Project description:We address the molecular mechanisms through which Myc supports mESC identity, by performing gene expression profile analyses of Myc- and LIF-maintained ESCs, together with Epiblast Stem Cell (EpiSC), as a control for a primed state of stemness. We then investigated whether the Myc-driven self-reinforcing circuit, installed in Myc-dependent ESCs, could support the maintenance of ES cell identity in absence of the originating stimulus, namely the MycER activation achieved by OHT stimulation. To this end, we derived ESCs from Myc-dependent cells, following MycER inactivation upon withdrawal of OHT and profile their gene expression.
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: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
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
Project description:c-Myc (Myc) is an important transcriptional regulator in embryonic stem (ES) cells, somatic cell reprogramming, and cancer, yet functionally differs from the core pluripotency transcription factors, such as Oct4, Sox, and Nanog. Here, we identify a Myc-centered regulatory network in ES cells by combining protein-protein interaction and protein-DNA interaction studies, and show that Myc interacts with the NuA4 histone acetyltransferase complex, previously identified as a critical regulator in ES cell identity. In combination with previously studied transcriptional regulatory network information, we construct three ES cell modules (Core, Polycomb, and Myc) and show that these modules are functionally separable in ES, iPS, MEFs, and partial iPS cells, suggesting that the overall ES cell transcription program is comprised of distinct functional units. With these regulatory modules as an analytical tool, we have reassessed data suggesting that cancer cells reactivate an ES cell-like transcriptional program. We find that the Myc module, independent of the Core module, is active in various cancers and predicts cancer outcome. These observations argue against the hypothesis linking an embryonic gene expression signature with cancer or cancer stem cells. The apparent similarity of cancer and ES cell signatures reflects in large part the pervasive nature of Myc regulatory network. Keywords: Biotin-mediated Chip-chip, Antibody ChIP-chip, Mouse embryonic stem cells
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 expression level changes at D0 and D2 MEFs
Project description:Other than in the development of the brain, SOX2 is essential for the long-term self-renewal of neural stem cells (NSCs). The mechanisms of how SOX2 maintains the stemness of NSCs is not yet understood. We have identified Fos as a downstream target of SOX2, and therefore used CUT&RUN to investigate where these transcription factors - and the c-FOS partner c-JUN - interact with the genome. By comparing binding patterns of c-FOS, c-JUN and SOX2, we find that they co-occupate the promoter of the SOCS3 locus, which we also have identified as a gene that rescues SOX2 deletion induced senescence when overexpressed in neurospheres grown from Sox2-deleted mouse NSCs. Taken together, our data provide a basis for elucidating a gene regulatory network necessary for the maintenance of self-renewal in post-embryonic neural stem cells.
Project description:Transcription factors and their specific interactions with targets are crucial in specifying gene expression programs. To gain insights into the transcriptional regulatory networks in embryonic stem cells, we use chromatin immunoprecipitation coupled to ultra-high-throughput DNA sequencing (ChIP-seq) to map the locations of thirteen sequence specific transcription factors (Nanog, Oct4, STAT3, Smad1, Sox2, Zfx, c-Myc, n-Myc, Klf4, Esrrb, Tcfcp2l1, E2f1 and CTCF) and two transcription regulators (p300 and Suz12). These factors are known to play different roles in ES cell biology as components of the LIF and BMP signaling pathways, self-renewal regulators and key reprogramming factors. Our study provides insights into the integration of the signaling pathways to the ES cell-specific transcription circuitries. Intriguingly, we find specific genomic regions extensively targeted by different transcription factors. Collectively, the comprehensive mapping of transcription factor binding sites identifies important features of the transcriptional regulatory networks that define ES cell identity. Keywords: Transcription factor binding sites in undifferentiated mouse embryonic stem cells ChIP-enriched DNA from pooled ChIP samples were analyzed by Solexa sequencing.