Hematopoietic potential of the AML1 mutants. Cells isolated from AML1-deficient P-Sp regions were infected with retrovirus containing the AML1 mutants. Each retrovirus contained (A) AML1bΔ444, (B) AML1bΔ397, (C) AML1bΔ335, (D) AML1bΔ288, (E) AML1a, (F) AML1bΔRD, (G) AML1bΔ(205-332), (H) AML1bΔ(181-210), (I) AML1b-R139G, (J) AML1b-S249/266A, or (K) AML1b-K24/43R. AML1bΔ444 (A), AML1bΔ397 (B), AML1bΔ(181-210) (H), AML1b-S249/266A (J), and AML1b-K24/43R (K) retain the ability to rescue the hematopoietic defect of AML1-deficient P-Sp regions, whereas other mutants do not. Shown are phase-contrast microscopic views of these cultures at 14 days. Photographs were taken with a Nikon Eclipse TE2000-U (Nikon Sankei) at a magnification of × 100.