MLL-ENL depletes HSC and HPC numbers when it is induced in fetal, but not adult, mice. (A-B) HSC and HPC numbers in P0 liver (n = 15-19) or 10-week-old bone marrow (n = 10-12) after fetal MLL-ENL induction or in 6-month-old bone marrow (n = 6 per genotype) or 14-month-old bone marrow (n = 10-11) after adult MLL-ENL induction. Bone marrow cell numbers reflect 2 hindlimbs (tibias and femurs). (C) Twenty-four-hour HSC and HPC BrdU incorporation percentages were measured in E18.5 livers (n = 5-7) or 10-week-old bone marrow (n = 7 per genotype) after fetal MLL-ENL induction. For all panels, error bars indicate standard deviations. **P < .01, ***P < .001 for Tet-OFF-MLL-ENL relative to controls. Groups were compared by the 2-tailed Student t test.