Conditional deletion of STAT5 causes rapid and sustained reduction in expression of quiescence-associated genes in HSCs. (A) BM was isolated from 4 independent pairs of wild-type and STAT5 KO mice, and KLS cells were sorted before mRNA isolation. Deletion of STAT5b is shown as a control. The relative mRNA expression levels of Tie-2, p57, p21, p27, Cyclin D1, Gfi-1, Bmi-1, CXCR4, CD44, and Myc were evaluated by quantitative real-time RT-PCR. Means from 3 or 4 independent experiments are shown with SD. (B) BM was isolated 1 month after 7 doses of pI:pC, and means from 3 independent experiments are shown for analysis of STAT5b, Tie-2, p57, and p21. From panels A and B, each batch of sorted KLS cells from WT and KO mice was analyzed by quantitative real-time PCR performed with the gene of interest and endogenous control GAPDH in triplicate.