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%，是中风和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具有遗传性，最近在流动人群中发现一个频繁的基因间4号染色体位点（4q25）与房颤有关。我们最近证明，在心脏手术后的重复队列高加索患者中，4q25位点的相同snp也与新发术后房颤相关。因此，动态房颤和术后房颤的遗传机制似乎是一致的，然而，其机制尚未确定。我们将利用心脏手术围手术期的环境，以及心房组织的可用性和频繁的房颤表型来确定4q25基因组变异与房颤之间关联的生物学机制。我们的总体目标是确定4q25位点遗传变异导致房颤的遗传和分子机制。为了实现这一目标，我们提出了检验4q25变异与房颤关联的假设：1)我们假设4q25变异导致导致房颤风险增加的初级蛋白质结构改变。为了鉴定已知和新的编码序列中的4q25变异，我们将使用cDNA标记的Solexa测序来测量新的心房多聚a转录物。然后，我们将对先前收集的1900多例心脏手术患者的所有多态性编码变异进行基因分型，以确定与术后房颤相关的所有4q25编码变异；2)我们假设4q25变异导致了顺式mRNA转录物的选择性剪接或差异表达。我们将根据4q25 AF相关基因型确定差异表达或选择性剪接的4q25转录本，方法是使用40例术后和非术后AF患者的结构化队列绘制人类心房的4q25 poly-A转录组，并进行Solexa mRNA测序；3)我们假设4q25变异通过miRNA或其他非编码RNA调节mRNA翻译导致AF。我们将在40例术后AF患者和非术后AF患者的相同结构化队列中，通过对4q25中所有已鉴定的心房poly-A和非poly-A RNA转录物进行重测序，来进行研究，以确定4q25 mRNA翻译调节的非编码RNA来源。我们将整合转录物和测序工作的结果来检验这一假设。通过开展这些研究，我们将为房颤的分子机制提供新的见解。这些见解可能有助于开发新的治疗策略，以减轻房颤在社区，特别是在老龄化人群中的负担。

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.