Background

eQTL analyses are important to improve the understanding of genetic association results. Here, we performed a genome-wide association and global gene expression study to identify functionally relevant variants affecting the risk of coronary artery disease (CAD).

Methods and Results

In a genome-wide association analysis of 2,078 CAD cases and 2,953 controls, we identified 950 single nucleotide polymorphisms (SNPs) that were associated with CAD at P<10-3. Subsequent in silico and wet-lab replication stages and a final meta-analysis of 21,428 CAD cases and 38,361 controls revealed a novel association signal at chromosome 10q23.31 within the LIPA (Lysosomal Acid Lipase A) gene (P=3.7×10-8; OR 1.1; 95% CI: 1.07-1.14). The association of this locus with global gene expression was assessed by genome-wide expression analyses in the monocyte transcriptome of 1,494 individuals. The results showed a strong association of this locus with expression of the LIPA transcript (P=1.3×10-96). An assessment of LIPA SNPs and transcript with cardiovascular phenotypes revealed an association of LIPA transcript levels with impaired endothelial function (P=4.4×10-3).

Conclusions

The use of data on genetic variants and the addition of data on global monocytic gene expression led to the identification of the novel functional CAD susceptibility locus LIPA, located on chromosome 10q23.31. The respective eSNPs associated with CAD strongly affect LIPA gene expression level, which itself was related to endothelial dysfunction, a precursor of CAD.

Dilated cardiomyopathy (DCM) is a structural heart disease with strong genetic background. Monogenic forms of DCM are observed in families with mutations located mostly in genes encoding structural and sarcomeric proteins. However, strong evidence suggests that genetic factors also affect the susceptibility to idiopathic DCM. To identify risk alleles for non-familial forms of DCM, we carried out a case-control association study, genotyping 664 DCM cases and 1,874 population-based healthy controls from Germany using a 50K human cardiovascular disease bead chip covering more than 2,000 genes pre-selected for cardiovascular relevance. After quality control, 30,920 single nucleotide polymorphisms (SNP) were tested for association with the disease by logistic regression adjusted for gender, and results were genomic-control corrected. The analysis revealed a significant association between a SNP in HSPB7 gene (rs1739843, minor allele frequency 39%) and idiopathic DCM (p = 1.06×10−6, OR = 0.67 [95% CI 0.57–0.79] for the minor allele T). Three more SNPs showed p < 2.21×10−5. De novo genotyping of these four SNPs was done in three independent case-control studies of idiopathic DCM. Association between SNP rs1739843 and DCM was significant in all replication samples: Germany (n = 564, n = 981 controls, p = 2.07×10−3, OR = 0.79 [95% CI 0.67–0.92]), France 1 (n = 433 cases, n = 395 controls, p = 3.73×10−3, OR = 0.74 [95% CI 0.60–0.91]), and France 2 (n = 249 cases, n = 380 controls, p = 2.26×10−4, OR = 0.63 [95% CI 0.50–0.81]). The combined analysis of all four studies including a total of n = 1,910 cases and n = 3,630 controls showed highly significant evidence for association between rs1739843 and idiopathic DCM (p = 5.28×10−13, OR = 0.72 [95% CI 0.65–0.78]). None of the other three SNPs showed significant results in the replication stage.

This finding of the HSPB7 gene from a genetic search for idiopathic DCM using a large SNP panel underscores the influence of common polymorphisms on DCM susceptibility.

Author Summary

Dilated cardiomyopathy is a severe disease of the heart muscle and often leads to chronic heart failure, eventually with the consequence of cardiac transplantation. Identification of genetic disease markers in at-risk persons could play an important role in preventive health care. Several mutations in familial forms of the disease are described. Here, we examine the role of common genetic variants on the sporadic form of dilated cardiomyopathy. By screening about 2,000 candidate genes previously related to cardiovascular disease in more than 1,900 cases and 3,600 controls, we show that a polymorphism in the HSPB7 gene (rs1739843) is strongly associated with susceptibility to dilated cardiomyopathy. We also show that the effect on disease risk is present in both German and French cohorts. Therefore, this study is an important step towards revealing insight in the genetic background of the sporadic form of dilated cardiomyopathy.

In a population-based cohort study of middle-aged people in Central Europe, Stefan Kääb and colleagues find an association between electrocardiographic early repolarization pattern and mortality risk.

