HoxA9 controls Gfi1-induced myeloid progenitor differentiation, in vivo accumulation, and in vitro life span. (A) Flow cytometric analyses of bone marrow cells from mice (WT, n = 4; HoxA9^−/−Gfi1^+/+, n = 4; HoxA9^−/−Gfi1^+/−, n = 4; HoxA9^−/−Gfi1^−/−, n = 4; HoxA9^+/−Gfi1^−/−, n = 2; HoxA9^+/+Gfi1^−/−, n = 4). Populations ± SD (insets) are shown. Photomicrographs (×100) of cytospins from whole bone marrow preparations of representative animals (right). (B) Graphic representation of GMP in panel A. (C) Methylcellulose serial replating assay of Lin⁻ bone marrow cells from mice in panel A. (D) Methylcellulose colony formation assays of bone marrow cells with percentages displayed are the average of independent analyses from individual mice in panel A. All assays represented (A-D) were initiated from 1 cohort of mice on the same day. Results shown are representative of at least 3 separate analyses on different cohorts. Error bars indicate SEM. **P ≤ .01