Defective fetal liver hematopoiesis in RapGEF2^−/− mice. (A-B) Histogram showing the average number of nucleated (A) and enucleated (B) erythroid cells in the peripheral blood of E10.5 RapGEF2^+/+ and RapGEF2^−/− embryos. (C) Representative photographs displaying the cytospined and stained peripheral blood of E10.5 RapGEF2^+/+ (C) and RapGEF2^−/− (D) embryos. Blue arrows indicate myeloid progenitors whereas remaining cells are nucleated erythroid cells. (E) Northern blot showing the expression level of RapGEF2 in the E16.5 liver, yolk sac, and embryo of RapGEF2^cko/ckoER⁺ (lane 1) and RapGEF2^cko/ckoER^cre (lane 2) mice. Females were injected with tamoxifen on day 11.5 and 13.5 of pregnancy. (F-G) Photographs showing the yolk sac blood vessels of E14.5 RapGEF2^cko/ckoER⁺ (F) and RapGEF2^cko/ckoER^cre (G) embryos. (H-I) Photographs of E17.5 RapGEF2^cko/ckoER⁺ (H) and RapGEF2^cko/ckoER^cre (I) embryos. The embryos were analyzed under Stemi SV11, Zeiss binocular microscope and photographed by Sony DSC-S85 digital camera. The E17.5 RapGEF2^cko/ckoER^cre embryos were pale, soft, fragile, and devoid of blood vessels. Timed matings were set up between the RapGEF2^cko/+ER^cre heterozygotes, and the pregnant females were given tamoxifen by injection to induce RapGEF2 deletion. First dose of tamoxifen was injected at E11.5, when yolk sac vascularization is mostly complete. Second dose was give at E13.5. If the induced deletion of RapGEF2 at this stage leads to embryonic lethality, we could conclude that the lethality in RapGEF2^cko/ckoER^cre mice was not due to yolk sac vascular defects. (J-K) Day-1 RapGEF2^cko/ckoER^cre (J) and RapGEF2^cko/ckoER⁺ (K) neonates. Pregnant females were given tamoxifen by injection on days 17.5 and 19.5 of pregnancy. (L) Representative FACS images showing the distribution of the CD71⁺Ter119⁺ population in the E16.5 fetal liver cells of RapGEF2^cko/ckoER⁺ and RapGEF2^cko/ckoER^cre embryos.