Figure 3.

DKO platelets lack normal cytoskeleton organization and granule complexity. Platelet-rich plasma was isolated from mouse blood. (A) Samples were spun onto poly-l-lysine–coated slides and fixed immediately or permitted to spread for 20 minutes on glass before fixation. Samples were permeabilized and probed for filamentous actin (red, phalloidin) and β1 tubulin (green). Quantification of phalloidin intensity by immunofluorescence showed decreased polymerized actin in Mkl1 KO and DKO platelets (bottom). Error bars represent SEM. (B) Thin-section electron micrographs highlight the heterogeneity in granule segregation and platelet morphology. DKO platelets lack α granules and their dense granules are not as opaque. Red squares in center panels indicate the magnified sections in the right panels. Magnified right panel images were modified for easier visualization of microtubule cross-sections by increasing contrast. Thick arrows indicate marginal band microtubules, which are increased in DKO mice (***P < .001).