Effects of E76K SHP-2 expression on erythroid progenitor growth. (A) Fetal liver (FL) and bone marrow (BM) cells transduced with E76K SHP-2 form large numbers of BFU-E colonies in methylcellulose medium supplemented with a saturating dose of EPO. In contrast, cells expressing WT SHP-2 form few colonies. Error bars indicate standard deviation of quadruplicate plates. (B) E76K SHP-2–expressing fetal liver cells show EPO-independent BFU-E colony growth. The addition of EPO increases both the number and the size of the BFU-E colonies. Error bars indicate standard deviation of duplicate plates.