Hematopoietic differentiation pattern of wt and Hhex^−/− Jet ES cell–derived progeny. As CD41⁺ definitive hematopoietic progenitors develop, they gain CD45 expression and down-regulate CD41 expression. (A) Representative flow cytometric analysis of CD41 and CD45 expression on days 6 to 9 of cocultures derived from differentiating wt and Hhex^−/− Jet ES cells. (B) The proportion of each hematopoietic population from the representative experiment shown in panel A, CD41⁺CD45⁻ (early progenitor) CD41⁺CD45⁺ (intermediate progenitor), and CD41⁻CD45⁺ (late progenitor), is indicated.