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P53 coordinates Wnt and TGF-β inputs on mesendoderm differentiation genes

ABSTRACT: The TGF-β superfamily member Nodal triggers mesendoderm differentiation in embryonic stem (ES) cells. This transition however requires cooperating Wnt signaling inputs. Here we report that p53, a powerful tumor suppressor in adult tissues, orchestrates this cooperation. We show that p53, which is released from inhibition as mouse ES cells exit from pluripotency, acts as a direct inducer of Wnt3 expression. Wnt-activated Tcf3 then converges with Nodal-activated Smad transcriptional complexes on mesendoderm specification super-enhancers. p53 and its homolog p73 act redundantly in Wnt induction. When p53 and p73 are depleted, the ES cells fail to secrete autocrine Wnt ligands, Tcf and Nodal-activated Smads fail to bind to mesendoderm gene enhancers, and the cells adopt ectoderm rather than mesendoderm identity. Enforced Wnt3 expression or addition of Wnt3a rescues mesendoderm differentiation in p53/p73-depleted ES cells. Thus, independently of their established role as tumor suppressors that guard genome integrity in mature cells, p53 and p73 serve a primordial role in ES cell differentiation by driving a cooperation of Wnt and TGF-β transcriptional inputs on mesendoderm identity gene enhancers.

ORGANISM(S): Mus musculus

PROVIDER: GSE70486 | GEO | 2017/01/06

SECONDARY ACCESSION(S): PRJNA288818

REPOSITORIES: GEO

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Project description:In Xenopus, establishment of the anterior-posterior axis involves two key signalling pathways, canonical Wnt and Nodal-related TGF-Î². There are also a number of transcription factors that feedback upon these pathways. The homeodomain protein Hex, an early marker of anterior positional information, acts as a transcriptional repressor suppressing induction and propagation of the Spemman organiser while specifying anterior identity. We show that Hex promotes anterior identity by amplifying the activity of canonical Wnt signalling. Hex exerts this activity by inhibiting the expression of Tle-4, a member of the Groucho family of transcriptional co-repressors that we identified as a Hex target in embryonic stem (ES) cells and Xenopus embryos. This Hex-mediated enhancement of Wnt signalling results in the up-regulation of the Nieuwkoop centre genes Siamois and Xnr-3 and the subsequent increased expression of the anterior endodermal marker Cerberus and other mesendodermal genes downstream of Wnt signalling. We also identified Nodal as a Hex target in ES cells. We demonstrate that in Xenopus, the Nodal-related genes Xnr-1 and 2, but not 5 and 6, are regulated directly by Hex. The identification of Nodal-related genes as Hex targets explains the ability of Hex to suppress induction and propagation of the organiser. Together these results support a model in which Hex acts early in development to reinforce a Wnt-mediated, Nieuwkoop-like signal to induce anterior endoderm, and later in this tissue to block further propagation of Nodal-related signals. The ability of Hex to regulate the same targets in both Xenopus and mouse implies this model is conserved. Experiment Overall Design: Identification of Hex target genes In Xenopus, the establishment of the anterior-posterior axis involves two key signalling pathways, the canonical Wnt and the Nodal-related TGF-Î² and a number of transcription factors that feedback upon these pathways. The homeodomain protein Hex, an early marker of anterior positional information, is a transcriptional repressor that suppresses the induction and propagation of the Spemman organiser while specifying anterior identity. Using microarray expression profiling we identified mouse Tle-4 as a Hex target in Embryonic Stem (ES) cells and showed that Tle-4 expression is directly regulated by Hex in Xenopus embryos. We also identified Nodal as a Hex target in ES cells. Taken together these results support a model in which Hex acts early in development to reinforce a Wnt-mediated, Nieuwkoop-like signal to induce anterior endoderm and later in this tissue to block further propagation of Nodal-related signals. The ability of Hex to regulate the same targets in both frog and mouse suggests that this model is conserved.

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P53 coordinates Wnt and TGF-β inputs on mesendoderm differentiation genes

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