Competitive repopulation of STAT5-deficient HSCs after crossing onto a RAG2^−/− background.

C57Bl/6 RAG2^−/− mice were crossed onto the C57Bl/6 STAT5ab^+/− background to allow for generation of triple knockout mice for RAG2, STAT5a, and STAT5b. BM was collected from young RAG2^−/− STAT5ab^−/− or littermate RAG2^−/− STAT5ab^+/+ mice and mixed at a 1:1 ratio with wild-type HW80 BM cells (Hb_d). The cells were transplanted into lethally irradiated recipient mice, and reconstitution was measured by hemoglobin electrophoresis. The results of two experiments are shown with the STAT5 wild-type (wt) competition on the left and the STAT5ab^−/− competition on the right. At the far right are positive controls for both the Hb_s and Hb_d patterns.