CTCF deletion alters the pluripotency and DNA methylation profile of human iPSCs (RNA-Seq)
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ABSTRACT: Pluripotent stem cells are characterized by their differentiation potential toward endoderm, mesoderm, and ectoderm. However, it is still largely unclear how these cell-fate decisions are mediated by epigenetic mechanisms. In this study, we explored the relevance of CCCTC-binding factor (CTCF), a zinc finger-containing DNA-binding protein, which mediates long-range chromatin organization, for directed cell-fate determination. We generated human induced pluripotent stem cell (iPSC) lines with deletions in the protein-coding region in exon 3 of CTCF, resulting in overall reduced expression and shorter transcripts. These lines showed a considerable loss of CTCF binding to target sites. The CTCF deletions resulted in slower growth and modest global changes in gene expression, with down-regulation of a subset of pluripotency-associated genes and neuroectodermal genes. CTCF deletion also evoked DNA methylation changes, which were moderately associated with differential gene expression. Notably, CTCF-deletions lead to up-regulation of endo-mesodermal associated marker genes and epigenetic signatures, whereas ectodermal differentiation was defective. These results indicate that CTCF plays an important role in the maintenance of pluripotency and differentiation, especially towards ectodermal lineages.
Project description:Pluripotent stem cells are characterized by their differentiation potential toward endoderm, mesoderm, and ectoderm. However, it is still largely unclear how these cell-fate decisions are mediated by epigenetic mechanisms. In this study, we explored the relevance of CCCTC-binding factor (CTCF), a zinc finger-containing DNA-binding protein, which mediates long-range chromatin organization, for directed cell-fate determination. We generated human induced pluripotent stem cell (iPSC) lines with deletions in the protein-coding region in exon 3 of CTCF, resulting in overall reduced expression and shorter transcripts. These lines showed a considerable loss of CTCF binding to target sites. The CTCF deletions resulted in slower growth and modest global changes in gene expression, with down-regulation of a subset of pluripotency-associated genes and neuroectodermal genes. CTCF deletion also evoked DNA methylation changes, which were moderately associated with differential gene expression. Notably, CTCF-deletions lead to up-regulation of endo-mesodermal associated marker genes and epigenetic signatures, whereas ectodermal differentiation was defective. These results indicate that CTCF plays an important role in the maintenance of pluripotency and differentiation, especially towards ectodermal lineages.
Project description:Sall1 is a multi-zinc finger transcription factor that regulates kidney organogenesis. It is considered to be a transcriptional repressor, preferentially localized on heterochromatin. Mutations or deletions of the human SALL1 gene are associated with the Townes-Brocks syndrome. Despite its high expression, no function was yet assigned for Sall1 in embryonic stem (ES) cells. In the present study we show that Sall1 is expressed in a differentiation-dependent manner and physically interacts with Nanog and Sox2, two components of the core pluripotency network. Genome-wide mapping of Sall1-binding loci has identified 591 genes, 80% of which are also targeted by Nanog. A large proportion of these genes are related to self-renewal and differentiation. Sall1 positively regulates and synergizes with Nanog for gene transcriptional regulation. In addition, our data show that Sall1 suppresses the ectodermal and mesodermal differentiation. Specifically, the induction of the gastrulation markers T brachyury, Goosecoid and Dkk1 and the neuroectodermal markers Otx2 and Hand1 was inhibited by Sall1 overexpression during embryoid body differentiation. These data demonstrate a novel role for Sall1 as a member of the transcriptional network that regulates stem cell pluripotency.
Project description:Histone variants are important epigenetic regulators known to play a role in governing the processes of self-renewal and lineage specific differentiation . Phosphorylation of the histone variant H2A.X (γH2A.X) has historically been associated with DNA damage response, but more recent investigations have further demonstrated it’s role in cell cycle, aging and early development. Through both genetic and chemical targeting approaches, we now reveal a direct involvement of γH2A.X in hPSC self-renewal and differentiation decisions in vitro and in vivo. Namely, reduction of γH2A.X levels enhance hPSC differentiation toward mesodermal derivatives with concomitant inhibition of ectodermal derivatives. In contrast, ectopic expression of a constitutively phosphorylated mimic of γH2A.X enhanced hPSCs differentiation toward ectodermal fate while mesodermal differentiation was hindered. These phenotypic observations were associated with γH2A.X occupancy in the promoter regions of key regulatory genes associated with pluripotency and lineage choice. Our study suggests γH2A.X is a functional epigenetic pluripotency marker and novel target for guiding cell-fate commitment during differentiation.
