Acute deletion of Moz results in the complete absence of transplantable HSCs. (A) Experimental design. Bone marrow from donor Moz^fl/fl;Mx1-cre (n = 6) and control Moz^fl/fl (n = 6) mice were used. Each donor bone marrow sample was transplanted into 3 recipients. (B) Genomic Moz deletion efficiency was 95.8 ± 3.2% in animals used in A assessed by qPCR; the residual 4.2% unrecombined alleles were derived from nonhematopoietic and interferon unresponsive cells. (C) Flow cytometric analysis of peripheral blood of recipient mice 5 and 15 weeks after competitive transplantation (1:4 ratio of competitor to test cells). (D) Quantitation of donor contribution to the peripheral blood of lethally irradiated mice at 5, 15, and 26 weeks after competitive transplantation. Note the absence of contribution from Moz^fl/fl;Mx1-cre bone marrow cells after 15 and 26 weeks. (E) Moz-deleted bone marrow contains myeloid colony-forming cells, albeit at reduced numbers. Moz^fl/fl (i-iv) and Moz^fl/fl;Mx1-cre cultures (i′-iv′) are shown after stimulation with SCF, EPO, and IL3. Comparison of typical plates. Note the reduction in colony number in the Moz^fl/fl;Mx1-cre cultures (i vs i′). Cultures of both genotypes contain cells with high proliferative capacity (ii vs ii′). Overview of a colony (iii vs iii′). Morphology of macrophages (arrow) and granulocytes (arrowhead) differentiating from cells of either genotype was similar (iv vs iv′). Likewise, morphology of cells (arrows) within blast cell colonies (asterisk) was indistinguishable between genotypes. (F) Enumeration of colonies in Moz^fl/fl and Moz^fl/fl;Mx1-cre cultures. (G) Genotyping of colonies, showing efficient recombination of the Moz^fl/fl allele after poly(I:C) induction of Mx1-driven cre-recombinase. Data are presented as the mean ± standard error of the mean (SEM).