Growth-limiting role of endothelial cells in endoderm development

► S1P1 is expressed by the blood vessels in developing endoderm. ► S1P1 ablation results in compromised growth of several foregut-derived organs. ► Reduced growth in the pancreas results from decreased proliferation of Pdx1+ cells. ► Blood vessel ablation does not mimic the S1P1−/− instead the opposite is observed. ► Hypervascularization is seen in the S1P1 mutants.