The + 23 Runx1 enhancer targets LacZ expression to clonogenic progenitors and definitive LTR-HSCs in the E11 AVU and FL of + 23-line1 transgenic embryos. (A) Representative dot plots of + 23 enhancer activity (measured by FDG). FDG-loaded tissues of wild-type littermates are shown as negative control. Sort gates as indicated. Purity of sorted populations was 96% (± 2.7%; mean ± SD; n = 13) and 86.0% (± 5.8%; n = 9) for AVU FDG⁻ and FDG⁺ cells, respectively, and 95.4% (± 3.1%; n = 10) and 85.8% (± 11.3%; n = 10) for FL FDG⁻ and FDG⁺ cells, respectively. (B,C) Analysis of clonogenic progenitors (CFU-C₇) among AVU and FL FDG⁻ and FDG⁺ cells. (B) Frequency of CFU-C₇ in each population tested (mean ± SD). (C) Absolute number of CFU-C₇ per embryo equivalent of AVU and FL FDG⁻ and FDG⁺ cells (mean ± SD; n = 3). (D) LTR-HSC activity in AVU and FL FDG⁻ and FDG⁺ cell populations. Frequency and absolute numbers of mice showing more than 10% PB donor-derived reconstitution at more than 4 months after transfer. (E) Percentage donor contribution in reconstituted mice as determined by semiquantitative PCR for the donor genetic marker in PB genomic DNA. (F,G) Multilineage analysis of recipients of FDG⁺ AVU cells with more than 50% donor-derived PB cells (F) and more than 10% donor-derived PB cells (G). In both cases, donor cells contributed to all hematopoietic tissues and lineages analyzed. Pb indicates peripheral blood; Th, thymus; LN, mesenteric lymph node; BM, bone marrow; Sp, spleen; E, erythroid cells; L, bone lymphoid cells; M, myeloid cells; B, B cells; and T, T cells. Percent donor reconstitution was determined by comparison with standards containing 0%, 0.1%, 1%, 10%, 50%, and 100% of donor genomic DNA.