Analysis of primitive and definitive hematopoietic potential of HAT^+/+, HAT^+/−, and HAT^−/− ES cells. (A) EBs were harvested from day 4 to day 11 of differentiation, and single-cell suspensions were replated in conditions supporting the generation of both primitive and definitive hematopoietic colonies. Primitive erythroid (EryP), definitive erythroid (EryD), macrophage (Mac), and mast cell (Mast) colonies were scored. Days of differentiation are indicated. Bars represent standard error of the mean number of colonies from at least 3 cultures. (B) Comparative size of primitive erythroid and macrophage colonies generated from HAT^+/+ and HAT^−/− day 6 EBs (magnification ×200).