Comparative effects of E76K, D61Y, and N308S SHP-2 expression on CFU-GM colony growth. (A) Fetal liver cells engineered to express D61Y SHP-2 show cytokine-independent CFU-GM colony formation but are less hypersensitive to GM-CSF than cells expressing E76K SHP-2. Error bars indicate standard deviation of duplicate plates. (B) Fetal liver cells expressing N308S SHP-2 do not demonstrate GM-CSF–independent colony formation and display modest hypersensitivity. Error bars indicate standard error of the mean of 3 independent experiments.