Morphology of WT, KLF2^−/−, EKLF^−/−, and EKLF^−/−KLF2^−/− E9.5 circulating blood cells. The total number of embryo samples examined for each genotype is indicated in the Figure 4 legend. (A-D) Representative cytospins of Giemsa-stained primitive erythroid cells. Cytospins were prepared from blood samples collected from E9.5 yolk sacs and embryos. (A) Wild-type. (B) KLF2^−/−. (C) EKLF^−/−. (D) EKLF^−/−KLF2^−/−. Photographs were taken at 1000 × magnification. See “Analysis of EKLF^−/−KLF2^−/− embryos” for more image information. (E) Semiquantitative assessment of abnormal cytoplasmic and nuclear morphology in WT, KLF2^−/−, EKLF^−/−, and EKLF^−/−KLF2^−/− cytospins. Ten primitive blood cells from each sample were scored from 1 to 3, based on severity of cytoplasmic pleiomorphism and nuclear atypia (white and black bars, respectively). A score of 1 indicates the most normal, and of 3 the most abnormal morphology. Error bars indicate standard deviation from the mean. For WT, EKLF^−/− and EKLF^−/−KLF2^−/−, n = 40 cells, and for KLF2^−/− samples, n = 20. * indicates a significant difference from WT at P < .001, and ** is significantly different from WT, KLF2^−/−, and EKLF^−/− at P < .001 using Student t test of comparison of means.