MEKK3 deficiency delayed arterial thrombosis but had no effect on platelet counts or hemostasis. (A) Washed platelets were prepared from MEKK3^f/f and MEKK3^−/− mice. Western blot results show that MEKK3 was depleted in MEKK3^−/− platelets. (B) Platelet counts in the peripheral blood of MEKK3^f/f and MEKK3^−/− mice (n = 10; mean ± SD; P > .05). (C) The mouse carotid artery was treated with 10% FeCl₃ for 3 minutes, and blood flow traces were monitored (n = 10, mean ± SD). (D) Mouse tail-bleeding time was determined as the time to visual cessation of bleeding (n = 10, mean ± SD; P > .05). ***P < .001. ns, not significant.