Time-course transcriptome of wild type and PRC2 mutant mouse embryonic stem cells during ground state conversion
Ontology highlight
ABSTRACT: Mouse embryonic stem cells (mESCs) represent an exceptional model for understanding how transcriptional responses are regulated by signalling pathways during development. Treatment with a cocktail of MEK and GSK3β inhibitors (“2i”) induces ground state pluripotency, characterized by increased self-renewal, reduced DNA methylation, and uniformly high expression of pluripotency markers. Polycomb Repressive Complex 2 (PRC2) is a key developmental regulator controlling stem cell self-renewal and differentiation decisions, and altered expression of PRC2 target genes is a signature of 2i-mediated ground state conversion. Here, we generated a comprehensive RNA sequencing dataset from mESCs subjected to 2i conversion time-course across five time points, representing six population doublings. We analysed two independently derived wild type lines, and two isogenic Cas9-edited lines carrying loss-of-function mutations in core PRC2 subunits Enhancer of Zeste Homolog 2 (Ezh2) or Embryonic Ectoderm Development (Eed). These data may provide a comprehensive resource to understand the temporal patterns of transcriptional responses to MEK and GSK3β inhibitors and explore the role of PRC2 function in regulation of pluripotency circuit.
Project description:The self-renewing pluripotent state was first captured in mouse embryonic stem cells (mESCs) over two decades ago. The standard condition requires the presence of serum and LIF, which provide growth promoting signals for cell expansion. However, there are pro-differentiation signals which destabilize the undifferentiated state of mESCs. The dual inhibition (2i) of the pro-differentiation Mek/Erk and Gsk3/Tcf3 pathways in mESCs is sufficient to establish an enhanced pluripotent “ground state” which bears features resembling the pre-implantation mouse epiblast. Gsk3 inhibition alleviates the repression of Esrrb, a transcription factor that can substitute for Nanog function in mESCs. The molecular mechanism that is mediated by Mek inhibition is however not clear. In this study, we investigate the pathway through which Mek inhibition operates to maintain ground state pluripotency. We have found that in mESCs, Kruppel-like factor 2 (Klf2) is a protein target of the Mek/Erk pathway; and that Klf2 protein is phosphorylated by Erk2 and subsequently degraded through the proteosome. It is therefore by Mek-inhibition through PD0325901 or 2i that enables the stabilization and accumulation of Klf2 to sustain ground state pluripotency. Importantly, we found that Klf2-null mESCs, while viable under LIF/Serum conditions, cannot be maintained and eventually gradually die within a few passages. Our result thus demonstrates that Klf2 is an essential factor of ground state pluripotency. Collectively, our study defines the Mek/Klf2 axis that cooperates with the Gsk3/Esrrb pathway in mediating ground state pluripotency.
Project description:The self-renewing pluripotent state was first captured in mouse embryonic stem cells (mESCs) over two decades ago. The standard condition requires the presence of serum and LIF, which provide growth promoting signals for cell expansion. However, there are pro-differentiation signals which destabilize the undifferentiated state of mESCs. The dual inhibition (2i) of the pro-differentiation Mek/Erk and Gsk3/Tcf3 pathways in mESCs is sufficient to establish an enhanced pluripotent “ground state” which bears features resembling the pre-implantation mouse epiblast. Gsk3 inhibition alleviates the repression of Esrrb, a transcription factor that can substitute for Nanog function in mESCs. The molecular mechanism that is mediated by Mek inhibition is however not clear. In this study, we investigate the pathway through which Mek inhibition operates to maintain ground state pluripotency. We have found that in mESCs, Kruppel-like factor 2 (Klf2) is a protein target of the Mek/Erk pathway; and that Klf2 protein is phosphorylated by Erk2 and subsequently degraded through the proteosome. It is therefore by Mek-inhibition through PD0325901 or 2i that enables the stabilization and accumulation of Klf2 to sustain ground state pluripotency. Importantly, we found that Klf2-null mESCs, while viable under LIF/Serum conditions, cannot be maintained and eventually gradually die within a few passages. Our result thus demonstrates that Klf2 is an essential factor of ground state pluripotency. Collectively, our study defines the Mek/Klf2 axis that cooperates with the Gsk3/Esrrb pathway in mediating ground state pluripotency.
