Impaired organelle motility in Myh9^−/−MKs. (A) Cultured Myh9^−/− and WT MKs were imaged using videomicroscopy after AF-488–fibrinogen incorporation. Image showing the maximal confocal projection of a MK cytoplasm portion (5.5 µm thickness). (B) Labeled organelles were tracked and their mean speed and displacement were measured. Only tracks that were longer than 25 seconds were evaluated to reliably determine the displacement. Data are mean ± SEM of 5260 (WT) and 3479 (Myh9^−/−) granules from at least 3 independent experiments. ***P < .0001. ns, not significant.