Background

Early repolarization pattern (ERP) on electrocardiogram was associated with idiopathic ventricular fibrillation and sudden cardiac arrest in a case-control study and with cardiovascular mortality in a Finnish community-based sample. We sought to determine ERP prevalence and its association with cardiac and all-cause mortality in a large, prospective, population-based case-cohort study (Monitoring of Cardiovascular Diseases and Conditions [MONICA]/KORA [Cooperative Health Research in the Region of Augsburg]) comprised of individuals of Central-European descent.

Methods and Findings

Electrocardiograms of 1,945 participants aged 35–74 y, representing a source population of 6,213 individuals, were analyzed applying a case-cohort design. Mean follow-up was 18.9 y. Cause of death was ascertained by the 9th revision of the International Classification of Disease (ICD-9) codes as documented in death certificates. ERP-attributable effects on mortality were determined by a weighted Cox proportional hazard model adjusted for covariables. Prevalence of ERP was 13.1% in our study. ERP was associated with cardiac and all-cause mortality, most pronounced in those of younger age and male sex; a clear ERP-age interaction was detected (p = 0.005). Age-stratified analyses showed hazard ratios (HRs) for cardiac mortality of 1.96 (95% confidence interval [CI] 1.05–3.68, p = 0.035) for both sexes and 2.65 (95% CI 1.21–5.83, p = 0.015) for men between 35–54 y. An inferior localization of ERP further increased ERP-attributable cardiac mortality to HRs of 3.15 (95% CI 1.58–6.28, p = 0.001) for both sexes and to 4.27 (95% CI 1.90–9.61, p<0.001) for men between 35–54 y. HRs for all-cause mortality were weaker but reached significance.

Conclusions

We found a high prevalence of ERP in our population-based cohort of middle-aged individuals. ERP was associated with about a 2- to 4-fold increased risk of cardiac mortality in individuals between 35 and 54 y. An inferior localization of ERP was associated with a particularly increased risk.

Please see later in the article for the Editors' Summary

Editors' Summary

Background

Cardiovascular diseases—disorders that affect the heart and the circulation—are the leading cause of death in the developed world. About half of cardiovascular deaths occur when the heart suddenly stops pumping (sudden cardiac arrest). The muscular walls of the four heart chambers contract in a set pattern to pump blood around the body. The heart's internal electrical system controls the rate and rhythm of these contractions and, if this system goes wrong, an abnormal heart beat or “arrhythmia” develops. Some arrhythmias—in particular, ventricular fibrillation in which the walls of the two lower heart chambers quiver or “fibrillate” instead of pumping—can cause sudden cardiac arrest and immediate loss of consciousness. Death follows within minutes in 95% of cases but immediate cardiopulmonary resuscitation (CPR; chest compression to pump the heart and inflation of the lungs by mouth-to-mouth resuscitation) can keep a person alive until a defibrillator can be used to restore the normal heart beat. People who survive sudden cardiac arrest can be given anti-arrhythmia drugs or have a pacemaker implanted to stabilize their heart beat.

Why Was This Study Done?

The beating heart generates tiny electric waves that can be detected by electrodes on the skin. The pattern of these waves (an electrocardiogram or ECG) provides information about the heart's health. One wave pattern that is often seen on ECGs is the “early repolarization pattern” (ERP), which some studies suggest is associated with an increased risk of cardiac death. Here, the researchers investigate the prevalence of ERP (the proportion of a population with ERP) and its association with death from heart-related problems (cardiac mortality) and from any cause (all-cause mortality) in the MONICA/KORA prospective, population-based case-cohort study. The MONICA Project (MONitoring of Trends and Determinants in CArdiovascular Disease) has studied cardiovascular disease in 10 million people in 21 countries; KORA denotes the study done in the Augsburg region of Germany. In a prospective study, specific baseline characteristics of the study's participants are determined and the participants are followed to see who experiences a predefined outcome. A case-cohort study investigates a randomly selected subcohort (subgroup) of the original participants of a study and any participants who experience the predefined outcome instead of all the participants.

What Did the Researchers Do and Find?

