Project description:Pluripotent stem cells (PSCs) can self-renew indefinitely while maintaining the ability to generate all cell types of the body. This plasticity is proposed to require heterogeneity in gene expression, driving a metastable state which may allow flexible cell fate choices. Contradicting this, naive PSC grown in fully defined ‘2i’ environmental conditions, containing small molecule inhibitors of MEK and GSK3, show homogenous pluripotency and lineage marker expression. Here we report that 2i induces greater genome-wide heterogeneity than traditional serum-containing growth conditions at the population level across both male and female PSCs. Heterogeneity is dynamic and reversible over time, consistent with a dynamic metastable equilibrium of the pluripotent state. We further show that 2i conditions increase heterogeneity specifically in the calcium signalling pathway at both the population and single-cell level. This is driven by loss of robustness regulators in the form of negative feedback to the upstream EGF receptor. Our findings show that metastability occurs in both 2i and serum PSCs which has implications for our understanding of the nature of the pluripotent state and the role of signalling pathways in the control of transcriptional heterogeneity. Furthermore, our results have critical implications for the current use of kinase inhibitors in the clinic, with induced heterogeneity potentially inducing cancer metastasis and drug resistance.
Project description:Current human pluripotent stem cells lack the transcription factor circuitry that governs the ground state of mouse embryonic stem cells (ESC). Here we report that short-term expression of two components, NANOG and KLF2, is sufficient to ignite other elements of the network and reset the human pluripotent state. Inhibition of ERK and protein kinase C signalling sustains a transgene-independent rewired state. Reset cells self-renew continuously without ERK signalling, are phenotypically stable and karyotypically intact. They differentiate in vitro and form teratomas in vivo. Metabolism is reprogrammed in reset cells with activation of mitochondrial respiration as in ESC. DNA methylation is dramatically reduced and transcriptome state is globally realigned across multiple cell lines. Depletion of ground state transcription factors, TFCP2L1 or KLF4 has marginal impact on conventional human pluripotent stem cells, but collapses the reset state. These findings demonstrate feasibility of installing and propagating functional control circuitry for ground state pluripotency in human cells. DNA methylation analysis in Conventional and Reset human embryonic stem cells by whole genome bisulfite sequencing, in triplicate, using the Illumina platform
Project description:Pluripotency is established in E4.5 preimplantation epiblast. Embryonic stem cells (ESCs) represent the immortalization of pluripotency, however, they only partially resemble the gene expression signature of developmental ground-state. Induced PRAMEL7 expression, a protein highly expressed in the ICM but lowly expressed in ESCs, reprograms developmentally advanced ESC+serum into ground-state pluripotency by inducing a gene expression signature close to developmental ground-state. However, how PRAMEL7 reprograms gene expression remains elusive. Here we show that PRAMEL7 associates with Cullin2 (CUL2) and this interaction is required to establish ground-state gene expression. PRAMEL7 recruits CUL2 to chromatin and targets for proteasomal degradation regulators of repressive chromatin, including NuRD complex. PRAMEL7 antagonizes NuRD-mediated repression of genes implicated in pluripotency by decreasing NuRD stability and promoter association in a CUL2-dependent manner. Our data link proteasome degradation pathways to ground-state gene expression, offering insights to generate in vitro models to reproduce the in vivo ground-state pluripotency.
Project description:Current human pluripotent stem cells lack the transcription factor circuitry that governs the ground state of mouse embryonic stem cells (ESC). Here we report that short-term expression of two components, NANOG and KLF2, is sufficient to ignite other elements of the network and reset the human pluripotent state. Inhibition of ERK and protein kinase C signalling sustains a transgene-independent rewired state. Reset cells self-renew continuously without ERK signalling, are phenotypically stable and karyotypically intact. They differentiate in vitro and form teratomas in vivo. Metabolism is reprogrammed in reset cells with activation of mitochondrial respiration as in ESC. DNA methylation is dramatically reduced and transcriptome state is globally realigned across multiple cell lines. Depletion of ground state transcription factors, TFCP2L1 or KLF4 has marginal impact on conventional human pluripotent stem cells, but collapses the reset state. These findings demonstrate feasibility of installing and propagating functional control circuitry for ground state pluripotency in human cells.
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.
Project description:The ground state of pluripotency is defined as a minimal unrestricted state as present in the Inner Cell Mass (ICM). Mouse embryonic stem cells (ESCs) grown in a defined serum-free medium with two kinase inhibitors (‘2i’) reflect this state, whereas ESCs grown in the presence of serum (‘serum’) share more similarities with post implantation epiblast cells. Pluripotency results from an intricate interplay between cytoplasmic, nuclear and chromatin-associated proteins. Therefore, quantitative information on the (sub)cellular proteome is essential to gain insight in the molecular mechanisms driving different pluripotent states. Here, we describe a full SILAC workflow and quality controls for proteomic comparison of 2i and serum ESCs. We demonstrate that this workflow is applicable for subcellular proteomics of the cytoplasm, nuclear and chromatin. The obtained quantitative information revealed increased levels of naïve pluripotency factors on the chromatin of 2i ESCs. Further, we demonstrate that these pluripotent states are supported by distinct metabolic programs, which include upregulation of free radical buffering by the glutathione pathway in 2i ESCs. Through induction of intracellular radicals, we show that the altered metabolic environment renders 2i ESCs less sensitive to oxidative stress. Altogether, this work provides novel insights into the proteome landscape underlying ground state pluripotency.
Project description:Mouse embryonic stem cells (mESCs) cultured in 2i (MEK and GSK3 kinase inhibitor)/LIF and serum/LIF that we called 2i-ESCs and serum-ESCs represent ground and confused pluripotent states, respectively. However, the transcription factors that regulate ground pluripotency through chromatin-associated characteristics are not yet fully understood. By mapping chromatin accessibility and transcription factor regulatory networks during the interconversion of 2i-ESCs and serum-ESCs, we have identified TEAD2 as highly enriched in 2i-specific peaks. While Tead2 knockout did not affect the pluripotency or differentiation ability of either 2i-ESCs or serum-ESCs, it did prevent the establishment of the 2i-specific state and the exit from the serum-specific state. TEAD2 binds to active regions in 2i-specific genes and activates their expression by regulating enhancer-promoter (EP) interactions during serum-to-2i transition. Remarkably, TEAD2-mediated EP interactions were independent of chromatin architecture proteins YY1 and CTCF, but instead appear to be facilitated by TEAD2 homodimer formation.