Project description:Histone variants are important epigenetic regulators known to play a role in governing the processes of self-renewal and lineage specific differentiation . Phosphorylation of the histone variant H2A.X (γH2A.X) has historically been associated with DNA damage response, but more recent investigations have further demonstrated it’s role in cell cycle, aging and early development. Through both genetic and chemical targeting approaches, we now reveal a direct involvement of γH2A.X in hPSC self-renewal and differentiation decisions in vitro and in vivo. Namely, reduction of γH2A.X levels enhance hPSC differentiation toward mesodermal derivatives with concomitant inhibition of ectodermal derivatives. In contrast, ectopic expression of a constitutively phosphorylated mimic of γH2A.X enhanced hPSCs differentiation toward ectodermal fate while mesodermal differentiation was hindered. These phenotypic observations were associated with γH2A.X occupancy in the promoter regions of key regulatory genes associated with pluripotency and lineage choice. Our study suggests γH2A.X is a functional epigenetic pluripotency marker and novel target for guiding cell-fate commitment during differentiation.
Project description:Core circuits of transcription factors stabilize stem and progenitor cells by suppressing genes required for differentiation. We do not know how such core circuits are reorganized during cell fate transitions to allow differentiation and lineage choice to proceed. Here, we asked how the pluripotency circuit, a core transcriptional circuit that maintains mouse embryonic stem (ES) cells in a pluripotent state, is dismantled as ES cells differentiate and choose between the neural ectodermal and mesendodermal progenitor cell fates. When ES cells are recultured from pluripotency maintaining conditions to the basal media N2B27, the expression of the pluripotency circuit genes begins to change. At 48 hours post N2B27 addition, the ES cells are competent to respond to differentiation signals. Here, our microarray analysis compares the gene expression profile of ES cells vs. the gene expression profile of cells that have been treated with N2B27 for 48 hours, reaching the competent state. 2 x mouse ES cells in pluripotency maintaining conditions. 3 x mouse ES cells after 48 hr of N2B27 culture
Project description:The generation of a self-formed, ectodermal, autonomous multi-zone (SEAM) from human induced pluripotent stem cells (hiPSCs) offers a unique perspective to study the dynamics of ocular cell differentiation over time. Here, by utilising single-cell transcriptomics, we have (i) identified, (ii) molecularly characterised and (iii) ascertained the developmental trajectories of ectodermally-derived ocular cell populations which emerge within SEAMs as they form. Our analysis reveals interdependency between tissues of the early eye and delineates the sequential formation and maturation of distinct cell types over a 12-week period. We demonstrate a progression from pluripotency through to tissue specification and differentiation which encompasses both surface ectodermal and neuroectodermal ocular lineages and the generation of iPSC-derived components of the developing cornea, conjunctiva, lens, and retina. Our findings not only advance the understanding of ocular development in a stem cell-based system of human origin, but also establish a robust methodological paradigm for exploring cellular and molecular dynamics during SEAM formation at single-cell resolution and highlight the potential of hiPSC-derived systems as powerful platforms for modelling human eye development and disease.
Project description:Naive and primed pluripotent human embryonic stem cells bear transcriptional similarity to pre- and post-implantation epiblast and thus constitute a developmental model for understanding the pluripotent stages in human embryo development. To identify new transcription factors that differentially regulate the unique pluripotent stages, we mapped open chromatin using ATAC-seq and found enrichment of the activator protein-2 (AP2) transcription factor binding motif at naive-specific open chromatin. We determined that the AP2 family member TFAP2C is upregulated during primed to naive reversion and becomes widespread at naive-specific enhancers. TFAP2C functions to maintain pluripotency and repress neuroectodermal differentiation during the transition from primed to naive by facilitating the opening of enhancers proximal to pluripotency factors. Additionally, we identify a previously undiscovered naive-specific POU5F1 (OCT4) enhancer enriched for TFAP2C binding. Taken together, TFAP2C establishes and maintains naive human pluripotency and regulates OCT4 expression by mechanisms that are distinct from mouse.
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:Core circuits of transcription factors stabilize stem and progenitor cells by suppressing genes required for differentiation. We do not know how such core circuits are reorganized during cell fate transitions to allow differentiation and lineage choice to proceed. Here, we asked how the pluripotency circuit, a core transcriptional circuit that maintains mouse embryonic stem (ES) cells in a pluripotent state, is dismantled as ES cells differentiate and choose between the neural ectodermal and mesendodermal progenitor cell fates. When ES cells are recultured from pluripotency maintaining conditions to the basal media N2B27, the expression of the pluripotency circuit genes begins to change. At 48 hours post N2B27 addition, the ES cells are competent to respond to differentiation signals. Here, our microarray analysis compares the gene expression profile of ES cells vs. the gene expression profile of cells that have been treated with N2B27 for 48 hours, reaching the competent state.
Project description:Embryonic stem cells (ESC) are able to give rise to any somatic cell type. A lot is known about how ESC pluripotency is maintained, but comparatively less is known about how differentiation is promoted. Cell fate decisions are regulated by interactions between signalling and transcriptional networks. Recent studies have shown that the overexpression or downregulation of the transcription factor Jun can affect the ESC fate. Here we have focussed on the role of the Jun in the exit of mouse ESCs from ground state pluripotency and the onset of early differentiation. Transcriptomic analysis of differentiating ESCs reveals that Jun is required to upregulate a programme of genes associated with cell adhesion as ESCs exit the pluripotent ground state.