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: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 ChIP-seq analysis was performed to map enhancers and associated transcription factors. We used H3K27ac, H3K4me1 and p300 to call enhancers from 2 different pluripotent cell states: ESC and EpiLC. In addition we performed ChIP-seq for Oct4 and Otx2 from these cell states. All these experiments were carried out in replicates, for the EpiLC state the replicates were performed with and without ActivinA. Additionally we carried out ChIPseq for Otx2 and Oct4 in Otx2ko cell lines in which we integrated an inducible Otx2 gene before and after induction with doxycycline.
Project description:The transition of pluripotent stem cells (PSCs) from primed to naïve states constitutes a prototypical example of cellular plasticity. The naïve state can be stabilized by defined chemical cocktails that block extracellular signals, notably including the MEK pathway. However, little is known regarding the underlying transcriptional mechanisms. Here, we report that the transcriptional landscape of the naïve state can be mimicked in mouse and human PSCs by stimulating transcriptional enhancers. This is attained by inhibiting the CDK8 and CDK19 kinases, which are negative regulators of Mediator, a critical component of enhancer function. Mechanistically, CDK8/19i triggers a global increase in the recruitment of RNA Pol II at promoters and enhancers, hyperactivating enhancers and their target genes. Lastly, the emergence of naïve pluripotency in the pre-implantation epiblast coincides with a marked reduction in CDK8/19 activity, and CDK8/19i blocks its subsequent developmental progression. These findings suggest that naïve pluripotency during development includes hyperactivation of enhancers and can be captured in vitro, either by blunting extracellular signaling, or by stimulating enhancer-driven transcription. These principles may apply to other cellular transitions.
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:Pluripotency can be maintained in the naïve state through manipulation of ERK and WNT signalling (2i), shielding embryonic stem cells (ESCs) from inductive cues. Alternatively, inhibiting CDK8/19 (CDK8/19i), a repressor of the Mediator co-activator complex, directly stimulates super-enhancer activity, and was recently shown to stabilize cells in a functional state that resembles naïve pluripotency. Naïve ESCs exhibit important epigenetic, transcriptional and metabolic features. However, our understanding on how these regulatory layers are inter-connected to promote the naive state is in progress. To fill this gap, here we used mass spectrometry to describe the dynamic molecular events (i.e. phosphoproteome, proteome and metabolome) executed by 2i and CDK8/19i, as they transition cell identity into naïve pluripotency. We observed rapid proteomic reprogramming, revealing widespread commonalities, and some important differences, between these two approaches, suggesting a largely over-lapping mechanism. CDK8/19i acts directly on the control of the transcriptional machinery, which elicits a rapid and direct activation of key identity genes including those that maintain the naïve program. Additional molecular changes in 2i are achieved by phosphorylation of critical downstream effectors that reinforce the naïve transcriptional circuitry while repressing factors from the more-differentiated formative and primed states. Comparing transcriptomic and proteomic changes, we found that post-transcriptional de-repression is a major feature of naïve pluripotency conferred by both 2i and CDK8/19i, and this may support the enhanced mitochondrial capacity of naive cells. Furthermore, at the level of metabolome, while 2i- and CDK8/19i-treated cells share similar aspects in one-carbon metabolism and beta-oxidation, in other regards they are divergent, a feature which may explain their differences in DNA methylation. These datasets provide a valuable resource for exploring the molecular mechanisms underlying pluripotency and cell identity transitions.
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.
Project description:Translational control plays a central role in regulation of gene expression and can lead to significant divergence between mRNA- and protein-abundance. The translational landscape of early mammalian development and its impact on cellular proteome, however, remains largely un-explored. Here we used genome-wide approaches combined with time-course analysis to measure the mRNA-abundance, mRNA-translation rate and protein expression during the transition of naïve into primed embryonic stem cells (ESCs). We found that the ground state ESCs cultured with GSK3- and MEK-inhibitors and LIF (2iL) display higher ribosome density on a selective set of mRNAs. These mRNAs show reduced translation during the exit from ground state pluripotency and transition to serum/LIF (SL) culture or upon commitment to primed epiblast-like stem cells (EpiLSCs). Strikingly, integrative analysis with cellular proteome indicate a strong translational buffering of this set of mRNAs in 2iL-ESCs leading to stable protein expression levels. Our data reveal that the global alteration of cellular proteome is largely accompanied by transcriptional rewiring. Furthermore, we identified a set of genes (including UHRF1 and KRAS) that undergo selective post-translational regulation during the transition of naïve into primed pluripotency and linked the observed changes to upstream GSK- and MEK/MAPK-signaling pathways using single inhibitor treated ESCs. Thus, we provide a comprehensive and detailed overview of the global changes in gene expression during the transition of naïve to primed pluripotency and dissect the relative contributions of RNA-transcription, translation and regulation of protein stability in controlling protein abundance.
Project description:The aim of this experiment was to investigate the role of TGFβ signalling pathway in human pluripotency, through ChIP-seq analysis of its main downstream effector SMAD2/3 in naïve and primed human pluripotent stem cells (hPSCs).