been shown to share target genes with the core transcription network to maintain embryonic stem (ES) cells including Oct4 and Nanog. Here we identify an essential role for PRC1 in repressing developmental regulators in ES cells, and thereby in maintaining ES cell pluripotency. A significant proportion of the PRC1 target genes are also repressed by Oct4. We demonstrate that engagement of PRC1 and PRC2 at target genes is Oct4-dependent and moreover that Ring1B interacts with Oct4. Collectively these results show that PcG complexes are instrumental in Oct4-dependent repression required to maintain pluripotency of ES cells. This study provides a first functional link between a core ES cell regulator and global epigenetic regulation of the genome. Keywords: genetic modification
Project description:Embryonic stem cells have a unique regulatory circuitry, largely controlled by the transcription factors Oct4, Sox2 and Nanog, which generates a gene expression program necessary for pluripotency and self-renewal (Boyer et al. 2005; Loh et al. 2006; Chambers et al. 2003; Mitsui et al. 2003; Nichols et al. 1998). How external signals connect to this regulatory circuitry to influence embryonic stem cell fate is not known. We report here that a terminal component of the canonical Wnt pathway in embryonic stem cells, the transcription factor Tcf3, co-occupies promoters throughout the genome in association with the pluripotency regulators Oct4 and Nanog. Thus Tcf3 is an integral component of the core regulatory circuitry of ES cells, which includes an autoregulatory loop involving the pluripotency regulators. Both Tcf3 depletion and Wnt pathway activation cause increased expression of Oct4, Nanog and other pluripotency factors and enhance pluripotency and self-renewal. Our results reveal that the Wnt pathway, through Tcf3, brings developmental signals directly to the core regulatory circuitry of ES cells to influence the balance between pluripotency and differentiation.
Project description:Orphan nuclear receptor Esrrb is vital in maintaining ES cells and like Oct4, Sox2 and Nanog is essential for self-renewal and pluripotency. Esrrb functions in somatic cells via LBD/AF-2-dependent coactivator recruitment to target genes. Here we show that in ES cells coactivator recruitment is similarly required and identify Ncoa3 as the Esrrb coactivator needed for activation of its target genes. Ncoa3 is essential for self-renewal and the induction of pluripotency in reprogramming, and genome-wide analysis of Ncoa3 binding reveals extensive overlap with Esrrb and pluripotency factors along with marks of active genes. Mechanistically, we show Ncoa3 is specifically required to bridge RNApol2 to Esrrb. We thus identify a new member of the ES pluripotency network and describe Esrrb and Ncoa3 as key factors linking core pluripotency factors to the general transcription machinery.
Project description:The core pluripotency factors (Oct4, Sox2, and Nanog), the Myc network, and the chromatin-modifying complexes such as PRC2 ensure the pluripotency and self-renewal of ES cells (ESC). How these factors coordinate with one another remains poorly understood. We report that Utf1, a target of Oct4 and Sox2, is a new bivalent chromatin component that buffers poised states of bivalent genes. By limiting PRC2 loading and Histone 3 lysine-27 trimethylation, Utf1 sets proper activation thresholds for bivalent genes. It also promotes nuclear tagging of mRNAs transcribed from insufficiently silenced bivalent genes for cytoplasmic degradation through mRNA de-capping. Whereas these opposing functions of Utf1 allow proper execution of ESC pluripotency, the mRNA pruning function also ensures rapid cell proliferation by blocking the Myc-Arf feedback regulation. Thus, Utf1 is an important regulator that couples the core pluripotency factors with Myc and PRC2 networks to promote proliferation and pluripotency execution of ESCs.
