Bclaf1 is required for fetal and adult HSC repopulation activity. (A-E) A total of 20 sorted HSCs from donor CD45.2⁺Bclaf1^f/f or Vav-Cre:Bclaf1^f/f fetal livers were transplanted with 300 000 CD45.1⁺ wild-type recipient BM cells into lethally irradiated CD45.1⁺ recipient mice (Bclaf1^f/f, n = 15; Vav-Cre:Bclaf1^f/f, n = 16). (A) Schematic of 20 HSC competitive transplant. (B) Peripheral blood donor engraftment at indicated times after transplant. (C) Donor-derived chimerism in peripheral blood leukocyte populations at 16 weeks after transplant. (D) Percentage of mice with multilineage engraftment (defined as ≥5% CD45.2⁺ donor in all cell lineages) at 16 weeks after transplant. (E) Frequency of donor-derived HSCs at 18 weeks after transplant. (F-J) Donor adult CD45.2⁺Bclaf1^f/f or Mx-Cre:Bclaf1^f/f mice were treated with pIpC, and then 4 weeks later, 300 000 BM cells from these mice were transplanted with 300 000 CD45.1⁺ wild-type recipient BM cells into lethally irradiated CD45.1⁺ recipient mice (Bclaf1^f/f, n = 14; Mx-Cre:Bclaf1^f/f, n = 15). (F) Schematic of 1:1 competitive transplant. (G) Peripheral blood donor engraftment at indicated times after transplant. (H) Donor-derived chimerism in peripheral blood leukocytes at 16 weeks after transplant. (I) Percentage of mice with multilineage engraftment (defined as ≥5% CD45.2⁺ donor in all cell lineages) at 16 weeks after transplant. (J) Frequency of donor-derived HSCs at 18 weeks after transplant. All transplants were conducted as 3 independent experiments of 5 to 10 mice per genotype, and data were combined for analyses. Data in panels B-C,E,G-H,J are mean ± SD, and statistical significance was determined by unpaired 2-tailed Student t test. Statistical significance in panels D,I was determined by Fisher exact test. ∗P ≤ .05; ∗∗P ≤ .01; ∗∗∗P ≤ .001. Gran, granulocytes; IR, irradiation; Mono, monocytes; ns, not significant.