The researchers selected 1945 MONIKA/KORA participants aged 35–74 years from a source population of about 6,000 people using a case-cohort study design. They analyzed the ECGs (recorded in 1984–1985 or 1989–1990) of this subcohort and ascertained the cause of death for those participants who died during the 18.9 year average follow-up. The overall prevalence of ERP in the study was 13.1%, report the researchers, and ERP was associated with cardiac mortality, particularly among younger and male participants. Specifically, among men and women aged 35–54 years, having ERP was associated with a nearly doubled risk of cardiac death. Among men aged 35–54 years, having ERP was associated with an increase in the risk of cardiac death by 2.65-fold. An ERP localized to the bottom of the heart (inferior localization) was associated with an increased risk of cardiac death among both sexes by more than 3-fold and among men by more than 4-fold in this age group. Finally, ERP was also significantly associated with an increased risk of all-cause mortality but less strongly than with cardiac mortality.

What Do These Findings Mean?

These findings suggest that the prevalence of ERP among the middle-aged people in the MONICA/KORA study is high (and somewhat higher than previously reported). They also show a clear association between ERP and the risk of cardiac death among 35–54-year-old people, particularly among men, but because of the study design, these findings do not show that ERP actually causes cardiac death; it could simply be a susceptibility marker. The researchers note that the increased risk of cardiac death associated with ERP is of a similar size to that associated with some other ECG abnormalities. However, although it might be worth paying special attention to young people with an inferior localization of ERP, finding ERP in a person without symptoms and without a family history of sudden cardiac death should not lead to further investigations or any preventative therapy, they suggest, because the absolute risk of cardiac arrest in such people is very low.

Additional Information

Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1000314.

The US National Heart Lung and Blood Institute provides information on cardiovascular conditions, including sudden cardiac arrest and on arrhythmias

The American Heart Association also information on sudden cardiac death and on arrhythmias

The German Cardiac Society (Deutsche Gesellschaft fr Kardiologie) and the German Heart Foundation (Deutsche Herzstiftung) provide further information (in German) on cardiovascular conditions

The Heart Rhythm Foundation provides information on all aspects of heart arrhythmia

The Fondation Leducq Alliance Against Sudden Cardiac Death provides information on sudden cardiac arrest

MedlinePlus provides links to other resources about cardiac arrest and arrhythmias (in English and Spanish)

The MedlinePlus Encyclopedia has a page on electrocardiograms (in English and Spanish)

The Nobel Foundation provides an interactive electrocardiogram game

More information about the MONICA project and the KORA Study or is available

The growth hormone secretagogue receptor (GHSR) (ghrelin receptor) plays an important role in the regulation of food intake and energy homeostasis. The GHSR gene lies on human chromosome 3q26 within a quantitative trait locus strongly linked to multiple phenotypes related to obesity and the metabolic syndrome. Because the biological function and location of the GHSR gene make it an excellent candidate gene, we tested the relation between common single nucleotide polymorphisms (SNPs) in the GHSR gene and human obesity. We performed a comprehensive analysis of SNPs, linkage disequilibrium (LD), and haplotype structure across the entire GHSR gene region (99.3 kb) in 178 pedigrees with multiple obese members (DNA of 1,095 Caucasians) and in an independent sample of the general population (MONICA Augsburg left ventricular hypertrophy substudy; DNA of 1,418 Caucasians). The LD analysis revealed a disequilibrium block consisting of five SNPs, consistent in both study cohorts. We found linkage among all five SNPs, their haplotypes, and BMI. Further, we found suggestive evidence for transmission disequilibrium for the minor SNP alleles (P < 0.05) and the two most common haplotypes with the obesity affection status (“susceptible” P = 0.025, “nonsusceptible” P = 0.045) in the family cohort using the family-based association test program. Replication of these findings in the general population resulted in stronger evidence for an association of the SNPs (best P = 0.00001) and haplotypes with the disease (“susceptible” P = 0.002, “nonsusceptible” P = 0.002). To our knowledge, these data are the first to demonstrate linkage and association of SNPs and haplotypes within the GHSR gene region and human obesity. This linkage, together with significant transmission disequilibrium in families and replication of this association in an independent population, provides evidence that common SNPs and haplotypes within the GHSR region are involved in the pathogenesis of human obesity.

Background

Recently, a large meta-analysis including over 28,000 participants identified nine different loci with association to serum uric acid (UA) levels. Since elevated serum UA levels potentially cause gout and are a possible risk factor for coronary artery disease (CAD) and myocardial infarction (MI), we performed two large case-control association analyses with participants from the German MI Family Study. In the first study, we assessed the association of the qualitative trait gout and ten single nucleotide polymorphisms (SNP) markers that showed association to UA serum levels. In the second study, the same genetic polymorphisms were analyzed for association with CAD.

