Overexpression of Bcl2 rescued HSC defects of Ku70^−/−mice. (A) Competitive repopulation assay. BM from 3-month-old WT, Ku70^−/− and TgBcl2, TgBcl2/Ku70^−/− mice (CD45.2) was isolated and mixed with WT BM (CD45.1) at a 1:1 ratio and transplanted into lethally irradiated WT mice (CD45.1, n = 5 per group). Then 16 weeks posttransplantation, donor chimerisms in the PB and BM LSK cells were analyzed. Similar results were obtained in 2 independent experiments. (B) BM from TgGFP mice was transplanted into 3-month-old mice with different genotypes without any preconditioning. Then 16 weeks posttransplantation, donor chimerisms (GFP+) in the PB and BM LSK cells were quantitated. The number of recipients were WT (n = 5), Ku70^−/− (n = 3), TgBcl2 (n = 5), and TgBcl2/Ku70^−/− (n = 3). Error bars indicate the SD, and significance was determined by a 2-tailed Student t test. *P < .005.