Project description:To explore the molecular basis of functional differences observed between Nodal versus Activin-derived endoderm, we compared their respective gene expression profiles. Sox17-GFP mouse ES cells were differentiated in the presence of Nodal or Activin for 7 days, after which GFP(+) cells were purified by FACs. Undifferentiated ES cells were also included for comparison as a control. Results indicate that the two endoderm populations are nearly identical at the level of global transcription. Subtle differences suggest a difference in the degree of endoderm progression.
Project description:To explore the molecular basis of functional differences observed between Nodal versus Activin-derived endoderm, we compared their respective gene expression profiles. Sox17-GFP mouse ES cells were differentiated in the presence of Nodal or Activin for 7 days, after which GFP(+) cells were purified by FACs. Undifferentiated ES cells were also included for comparison as a control. Results indicate that the two endoderm populations are nearly identical at the level of global transcription. Subtle differences suggest a difference in the degree of endoderm progression. Total RNA obtained from SOX17-GFP (+) mouse ES cells, Sox17-GFP treated with Nodal, Sox17-GFP treated with Activin. Two replicates for each sample; Sample data table contains average values of two replicates. The non_normalized.txt file contains individual signal values for each replicate.
Project description:Nodal and Activin are morphogens of the TGFbeta superfamily of signaling molecules that direct differential cell fate decisions in a dose- and distance-dependent manner. During early embryonic development the Nodal/Activin pathway is responsible for the specification of mesoderm, endoderm, node and mesendoderm. In contradiction to this drive towards cellular differentiation, the pathway also plays important roles in the maintenance of self-renewal and pluripotency in embryonic and epiblast stem cells. The molecular basis behind stem cell interpretation of Nodal/Activin signaling gradients and the undertaking of disparate cell fate decisions remains poorly understood. Here, we show that any perturbation of endogenous signaling levels in mouse ES cells leads to their exit from self renewal towards divergent differentiation programs. Increasing Nodal signals above basal levels by direct stimulation with Activin promotes differentiation towards the mesendodermal lineages while repression of signaling with the specific Nodal/Activin receptor inhibitor SB431542 induces trophectodermal differentiation. To address how quantitative Nodal/Activin signals are translated qualitatively into distinct cell fates decisions, we performed chromatin immunoprecipitation of phospho-Smad2 the primary downstream transcriptional factor of the Nodal/Activin pathway followed by massively parallel sequencing and show that phospho-Smad2 binds to and regulates distinct subsets of target genes in a dose-dependent manner. Crucially, Nodal/Activin signaling directly controls the Oct4 master regulator of pluripotency by graded phospho-Smad2 binding in the promoter region. Hence stem cells interpret and carry out differential Nodal/Activin signaling instructions via a corresponding gradient of Smad2 phosphorylation that selectively titrates self-renewal against alternative differentiation programs by direct regulation of distinct target gene subsets and Oct4 expression. Four biological replicates consisting of 4 different passages of E14TG2a ES cells at P20, P21, P23 and P24
Project description:Nodal and Activin are morphogens of the TGFbeta superfamily of signaling molecules that direct differential cell fate decisions in a dose- and distance-dependent manner. During early embryonic development the Nodal/Activin pathway is responsible for the specification of mesoderm, endoderm, node and mesendoderm. In contradiction to this drive towards cellular differentiation, the pathway also plays important roles in the maintenance of self-renewal and pluripotency in embryonic and epiblast stem cells. The molecular basis behind stem cell interpretation of Nodal/Activin signaling gradients and the undertaking of disparate cell fate decisions remains poorly understood. Here, we show that any perturbation of endogenous signaling levels in mouse ES cells leads to their exit from self renewal towards divergent differentiation programs. Increasing Nodal signals above basal levels by direct stimulation with Activin promotes differentiation towards the mesendodermal lineages while repression of signaling with the specific Nodal/Activin receptor inhibitor SB431542 induces trophectodermal differentiation. To address how quantitative Nodal/Activin signals are translated qualitatively into distinct cell fates decisions, we performed chromatin immunoprecipitation of phospho-Smad2 the primary downstream transcriptional factor of the Nodal/Activin pathway followed by massively parallel sequencing and show that phospho-Smad2 binds to and regulates distinct subsets of target genes in a dose-dependent manner. Crucially, Nodal/Activin signaling directly controls the Oct4 master regulator of pluripotency by graded phospho-Smad2 binding in the promoter region. Hence stem cells interpret and carry out differential Nodal/Activin signaling instructions via a corresponding gradient of Smad2 phosphorylation that selectively titrates self-renewal against alternative differentiation programs by direct regulation of distinct target gene subsets and Oct4 expression.
