Background and Purpose ANRIL has long been considered as the strongest candidate gene at the 9p21 locus, robustly associated with stroke and coronary artery disease (CAD). However, the underlying molecular mechanism remains unknown. The present study works to elucidate such a mechanism. Methods Utilizing eQTL analysis we identified potential genes whose expression may be influenced by genetic variation in ANRIL. To verify the identified gene(s), knockdown and over-expression of ANRIL was evaluated in HUVECs and HepG2 cells. Ischemic stroke and CAD risk was then evaluated in the gene(s) demonstrated to be mediated by ANRIL in 3 populations of Chinese Han ancestry; two ischemic stroke populations including the Central China cohort (903 cases and 873 controls) and the Northern China cohort (816 cases and 879 controls), and one CAD cohort consisting of 772 patients and 873 controls. Results eQTL analysis identified CARD8 among others, with knockdown of ANRIL expression decreasing CARD8 expression and over-expression of ANRIL increasing CARD8 expression. The minor T allele of a previously identified CARD8 variant (rs2043211) was found to be significantly associated with a protective effect of ischemic stroke under the recessive model in two independent stroke cohorts. No significant association was found between rs2043211 and CAD. Conclusion CARD8 is a downstream target gene regulated by ANRIL. SNP rs2043211 in CARD8 is significantly associated with ischemic stroke. ANRIL may increase the risk of ischemic stroke through regulation of the CARD8 pathway.

Atrial fibrillation (AF) is the most common cardiac arrhythmia at the clinic. Recent GWAS identified several variants associated with AF, but they account for <10% of heritability. Gene-gene interaction is assumed to account for a significant portion of missing heritability. Among GWAS loci for AF, only three were replicated in the Chinese Han population, including SNP rs2106261 (G/A substitution) in ZFHX3, rs2200733 (C/T substitution) near PITX2c, and rs3807989 (A/G substitution) in CAV1. Thus, we analyzed the interaction among these three AF loci. We demonstrated significant interaction between rs2106261 and rs2200733 in three independent populations and combined population with 2,020 cases/5,315 controls. Compared to non-risk genotype GGCC, two-locus risk genotype AATT showed the highest odds ratio in three independent populations and the combined population (OR=5.36 (95% CI 3.87-7.43), P=8.00×10-24). The OR of 5.36 for AATT was significantly higher than the combined OR of 3.31 for both GGTT and AACC, suggesting a synergistic interaction between rs2106261 and rs2200733. Relative excess risk due to interaction (RERI) analysis also revealed significant interaction between rs2106261 and rs2200733 when exposed two copies of risk alleles (RERI=2.87, P<1.00×10-4) or exposed to one additional copy of risk allele (RERI=1.29, P<1.00×10-4). The INTERSNP program identified significant genotypic interaction between rs2106261 and rs2200733 under an additive by additive model (OR=0.85, 95% CI: 0.74-0.97, P=0.02). Mechanistically, PITX2c negatively regulates expression of miR-1, which negatively regulates expression of ZFHX3, resulting in a positive regulation of ZFHX3 by PITX2c; ZFHX3 positively regulates expression of PITX2C, resulting in a cyclic loop of cross-regulation between ZFHX3 and PITX2c. Both ZFHX3 and PITX2c regulate expression of NPPA, TBX5 and NKX2.5. These results suggest that cyclic cross-regulation of gene expression is a molecular basis for gene-gene interactions involved in genetics of complex disease traits.

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Background The CAV1 gene encodes caveolin-1 expressed in cell types relevant to atherosclerosis. Cav-1-null mice showed a protective effect on atherosclerosis under the ApoE−/− background. However, it is unknown whether CAV1 is linked to CAD and MI in humans. In this study we analyzed a tagSNP for CAV1 in intron 2, rs3807989, for potential association with CAD. Methods and Results We performed case-control association studies in three independent Chinese Han populations from GeneID, including 1,249 CAD cases and 841 controls in Population I, 1,260 cases and 833 controls in Population II and 790 cases and 1,212 controls in Population III (a total of 3,299 cases and 2,886 controls). We identified significant association between rs3807989 and CAD in three independent populations and in the combined population (Padj=2.18×10−5, OR=1.19 for minor allele A). We also detected significant association between rs3807989 and MI (Padj=5.43×10−5, OR=1.23 for allele A). Allele A of SNP rs3807989 was also associated with a decreased level of LDL cholesterol. Although rs3807989 is a tagSNP for both CAV1 and nearby CAV2, allele A of SNP rs3807989 was associated with an increased expression level of CAV1 (both mRNA and protein), but not CAV2. Conclusions The data in this study demonstrated that rs3807989 at the CAV1/CAV2 locus was associated with significant risk of CAD and MI by increasing expression CAV1 (but not CAV2). Thus, CAV1 becomes a strong candidate susceptibility gene for CAD/MI in humans.

