Mus musculus
Ontology highlight
ABSTRACT:
PROVIDER: PRJNA201855 | ENA |
REPOSITORIES: ENA
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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)
2013-05-08 | E-GEOD-46700 | biostudies-arrayexpress
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.
2013-05-08 | GSE46700 | GEO
Project description:Global DNA demethylation is an integral part of reprogramming processes in vivo and in vitro, but whether it occurs in the derivation of induced pluripotent stem cells (iPSCs) is not known. Here we show that iPSC reprogramming involves both global and targeted demethylation, which are separable mechanistically and by their biological outcomes. Cells at intermediate-late stages of reprogramming undergo transient genome-wide demethylation, which is more pronounced in female cells. Global demethylation requires AID-mediated downregulation of UHRF1 protein and abolishing demethylation leaves thousands of hypermethylated regions in the iPSCs genome. Independently of AID and global demethylation, regulatory regions, particularly ESC enhancers and super-enhancers, are specifically targeted for hypomethylation in association with transcription of the pluripotency network. Our results show that global and targeted DNA demethylation are conserved and distinct reprogramming processes, presumably because of their respective roles in epigenetic memory erasure and in the establishment of cell identity.
2017-01-27 | GSE69823 | GEO
Project description:Somatic cells can be reprogrammed to pluripotency using different methods. In comparison to pluripotent cells obtained through somatic nuclear transfer, induced pluripotent stem cells (iPSCs) exhibit a higher number of epigenetic errors. Furthermore, most of these abnormalities have been described to be intrinsic to the iPSC technology. Here we investigate whether the aberrant epigenetic patterns detected in iPSCs are specific to transcription factor-mediated reprogramming. We used germline stem cells (GSCs), which are the only adult cell type that can be converted into pluripotent cells (gPSCs) under specific culture conditions, and compared GSC-derived iPSCs and gPSCs at the transcriptomic, epigenetic and functional level. Our results show that both reprogramming methods generate indistinguishable states of pluripotency. GSC-derived iPSCs and gPSCs retained similar levels of donor cell-type memory and exhibited comparable numbers of reprogramming errors. Therefore, our study demonstrates that the epigenetic memory detected in iPSCs is not intrinsic to transcription-factor mediated reprogramming. Total RNA from 12 different in vitro mouse cell lines, 2 technical replicates per sample: germline stem cells (GSCs, 2 independent cell lines), GSC-derived induced pluripotent stem cells (iPSCs, 4 independent cell lines), germline-derived pluripotent stem cells (gPSCs, 4 independent cell lines), embryonic stem cells (ESCs), fibroblast-derived induced pluripotent stem cells (Fib-iPSCs)
2015-03-07 | E-GEOD-66613 | biostudies-arrayexpress
Project description:Embryonic stem cells are maintained in a self-renewing and pluripotent state by multiple regulatory pathways. Pluripotent-specific transcriptional networks are sequentially reactivated as somatic cells reprogram to achieve pluripotency. How epigenetic regulators modulate this process and contribute to somatic cell reprogramming is not clear. Here we perform a functional RNAi screen to identify the earliest epigenetic regulators required for reprogramming. We identify components of the SAGA histone acetyltransferase complex, in particular Gcn5, as critical regulators of reprogramming initiation. Furthermore, we show in mouse pluripotent stem cells that Gcn5 strongly associates with Myc and that upon initiation of somatic reprogramming, Gcn5 and Myc form a positive feed forward loop that activates a distinct alternative splicing network and the early acquisition of pluripotency-associated splicing events. These studies expose a Myc-SAGA pathway that drives expression of an essential alternative splicing regulatory network during somatic cell reprogramming. Examination of 2 Gcn5-chromatin interactions in mouse embryonic stem cells
2015-04-15 | E-GEOD-67710 | biostudies-arrayexpress
Project description:The maintenance of immune homeostasis requires regulatory T cells (Tregs). Given their intrinsic self-reactivity, Tregs must stably maintain a suppressive phenotype to avoid autoimmunity. We report that impaired expression of the transcription factor (TF) Helios by FoxP3+ CD4 and Qa-1-restricted CD8 Tregs results in defective regulatory activity and autoimmunity in mice. Helios-deficient Treg develop an unstable phenotype during inflammatory responses characterized by reduced FoxP3 expression and increased effector cytokine expression secondary to diminished activation of the STAT5 pathway. CD8 Treg also require Helios-dependent STAT5 activation for survival and to prevent terminal T cell differentiation. Definition of Helios as a key transcription factor that stabilizes regulatory T-cells in the face of inflammatory responses provides a genetic explanation for a core property of regulatory T-cells. We used microarrays to detail the global programs of gene expression by CD8 Treg (CD44+CD122+Ly49+) and conventional memory type of CD8 cells (CD44+CD122+Ly49-).