Project description:The signaling pathway for Nodal, a ligand of the transforming growth factor-beta (TGF-beta) superfamily, plays a central role in regulating the maintenance and/or differentiation of stem cell types that can be derived from the peri-implantation mouse embryo. Extraembryonic endoderm stem (XEN) cells are derived from the primitive endoderm of the blastocyst, which normally gives rise to the parietal and the visceral endoderm in vivo, but XEN cells do not contribute efficiently to the visceral endoderm in chimeric embryos. We have found that treatment of XEN cells with Nodal and/or Cripto, an EGF-CFC co-receptor for Nodal, results in up-regulation of markers for visceral endoderm as well as anterior visceral endoderm (AVE). Re-introduction of treated XEN cells into chimeric embryos by blastocyst injection or morula aggregation results in contribution to visceral endoderm and AVE. In culture, XEN cells do not express Cripto, but do express the related EGF-CFC co-receptor Cryptic and require Cryptic for Nodal signaling. Notably, the response to Nodal can be blocked by treatment with the ALK4/ALK5/ALK7 inhibitor SB431542, but Cripto treatment is unaffected, suggesting that its activity is independent of type I activin receptors. Gene set enrichment analysis of genome-wide expression signatures generated from XEN cells under these treatment conditions confirms the differing responses of Nodal- and Cripto-treated XEN cells to SB431542. Our findings define distinct pathways for Nodal and Cripto in the differentiation of visceral endoderm and AVE from XEN cells, and provide new insights into the specification of these cell types in vivo. Murine Xen-eyfg cell line treated with Alk4 inhibitor SB431542, Nodal and Cripto recombinant proteins.
Project description:Members of the transforming growth factor (TGF)-β superfamily play essential roles in the pluripotency, self-renewal, and differentiation of embryonic stem cells. While bone morphogenic proteins maintain pluripotency of undifferentiated mouse ES cells, the role of Activin/Nodal signaling is less clear. To determine the target genes of Activin/Nodal-Smad2 signaling in undifferentiated embryonic stem cells, changes in gene expression were examined following stimulation with recombinant Activin (2 hours) or after inhibition of Activin/Nodal with SB431542 (24 hours) using defined media culture conditions with LIF and 20 ng/mL BMP4. SB431542 is a specific inhibitor of ALK4/5/7 receptors and antagonizes both Activin and Nodal signaling. Via western analysis, Activin stimulation increased pSmad2 in ES cells after 2 hours, and treatment with SB431542 for 24 hours virtually eliminated pSmad2. Total Smad2 expression remained unchanged through these manipulations. RNA from cells treated with Activin or SB431542 was extracted by standard methods with Qiagen RNeasy columns. The RNA was analyzed with the Mouse Genome 430A Array from Affymetrix. Samples were performed in duplicate, and RNA from cells treated with Activin or SB431542 was compared to untreated embryonic stem cells.
Project description:Activin/Nodal signalling is necessary to maintain pluripotency of human Embryonic Stem Cells (hESCs) and to induce their differentiation towards endoderm. However, the mechanisms by which Activin/Nodal signalling achieves these opposite functions remain unclear. To unravel these mechanisms, we examined the transcriptional network controlled in hESCs by Smad2 and Smad3 which represent the direct effectors of Activin/Nodal signalling. These analyses reveal that Smad2/3 participate in the control of the core transcriptional network characterising pluripotency which includes Oct-4, Nanog, FoxD3, Dppa4, Tert, Myc and UTF-1. In addition, similar experiments performed on endoderm cells confirm that a broad part of the transcriptional network directing differentiation is downstream of Smad2/3. Therefore, Activin/Nodal signalling appears to control divergent transcriptional networks in hESCs and in endoderm. Importantly, we observed an overlap between the transcriptional network downstream of Nanog and Smad2/3 in hESCs while functional studies showed that both factors cooperate to control the expression of pluripotency genes. Therefore, the effect of Activin/Nodal signalling on pluripotency and differentiation could be dictated by tissue specific Smad2/3 partners such as Nanog, explaining the mechanisms by which signalling pathways can orchestrate divergent cell fate decisions. Identification of Smad2/3 binding sites in pluripotent hESCs. 5 ChIP-Seq samples including 1 input control sample and 4 ChIP samples (two conditions x two replicates).
Project description:Members of the transforming growth factor (TGF)-β superfamily play essential roles in the pluripotency, self-renewal, and differentiation of embryonic stem cells. While bone morphogenic proteins maintain pluripotency of undifferentiated mouse ES cells, the role of Activin/Nodal signaling is less clear. To determine the target genes of Activin/Nodal-Smad2 signaling in undifferentiated embryonic stem cells, changes in gene expression were examined following stimulation with recombinant Activin (2 hours) or after inhibition of Activin/Nodal with SB431542 (24 hours) using defined media culture conditions with LIF and 20 ng/mL BMP4. SB431542 is a specific inhibitor of ALK4/5/7 receptors and antagonizes both Activin and Nodal signaling. Via western analysis, Activin stimulation increased pSmad2 in ES cells after 2 hours, and treatment with SB431542 for 24 hours virtually eliminated pSmad2. Total Smad2 expression remained unchanged through these manipulations. RNA from cells treated with Activin or SB431542 was extracted by standard methods with Qiagen RNeasy columns. The RNA was analyzed with the Mouse Genome 430A Array from Affymetrix. Samples were performed in duplicate, and RNA from cells treated with Activin or SB431542 was compared to untreated embryonic stem cells. Experiment Overall Design: RNA from cells treated with Activin or SB431542 was extracted by standard methods with Qiagen RNeasy columns. The RNA was analyzed with the Mouse Genome 430A Array from Affymetrix. Samples were performed in duplicate, and RNA from cells treated with Activin or SB431542 was compared to untreated embryonic stem cells.