Bone marrow suppression in head and neck irradiated SMAD3−/−, Fancd2−/− compared to double-knockout SMAD3−/− (129/ Sv) Fancd2−/− (129/Sv) mice. Mice of each genotype (all 129/Sv genetic background) (n = 5/group) were 30 Gy irradiated, and at 5 days postirradiation, femur marrow was assayed for CFU-GEMM and CFU-GM/2 × 144 cells explanted, as described in Materials and Methods. Results are for 5 mice per mouse strain and summary of 4 plates per mouse. Panel A: CFU-GM; panel B: CFU-GEMM. In panel A, compared to 0 Gy, *P = 0.0330 (129/Sv), *P =0.0171 (Smad3−/−) or *P = 0.0438 (DKO2). In panel B, compared to 0 Gy, *P =0.0041 (Smad3−/−) or *P = 0.0159 (double-knockout 2).