2015-09-15 | E-GEOD-73015 | biostudies-arrayexpress
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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2005-01-01 | MODEL1305010000 | BioModels
Project description:Epigenetic reprogramming is a cancer hallmark but how it unfolds during early neoplastic events and its role in carcinogenesis and cancer progression is not fully understood. Here we show that resetting from primed to naïve human pluripotency results in acquisition of a DNA methylation landscape mirroring the cancer DNA methylome, with gradual hypermethylation of bivalent developmental genes. We hypothesised that unknown proteins and transcription factors play a role in the DNA hypermethylation process and analysed therefore the proteomics of the very early stages of the resetting process which involves overexpression of Nanog and Klf2. The samples analysed were Primed hESCs (Conventional stem cells), 72hours after induction and 1 week after induction, in triplicate. For our purposes we identified candidate transcription factors and subsequently knocked them down to test their involvement in the DNA hypermethylation (as described in the manuscript related to this data, Patani et al. Nature Communications). More broadly, we believe, this dataset is a useful resource for the wider community interested in pluripotency, resetting, reprogramming, cell identity transitions etc. Our results indicate that transition to naïve pluripotency and oncogenic transformation share common epigenetic trajectories, which implicates reprogramming and the pluripotency network as a central hub in cancer formation.
2020-07-13 | PXD019893 | Pride
Project description:Although cell therapies require large numbers of quality-controlled hPSCs, existing technologies are limited in their ability to efficiently grow and scale stem cells. We report here that cell-state conversion from primed-to-naïve pluripotency enhances the biomanufacturing of hPSCs. Naïve hPSCs exhibit superior growth kinetics and aggregate formation characteristics in stirred suspension bioreactors compared to their primed counterparts. Moreover, we demonstrate the role of the bioreactor mechanical environment in the maintenance of naïve pluripotency, through transcriptomic enrichment of mechano-sensing signaling for cells in the bioreactor along with a decrease in expression of lineage-specific and primed pluripotency hallmarks. Bioreactor-cultured, naïve hPSCs express epigenetic regulatory transcripts associated with naïve pluripotency, and display hallmarks of X-chromosome reactivation. They exhibit robust production of naïve pluripotency metabolites and display reduced expression of primed pluripotency cell surface markers. We also show that these cells retain the ability to undergo targeted differentiation into beating cardiomyocytes, hepatocytes, and neural rosettes. They additionally display faster kinetics of teratoma formation compared to their primed counterparts. Naïve bioreactor hPSCs also retain structurally stable chromosomes. Our research corroborates that converting hPSCs to the naïve state enhances hPSC manufacturing and indicates a potentially important role for the bioreactor’s mechanical environment in maintaining naïve pluripotency.
2020-05-08 | ST001377 | MetabolomicsWorkbench
Project description:Embryonic stem cells are maintained in a self-renewing and pluripotent state by multiple regulatory pathways. Pluripotent-specific transcriptional networks are sequentially reactivated as somatic cells reprogram to achieve pluripotency. How epigenetic regulators modulate this process and contribute to somatic cell reprogramming is not clear. Here we perform a functional RNAi screen to identify the earliest epigenetic regulators required for reprogramming. We identify components of the SAGA histone acetyltransferase complex, in particular Gcn5, as critical regulators of reprogramming initiation. Furthermore, we show in mouse pluripotent stem cells that Gcn5 strongly associates with Myc and that upon initiation of somatic reprogramming, Gcn5 and Myc form a positive feed forward loop that activates a distinct alternative splicing network and the early acquisition of pluripotency-associated splicing events. These studies expose a Myc-SAGA pathway that drives expression of an essential alternative splicing regulatory network during somatic cell reprogramming. Examination of Myc-chromatin interactions in reprogramming cells
2015-04-15 | E-GEOD-67694 | biostudies-arrayexpress