Identification of Genetic and Molecular Mechanisms of Atrial Fibrillation

描述（由申请人提供）：房颤是最常见的持续性心律失常，终生风险为20-24%，是卒中以及其他发病率和死亡率的重要原因。有强有力的证据表明房颤的遗传性，最近在非卧床人群中，一个频繁的基因间4号染色体位点（4 q25）与房颤相关。我们最近证明，在心脏手术后的高加索患者重复队列中，4 q25位点的相同SNP也与新发术后AF相关。因此，非卧床房颤和术后房颤的遗传机制似乎是一致的，但机制尚未确定。我们将使用围手术期心脏手术环境，其可用性心房组织和频繁的AF表型，以确定4 q25基因组变异和AF之间的关联的生物学机制。我们的总体目标是确定4 q25基因座的遗传变异导致房颤的遗传和分子机制。为了实现这一目标，我们建议检查4 q25变异与AF相关的假设：1）我们假设4 q25变异导致主要蛋白质结构改变，导致AF风险增加。为了鉴定位于已知和新编码序列内的4 q25变异，我们将使用cDNA标签的Solexa测序来测量新的心房多聚腺苷酸转录物。然后，我们将对1900多名先前收集的心脏手术患者的所有多态性编码变异进行基因分型，以确定与术后AF相关的所有4 q25编码变异; 2）我们假设4 q25变异导致顺式mRNA转录物的选择性剪接或差异表达。我们将根据4 q25 AF相关基因型，通过使用40例术后AF和非术后AF患者的结构化队列和Solexa mRNA测序绘制人心房4 q25 poly-A转录组，鉴定差异表达或可变剪接的4 q25转录物; 3）我们假设4 q25变异体通过miRNA或其他非编码RNA调节mRNA翻译而引起AF。我们将进行研究，以确定4 q25 mRNA翻译调节的非编码RNA来源，通过重新测序4 q25内所有确定的心房多聚腺苷酸和非多聚腺苷酸RNA转录本，在相同的结构队列的40例患者术后AF和没有。我们将整合从转录本和测序工作的结果，以检验假设。通过进行这些研究，我们将提供新的见解的分子机制，启动AF。这些见解可能有助于开发新的治疗策略，以减轻AF的负担在社区，特别是在老龄化人口。 公共卫生相关性：心房颤动是最常见的持续性心律失常，终生风险为20-24%，并且是中风和其他发病率和死亡率的重要原因。基因间染色体4位点最近已与AF。我们已经证明，同样的4 q25位点也与心脏手术后新发AF。然而，4 q25位点与非卧床或术后房颤相关的机制尚未确定。因此，我们建议使用围手术期心脏手术环境，其心房组织的现成可用性和频繁的AF表型，以确定4 q25基因组变异和AF之间的关联的生物学机制。

DESCRIPTION (provided by applicant): Atrial fibrillation is the most frequent sustained arrhythmia with a lifetime risk of 20-24% and is a significant cause of stroke, and other morbidity and mortality. There is strong evidence for heritability of AF, with a frequent intergenic chromosome 4 locus (4q25) being recently associated with AF in ambulatory populations. We have recently demonstrated that the same SNPs in the 4q25 locus, are also associated with new-onset postoperative AF in replicated cohorts of Caucasian patients after cardiac surgery. Thus, the genetic mechanisms of ambulatory AF and postoperative AF appear to be aligned, however, the mechanism(s) have not yet been identified. We will use the perioperative cardiac surgical environment, with its availability of atrial tissue and frequent AF phenotype to determine the biological mechanism(s) of the association between 4q25 genomic variation and AF. Our overall goal is to identify the genetic and molecular mechanisms whereby genetic variation in the 4q25 locus causes atrial fibrillation. In order to achieve this goal, we propose examining hypotheses for the association of 4q25 variants with AF: 1) We hypothesize that 4q25 variant(s) cause altered primary protein structure responsible for increased risk of AF. In order to identify 4q25 variants that lie within known and novel coding sequences we will measure novel atrial poly-A transcripts using Solexa sequencing of cDNA tags. We will then genotype all polymorphic coding variants in over 1900 previously collected cardiac surgical patients to identify all 4q25 coding variation associated with postoperative AF; 2) We hypothesize that 4q25 variants cause alternative splicing or differential expression of cis mRNA transcripts. We will identify 4q25 transcripts that are either differentially expressed or alternatively spliced, depending upon 4q25 AF-associated genotype, by mapping the 4q25 poly-A transcriptome of the human atrium using a structured cohort of 40 patients with and without postoperative AF, and Solexa mRNA sequencing; 3) We hypothesize 4q25 variants cause AF by regulation of mRNA translation by miRNA or other non-coding RNA. We will perform studies to identify non-coding RNA sources of regulation of 4q25 mRNA translation by resequencing all identified atrial poly-A and non poly-A RNA transcripts within 4q25 in the same structured cohort of 40 patients with and without postoperative AF. We will integrate the findings from the transcript and sequencing efforts to test the hypothesis. By performing these studies we will provide new insights into the molecular mechanisms that initiate AF. These insights may facilitate the development of novel therapeutic strategies to alleviate the burden of AF in the community, notably in the aging population. PUBLIC HEALTH RELEVANCE: Atrial fibrillation is the most frequent sustained arrhythmia with a lifetime risk of 20-24% and is a significant cause of stroke, and other morbidity and mortality. An intergenic chromosome 4 locus has recently been associated with AF. We have demonstrated that the same 4q25 locus is also associated with new-onset postoperative AF after cardiac surgery. However the mechanisms underlying the association of the 4q25 locus and either ambulatory or postoperative AF has not yet been identified. We therefore propose to use the perioperative cardiac surgical environment, with its ready availability of atrial tissue and frequent AF phenotype to determine the biological mechanism(s) of the association between 4q25 genomic variation and AF.