Mll5^−/− mice die of sublethal WBI because of BM failure. (A) Survival curves of Mll5^−/− mice (KO/KO) and WT littermate controls (WT/WT) exposed to 750 cGy of WBI (P < .001; log rank test). (B) Survival curves of Mll5^−/− mice reconstituted with Lin-negative WT C57BL/6 BM cells or PBS immediately after WBI with 750 cGy (P < .001; log rank test). (C) Similar radiation sensitivity of Mll5^−/− () and WT (■) thymocytes. The number of viable cells was determined 6 and 16 hours after irradiation by FACS using propidium iodide and annexin V staining. (D) There was no difference in radiation sensitivity between MEFs isolated from day 14.5 Mll5^−/− (red solid line) and WT (black dashed line) embryos. The number of viable cells was determined 6 days after irradiation by trypan blue exclusion. Data in panels C and D summarize 3 independent experiments with cells from 3 different mice/embryos of each genotype.