Effect of Ras on lineage specification. (A) CD34⁺ GFP⁺ lin⁻ cells (day 3) were single-cell sorted as 3 subpopulations representing multipotent myeloid cells (CMP) and bipotent populations: GMP and MEP on the basis of CD123 and CD45RA expression. Figures indicate mean ± SD population frequencies. Data illustrated are for Ras-transduced cells. (B) Frequency distribution of colonies derived from each uncommitted subpopulation: E indicates erythroid; G, granulocytic; M, macrophage; GM, granulocyte/macrophage; U, indefinable by surface phenotype. Individual cells were cultured in IL-3, IL-6, GM-CSF, G-CSF, SCF, and Epo and harvested 7 days later.