Deletion of Puma renders mice resistant to γ-irradiation. (A) Kaplan-Meier survival curves of mice exposed to 9 Gy TBI. Puma^+/+ (n = 9), Puma^+/− (n = 6), and Puma^−/− (n = 8) mice were given a single dose of TBI (9 Gy) and were monitored for survival. The enhanced survival rate of Puma^−/− and Puma^+/− mice was significantly greater than Puma^+/+ mice (P < .001 and P < .01, respectively), but the survival rate was not significantly different between Puma^−/− mice versus Puma^+/− mice (P > .05). (B) Kaplan-Meier survival curves of mice exposed to 9.5 Gy TBI. Puma^+/+ (n = 6), Puma^+/− (n = 9), and Puma^−/− (n = 7) mice were then administrated a lethal TBI dose (9.5 Gy) and monitored daily for survival. The survival rate of Puma^−/− and Puma^+/− mice was significantly greater than Puma^+/+ mice (Puma^−/− mice vs Puma^+/+ mice, P < .001; Puma^+/− mice vs Puma^+/+ mice, P < .01). (C) Diagram for generation of reconstituted mice. C57BL6/N recipients were lethally irradiated for a total of 13 Gy (6.5 Gy, 2 times, 3 hours apart) and received 1 × 10⁷ total BM cells from Puma^+/+ mice or Puma^−/− mice (n = 6 mice/group). (D) Kaplan-Meier survival curves of reconstituted mice after 9 Gy TBI. After 8 weeks, the mice in panel C were given a second course of TBI (9 Gy) and monitored for survival. The survival rate of mice reconstituted with Puma^−/− BM cells was significantly higher than in mice reconstituted with Puma^+/+ BM cells (P < .001).