Impaired erythroid differentiation in Tr4 heterozygous mutant fetal liver cells. Representative flow cytometry diagrams of fetal liver cells recovered from WT and Tr4^+/− embryos at (A) E13.5 and (D) E15.5, stained with α-CD71 and α-TER119 antibodies. The percentage of cells within each gate (II-IV) is indicated on the plots. (B,E) Graph reporting the percentage of cells within each gate describing erythroid differentiation (II-IV) in (B) E13.5 (E) and E15.5 in WT (closed circles) and Tr4^+/− (open circles) fetal liver cells.^32,33  (C,F) Total cells per fetal liver were calculated for WT and Tr4^+/− mice. *P ≤ .05 as determined by Student t test comparing Tr4^+/− with WT.