Abstract 1812: The Chromosome 9p21.3 Coronary Artery Disease Risk Locus is Associated with Altered Cardiac Gene Expression in Individuals without Overt Cardiac Abnormality
Several genome-wide association studies have recently identified a region on chromosome 9p21.3 strongly associated with risk of coronary heart disease. The region contains no annotated genes, and the mechanism underlying its association with coronary disease is unknown. We hypothesized that variants within the 9p21.3 risk locus may subtly alter cardiac gene expression in pathways that influence cardiac function before the onset of overt heart disease, leading to a greater cardiovascular risk. We investigated associations between global cardiac gene expression and rs1333049, a single nucleotide polymorphism representing the 9p21.3 locus, in 108 heart transplant donors without diagnosed heart disease. Individual cardiac gene expression profiles were generated with Affymetrix Human Gene 1.0 ST arrays (RMA normalized). Taqman assays were used for DNA genotyping and subsequent real-time PCR gene expression quantitation. Associations between cardiac gene expression and rs1333049 genotype (recessive model) were analysed with R package aroma.affymetrix. Donor mean age was 48 years, ancestry was European (96%) or African American (4%) and 51% were male. The rs1333049 genotype frequency (C=risk allele) was 30% GG, 51% GC and 19% CC. Of 133 genes found to be differentially expressed in donors with a CC genotype (p<0.01), 72% were down-regulated. Several genes identified reportedly play a protective role in cardiac pathophysiology, including periostin (down-regulated 1.9 fold, p=0.004) and regulator of G-protein signalling 2 (down-regulated 1.4-fold, p=0.006). None of the associations remained significant after correction for multiple comparisons. Array data was corroborated by real-time PCR of four genes (HEYL, BNC2, KCNMB1 and CXCL1), which gave fold-changes of equivalent magnitude and direction. Expression levels of CDKN2A and CDKN2B, the closest genes to rs1333049, and ANRIL, a large antisense non-coding RNA spanning rs1333049, were not associated with rs1333049 genotype. Our data suggest that individuals without cardiac disease homozygous for the 9p21.3 risk allele have a different pattern of cardiac gene expression compared with other individuals, which is unlikely to be explained by dysregulation of genes proximal to the 9p21.3 locus.