Recent evidence supports a model where, during gastrulation and early somite stages, differential Wnt and FGF signaling along the A-P axis patterns the naïve endoderm into foregut, midgut and hindgut progenitor domains that express the transcription factors Hhex, Pdx1 and Cdx respectively. While this model remains to be validated genetically in the mouse, the available data suggests that Wnt and FGF ligands expressed in a graded fashion in the mesoderm (red) signal to the adjacent endoderm (yellow) to repress foregut identity and promote hindgut fate. Secreted Wnt-antagonists expressed in the anterior endoderm are predicted to repress canonical Wnt/β-catenin activity.
From: Liver development
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