Colony formation of the rescued cells from AML1-deficient P-Sp. The hematopoietic defect of AML1-deficient P-Sp regions was rescued by retroviral expression of AML1b, and the rescued cells were plated into MethoCult3434 medium. The rescued cells generated various types of hematopoietic colonies including definitive origins. Representative hematopoietic colonies by 7 days of culture are shown. (A-C) Morphology of the colonies. (D-F) Cytospin preparation of corresponding cell populations. Cytospins were stained with Wright-Giemsa. Mix indicates mixed colony; GM, granulocyte/macrophage colony; and E, erythroid colony. Photographs were taken with a Nikon Eclipse TE2000-U (Nikon Sankei) at a magnification of × 100.