Model summarizing molecular regulation of YS and allantois mesodermal lineage specification. Eomes plays a crucial role in differentiation toward the YS mesoderm fate, causing Eomes loss-of-function cells to be redirected toward the allantois lineage. Etv2, required for hematovascular differentiation, is controlled by Eomes during YS formation but not during the formation of allantois endothelium. The simultaneous KO of Eomes and T, but not their individual KOs, completely ablates the formation of ExEM. Orange bars indicate Eomes expression levels along differentiation trajectories. , Pdgfra; EC, endothelial cell; YS, yolk sac; PS, primitive streak; Ery-P, primitive erythroid; HE, hematoendothelium; Posterior-Mes, posterior mesoderm; Early-Mes, early mesoderm; EMP, erythro-myeloid progenitor.
