Polymorphisms but not mutations of the KCNQ1 gene are associated with lone atrial fibrillation in the Chinese Han population. ScientificWorldJournal. 2013;2013:373454. [PMID: 23710137 PMCID: PMC3654283 DOI: 10.1155/2013/373454]

Genetic variants on chromosomes 7p31 and 12p12 are associated with abnormal atrial electrical activation in patients with early-onset lone atrial fibrillation

BACKGROUND

Abnormal P-wave morphology (PWM) has been associated with a history of atrial fibrillation (AF) in earlier studies. Although lone AF is believed to have substantial genetic basis, studies on associations between single nucleotide polymorphisms (SNP) linked to lone AF and PWM have not been reported. We aimed to assess whether SNPs previously associated with lone AF (rs2200733, rs13376333, rs3807989, and rs11047543) are also linked to P-wave abnormalities.

METHODS

Four SNPs were studied in 176 unrelated individuals with early-onset lone AF (age at onset <50 years), median age 38 years (19-63 years), 149 men. Using sinus rhythm ECG, orthogonal PWM was classified as Type 1-positive in leads X and Y and negative in lead Z, Type 2-positive in leads X and Y and biphasic (-/+) in lead Z, Type 3-positive in lead X and biphasic in lead Y (+/-), and the remaining as atypical.

RESULTS

Two SNPs were found to be significantly associated with altered P-wave morphology distribution: rs3807989 near the gene CAV1/CAV2 and rs11047543 near the gene SOX5. Both SNPs were associated with a higher risk of non-Type 1 P-wave morphology (rs3807989: OR = 4.8, 95% CI = 2.3-10.2, p < 0.001; rs11047543: OR = 4.7, 95% CI = 1.1-20.5, p = 0.04). No association was observed for rs2200733 and rs13376333.

CONCLUSION

In this study, the two variants rs3807989 and rs11047543, previously associated with PR interval and lone AF, were associated with altered P-wave morphology distribution in patients with early-onset lone AF. These findings suggest that common genetic variants may modify atrial conduction properties.

Gene regulatory networks in atrial fibrillation

Atrial fibrillation (AF) is the most frequent arrhythmogenic syndrome in humans. With an estimate incidence of 1%-2% in the general population, AF raises up to almost 10%-12% in 80+ years. Thus, AF represents nowadays a highly prevalent medical problem generating a large economic burden. At the electrophysiological level, distinct mechanisms have been elucidated. Yet, despite its prevalence, the genetic and molecular culprits of this pandemic cardiac electrophysiological abnormality have remained largely obscure. Molecular genetics of AF familiar cases have demonstrated that single nucleotide mutations in distinct genes encoding for ion channels underlie the onset of AF, albeit such alterations only explain a minor subset of patients with AF. In recent years, analyses by means of genome-wide association studies have unraveled a more complex picture of the etiology of AF, pointing out to distinct cardiac-enriched transcription factors, as well as to other regulatory genes. Furthermore a new layer of regulatory mechanisms have emerged, i.e., post-transcriptional regulation mediated by non-coding RNA, which have been demonstrated to exert pivotal roles in cardiac electrophysiology. In this manuscript, we aim to provide a comprehensive review of the genetic regulatory networks that if impaired exert electrophysiological abnormalities that contribute to the onset, and subsequently, on self-perpetuation of AF.

Your Father and Grandfather's Atrial Fibrillation: A Review of the Genetics of the Most Common Pathologic Cardiac Dysrhythmia

Atrial fibrillation (AF) remains the most common pathologic dysrhythmia in humans with a prevalence of 1-2% of the total population and as high as 10% of the elderly. AF is an independent risk marker for cardiovascular mortality and morbidity, and given the increasing age of the population, represents an increasing burden of disease. Although age and hypertension are known risk factors for development of AF, the study of families with early onset AF revealed mutations in genes coding for ion channels and other proteins involved in electrotonic coupling as likely culprits for the pathology in select cases. Recent investigations using Genome-Wide Association Studies have revealed several single nucleotide polymorphisms (SNPs) that appear to be associated with AF and have highlighted new genes in the proximity of the SNPs that may potentially contribute to the development of the dysrhythmia. Here we review the genetics of AF and discuss how application of GWAS and next generation sequencing have advanced our knowledge of AF and further investigations may yield novel therapeutic targets for the disease.

Genetic variants of potassium voltage-gated channel genes (KCNQ1, KCNH2, and KCNE1) affected the risk of atrial fibrillation in elderly patients

BACKGROUND

Atrial fibrillation (AF) is a common type of cardiac arrhythmia and is a major healthcare burden. Around 20% of patients show no obvious clinical manifestations; this can lead to a delay of AF diagnosis and prevention. Genetic mutations are one of the important risk factors for AF. This study aimed to assess the associations between polymorphisms on KCNE1, KCNQ1, and KCNH2 with the risk of AF in a Chinese population.

MATERIALS AND METHODS

A case-control study comprised of 438 AF patients and 450 controls. The tag single-nucleotide polymorphisms (SNPs) were retrieved in the International HapMap database and Haploview software was used to capture all the polymorphisms on KCNE1, KCNQ1, and KCNH2. DNA was extracted from blood and polymerase chain reaction-based assays were used to genotype polymorphisms of the KCNE1, KCNQ1, and KCNH2 genes. Chi-square test and student t-tests were used to evaluate the differences in the clinical characteristics between AF cases and controls. Odds ratios (OR) and corresponding 95% confidence intervals (CIs) were calculated to assess the association between genetic variants of KCNQ1, KCNH2, KCNE1, and AF risk.

RESULTS

Among the nine tag SNPs, three were significantly associated with the risk of AF: the rs1805127*G allele on KCNE1, and the rs2283228*C and rs1057128*A alleles on KCNQ1. In contrast, rs1805120*T variant was correlated with lower risk of AF. However, the other five genetic variants (rs2237892, rs2237895, rs2237897, rs2070357, and rs2070356) showed no significant association with AF risk (all p>0.05).

CONCLUSIONS

Our study suggested that the rs1805127*G allele of KCNE1, and the rs2283228*C and rs1057128*A alleles on KCNQ1 are risk factors for AF, while the rs1805120*T allele on KCNH2 may serve as a protective factor for AF.

Contribution of miRNAs to ion-channel remodelling in atrial fibrillation

Atrial fibrillation (AF) is the most commonly encountered clinical arrhythmia associated with pronounced mortality and morbidity, which are related to palpitations, fainting, congestive heart failure, and stroke. Prolonged episodes of AF promote AF persistence mainly due to electrical remodelling that alters ion-channel expression and/or function. MicroRNAs (miRNAs), a new class of non-coding mRNAs of around 22 nucleotides in length, have recently emerged as one of the key players in the gene-expression regulatory networks. The potential roles of miRNAs in controlling AF have recently been investigated. Several recent studies have provided promising results for a better understanding of the molecular mechanisms of AF. In this review, we summarize the mechanism of miRNAs as regulators of ion-channel gene expression and their role in causing AF through electrical remodelling.