Project description:The core pluripotency factors (Oct4, Sox2, and Nanog), the Myc network, and the chromatin-modifying complexes such as PRC2 ensure the pluripotency and self-renewal of ES cells (ESC). How these factors coordinate with one another remains poorly understood. We report that Utf1, a target of Oct4 and Sox2, is a new bivalent chromatin component that buffers poised states of bivalent genes. By limiting PRC2 loading and Histone 3 lysine-27 trimethylation, Utf1 sets proper activation thresholds for bivalent genes. It also promotes nuclear tagging of mRNAs transcribed from insufficiently silenced bivalent genes for cytoplasmic degradation through mRNA de-capping. Whereas these opposing functions of Utf1 allow proper execution of ESC pluripotency, the mRNA pruning function also ensures rapid cell proliferation by blocking the Myc-Arf feedback regulation. Thus, Utf1 is an important regulator that couples the core pluripotency factors with Myc and PRC2 networks to promote proliferation and pluripotency execution of ESCs. First we mapped Utf1 binding sites in ESCs using the biotin-mediated and cross-linked ChIP-sequencing. To investigate how Utf1 might regulate gene expression, we did RNA-seq on WT and Utf1-KO ES cells. Then we did ChIP-seq of Suz12 and H3K27me3 on WT and Utf1-KO ES cells to study whether Utf1 affects PRC2 loading and H3K27me3 modofication, using H3 as control. Finally, we did RNAseq on WT and Dcp1a-KD ES cells to confirm Utf1 repress gene expression by recruiting Dcp1a complex.
Project description:Chavez2009 - a core regulatory network of OCT4 in human embryonic stem cells
A core OCT4-regulated network has been identified as a test case, to analyase stem cell characteristics and cellular differentiation.
This model is described in the article:
In silico identification of a core regulatory network of OCT4 in human embryonic stem cells using an integrated approach.
Chavez L, Bais AS, Vingron M, Lehrach H, Adjaye J, Herwig R
BMC Genomics, 2009, 10:314
Abstract:
BACKGROUND: The transcription factor OCT4 is highly expressed in pluripotent embryonic stem cells which are derived from the inner cell mass of mammalian blastocysts. Pluripotency and self renewal are controlled by a transcription regulatory network governed by the transcription factors OCT4, SOX2 and NANOG. Recent studies on reprogramming somatic cells to induced pluripotent stem cells highlight OCT4 as a key regulator of pluripotency.
RESULTS: We have carried out an integrated analysis of high-throughput data (ChIP-on-chip and RNAi experiments along with promoter sequence analysis of putative target genes) and identified a core OCT4 regulatory network in human embryonic stem cells consisting of 33 target genes. Enrichment analysis with these target genes revealed that this integrative analysis increases the functional information content by factors of 1.3 - 4.7 compared to the individual studies. In order to identify potential regulatory co-factors of OCT4, we performed a de novo motif analysis. In addition to known validated OCT4 motifs we obtained binding sites similar to motifs recognized by further regulators of pluripotency and development; e.g. the heterodimer of the transcription factors C-MYC and MAX, a prerequisite for C-MYC transcriptional activity that leads to cell growth and proliferation.
CONCLUSION: Our analysis shows how heterogeneous functional information can be integrated in order to reconstruct gene regulatory networks. As a test case we identified a core OCT4-regulated network that is important for the analysis of stem cell characteristics and cellular differentiation. Functional information is largely enriched using different experimental results. The de novo motif discovery identified well-known regulators closely connected to the OCT4 network as well as potential new regulators of pluripotency and differentiation. These results provide the basis for further targeted functional studies.