Project description:Mouse embryonic stem cells (mESCs) can convert to a ground state by dual inhibition of MEK and GSK3β signalling in defined media in the presence of LIF (2i). The cellular transition in 2i leads to uniform expression of pluripotency markers and global DNA hypomethylation. Whether hypomethylation is required for achieving ground state or is an outcome of the conversion process is still not clear. Here we show that J1 wild type and hypomethylated mESCs (dnmt3a-/-, dnmt3b-/-, dnmt1-/- [TKO]) lacking DNA methyltransferases undergo similar morphological and expression changes upon culturing in 2i that are consistent with conversion of both to a more naive state. Maintenance of global DNA methylation levels in 2i media by constitutive expression of de novo methyltransferases is also not a barrier to conversion. Hence, signalling pathways in mES cells regulate pluripotency networks and cell state independently of their global DNA methylation status. Indicated mESCs were cultured in 2i/LIF for 2 weeks and then harvested along with serum/LIF counterparts for microarray analysis. 1ug of total RNA was used to prepare Cy3 labelled aRNA using an Amino Allyl MessageAmp II aRNA kit (Ambion) following manufacturers protocol. The samples were hybridised to SurePrint G3 mouse GE 8x60k microarrays (Agilent) and were scanned using NimbleGen MS 200 (Roche). Results were analysed with custom-written scripts implemented in the statistical programming language R (http://www.R-project.org).
Project description:The combination of Wnt pathway activation by the GSK3 inhibitor and ERK pathway inhibition by the MEK inhibitor, which is known as 2i is a well-established method to maintain mouse embryonic stem cell (mESC) self-renewal. Here we show that Activin A also has the ability to promote naive pluripotency of mESCs when combined with the MEK inhibitor PD0325901. mESCs were efficiently propagated in a medium containing both Activin A and the MEK inhibitor (PD0325901). mESCs cultured in Activin+PD retained a pluripotency state that expresses high levels of naive pluripotency-related transcription factors and is able to differentiate into three germ layers under appropriate conditions. They also showed naive pluripotency features, including the preferential usage of the Oct4 distal enhancer and the self-renewal response to Wnt pathway activation. Our finding provides another way to maintain the naive pluripotency state and reveals a role of Activin/Nodal/TGF-β signaling in stabilizing self-renewal gene regulatory networks in mESCs. To compare the gene expression patterns of naive and primed pluripotency states and their responses to Wnt and ERK1/2 MAPK pathway, we performed genome-wide gene expression analysis of mESCs and EpiLCs, and those treated with Wnt pathway activator alone or Wnt pathway activator combined with ERK1/2 MAPK pathway inhibitior.
Project description:Activin/Nodal/TGF-β signaling pathway plays a major role in maintaining mouse epiblast stem cells (mEpiSCs). The mEpiSC medium which contains Activin A and bFGF induces differentiation of mouse embryonic stem cells (mESCs) to mEpiSC. Here we show that Activin A also has an ability to efficiently propagate mESCs without differentiation to mEpiSCs when combined with a MEK inhibitor PD0325901. mESCs cultured in Activin+PD retained high-level expression of naive pluripotency-related transcription factors. Genome-wide analysis revealed that the gene expression profile of mESCs cultured in Activin+PD resembles that of mESCs cultured in 2i. mESCs cultured in Activin+PD also showed features which are related to naive pluripotency of mESCs, including the preferential usage of the Oct4 distal enhancer and the self-renewal response to Wnt pathway activation. Our finding reveals a role of Activin/Nodal/TGF-β signaling in stabilizing self-renewal gene regulatory networks in mESCs. To compare the gene expression patterns of mESCs cultured in Activin+PD, 2i and LIF+BMP4 and mEpiSCs, we performed genome-wide gene expression analysis by using Affymetrix GeneChip oligonucleotide microarrays
Project description:Mouse embryonic stem cells (mESCs) fluctuate between a naïve inner cell mass (ICM)-like state and a primed epiblast-like state of pluripotency in serum, but are harnessed exclusively in a distinctive, apparently more naïve state of pluripotency (the ground state) with inhibitors for mitogen-activated protein kinase (MAPK) and glycogen synthase kinase 3 pathways (2i). Understanding the mechanism ensuring a naïve state of pluripotency would be critical in realizing a full potential of ESCs. We show here that PRDM14, a PR domain-containing transcriptional regulator, ensures a naïve pluripotency by a dual mechanism: Antagonizing fibroblast growth factor receptor (FGFR) signaling that is activated paradoxically by the core transcriptional circuitry for pluripotency and directs a primed state and repressing de novo DNA methyltransferases that create a primed epiblast-like epigenome. PRDM14 exerts these functions by recruiting polycomb repressive complex 2 (PRC2) specifically to key targets and repressing their expression. Mouse Embryonic Stem Cells (mESCs) or mESC-like cells with different Prdm14 genotypes {Prdm14(+/+), Prdm14(-/-), and Prdm14(-/-) rescued with Avitag-EGFP-Prdm14 transgene [Prdm14(-/-)+AGP14]} are cultured on MEF in different medium [2i, Serum(day 2), Serum+MEK inhibitor (PD0325901) (day 2), Serum without LIF (day2)].
