(A) Colony-forming capacity of Stat5-/- HSCs expressing ETV6-LYN. CD150+KSL haematopoietic stem/progenitor cells from E14.5 fetal livers of wild-type and Stat5-/- embryos were transduced with either control vector or the ETV6-LYN retrovirus. Colonies were formed in the presence and absence of cytokines (20 ng/ml murine SCF, 20 ng/ml murine IL-3, 2 units/ml human erythropoietin, and 50 ng/ml human thrombopoietin). Colony numbers with the indicated size per 150 CD150+KSL cells are depicted as the mean ± SD for triplicate cultures. C and EL denote control and ETV6-LYN, respectively. (B) Proportion of colony types. The colonies were recovered and examined by microscopy to determine their composition (n; neutrophil, m; macrophage, E; erythroblast, M; megakaryocyte). C and EL denote control and ETV6-LYN, respectively. (C) Survival of recipient mice infused with wild-type and Stat5-/- cells transduced with ETV6-LYN. Wild-type and Stat5-/- c-Kit+ cells from E14.5 fetal livers were transduced with ETV6-LYN and transplanted into lethally irradiated B6-Ly5.1 mice. One out of the 5 recipient mice transplanted with Stat5-/- cells expressing ETV6-LYN died following a non-haematological accident (*).