Competitive BMT assays show survival advantage of Runx1^KTAMK/KTAMKcells in vivo. (A) Lethally irradiated (9.5 Gy) Ly5.1 recipient mice were coinjected with a mixture of either 10⁴Runx1^+/+ or Runx1^KTAMK/KTAMK LSK cells (Ly5.2) and 10⁶ competitor whole bone marrow (BM) cells (Ly5.1). After BMT, mice were treated with 4 mg/kg of pIpC intraperitoneally twice a week, and peripheral blood donor chimerism was analyzed 2 and 4 weeks later. The lower graphs show the frequency of donor-derived Runx1^+/+ (blue) or Runx1^KTAMK/KTAMK (red) cells in peripheral blood (n = 3 to 6 mice from 2 independent experiments). Donor cells were from mice 7 to 9 weeks old. (B) Lethally irradiated (9.5 Gy) Ly5.1 recipient mice were coinjected with a mixture of either 2000 Runx1^+/+ or Runx1^KTAMK/KTAMK LSK cells (Ly5.2) and 10⁶ competitor whole BM cells (Ly5.1). After BMT, mice were irradiated (2 Gy) once a week, and peripheral blood donor chimerism was analyzed 2 weeks later. The right graph shows the frequency of donor-derived Runx1^+/+ (blue) or Runx1^KTAMK/KTAMK (red) cells in peripheral blood (n = 5 to 8 mice from 2 independent experiments). Donor cells were from mice 7 to 8 weeks old. NS, not significant.