Abnormal erythropoiesis in Dhh^−/− mice. (A) Photograph represents typical spleen from WT (left) and Dhh^−/− (right). Histogram represents the mean spleen cell number from WT and Dhh^−/−. The difference in mean between WT and Dhh^−/− is statistically significant (P = .003). (B) Bar chart represents the mean RBC count in WT (8.1 × 10⁹/mL, shaded bar) and Dhh^−/− (8.8 × 10⁹/mL, open bar) blood. (C) Bar chart represents the mean percentage of reticulocytes in RBCs from WT (shaded bar) and Dhh^−/− (open bar) blood. The increase in mean percentage of reticulocytes in Dhh^−/− compared with WT was statistically significant (P = .014). (D) Spleen (top panel) and BM (bottom panel) cells from WT and Dhh^−/− were stained with antibodies against CD71 and Ter119. Dot plots represent the percentage of cells in the 4 erythroblast subsets (I-IV), defined by CD71 and Ter119 expression, as shown in the regions indicated, in WT (left) and Dhh^−/− (right). For spleen, bar charts represent the mean of the number of cells in each erythroblast subset in Dhh^−/−, divided by the number of cells in their counterpart subset in WT spleen, for each erythroblast population. The difference between the mean of Dhh^−/− and WT was statistically significant for population II (P = .012), population III (P = .015), and population IV (P = .006). For BM, the bar chart represents the mean relative percentage of erythroblast populations I to IV, in Dhh^−/−, relative to WT littermate. The difference between the means of Dhh^−/− and WT was statistically significant for population III (P = .022) and population IV (P = .02). (E) Cell cycle analysis of erythroblasts from WT and Dhh^−/− BM and spleen. Bar charts represent the mean percentage of cells in G₀/G₁ and S + G₂/M, as assessed by PI staining and flow cytometry in magnetic-bead-purified Ter119⁺ cells from WT (filled bars) and Dhh^−/− (open bars) BM (left) and spleen (right). There were no significant differences between WT and Dhh^−/− in either BM or spleen.