Overexpression of Bcl2 partially increased HSC/progenitor pools and restored HSC quiescence in Ku70^−/−mice. (A) BM cells from age-matched WT (n = 6), Ku70^−/− (n = 6), TgBcl2 (n = 5), and TgBcl2/Ku70^−/− (n = 4) mice were assayed by multiparameter FACS for proportion of HSC/progenitor populations. Frequency of LSK cells was analyzed. (B) Within the LSK fraction, frequency of SLAM-LSK cells was quantitated. (C) BM cells were isolated from age-matched mice with different genotypes and staining with surface markers after treatment with Hoechst 33342 and pyronin Y. LSK and SLAM-LSK cells were analyzed by HO33342 contents and pyronin Y intensity, and proportion of cells in G₀ phase was quantitated. Three separate experiments were performed with 3 to 5 mice per genotype compared. (D) BrdU incorporation. WT (n = 5), Ku70^−/− (n = 3), TgBcl2 (n = 5), and TgBcl2/Ku70^−/− (n = 3) mice were injected and fed with BrdU for 30 hours. BM cells were isolated and BrdU+ proportion within LSK fraction was analyzed. Error bars indicate the SD, and significance was determined by a 2-tailed Student t test. *P < .05. (E) BM cells from WT, Ku70^−/−, TgBcl2, and TgBcl2/Ku70^−/− mice were isolated and subjected to FACS analysis after staining with surface markers along with annexin V and DAPI. The proportion of annexin V–positive (DAPI-negative) cells within the SLAM-LSK fraction is quantitated.