Effect of Tmprss6 inactivation on hematologic parameters and erythroid maturation of thalassemic mice. (A) Time course (1, 2, 4, and 6 months of age) analysis of RBC count and Hb levels of male and female WT, Tmprss6^−/−, Hbb^th3/+ (th3/+), and Tmprss6^−/−Hbb^th3/+ (Tmprss6^−/−th3/+) mice. Asterisks refer to a statistically significant difference between Hbb^th3/+ and Tmprss6^−/−Hbb^th3/+ mice. (B) Blood smears stained with May-Grunwald-Giemsa showing the morphology of RBC of representative WT, Hbb^th3/+ (th3/+), and Tmprss6^−/−Hbb^th3/+ (Tmprss6^−/−th3/+) mice (Original magnification 40×). (C) Percentages of reticulocytes in peripheral blood of 2-, 4-, and 6-month-old male and female WT, Tmprss6^−/− (only 6 months old), Hbb^th3/+ (th3/+), and Tmprss6^−/−Hbb^th3/+ (Tmprss6^−/−th3/+) mice. (D) FACS analysis performed on splenic erythroid cells of 6-month-old male and female WT, Tmprss6^−/−, Hbb^th3/+ (th3/+), and Tmprss6^−/−Hbb^th3/+ (Tmprss6^−/−th3/+) mice using CD71 (transferrin receptor 1) and Ter119 (erythroid specific) costaining. The graphs indicate the percentages of early erythroid precursors (CD71⁺Ter119⁺), which correspond to basophilic erythroblasts and late basophilic and chromatophilic erythroblasts, and those of mature erythroid cells (CD71⁻ Ter119⁺), which correspond to orthocromatophilic erythroblasts. Anucleated cells were excluded from analysis. Mean values of 4 to 8 animals for sex and genotype are graphed and error bars indicate SD. Asterisks refer to a statistically significant difference (*P < .05; **P < .01; ***P < .005). For complete statistical analysis see supplemental Table 2.