Project description:Enhancer reactivation and pluripotency gene (PpG) expression could induce stemness and enhance tumorigenicity in cancer stem cells. Silencing of PpG enhancers (PpGe) during embryonic stem cell differentiation involves Lsd1–mediated H3K4me1 demethylation followed by DNA methylation. Here, we observed a widespread retention of H3K4me1 and DNA hypomethylation at PpGe associated with a partial repression of PpGs in F9 embryonal carcinoma cells (ECCs) post-differentiation. The absence of H3K4me1 demethylation could not be rescued by Lsd1 overexpression. Based on the observation that H3K4me1 demethylation is accompanied by strong Oct4 repression in P19 ECCs, we tested if Lsd1-Oct4 interaction affects Lsd1 catalytic activity. Our data show a dose-dependent inhibition of Lsd1 by Oct4 in vitro and retention of H3K4me1 at PpGe post-differentiation in Oct4 overexpressing P19 ECCs. These data suggest that Lsd1-Oct4 interaction in cancer stem cells may establish a primed enhancer state that is susceptible to reactivation leading to aberrant PpG expression.
Project description:Enhancer reactivation and pluripotency gene (PpG) expression could induce stemness and enhance tumorigenicity in cancer stem cells. Silencing of PpG enhancers (PpGe) during embryonic stem cell differentiation involves Lsd1–mediated H3K4me1 demethylation followed by DNA methylation. Here, we observed a widespread retention of H3K4me1 and DNA hypomethylation at PpGe associated with a partial repression of PpGs in F9 embryonal carcinoma cells (ECCs) post-differentiation. The absence of H3K4me1 demethylation could not be rescued by Lsd1 overexpression. Based on the observation that H3K4me1 demethylation is accompanied by strong Oct4 repression in P19 ECCs, we tested if Lsd1-Oct4 interaction affects Lsd1 catalytic activity. Our data show a dose-dependent inhibition of Lsd1 by Oct4 in vitro and retention of H3K4me1 at PpGe post-differentiation in Oct4 overexpressing P19 ECCs. These data suggest that Lsd1-Oct4 interaction in cancer stem cells may establish a primed enhancer state that is susceptible to reactivation leading to aberrant PpG expression.
Project description:Understanding the molecular underpinnings of pluripotency is a prerequisite for optimal maintenance and application of embryonic stem cells (ESCs). While the protein-protein interactions of core pluripotency factors have been identified in mouse ESCs, their interactome in human ESCs (hESCs) has not to date been explored. Here we mapped the OCT4 interactomes in naïve and primed hESCs, revealing extensive connections to mammalian ATP-dependent nucleosome remodeling complexes.
Project description:An aberrant increase in pluripotency gene (PpG) expression due to enhancer reactivation could induce stemness and enhance the tumorigenicity of cancer stem cells. Silencing of PpG enhancers (PpGe) during embryonic stem cell differentiation involves Lsd1-mediated H3K4me1 demethylation and DNA methylation. Here, we observed retention of H3K4me1 and DNA hypomethylation at PpGe associated with a partial repression of PpGs in F9 embryonal carcinoma cells (ECCs) post-differentiation. H3K4me1 demethylation in F9 ECCs could not be rescued by Lsd1 overexpression. Given our observation that H3K4me1 demethylation is accompanied by strong Oct4 repression in P19 ECCs, we tested if Oct4 interaction with Lsd1 affects its catalytic activity. Our data show a dose-dependent inhibition of Lsd1 activity by Oct4 and retention of H3K4me1 at PpGe in Oct4-overexpressing P19 ECCs. These data suggest that Lsd1-Oct4 interaction in cancer stem cells could establish a "primed" enhancer state that is susceptible to reactivation, leading to aberrant PpG expression.
