Fig 1: Abnormal number, expression of surface proteins, and activation of platelets in the absence of SNAP23. Color legend on top applies to all graphs. Whole-blood samples were loaded with a predetermined number of fluorescent beads, labeled with fluorescent antibodies against CD41 and P-selectin, and studied under flow cytometry. A, representative scattergrams of samples from SNAP23F/F and SNAP23pΔ/Δ littermates. FSC, forward scatter; SSC, side scatter; orange dots, CD41+ particles. B, representative histograms comparing CD41 fluorescence and FSC in the same F/F and pΔ/Δ samples. C, concentration of platelets (CD41+ particles) in whole-blood samples using fluorescent beads to calculate the original volume. n = 7; applies to C–F. D, difference in particle sizes estimated using the mean FSC values of CD41+ particles. E, mean fluorescence intensity (MFI) for CD41 in CD41+ particles. F, MFI for P-selectin in CD41+ particles. G, MFI for PAR4 in fixed and permeabilized platelets (total) or intact platelets (surface). n = 11. H, peak and area under the curve (AUC) over time of intracellular calcium concentrations ([Ca2+]i) measured by ratiometry in Fura-2 AM-loaded platelets activated with thrombin (0.1 U/ml). n = 12. I, MFI of intact platelets labeled with an antibody (Jon/A) against the activated conformation of αIIbβ3 before and after exposure to thrombin (Thr; 0.1 U/ml) with and without ADP (10 μM). n = 7. White line, mean; box, 25th to 75th percentile; whiskers, 5th to 95th percentile. ∗p ≤ 0.05, ∗∗p ≤ 0.01; all compared to F/F.