Competitive repopulation assays of Ptch1-null hematopoietic stem cells. (A) Donor leukocyte contribution in peripheral blood of recipient mice 4 weeks after transplantation with a 1:1 ratio of donor (Ptch^fl/fl, MxPtch1^+/Δ, or MxPtch1^Δ/Δ) and wild-type CD45.1 competitor BM cells. Mean plus SD calculated from 4 recipients of each donor genotype. (B) Donor contribution 16 weeks after transplantation. Mice were killed to determine donor contribution to the myeloid lineage (Mac-1⁺ BM cells), B-cell lineage (B220⁺ BM cells), and T-cell lineage (CD4⁺CD8⁺ DP thymocytes). Mean plus SD calculated from 4 recipients of each donor genotype. (C) Donor contribution to hematopoiesis of secondary recipients that received transplants of BM cells from primary recipients shown in panel B. Mice were analyzed 12 weeks after transplantation. Mean plus SD calculated from 4 recipients of each donor genotype.