Healthy E2f1^−/−SPCs cells retain functionality. (A) E2f1^−/− or WT BM LSK cells transplanted into lethally irradiated CD45.1⁺ WT recipient mice (n = 5) for long-term reconstitution (i). Sixteen weeks posttransplantation, CD45.2⁺ LSK WT or E2f1^−/− cells purified from harvested BM and transplanted into lethally irradiated CD45.1⁺ WT secondary recipient mice (N = 4/5) (ii). The engraftment ability of E2f1^+/+ WT (black) and E2f1^−/− (gray) LSK cells was assessed by the percentage of CD45.2⁺/CD45.1⁻ cells in PB at weeks 4, 8, 12, and 16 post primary and secondary transplantation. (Bi) Schematic representation of experimental design. E2f1^−/− (CD45.2⁺) and E2f1^+/+ WT BM cells (CD45.1⁺) were transplanted in ratios of 9:1, 1:1, and 1:9 into lethally irradiated (7Gy) CD45.1⁺ WT recipient mice (N = 5) for long-term reconstitution. (ii) Percentages of CD45.2⁺E2f1^−/− donor vs recipient cells (CD45.1⁺) at weeks 4, 8, 12, and 16 posttransplant. NS, not significant with P > .05.