Platelet mRNA profiling in 6 healthy subjects and downregulation of WDR1 expression in participants with hyperreactive vs hyporeactive participants. (A) Platelet aggregation measurements by aggregometry in response to low doses of platelet agonists. Each dot represents the percentage of aggregation for each individual subject in response to submaximal collagen (0.05 µg/mL), epinephrine (0.1 µM), AA (300 µM), or ADP (1 µM). Subjects with hyperreactive platelets have >80% aggregation whereas subjects with hyporeactive platelets have <20% aggregation in response to collagen, epinephrine, AA, and ADP. Red and blue dots represent the 6 subjects with hyperreactive (n = 3) and hyporeactive (n = 3) platelet phenotypes, respectively. The maximum aggregation response was used to classify groups and was thus significantly different between the 3 hyperreactive and 3 hyporeactive subjects (ADP, 94.5% ± 2.7% vs 11.3% ± 3.7%; collagen, 90.9% ± 2.6% vs 5.5% ± 3.8%; epinephrine, 92.7% ± 2.9% vs 8.0% ± 4.4%; AA, 91.1% ± 3.6% vs 9.0% ± 6.9%; mean ± SEM). (B) Heatmap of platelet mRNA gene expression in subjects with a hyperreactive vs a hyporeactive platelet phenotype. Red and blue characterize upregulated and downregulated genes, respectively. (C) Volcano plot for genes with a fold change higher than 1.5 between hyperreactive and hyporeactive platelets. (D) Validation of WDR1 expression by quantitative PCR in subjects with a hyperreactive (n = 3) vs a hyporeactive (n = 3) platelet phenotype (P = .10, 1-sided Mann-Whitney U test). Data are median ± IQR. *P < .05, hyperreactive vs hyporeactive group.