Cell cycle and apoptosis status of PU.1-deficient fetal liver cells. Cells from e14.5 wild-type or PU.1^-/- fetal liver were incubated with Hoechst 33342 for 30 minutes at 37°C and then stained for expression of c-Kit and lineage markers. The data shown are representative of 4 wild-type and 3 PU.1^-/- embryos analyzed for Hoechst 33342 staining (A) and 3 wild-type and 4 knockout embryos for annexin V (B). Annexin V staining was done using a combination of Annexin V^FITCc-Kit^APCLin^PE. The numbers indicated in both (A) and (B) represent percentages of cells that fall within the gate plus or minus the standard deviation from the mean.