Severe reduction in c-Kit⁺Lin^-CD34⁺ and c-Kit⁺Lin^-AA4.1⁺ cells in PU.1^-/- embryos. Single-cell suspensions from representative e14.5, PU.1^+/+ (n = 7), or PU.1^-/- (n = 3) embryos were stained with c-Kit^APC, Lin^PE, and either CD34^FITC or AA4.1^{biotin/avidin-TexasRed} and then analyzed by FACS. The percentage of each subset among total fetal liver cells is indicated. The average fold difference in absolute numbers of c-Kit⁺Lin^-CD34⁺ and c-Kit⁺Lin^-AA4.4⁺ cells between wild-type and PU.1^-/- fetal liver at e14.5 was 9.1-fold and 6.4-fold, respectively.