Genome-wide association studies (GWAS) have identified genetic variants in a number of chromosomal regions that are associated with atrial fibrillation (AF). The mechanisms underlying these associations are unknown, but are likely to involve effects of the risk haplotypes on expression of neighbouring genes. To investigate the association between genetic variants at AF-associated loci and expression of nearby candidate genes in human atrial tissue and peripheral blood. Right atrial appendage (RAA) samples were collected from 122 patients undergoing cardiac surgery, of these, 12 patients also had left atrial appendage samples taken. 22 patients had a history of AF. Peripheral blood samples were collected from 405 patients undergoing diagnostic cardiac catheterisation. In order to tag genetic variation at each of nine loci, a total of 367 single nucleotide polymorphisms (SNPs) were genotyped using the Sequenom platform. Total expression of 16 candidate genes in the nine AF-associated regions was measured by quantitative PCR. The relative expression of each allele of the candidate genes was measured on the Sequenom platform using one or more transcribed SNPs to distinguish between alleles in heterozygotes. We tested association between the SNPs of interest and gene expression using total gene expression (integrating cis and trans acting sources of variation), and allelic expression ratios (specific for cis acting influences), in atrial tissue and peripheral blood. We adjusted for multiple comparisons using a Bonferroni approach. In subsidiary analyses, we compared the expression of candidate genes between patients with and without a history of AF. Total expression of 15 transcripts of 14 genes and allelic expression ratio of 14 transcripts of 14 genes in genomic regions associated with AF were measured in right atrial appendage tissue. 8 of these transcripts were also expressed in peripheral blood. Risk alleles at AF-associated SNPs were associated in cis with an increased expression of PITX2a (2.01-fold, p=6.5×10(-4)); and with decreased expression of MYOZ1 (0.39 fold; p=5.5×10(-15)), CAV1 (0.89 fold; p=5.9×10(-8)), C9orf3 (0.91 fold; 1.5×10(-5)), and FANCC (0.94-fold; p=8.9×10(-8)) in right atrial appendage. Of these five genes, only CAV1 was expressed in peripheral blood; association between the same AF risk alleles and lower expression of CAV1 was confirmed (0.91 fold decrease; p=4.2×10(-5)). A history of AF was also associated with a decrease in expression of CAV1 in both right and left atria (0.84 and 0.85 fold, respectively; p=0.03), congruent with the magnitude of the effect of the risk SNP on expression, and independent of genotype. The analyses in peripheral blood showed association between AF risk SNPs and decreased expression of KCNN3 (0.85-fold; p=2.1×10(-4)); and increased expression of SYNE2 (1.12-fold; p=7.5×10(-24)); however, these associations were not detectable in atrial tissue. We identified novel cis-acting associations in atrial tissue between AF risk SNPs and increased expression of PITX2a/b; and decreased expression of CAV1 (an association also seen in peripheral blood), C9orf3 and FANCC. We also confirmed a previously described association between AF risk variants and MYOZ1 expression. Analyses of peripheral blood illustrated tissue-specificity of cardiac eQTLs and highlight the need for larger-scale genome-wide eQTL studies in cardiac tissue. Our results suggest novel aetiological roles for genes in four AF-associated genomic regions.

中文翻译：

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与心房颤动风险相关的遗传变异调节 PITX2、CAV1、MYOZ1、C9orf3 和 FANCC 的表达。


全基因组关联研究 (GWAS) 已发现许多染色体区域中与心房颤动 (AF) 相关的遗传变异。这些关联的机制尚不清楚，但可能涉及风险单倍型对邻近基因表达的影响。研究 AF 相关位点的遗传变异与人类心房组织和外周血中附近候选基因表达之间的关联。右心耳 (RAA) 样本采集自 122 名接受心脏手术的患者，其中 12 名患者还采集了左心耳样本。 22名患者有房颤病史。外周血样本采集自 405 名接受诊断性心导管插入术的患者。为了标记 9 个基因座中每个基因座的遗传变异，使用 Sequenom 平台对总共 367 个单核苷酸多态性 (SNP) 进行了基因分型。通过定量 PCR 测量 9 个 AF 相关区域中 16 个候选基因的总表达。在 Sequenom 平台上使用一个或多个转录的 SNP 测量候选基因的每个等位基因的相对表达，以区分杂合子中的等位基因。我们使用心房组织和外周血中的总基因表达（整合顺式和反式作用变异来源）和等位基因表达比率（特定于顺式作用影响）测试了感兴趣的 SNP 与基因表达之间的关联。我们使用 Bonferroni 方法对多重比较进行了调整。在辅助分析中，我们比较了有房颤病史和无房颤病史的患者之间候选基因的表达。 测量右心耳组织中与 AF 相关的基因组区域中 14 个基因的 15 个转录本的总表达量以及 14 个基因的 14 个转录本的等位基因表达比。其中 8 个转录物也在外周血中表达。 AF 相关 SNP 的风险等位基因顺式与 PITX2a 表达增加相关（2.01 倍，p=6.5×10(-4)）；并且MYOZ1（0.39倍；p=5.5×10(-15)）、CAV1（0.89倍；p=5.9×10(-8)）、C9orf3（0.91倍；1.5×10(-5)）表达减少和 FANCC（0.94 倍；p=8.9×10(-8)）在右心耳中。这5个基因中，只有CAV1在外周血中表达；证实了相同 AF 风险等位基因与 CAV1 较低表达之间的关联（降低 0.91 倍；p=4.2×10(-5)）。 AF 病史还与右心房和左心房 CAV1 表达下降相关（分别为 0.84 倍和 0.85 倍；p=0.03），与风险 SNP 对表达的影响程度一致，并且独立于基因型。外周血分析显示AF风险SNP与KCNN3表达降低之间存在关联（0.85倍；p=2.1×10(-4)）； SYNE2 表达增加（1.12 倍；p=7.5×10(-24)）；然而，在心房组织中无法检测到这些关联。我们在心房组织中发现了 AF 风险 SNP 与 PITX2a/b 表达增加之间的新顺式作用关联； CAV1（外周血中也存在这种关联）、C9orf3 和 FANCC 的表达降低。我们还证实了先前描述的 AF 风险变异与 MYOZ1 表达之间的关联。外周血分析说明了心脏 eQTL 的组织特异性，并强调了在心脏组织中进行更大规模全基因组 eQTL 研究的必要性。 我们的结果表明四个 AF 相关基因组区域中的基因具有新的病因学作用。