Ews^−/− cells display impaired DNA repair capacity and show a diminished capacity to sustain survival of lethally irradiated animals in serial transplantation. (A) BM mononuclear cells (top panel) and Lin⁻ cells (bottom panel) from Ews^+/+ and Ews^−/− mice were irradiated (2 Gy) in vitro. Cells were collected at the indicated times after IR and stained with anti–γ-H2AX antibodies. The nuclei of cells were visualized with DAPI staining (right panel). The cells containing distinct γ-H2AX foci were counted as positive and reported as a percentage of the total cells counted. The number of γ-H2AX–positive cells were counted from 3 different fields by 2 independent and blinded individuals and plotted with ± SD. An asterisk indicates a statistically significant difference. (2-tailed Student t test, n = 3, *P = .035 and *P = .02). A representative image of γ-H2AX immunofluorescence of Lin⁻ cells is shown in the right panel. (B) BM cells (5 × 10⁶) from Ews^+/+ and Ews^−/− mice were transplanted into lethally irradiated recipient mice. Two months after transplantation, 5 × 10⁶ BM cells derived from these primary recipient mice were pooled and transplanted into secondary recipients, and the same procedure was repeated in tertiary transplantations. The accompanying table indicates the number of surviving recipient mice. Numbers in parentheses denote the numbers of recipient mice used for each group.