Asxl1 loss impaired the hematopoietic repopulation capacity of HSCs. CD45.2⁺ BM cells from young WT, Asxl1^+/−, or Asxl1^−/− mice were mixed with CD45.1⁺ competitor cells at a ratio of 1:1 (1 × 10⁶ cells each) and transplanted into lethally irradiated F1 recipients. (A) The kinetics of CD45.2 chimerism in the PB of mice receiving WT, Asxl1^+/−, or Asxl1^−/− BM cells are shown (mean ± SD of 3-7 animals). (B) Flow cytometric analysis of BM cells from representative mice receiving WT, Asxl1^+/−, or Asxl1^−/− BM cells 10 months after transplantation using indicated antibody combinations. The percent CD45.2⁺ cells as well as Gr1⁺/Mac1⁺, B220⁺, and LSK distribution within the CD45.2⁺ cells in the BM of each group of recipient mice is shown (mean ± SD of 3-5 animals). (C) Serial transplantations were performed as described in supplemental Material and methods. The percent CD45.2 chimerism in the BM of recipient mice 4 months after each round of transplantation is show as mean ± SEM. *P < .05, **P < .01.