Tamoxifen-induced recombination within embryonic hematopoiesis. (A) Maternal tamoxifen injections were carried out on day E10.5 (1 mg) and E11.5 (2 mg). Embryonic fetal livers were harvested for flow cytometric analysis 3 days later (E14.5). (B) The proportion of Eyfp-expressing cells within total fetal liver cells from R26R-EYFP (left panel) and HSC-SCL-Cre-ER^T;R26R-EYFP (right panel, SD ± 1.0%) littermates was determined. (C) The percentage of Eyfp-expressing cells also was determined within the c-kit⁺Sca-1⁺lineage^–/low population (SD ± 2.2%). (D) Additionally, Eyfp expression within lineage-committed fetal liver cells was determined: Mac-1⁺ (SD ± 1.3%) and Ter119⁺ (SD ± 0.8%) populations. Representative plots are shown, and indicated percentages represent means (n = 7).