p53 coordinates Wnt and TGF-ß inputs on mesendoderm differentiation genes

The TGF-ß 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-ß transcriptional inputs on mesendoderm identity gene enhancers. Overall design: In this study, 14 RNA-Seq samples and 20 ChIP-Seq samples are included.