Platelet counts and ultrastructure. (A) MYH9Δ mice exhibited thrombocytopenia. The mean is represented in the figure (n = 17-18). (B,C) Heterogeneity in platelet size as observed both by TEM (left panels) and by flow cytometry (right panels, showing representative dot plots of whole blood; FSC indicates forward scatter; SSC, side scatter; α_IIbβ₃-positive platelets are visualized by red dots). Control (B) and MYH9Δ (C) mouse platelets (bars 2 μm). (D) Higher magnification of a MYH9Δ platelet showing the highly developed RER (bar 2 μm).