Reduced SM-rich rafts and delayed clot retraction in SM synthase-deficient platelets. (A) Flow cytometry of SM-rich rafts of (a) wild-type, (b) SMS1-deficient, and (c) SMS2-deficient mouse platelets. (B) Time-dependent clot retraction of SMS1-deficient PRP (red diamonds) and wild-type PRP (black circles). The extent of clot retraction was assessed at the indicated times by measuring clot area. (C) Time-dependent clot retraction of SMS2-deficient PRP (blue triangles) and wild-type PRP (black circles). Data are presented as the means plus or minus SD of quadruplicates. *Statistically significant difference (P < .001). **Statistically significant difference (P < .005).