Orai1 is the platelet SOC channel. (A) RT-PCR and Western blot analysis of human platelets. Orai1, Orai2, and Orai3 were assessed with the primer pairs described in Takahashi et al,²²  and Western blot was performed using an antibody from ProSci. (B) Wild-type and Orai1^−/− littermates (3 weeks old). (C) Body weights of wild-type (+/+) and Orai1^−/− (−/−) mice. Error bars represent plus or minus SD. (D) RT-PCR analyses of platelet and thymocyte mRNA from wild-type (+/+), original Orai1^−/− (−/−), and Orai1^−/− bone marrow chimera (−/− BMc) mice. Orai1-, Orai2-, and Orai3-specific forward and reverse primers were used²² ; actin served as control. (E) Fura-2–loaded platelets were stimulated with 5 μM TG for 10 minutes, followed by addition of 1 mM extracellular Ca²⁺ and monitoring of [Ca²⁺]_i. Representative measurements (left) and maximal Δ[Ca²⁺]_i plus or minus SD (n = 4 per group) before and after addition of 1 mM Ca²⁺ (right) are shown. □ represents Stim1^−/− platelets.