Abstract 4410: A Novel and Common Insertion/Deletion Polymorphism in the GJA5 Gene Encoding Connexin-40 Is Associated with Connexin-40 Expression in Human Atrial Tissue
Background: Variations in the gene GJA5, encoding the atrial-specific gap junction protein connnexin-40, have been associated with risk for atrial fibrillation (AF). We sought to identify genetic variants associated with altered GJA5 expression in human tissue.
Methods: 48 human atrial tissue surgical samples were genotyped at 6 single nucleotide polymorphisms (SNPs) located within GJA5 and 30 kb flanking the gene. Tissues were also typed for a novel 25 bp insertion/deletion polymorphism in the GJA5 3′-untranslated region (UTR). Total RNA from these tissues was analyzed on Illumina Human Ref-8 v2 Expression Bead Chips. GJA5 expression data were adjusted for sex, history of AF, and presence or absence of AF at the time of tissue harvest, and expression levels were interrogated against the genotypes at each SNP as well as the insertion/deletion polymorphism.
Results: Upon sequencing the GJA5 gene from 9 human subjects, we discovered a common 25 bp insertion/deletion polymorphism in the 3′-UTR. We developed a rapid PCR-based assay for this polymorphism and found a minor insertion allele frequency of 0.46 in a cohort of 72 human atrial tissue surgical samples. This polymorphism was significantly associated with GJA5 expression in a dominant model (p=0.0061), with 15% of the variation in GJA5 expression explained by the insertion/deletion polymorphism. The association was also significant in an additive model (p=0.021), with the polymorphism explaining 13% of GJA5 expression variation, yielding a 1.3-fold higher level of GJA5 expression in the homozygotes for the insertion allele versus the homozygotes for the deletion allele. One SNP in our analysis, located in the first exon of GJA5, is in complete linkage disequilibrium with a GJA5 promoter SNP previously shown to be associated with AF in case-control studies and with GJA5 expression in in vitro studies. However, our analysis revealed no significant association of this SNP with GJA5 expression levels in human atria.
Conclusion: We have discovered a novel insertion/deletion polymorphism in the GJA5 3′UTR that is strongly associated with GJA5 expression in human atria. Our data suggest that a promoter SNP, previously shown to be associated with AF, is not associated with GJA5 expression in vivo.