Summary model of the differential effects of Cdx genes on ESC-derived hematopoiesis. Our data support a model in which Cdx genes differentially affect both the formation (ie, induction of Cdx gene expression during EB differentiation) and the hematopoietic activity (ie, induction of Cdx genes expression in purified CD41⁺c-kit⁺ hematopoietic progenitors) of already specified hematopoietic progenitor cells. Cdx1 and Cdx4 both promote the specification of hematopoietic progenitors, whereas Cdx2 inhibits this process. However, only Cdx4 can enhance the expansion/differentiation of hematopoietic progenitors; Cdx1 and Cdx2 both suppress these functions.