Platelet aggregation in response to arachidonic acid. Platelets of male and female littermates were collected and counted as described in “Materials and methods.” The platelet number was adjusted to 3 × 10⁸/mL and 400 μL was used. AA (final concentration 1 mM) was added to induce aggregation at 37° C. +/+ indicates WT; +/–, heterozygous; and –/–, homozygous littermates.