Pten^+/-SHIP^-/- mice show increased sensitivity to GM-CSF. Bone marrow cells plated in methylcellulose in the presence of decreasing amounts of growth factors: GM-CSF (A), IL-3 (B), and SF (C). Total number of colonies growing after 10 days was scored and expressed as the percentage of colonies growing in the presence of the maximal dose of each growth factor. Both Pten^+/-SHIP^-/- and SHIP^-/- showed increased low-dose sensitivity over Pten^+/- and wild-type for GM-CSF, IL-3, and SF, and Pten^+/-SHIP^-/- cells showed significantly increased response over all genotypes at 0.001 ng/mL GM-CSF. These are the combined results of data from 3 to 4 mice per group plated in duplicate and are shown ± SEM. ^***P < .05 compared with all genotypes.