Background and Purpose— Genome-wide association studies found that the common allele T of single nucleotide polymorphism rs11206510 on chromosome 1p32 was associated with increased low-density lipoprotein-cholesterol levels (LDL-C) and with risk of coronary artery disease (CAD) in white populations. The goals of this study are to determine whether rs11206510 is associated with LDL-C and CAD in a different ethnic population, namely a Chinese cohort, and to investigate whether rs11206510 is associated with ischemic stroke. Methods— The association of rs11206510 with LDL-C was analyzed in 1415 Chinese Han subjects. The CAD study utilized a GeneID cohort with 1543 CAD patients and 1240 controls. For stroke studies, 2 independent cohorts were used and included the GeneID North cohort, with 1205 cases and 1205 controls, and the GeneID Central cohort, with 692 cases and 882 controls. Results— Different from white populations, the minor allele C of rs11206510 was associated with increased LDL-C levels in the Chinese Han population (adjusted P =0.002) and conferred risk of early-onset CAD (380 cases vs 1240 controls; adjusted P =0.002, odds ratio, 1.89), but not with overall CAD (adjusted P =0.82). The allelic association with ischemic stroke was highly significant in 2 independent cohorts, with adjusted P =1.13×10 −5 (odds ratio,1.71) in the GeneID North cohort and adjusted P =9.32×10 −5 (odds ratio, 1.70) in the GeneID Central cohort. Genotypic association was also significant for both early-onset CAD and ischemic stroke. Conclusions— Our results indicate that single nucleotide polymorphism rs11206510 is associated with LDL-C levels and early-onset CAD in the Chinese Han population. For the first time to our knowledge, this study also demonstrates that rs11206510 confers a significant risk of ischemic stroke.

Background Genomic variants identified by genome-wide association studies (GWAS) explain <20% of heritability of coronary artery disease (CAD), thus many risk variants remain missing for CAD. Identification of new variants may unravel new biological pathways and genetic mechanisms for CAD. To identify new variants associated with CAD, we developed a candidate pathway-based GWAS by integrating expression quantitative loci (eQTL) analysis and mining of GWAS data with variants in a candidate pathway. Methods and Results Mining of GWAS data was performed to analyze variants in 32 complement system genes for positive association with CAD. Functional variants in genes showing positive association were then identified by searching existing expression quantitative loci databases and validated by RT-PCR. A follow-up case control design was then used to determine whether the functional variants are associated with CAD in two independent GeneID Chinese populations. Candidate pathway-based GWAS identified positive association between variants in C3AR1 and C6 and CAD. Two functional variants, rs7842 in C3AR1 and rs4400166 in C6, were found to be associated with expression levels of C3AR1 and C6, respectively. Significant association was identified between rs7842 and CAD (P=3.99×10−6, OR=1.47) and between rs4400166 and CAD (P=9.30×10−3, OR=1.24) in the validation cohort. The significant findings were confirmed in the replication cohort (P=1.53×10−5, OR=1.37 for rs7842; P=8.41×10−3, OR=1.21 for rs4400166. Conclusions Integration of GWAS with biological pathways and eQTL is effective in identifying new risk variants for CAD. Functional variants increasing C3AR1 and C6 expression were shown to confer significant risk of CAD for the first time.

The interleukin 1 family plays an important role in the immune and inflammatory responses. Coronary artery disease (CAD) is a chronic inflammatory disease. However, the genetic association between IL-37, the seventh member of the IL-1 family, and CAD is unknown. Here we show that a single nucleotide polymorphism in the IL-37 gene (rs3811047) confers a significant risk of CAD. We have performed an association analysis between rs3811047 and CAD in two independent populations with 2,501 patients and 3,116 controls from China. Quantitative RT-PCR analysis has been performed to determine if the IL-37 expression level is influenced by rs3811047. We show that the minor allele A of rs3811047 is significantly associated with CAD in two independent populations under a recessive model (Padj = 5.51 × 10−3/OR = 1.56 in the GeneID Northernern population and Padj = 1.23 × 10−3/OR = 1.45 in the GeneID Central population). The association became more significant in the combined population (Padj = 9.70 × 10−6/OR = 1.47). Moreover, the association remains significant in a CAD case control population matched for age and sex. Allele A of rs3811047 shows significant association with a decreased mRNA expression level of IL-37 (n = 168, P = 3.78 × 10−4). These data suggest that IL37 is a new susceptibility gene for CAD, which provides a potential target for the prevention and treatment of CAD.

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