Project description:Mouse embryonic stem cells (mESCs), derived from pre-implantation blastocyst cells, can be maintained in vitro in defined N2B27 medium supplemented with two chemical inhibitors for GSK3 and MEK (2i) and the cytokine leukemia inhibitory factor (LIF), which act synergistically to promote self-renewal and pluripotency. Many efforts have been devoted to identify genes that promote exit from the pluripotent state and the transition to a primed state of differentiation. One of the first identified players in this process was the Wnt/b-catenin effector TCF7L1 (previously referred to as TCF3), belonging to the family of four TCF/LEF transcription factors, which acts as pro-differentiation factor by repressing pluripotency genes. Of note, there is little evidence that the genetic abrogation of the mechanisms required for the exit from the pluripotent state is sufficient to enable self-renewal in the absence of 2iL. Here, we found that complete loss-of-function of Tcf7, Lef1, Tcf7l1 and Tcf7l2, the genes encoding for the four TCF/LEF transcription factors, (refered to as qKO) allows mESCs to become fully 2iL-independent and to propagate in basal N2B27. To understand the genetic program that allows qKO cells to achieve 2iL-independent self-renewal, we performed RNA sequencing (RNA-seq) of qKO and wild type mESCs.
Project description:Mouse embryonic stem (ES) cells are locked into self-renewal by shielding from inductive cues. Release from this ground state in minimal conditions offers a system for delineating developmental progression from naive pluripotency. Here we examined the initial transition process. The ES cell population behaves asynchronously. We therefore exploited a short-half-life Rex1::GFP reporter to isolate cells either side of exit from naive status. Differentiation of Rex1-GFPd2 ES cells was initiated by withdrawing 2i (Kalkan et al., 2016). Undifferentiated 2i-cells and post-2i withdrawal differentiating populations (16h, 25h-Rex1-High, 25h-Rex1-Low) were subjected to proteomic analysis by Mass Spectrometry.
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.
Project description:Mouse embryonic stem cells (ESCs) cultured with MEK and GSK3 inhibitors (2i) more closely resemble the inner cell mass of pre-implantation blastocysts than those cultured with serum/LIF (SL). The transcriptional mechanisms governing this pluripotent ground state are yet unresolved. Release of promoter-proximal paused RNA polymerase II (Pol2) is a multistep process necessary for pluripotency and cell cycle gene transcription in SL. Here, we show that β-catenin, stabilized by GSK3 inhibition in 2i, supplies transcriptional co-regulators including BRD4, CDK9, Mediator, Cohesin, and p300 at pluripotency loci. This selectively strengthens pluripotency loci and renders them addicted to transcription initiation for productive gene body elongation in detriment to Pol2 pause release. By contrast, cell cycle genes are not bound by β-catenin and, thus, proliferation/self-renewal are still tightly controlled by the Pol2 pause release mechanism under 2i conditions. Our findings help to explain how pluripotency is preserved in the ground state and also provide a general model for transcriptional resilience/adaptation upon network perturbation in other biological contexts.