Analysis of multilineage and lineage-committed progenitors in the BM of AML1+/+ and +/– mice. (A) Total bone marrow (TBM) cells (1 × 10⁴) from AML1+/+ or +/– mice were plated in duplicate in methylcellulose cultures containing IL-3, IL-6, SCF, and EPO, and the number of hematopoietic colonies was morphologically determined after 12 days of culture. Results are the average ± standard deviation from 5 mice for each genotype. The groups with statistically significant difference are marked by an asterisk. (B) TBM cells from AML1+/+ and +/– mice (6 mice per genotype) were analyzed by FACS to determine the number of c-Kit⁺Sca1⁺Lin^low/– (KSL). The percentage of KSL cells in total BM is indicated for each pair of age- and sex-matched AML1+/+ and +/– mice. The average percentage of KSL cells in AML1+ /+ versus +/– mice was 0.28 ± 0.02 and 0.47 ± 0.05, respectively (P = .01). (C) TBM cells from AML1+/+ and +/– mice were serial diluted and then plated in long-term stromal-supported hematopoietic cultures using a 96-well format. Twenty replicate wells were seeded at each dilution, and wells containing clusters of 6 or more cobblestone cells after 28 days of culture were scored as positive. The combined data from 3 independent experiments were used to estimate the number of CAFC day 28 by Poisson statistics. This analysis indicated an increase in the frequency of CAFC-d₂₈ in AML1+/– versus +/+ mice (1 in 50 263 ± 5 871 versus 1 in 82 953 ± 9298, respectively; P < .001).