Loss of Cardioprotective Effects at the ADAMTS7 Locus as a Result of Gene-Smoking Interactions

BACKGROUND: Common diseases such as coronary heart disease (CHD) are complex in etiology. The interaction of genetic susceptibility with lifestyle factors may play a prominent role. However, gene-lifestyle interactions for CHD have been difficult to identify. Here, we investigate interaction of smoking behavior, a potent lifestyle factor, with genotypes that have been shown to associate with CHD risk. METHODS: We analyzed data on 60 919 CHD cases and 80 243 controls from 29 studies for gene-smoking interactions for genetic variants at 45 loci previously reported to be associated with CHD risk. We also studied 5 loci associated with smoking behavior. Study-specific gene-smoking interaction effects were calculated and pooled using fixed-effects meta-analyses. Interaction analyses were declared to be significant at a P value of <1.0x10(-3) (Bonferroni correction for 50 tests). RESULTS: We identified novel gene-smoking interaction for a variant upstream of the ADAMTS7 gene. Every T allele of rs7178051 was associated with lower CHD risk by 12% in never-smokers (P= 1.3x10(-16)) in comparison with 5% in ever-smokers (P= 2.5x10(-4)), translating to a 60% loss of CHD protection conferred by this allelic variation in people who smoked tobacco (interaction P value= 8.7x10(-5)). The protective T allele at rs7178051 was also associated with reduced ADAMTS7 expression in human aortic endothelial cells and lymphoblastoid cell lines. Exposure of human coronary artery smooth muscle cells to cigarette smoke extract led to induction of ADAMTS7. CONCLUSIONS: Allelic variation at rs7178051 that associates with reduced ADAMTS7 expression confers stronger CHD protection in never-smokers than in ever-smokers. Increased vascular ADAMTS7 expression may contribute to the loss of CHD protection in smokers.Peer reviewe

Clinical characteristics of the study samples at time of DNA collection^α.

α<p>Data are means ± standard deviations or percentages;</p>β<p>Age here refers to the age when the DNA samples.</p

Kaplan-Meier survival function for rs4149313 and survival of MI in STR (A) and ULSAM (B).

<p>Survival function of MI for individuals having no (A/A; blue line); one (A/G; red line) or two (G/G; green line) risk alleles at <i>ABCA1</i> rs4149313 locus.</p

Forest plot for independent replication of association between rs4149313 and CAD in CARDIoGRAMplusC4D.

<p>Fixed-effect meta-analysis was applied for effect of rs4149313 on CAD in CARDIoGRAMplusC4D consortium. The diamond in the bottom represents the confidence interval of this independent replication.</p

Region plot of the <i>ABCA1</i> locus (chromosome 9 co-ordinates 106157871–107157392) in the Swedish Twin Registry.

<p>The SNP rs4149313 with the strongest association is marked by a bright blue diamond. Each rhomb represents a SNP and the brightness represents the extent of linkage disequilibrium with the lead SNP. The recombination rates are marked with yellow lines. Relevant genes and genomic coordinates are shown below the plots. Plots were generated using SNAP (<a href="http://www.broadinstitute.org/mpg/snap/ldplot.php" target="_blank">http://www.broadinstitute.org/mpg/snap/ldplot.php</a>. Accessed 2013 Mar 1.) and based on HapMap CEU release 22, NCBI B36 assembly, dbSNP build 126.</p

Associations of genetic loci with MI in primary and replication analyses.

α<p>Only SNPs associated with MI with a nominal P<0.01 in STR are presented. Data are hazard ratios with 95% confidence intervals and P-values from Cox proportional hazards regression models using age as time scale and study entry at age 18, adjusting for sex. The effect allele was defined as the minor allele in our study.</p>β<p>Proxies rs2236513, rs4759275, and rs8066560 were used instead of lead SNPs rs3183702, rs11172106 and rs9899634, respectively in ULSAM (r² = 1, 0.84 and 1) in all the results from the replication study.</p>γ<p>CELSR2 and SORT1 reside in a cluster consisting of CELSR2/PSRC1/SORT1; APOA4 resides in a cluster of apolipoproteins APOA5/APOA4/APOC3/APOA1.</p>δ<p>rs5090 was not successfully genotyped in ULSAM.</p>ε<p>Alleles are presented as effect/other alleles.</p><p>Abbreviations: SNP, single nucleotide polymorphism; HR, hazard ratio; CI, confidence interval.</p

Schematic approach.

<p>1) Identification of reported adverse effect of GA 2) Identify genes reported to interact with GA. 3) Establish a link between the genes identified in 2. and the adverse effect identified in 1).</p

TGFB1 locus.

<p>TGFB1 locus.</p

GA interacts with CCR, TGFB1, IFNAR1 and HLA-DRB1 (solid line).

<p>Moreover, it is known that GA affects CAD (Coronary Artery Disease) risk (dashed line). In this work, we searched for SNPs associated with CAD in the gene regions representing the GA off target effects (dotted lines). We found a genome-wide significant association for the TGFB1 locus with a p-value of 1.58 × 10⁻¹² (red dotted line). n.s.: non-significant; TGFB1: Transforming Growth Factor, Beta 1; CCR5: Chemokine (C-C Motif) Receptor 5 (Gene/Pseudogene); IFNAR1: Interferon (Alpha, Beta And Omega) Receptor 1; HLA-DRB1: Major Histocompatibility Complex, Class II, DR Beta 1.</p

Association sub-loci signal for the TGFB1 locus.

<p>The three lead SNPs are shown with the corresponding high-LD blocks (SNPs within r2>0.2.) depicted in orange, red and green. Independent sub-loci were identified with the GCTA conditional analysis tool (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0182999#sec002" target="_blank">methods</a>). The LD between the lead SNPs indicated and under r²<0.1. The three individual LocusZoom plots are found in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0182999#pone.0182999.s002" target="_blank">S2 Fig</a>.</p