Background: Variation in platelet reactivity contributes to disorders of hemostasis and thrombosis, but the molecular mechanisms are not well understood. Objectives: To discover associations between interindividual platelet variability and the responsible platelet genes, and to begin to define the molecular mechanisms altering platelet gene expression. Subjects/methods:Two hundred and eighty‐eight healthy subjects were phenotyped for platelet responsiveness. Platelet RNA from subjects demonstrating hyperreactivity (n = 18) and hyporeactivity (n = 11) was used to screen the human transcriptome. Results: Distinctly different mRNA profiles were observed between subjects with differing platelet reactivity. Increased levels of mRNA for VAMP8/endobrevin, a critical v‐SNARE involved in platelet granule secretion, were associated with platelet hyperreactivity (Q = 0.0275). Validation studies of microarray results showed 4.8‐fold higher mean VAMP8 mRNA levels in hyperreactive than hyporeactive platelets (P = 0.0023). VAMP8 protein levels varied 13‐fold among platelets from these normal subjects, and were 2.5‐fold higher in hyperreactive platelets (P = 0.05). Among our cohort of 288 subjects, a VAMP8 single‐nucleotide polymorphism (rs1010) was associated with platelet reactivity in an age‐dependent manner (P < 0.003). MicroRNA‐96 was predicted to bind to the 3′‐untranslated regionof VAMP8 mRNA and was detected in platelets. Overexpression of microRNA‐96 in VAMP8‐expressing cell lines caused a dose‐dependent decrease in VAMP8 protein and mRNA, suggesting a role in VAMP8 mRNA degradation. Conclusions: These findings support a role for VAMP8/endobrevin in the heterogeneity of platelet reactivity, and suggest a role for microRNA‐96 in the regulation of VAMP8 expression.
