Impaired repopulation of irradiated recipients by Mll5^−/− bone marrow cells. (A) Experimental strategy for the competitive repopulation assay. (B) Representative FACS data showing the frequencies of T cells (CD3⁺), B cells (CD19⁺), neutrophils (Gr-1^hi, CD11b⁺), monocytes/macrophages (Gr-1⁺, CD11b⁺), and LSK cells in recipient mice 3 months after transplantation with mixtures of CD45.2⁺ test cells (wild-type or Mll5^−/−) and CD45.1⁺CD45.2⁺ competitor cells. (C) The graph shows the averages of the ratios of test versus competitor populations of the indicated cell types in repopulated mice 3 months after transplantation. The data for each cell type are normalized to the average ratios obtained with mice that received wild-type test cells and are expressed as percentages. A value of less than 100% indicates impaired competitiveness of the test population. The differences between genotypes were statistically significant by Student t test (P < .05 for all comparisons except LSK cells, P < .01). The data are representative of 3 independent experiments performed with bone marrow cells and 1 experiment performed with fetal liver cells (Figure S5). (D) The graph shows the fold decrease in the Mll5^−/− repopulation ratios in the 4 independent experiments (relative to wild-type in each experiment).