(A) Experimental scheme for investigating normal and transformed LSK cells. Leukemia initiation experiment was performed using the murine MLL-AF9 model. (B) Ikzf2 is dispensable for colony-forming ability of normal stem cells. Colony Assay was performed with LSK cells from Ikzf2f/f n=4 and Ikzf2Δ/Δ n=4 mice (C) Ikzf2 deletion in MLL-AF9 transformed LSK cells reduced colony formation. MLL-AF9 transformed LSK cells from Ikzf2f/f n=3 and Ikzf2Δ/Δ n=3 mice were used for colony assay. Mean +/− S.E.M of three independent experiments, Student’s t test **, p<0.01. (D) Deletion of Ikzf2 delays leukemia progression in MLL-AF9 model. Survival analysis is from the result of three combined transplants with genotypes Ikzf2f/f n=13 and Ikzf2Δ/Δ n=28 mice. **, p<0.01 logrank test. (E,F) Ikzf2Δ/Δ deleted leukemic mice have reduced disease burden. (E) Spleen and (F) liver weights of moribund Ikzf2f/f and Ikzf2Δ/Δ mice with proper deletion. Result is from Ikzf2f/f n=12 and Ikzf2Δ/Δ n=8 mice. **P < 0.01, unpaired Student’s t test. (G) QPCR of Ikzf2 in bone marrow leukemic cells from Ikzf2f/f n=12 and Ikzf2Δ/Δ n=8 mice. ****p<0.0001. unpaired Student’s t test. (H) Bone marrow leukemic cells from Ikzf2Δ/Δ mice have reduced IKZF2 expression. Frequency of IKZF2High cells in primary leukemic mice was examined by intracellular flow cytometry for IKZF2. Result from Ikzf2f/f n=12 and Ikzf2Δ/Δ n=10 mice is shown. ***, p<0.001. unpaired Student’s t test.