Methods and Findings

A total of 683 patients suffering from gout and 1,563 healthy controls from the German MI Family Study were genotyped. Nine SNPs were identified from a recently performed genome-wide meta-analysis on serum UA levels (rs12129861, rs780094, rs734553, rs2231142, rs742132, rs1183201, rs12356193, rs17300741 and rs505802). Additionally, the marker rs6855911 was included which has been associated with gout in our cohort in a previous study. SNPs rs734553 and rs6855911, located in SLC2A9, and SNP rs2231142, known to be a missense polymorphism in ABCG2, were associated with gout (p = 5.6*10−7, p = 1.1*10−7, and p = 1.3*10−3, respectively). Other SNPs in the genes PDZK1, GCKR, LRRC16A, SLC17A1-SLC17A3, SLC16A9, SLC22A11 and SLC22A12 failed the significance level. None of the ten markers were associated with risk to CAD in our study sample of 1,473 CAD cases and 1,241 CAD-free controls.

Conclusion

SNP markers in SLC2A9 and ABCG2 genes were found to be strongly associated with the phenotype gout. However, not all SNP markers influencing serum UA levels were also directly associated with the clinical manifestation of gout in our study sample. In addition, none of these SNPs showed association with the risk to CAD in the German MI Family Study.

Background

Serum uric acid (UA) levels have recently been shown to be genetically influenced by common polymorphisms in the GLUT9 gene in two genome-wide association analyses of Italian and British populations. Elevated serum UA levels are often found in conjunction with the metabolic syndrome. Hyperuricemia is the major risk factor for gout and has been associated with increased cardiovascular morbidity and mortality. The aim of the present study was to further elucidate the association of polymorphisms in GLUT9 with gout and coronary artery disease (CAD) or myocardial infarction (MI). To test our hypotheses, we performed two large case-control association analyses of individuals from the German MI Family Study.

Methods and Findings

First, 665 patients with gout and 665 healthy controls, which were carefully matched for age and gender, were genotyped for four single nucleotide polymorphisms (SNPs) within or near the GLUT9 gene. All four SNPs demonstrated highly significant association with gout. SNP rs6855911, located within intron 7 of GLUT9, showed the strongest signal with a protective effect of the minor allele with an allelic odds ratio of 0.62 (95% confidence interval 0.52–0.75; p  =  3.2*10−7). Importantly, this finding was not influenced by adjustment for components of the metabolic syndrome or intake of diuretics. Secondly, 1,473 cases with severe CAD or MI and 1,241 healthy controls were tested for the same four GLUT9 SNPs. The analyses revealed, however, no significant association with CAD or with MI. Additional screening of genome-wide association data sets showed no signal for CAD or MI within the GLUT9 gene region.

Conclusion

Thus, our results provide compelling evidence that common genetic variations within the GLUT9 gene strongly influence the risk for gout but are unlikely to have a major effect on CAD or MI in a German population.

The tumour suppressor protein p53 has functions in controlling the G1/S and G2/M transitions. Central regulators for progression from G2 to mitosis are B-type cyclins complexed with cdc2 kinase. In mammals two cyclin B proteins are found, cyclin B1 and B2. We show that upon treatment of HepG2 cells with 5-fluorouracil or methotrexate, p53 levels increase while concentrations of cyclin B2 mRNA, measured by RT–PCR with the LightCycler system, are reduced. In DLD-1 colorectal adenocarcinoma cells (DLD-1-tet-off-p53) cyclin B1 and B2 mRNA levels drop after expression of wild-type p53 but not after induction of a DNA binding-deficient mutant of p53. Analysis of the cyclin B2 promoter reveals specific repression of this gene by p53. Transfection of wild-type p53 into SaOS-2 cells shuts off transcription from a cyclin B2 promoter–luciferase construct whereas a p53 mutant protein does not. The cyclin B2 promoter does not contain a consensus p53 binding site. Most of the p53-dependent transcriptional responsiveness resides in its 226 bp core promoter. Taken together with earlier observations on p53-dependent transcription of cyclin B1, our results suggest that one way of regulating G2 arrest may be a reduction in cyclin B levels through p53-dependent transcriptional repression.