Developmental potential of Runx1^−/− blast colonies.

(A) Morphology of Runx1^+/+ andRunx1^−/− blast cell colonies (top, original magnification × 200) and the adherent and nonadherent cells generated from them following 2 days of culture (bottom, original magnification × 400). (B) Gene expression analysis of adherent cells generated by individual blast colonies. Analysis was performed by the polyA⁺ global amplification method. Each lane represents adherent cells derived from one blast colony. Control primitive erythroid (E^P) and definitive erythroid (E^D) samples are indicated. (C) Hematopoietic potential of the nonadherent population derived from expandedRunx1^+/+ (+/+), Runx1^+/−(+/−), and Runx1^−/− (−/−) blast colonies. Nonadherent cells derived from individual colonies were harvested, and the cells were plated in conditions that support the growth of primitive and definitive colonies. The frequency of wells giving rise to total secondary colonies (clonal precursors), primitive erythroid colonies (ERY/P), or definitive hematopoietic colonies (MAC, macrophage; ERY/D, definitive erythroid; and MIX, multilineage) is represented. (D) β H1 globin expression in nonadherent cells generated by individual colonies. Each lane corresponds to the nonadherent cells from one expanded blast colony.