Project description:FGF4 paracrine signaling through FGF receptors is believed to induce Erk activity and promotes the exit from pluripotency. However, we have recently observed that FGF4 and FGF2 have opposing effects on mES cell fate. The aim of this study was to understand the underlying transcriptional changes associated with these opposing actions.
Project description:Esrrb is a transcription factor implicated in embryonic stem (ES) cell self-renewal, yet its knockout causes intrauterine lethality due to defects in trophoblast development. Here we show that in trophoblast stem (TS) cells, Esrrb is a downstream target of fibroblast growth factor (Fgf) signalling and is critical to drive TS cell self-renewal. In contrast to its occupancy of pluripotency-associated loci in ES cells, Esrrb sustains the stemness of TS cells by direct binding and regulation of TS cell-specific transcription factors including Elf5 and Eomes. To elucidate the mechanisms whereby Esrrb controls the expression of its targets, we characterized its TS cell-specific interactome by mass spectrometry. Unlike in ES cells, Esrrb interacts in TS cells with the histone demethylase Lsd1 and with the RNA Polymerase II-associated Integrator complex. Our findings provide new insights into both, the general and context-dependent wiring of transcription factor networks in stem cells by master transcription factors.
Project description:Embryonic stem (ES) cells continuously decide whether to maintain pluripotency or differentiate. While exogenous LIF and BMP4 perpetuate a pluripotent state, less is known about factors initiating differentiation. We show that heparan sulfate (HS) proteoglycans are critical co-receptors for signals inducing ES cell differentiation. Genetic targeting of NDST1 and 2, two enzymes required for N-sulfation of proteoglycans, blocked differentiation. This phenotype was rescued by HS presented in trans or by soluble heparin. NaClO3-, which reduces sulfation of proteoglycans, potently blocked differentiation of wild type cells. Mechanistically, N-sulfation was identified to be critical for functional autocrine FGF4 signalling. Micro array analysis identified the pluripotency maintaining transcription factors Nanog, KLF2/4/8, Tbx3 and Tcf3 to be negatively regulated, whereas markers of differentiation such as Gbx2, Dnmt3b, FGF5 and Brachyury were induced by sulfation-dependent-FGFR signalling. We show that several of these genes are heterogeneously expressed in ES cells and targeting of heparan sulfation or FGFR-signalling facilitated a homogenous Nanog/KLF4/Tbx3 positive ES cell state. This finding suggests that the recently discovered heterogeneous state of ES cells is regulated by HS-dependent FGFR signalling. Similarly, culturing blastocysts with NaClO3- eliminated GATA6 positive primitive endoderm progenitors generating a homogenous Nanog positive inner cell mass. Functionally, reduction of sulfation robustly improved de novo ES cell derivation efficiency. We conclude that N-sulfated HS is required for FGF4 signalling to maintain ES cells primed for differentiation in a heterogeneous state. Inhibiting this pathway facilitates a more naïve ground state.
Project description:Genes regulated by the fibroblast growth factor (FGF) signalling pathway were indentified in the early development of the amphibian Xenopus laevis by comparing gene expression in control embryos and embryos in which FGF signalling was inhibited by two different dominant negative FGF receptors.
