Even after successful reconstitution, aged Moz-deleted Moz^fl/fl;Mx1-cre bone marrow cells do not exhibit a typical HSC cell surface phenotype. (A) Experimental design. Mice were treated with poly(I:C) and then left undisturbed for 15 months prior to transplantation (same cohort as in Figure 4). Bone marrow stem cell and progenitor subsets were analyzed 4.5 months after transplantation. (B) Flow cytometry plots showing analyses of the LSK-CD34^–FLT3^– and the LSK-CD48^–CD150⁺ populations in Moz^fl/fl and Moz^fl/fl;Mx1-cre bone marrow cells after transplantation. (C-D) Quantification of cells with stem cell surface markers by flow cytometry of recipients of Moz^fl/fl and Moz^fl/fl;Mx1-cre bone marrow cells. Note the reduction in typical LSK-CD34^–FLT3^– and the LSK-CD48^–CD150⁺ populations after transplantation. (E) CD45.2 (donor) cells were isolated by FACS from primary recipients and 1 × 10⁶ cells transplanted into lethally irradiated secondary recipients; CD45.2 cells from aged Moz^fl/fl control mice were able to rescue recipients with high efficiency. In contrast, recipients of CD45.2 Moz^fl/fl;Mx1-cre cells rapidly became moribund. PCR genotyping of progenitor colonies from these bone marrow samples are shown in Figure 5E. Data are presented as the mean ± SEM.