A functional polymorphism of PON1 interferes with microRNA binding to increase the risk of ischemic stroke and carotid atherosclerosis.

OBJECTIVE

Single nucleotide polymorphisms (SNPs) located at microRNA (miRNA) binding sites (miR-SNPs) can affect the expression of genes. This study aimed to identify the miR-SNPs associated with atherosclerosis and stroke.

METHODS

Patients with ischemic stroke (n = 657) and stroke- and myocardial infarction-free volunteers (n = 1571) were enrolled. The carotid intima-media thickness (IMT) was measured in the control participants. Seventy-nine stroke susceptibility genes were initially selected and 13 genes were predicted to have miR-SNPs at their 3' untranslated regions (3'UTR). The miRNA arrays were used to further identify potential miR-SNPs. The miR-SNP rs3735590 at the paraoxonase 1 (PON1) gene was finally selected and its associations with stroke and carotid IMT were evaluated. The 3'UTR reporter and SNP functional assays were then performed to validate the results.

RESULTS

Compared with CC genotype, patients with CT or TT genotype at rs3735590 had lower risk of ischemic stroke (OR = 0.72, p = 0.036; OR = 0.83, p = 0.077, respectively). Among the healthy participants, the CT or TT genotype was associated with thinner IMT in the internal carotid arteries in comparison with CC genotype (β = -0.76, p = 0.003; β = -0.022, p = 0.452, respectively). Our findings suggested that the minor allele T had a protective effect on atherosclerosis. Results from 3'UTR reporter assays showed that PON1 is a direct target gene of miR-616. In plasmid constructs carrying the risk allele C at rs3735590, miR-616 inhibited the genetic expression of PON1. However, substitution of C by T at rs3735590 reduced the miR-616 binding affinity, leading to overexpression of the PON1 gene.

CONCLUSION

Our study is the first to show that the miR-SNP at PON1 could affect genetic expression and is associated with an elevated risk for ischemic stroke and subclinical atherosclerosis.