Erythroid differentiation is blocked at the late erythroblast stage in PCFT^−/− mice. (A) BM cells of the indicated mice were analyzed by FACS for expression of the designated differentiation markers. Dashed vertical lines in the top histograms indicate the Ter119⁺ cells analyzed in the bottom density plots. Rectangular gates represent proerythroblasts (I), early basophilic precursors (II), late basophilic and chromatophilic erythroblasts (III), and orthochromatophilic eryhthroblasts and reticulocytes (IV). Fraction of cells in the different maturation stages are indicated close to the respective gates (mean ± SEM; n = 10 mice each cohort). BM and splenic cellularity and the percentages of erythroid progenitor subsets in the BM and spleen, including the percentages of annexin V⁺ intermediate erythroblasts, are summarized in panel B (mean ± SEM; n = 10 mice each cohort). Data are from one of 2 independent experiments showing similar results. *P < .05 compared with WTs.