Lack of increased platelet turnover in RhoB^−/− mice. (A) For the determination of platelet lifespan, wt and RhoB^−/− platelets were labeled with an α-GPIX antibody, and the labeled platelet population was analyzed over 5 consecutive days (n = 5 mice per genotype). Unpaired t test with individual variances computed for each comparison, mean plus or minus SD. (B) Ratio of spleen weight (mg) to body weight (g) of RhoB^−/− mice normalized to wt (n = 10 miceper genotype). (C) Paraffin sections of murine spleens stained using hematoxylin and eosin. Analysis was performed at a Leica DMI4000 B microscope. Scale overview, 100 µm; inset, 80 µm. (D) Number of MKs per visual field determined in spleen paraffin sections (n = 3; 4 visual fields per genotype; visual field, 2.3 mm²). (E) Assessment of Erythrina cristagalli lectin–FITC (ECL-FITC) binding to wt and RhoB^−/− platelets by flow cytometry at resting state (rest) or upon neuraminidase treatment (Neu) (n = 3). (F) Ratio of lectin binding (neuraminidase-treated platelets vs untreated platelets) for both genotypes (n = 3). (G) Percentage of reticulated (RNA-rich) platelets assessed by thiazole orange binding in flow cytometry (wt n = 7; RhoB^−/− n = 9). ***P < .001; Mann-Whitney U test, mean plus or minus SD. MFI, meanfluorescence intensity.