ET2 expression at the LSK but not the MP stage suppresses myeloid potential. (A) GFP-positive (ET2⁺) and -negative (ET2⁻) LSK and myeloid progenitor (MP) populations were isolated from mice as described for Figure 4 and seeded at 200 cells/well in media containing SCF, IL-3, IL-6, and G-CSF. Four days later, cells were stained with antibodies against F4/80 and Mac-1 and analyzed by flow cytometry. Percentages of Mac-1⁺ cells are indicated within the gate. Average numbers of Mac1⁺ cells/well (n = 6) produced are shown in the bar graphs below the plots. Data are representative of 2 experiments. (B) Colony formation assays. Additional aliquots of the cells as used for panel A were placed into myeloid-promoting methylcellulose media at a density of 1000 cells/plate and grown for 6 days. Colonies were then enumerated, and the average number of colonies per plate is shown in the bar graph (n = 2).