Effect of ST3Gal-IV sialyltransferase deficiency on platelet production. (A) Staining of reticulated platelets with Thiazole Orange revealed that the total number of circulating reticulocytes was similar between the 2 genotypes (P = .490). Total WT and ST3Gal-IV^−/− platelet counts are also shown (). (B) The average ST3Gal-IV^−/− platelet size (dotted line) was larger than that of ST3Gal-IV^+/+ and ST3Gal-IV^+/− platelets (solid and broken lines, respectively) as measured by FSC, indicating that the ST3Gal-IV^−/− platelet population on average is younger. (C) Reticulated platelets (■) were larger than nonreticulated platelets () in both genotypes. The nonreticulated platelets were larger in ST3Gal-IV^−/− mice than in WT mice.