Fga^270/270 platelets form weaker aggregates in response to ADP stimulation. Representative aggregation traces of platelet-rich plasma collected from Fga^WT/WT, Fga^WT/270, Fga^270/270, and Fga^−/− mice following stimulation with (A) 3 μM ADP or (B) 10 μM ADP (n = 4 per genotype). (C) Representative aggregation traces of platelet-rich plasma collected from untreated or siLuc- or siFga- treated mice following stimulation with 5 μM ADP (n = 4-5 per group). (D) Representative aggregation traces of platelet-rich plasma collected from Fga^WT/WT, Fga^WT/270, Fga^270/270, and Fga^−/− mice following stimulation with 250 μM of protease-activated receptor 4 activating peptide (PAR4-AP) (n = 4 per genotype). (E) Representative images and (F) quantification of platelet adhesion (indicated in red) to collagen coated surface at venous (400 seconds⁻¹) shear rate using heparinized whole blood from Fga^WT/WT, Fga^WT/270, Fga^270/270, and Fga^−/− mice (n = 4 per genotype). (G) Adhesion and spreading of Fga^−/− platelets on uncoated or FibAα^WT- or FibAα²⁷⁰- coated coverslips following stimulation with 50 μM of ADP for 30 minutes (n = 3 per fibrinogen). One-way ANOVA was used to determine statistical significance. Expression of (H) GPIIb/IIIa, (I) GPIX, and (J) GPIbα on platelet membrane of Fga^WT/WT, Fga^WT/270, Fga^270/270, and Fga^−/− mice (n = 5 per genotype). One-way ANOVA was used to determine statistical significance. **P < .01, ****P < .0001. ns, no statistical significance.