Abstract 536: RNA-Seq Identifies Differential Expression of Platelet Transcripts Between People With Hyper- and Hypoaggregation to Collagen

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Background: Platelet aggregation plays an important role in the pathogenesis of myocardial infarction, and high platelet aggregability is associated with increased risk of events. We hypothesized that inter-individual variability in platelet function is associated with differences in the mRNA transcripts found in platelets from hyper-aggregators and hypo-aggregators. Methods: Eight African American (discovery cohort) and four European American (validation cohort) males with family history of early onset coronary artery disease were enrolled. Individuals were divided into hyper- and hypo-aggregators based on maximal aggregation to collagen using whole blood impedance aggregometry. RNA was extracted from leukocyte-depleted platelet-rich plasma and approximately 70 million 100bp paired-end reads per sample were obtained using an Illumina HiSeq 2500. RNA-seq analysis was performed using Bowtie/TopHat/Cufflinks software pipeline. Genes with expression ≥ 1 fragments per kilobase of transcript per million reads (FPKM) were considered to be expressed. On log2 scale, ≥ 2-fold (discovery cohort) and ≥ 1-fold (replication cohort) change in gene expression were considered to be significantly differentially expressed. Results: Among the 9,373 expressed genes, the most highly expressed nonubiquitous genes included GP1BB, GP9, PPBP, PF4, & TUBB1, confirming our methods. Hyper-aggregability was associated with up-regulation of 239 genes and down-regulation of 29 genes in the discovery cohort (44 and 2 replicated in validation cohort respectively). Pathway analysis found that genes related to sphingosine-1P3 (such as RHOA [ras homolog family member A], GNAZ [G protein, alpha z polypeptide], VEGFA [vascular endothelial growth factor A]) and platelet aggregation pathways (such as GP9 [platelet glycoprotein IX], TLN1 [talin 1], ITGB3 [platelet glycoprotein IIIa]) were up-regulated in hyper-aggregators. Conclusion: RNA-seq and pathway analyses found that hyper- and hypo-aggregators have significant differences in gene expression. Increased expression of sphingosine-1P3 and platelet aggregation pathway genes in hyper-aggregators highlights the relationship of signal transduction with increased platelet aggregation.