Project description:Embryonic stem (ES) cells continuously decide whether to maintain pluripotency or differentiate. While exogenous LIF and BMP4 perpetuate a pluripotent state, less is known about factors initiating differentiation. We show that heparan sulfate (HS) proteoglycans are critical co-receptors for signals inducing ES cell differentiation. Genetic targeting of NDST1 and 2, two enzymes required for N-sulfation of proteoglycans, blocked differentiation. This phenotype was rescued by HS presented in trans or by soluble heparin. NaClO3-, which reduces sulfation of proteoglycans, potently blocked differentiation of wild type cells. Mechanistically, N-sulfation was identified to be critical for functional autocrine FGF4 signalling. Micro array analysis identified the pluripotency maintaining transcription factors Nanog, KLF2/4/8, Tbx3 and Tcf3 to be negatively regulated, whereas markers of differentiation such as Gbx2, Dnmt3b, FGF5 and Brachyury were induced by sulfation-dependent-FGFR signalling. We show that several of these genes are heterogeneously expressed in ES cells and targeting of heparan sulfation or FGFR-signalling facilitated a homogenous Nanog/KLF4/Tbx3 positive ES cell state. This finding suggests that the recently discovered heterogeneous state of ES cells is regulated by HS-dependent FGFR signalling. Similarly, culturing blastocysts with NaClO3- eliminated GATA6 positive primitive endoderm progenitors generating a homogenous Nanog positive inner cell mass. Functionally, reduction of sulfation robustly improved de novo ES cell derivation efficiency. We conclude that N-sulfated HS is required for FGF4 signalling to maintain ES cells primed for differentiation in a heterogeneous state. Inhibiting this pathway facilitates a more naïve ground state. Four groups with three biological replicates and a technical duplicate in each
Project description:We report that FGF exposure of sensory progenitors (pPPR) leads to rapid deposition of active chromatin marks H3K27ac near hundreds of FGF-responsive, otic-epibranchial progenitor (OEP) genes, while H3K27ac is depleted in the vicinity of non-otic genes. Genomic regions that gain H3K27ac act as cis-regulatory elements controlling OEP gene expression in time and space and define a unique transcription factor signature likely to control their activity. Thus, during ear induction FGF signalling modifies the chromatin landscape to promote enhancer activation and chromatin accessibility.
Project description:Here, we demonstrate that upon inhibition of the Fgf/Erk pathway in mouse trophoblast stem cells (TSCs), the Ets2 repressor factor (Erf) interacts with components of the Nuclear Receptor Corepressor Complex 1 and 2 (NCoR1 and NCoR2). Upon attenuation of Fgf signalling, unphosphorylated, nuclear Erf recruits the NCoR1/2 complex to key trophoblast genes, brings about their transcriptional silencing and facilitates differentiation and placental development.
Project description:Activation of Map kinase/Erk signalling downstream of fibroblast growth factor (Fgf) tyrosine kinase receptors regulates gene expression required for mesoderm induction and patterning of the anteroposterior axis during Xenopus development. We have proposed that a subset of Fgf target genes are activated in the embyo in response to inhibition of a transcriptional repressor. Here we investigate the hypothesis that Cic (Capicua), which was originally identified as a transcriptional repressor negatively regulated by receptor tyrosine kinase/Erk signalling in Drosophila, is involved in regulating Fgf target gene expression in Xenopus. We characterise Xenopus Cic and show that it is widely expressed in the embryo. Fgf overexpression or ectodermal wounding, both of which potently activate Erk, reduce Cic protein levels in embryonic cells. A similar mechanism of Cic protein degradation downstream of the Torso receptor tyrosine kinase receptor negatively regulates Cic activity in Drosophila. In keeping with our hypothesis, we show that Cic knockdown and Fgf overexpression have overlapping effects on embryo development and gene expression. Transcriptomic analysis identifies a cohort of genes that are up-regulated by Fgf overexpression and Cic knockdown. We investigate two of these genes, fos and rasl11b, which, respectively, encode a leucine zipper transcription factor and a ras family GTPase, as putative targets of the proposed Fgf/Erk/Cic axis. We identify Cic consensus binding sites in a highly conserved region of intron 1 in the fos gene and Cic sites in the upstream regions of several other Fgf/Cic co-regulated genes, including rasl11b. We show that expression of fos and rasl11b is blocked in the early mesoderm when Fgf and Erk signalling is inhibited. In addition, we show that fos and rasl11b expression is associated with the Fgf independent activation of Erk at the site of ectodermal wounding. Our data support a role for a Fgf/Erk/Cic axis in regulating a subset of Fgf target genes during gastrulation and is suggestive that Erk signalling is involved in regulating Cic target genes at the site of ectodermal wounding.