Project description:The enhancer landscape is dramatically restructured as naïve preimplantation epiblasts transition to the post-implantation state of primed pluripotency. A key factor in this process is Otx2, which is upregulated during the early stages of this transition and ultimately recruits Oct4 to a different set of enhancers. In this study we discover that the acetylation status of Oct4 regulates the induction of the primed pluripotency gene network. Maintenance of the naïve state requires Oct4 deacetylation by the NAD-dependent deacetylase, SirT1. The activity of SirT1 is reduced during the naïve to primed transition, thereby increasing the acetylation of Oct4 and promoting its binding to an Otx2 enhancer to induce Otx2 expression. Induction of Otx2 causes the reorganization of acetylated Oct4 and results in the induction of the primed pluripotency gene network. Regulation of Oct4 by SirT1 may link stem cell development to environmental conditions and provide strategies to manipulate epiblast cell state.
Project description:Oct4 is considered a master transcription factor for pluripotent cell self-renewal and embryo development. It primarily collaborates with other transcriptional factors or coregulators to maintain pluripotency. However, it is still unclear how Oct4 interacts with its partners. Here, we show that the Oct4 linker interface mediates competing and balanced Oct4 protein interactions which are crucial for maintaining pluripotency. Linker mutant ESCs maintain the key pluripotency genes expression, but show decreased expression of self-renewal genes and increased expression of differentiation genes which result in impaired ESCs self-renewal and early embryonic lethality. Linker mutation dose not affect Oct4 genomic binding and transactivation potential, but breaks the balanced Oct4 interactome. In mutant ESCs, the interaction between Oct4 and Klf5 was decreased, but interactions between Oct4 and Cbx1, Ctr9, Cdc73 were increased which disrupt the epigenetic state of ESCs. Overexpression of Klf5 or knockdown Cbx1, Cdc73 rescue the cellular phenotype of linker mutant ESCs by rebalancing Oct4 interactome indicating that different partners interact with Oct4 competitively. Thus, by showing how Oct4 interacts with different partners, we provide novel molecular insights to explain how Oct4 contributes to the maintenance of pluripotency.
Project description:Naïve and primed pluripotency is characterized by distinct signaling requirements, transcriptomes and developmental properties, but both cellular states share key transcriptional regulators, Oct4, Sox2 and Nanog. Here we demonstrate that transition between these two pluripotent states is associated with widespread Oct4 relocalization, mirrored by global rearrangement of enhancer chromatin landscapes. Our genomic and biochemical analyses identified candidate mediators of primed state-specific Oct4 binding, including Otx2 and Zic2/3. Even in the absence of other differentiation cues, premature Otx2 overexpression is sufficient to exit the naïve state, induce transcription of a large subset of primed pluripotency-associated genes and redirect Oct4 to thousands of previously inaccessible sites. However, ability of Otx2 to engage new enhancer regions is determined by its levels, cis-encoded properties of the sites and signaling environment. Our results illuminate regulatory mechanisms underlying pluripotency and suggest that capacity of transcription factors such as Otx2 and Oct4 to function as pioneers is highly context-dependent transcription profile of ESCs and EpiLCs to analzye changes during differentiation and the effect of Otx2 loss and overexpression on the differentiation properties
Project description:Naïve and primed pluripotent stem cells (PSCs) and germ cells express the Pou5f1 (Oct4) gene. The Oct4 gene contains two cis-regulatory elements, the distal (DE) and proximal enhancer (PE), which differentially control Oct4 expression in a cell-type- and stage-specific manner. Here, we generated double transgenic mice carrying both Oct4-ΔPE-GFP and Oct4-ΔDE-tdTomato (RFP), enabling us to simultaneously monitor the activity of DE and PE. Oct4 expression is stage-specifically regulated by DE and PE during embryonic and germ cell development. Using this dual reporter system, we successfully cultured pure populations of naïve (GFP+RFP-) and primed (GFP-RFP+) PSCs. We found that GFP+RFP- cells were metastable in serum-containing medium; stable naïve pluripotent cells were observed in medium containing two inhibitors (Meki and GSKi) but lacking serum. Finally, we suggest that the activity of Oct4 DE and PE is regulated by the repressive histone marks H3K9me3 and DNA methylation.