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Project description:Orphan nuclear receptor Esrrb is vital in maintaining ES cells and like Oct4, Sox2 and Nanog is essential for self-renewal and pluripotency. Esrrb functions in somatic cells via LBD/AF-2-dependent coactivator recruitment to target genes. Here we show that in ES cells coactivator recruitment is similarly required and identify Ncoa3 as the Esrrb coactivator needed for activation of its target genes. Ncoa3 is essential for self-renewal and the induction of pluripotency in reprogramming, and genome-wide analysis of Ncoa3 binding reveals extensive overlap with Esrrb and pluripotency factors along with marks of active genes. Mechanistically, we show Ncoa3 is specifically required to bridge RNApol2 to Esrrb. We thus identify a new member of the ES pluripotency network and describe Esrrb and Ncoa3 as key factors linking core pluripotency factors to the general transcription machinery. ChIP experiments were carried out with chromatin prepared from E14 cells as previously described (Stock et al., 2007), using 8-10 ug primary antibody for NcoA3 and 600 ug pre-cleared chromatin per IP. Antibody for NcoA3 was from Santacruz (sc-9119) .
Project description:The pluripotency of embryonic stem cells (ESCs) is maintained by a small group of master transcription factors including Oct4, Sox2 and Nanog. These core factors form a regulatory circuit controlling the transcription of a number of pluripotency factors including themselves. Although a lot of previous studies have identified key factors regulating this core network in trans, the contribution of cis-regulatory DNA sequences on the transcription of these key pluripotency factors remains elusive. We analyzed epigenomic data within the 1.5 Mb gene-desert regions around Sox2 gene and predicted only one 13kb-long enhancer located 100kb downstream of Sox2 in mouse ES cells. This enhancer is occupied by Oct4, Sox2, Nanog, and mediator complex and forms a long-range DNA looping to Sox2 locus. We hypothesized that this enhancer is critical for Sox2 gene expression and tested this hypothesis by deleting this entire 13-kb enhancer with a simple highly-efficient double-excision CRISPR strategy. Allele-specific of Sox2 transcripts in heterozygous enhancer-deletion clones showed that the enhancer affects expression through a cis-acting mechanism. Strikingly, although this distal enhancer is not conserved in other mammals including human, it is responsible for over 90% of Sox2 expression in mouse ESCs. Taken together, our results provide direct evidence that in mouse ESCs, Sox2 transcription is primarily driven by a species-specific distal enhancer, which may provide new perspectives explaining the physiological difference between human and mouse ES cells. This dataset include ChIP-seq of H3K4me3 and H3K27ac in a hybrid mouse ES cells (F123). H3K27ac in J1 mouse ES cells. And RNA-seq in F123 mESCs with complete Sox2 enhancer deletion or enhancer haploinsufficient clones.
Project description:Protein-protein proximity of core pluripotency transcription factors plays an important role during cell reprogramming. Pluripotent embryonic stem (ES) cell identity is controlled by a trio of transcription factors: Sox2, Oct4, and Nanog. These proteins often bind to closely localized genomic sites. The precise mode by which Sox2, Oct4, and Nanog interact with DNA is likely to make a crucial contribution to their function. Here, a detailed protocol for in vivo detection and quantitative analysis of protein-protein proximity of Sox2 and Oct4 using Proximity Utilizing Biotinylation (PUB) method based on the use of the BAP/BirA (target/enzyme) system is described. The method includes design and cloning of DNA plasmid construct, transient transfection of HEK293T cells, Western blot analysis of nuclei fraction and LC-MS/MS analysis. Experiments with coexpression of BAP-X+BirA-Y (X, Y=Sox2, Oct4 and GFP as control) revealed strong biotinylation level of target proteins when X and Y were pluripotency transcription factors compared with control when X=GFP. Since mass spectrometry provides both high sensitivity and more accurate quantification of data a modified workflow was used, in which SDS-PAGE step was eliminated and His-tagged BAP-fused proteins from cell lysate were purified in 6M guanidine HCl buffer, washed, propionylated, digested directly on the Ni sepharose beads using trypsin and analysed on Q-TOF Impact II instrument. Using mass spectrometry allows making quantitative estimation of in vivo interaction of BAP-Sox2 and BirA-Oct4 which was demonstrated by measuring ratios of biotinylation levels of BAP fused either with Sox2 or GFP at different biotin pulse times. After vector preparation this protocol can be completed in seven working days.