Fetal liver cellularity is severely reduced and erythroblast maturation delayed in RhoA^Δ/Δ embryos. (A) Beginning at E12.5, RhoA^Δ/Δ fetal livers have reduced cellularity compared with the WTs. Cellularity is unaffected in the heterozygous (RhoA^WT/Δ) fetal livers. Data are represented as mean ± SEM of the cell count of at least 5 fetal livers for each embryonic date. *P < .05 of RhoA^Δ/Δ vs WT. (B) The number of cells per fetal liver with BFU-E (left panel) and CFU-E (right panel) activity is unaffected in E12.5 RhoA^Δ/Δ embryos compared with the WT. Data are represented as mean ± SEM of 3 fetal liver samples per each genotype, each sample evaluated by colony assay in triplicate plates. (C-D) Flow cytometry analysis of fetal liver cells from E12.5 embryos shows that RhoA^Δ/Δ erythroblasts diminish in number as they move through the stages of erythroid maturation. Flow cytometry dot plots are representative of 3 different biological repeats (C). Bar graph of mean ± SEM of the cell count per each erythroid population as defined by CD71-Ter119 analysis of 3 fetal livers per each genotype (D). *P < .05 of RhoA^Δ/Δ vs WT. (E) Touch preps prepared from E13.0 fetal livers show an abundance of larger, more immature cells in RhoA^Δ/Δ fetal livers compared with the WT. Binucleated erythroblasts (arrows) are evident in RhoA^Δ/Δ fetal livers, though they are less prominent than among the primitive erythroid cells in circulation. The scale bar represents 10 µm.