HSC defects in Dot1l-deficient cells are cell-autonomous. CD45.2⁺Dot1l^wt/wt;CreER⁺ (Dot1l^+/+) or Dot1l^F/F;CreER⁺ (Dot1l^F/F) cells and CD45.1⁺ competitors were mixed at 1:1 ratio and transplanted into lethally irradiated (900 cGy) CD45.1⁺ congenic recipients. (A) Once bone marrow was reconstituted 8 weeks after transplantation, recipients were injected with tamoxifen. Blood was collected from recipients on indicated weeks after tamoxifen injection and stained for 3 lineages. After the Dot1l excision, Dot1l^F/F cells rapidly disappeared from peripheral blood. Data are mean ± SD. (B) Bar graph of bone marrow and thymus reconstitution by CD45.2⁺ cells 16 weeks after tamoxifen injection. Dot1l^F/F cells minimally remained in the recipients. Data are mean ± SD.