BaF3 cells expressing the hEPOR (upper panel) or the mEPOR (lower panel) were infected with MSCVp expressing wild-type LH5 or mutants containing all combinations of isoleucine, leucine, valine, and alanine at positions 9 and 10. After puromycin selection, cells were tested for IL-3 independence. The right axis indicates the residue at position 10. The horizontal axis indicates the residue at position 9. The vertical axis shows the number of live cells six days after IL-3 removal. The bars representing cells expressing LH5, LH5-L9I, and LH5-I10L are labeled. The bars show mean ± SEM for three independent experiments. The results for the LH5 sample were significantly different (p≤0.005, as assessed by two-tailed Student’s t-test) compared to cells expressing each mutant, except for the mutants with isoleucine at position 10 (top panel) or leucine at position 10 and LH5-L9A (bottom panel).