Association between SNP rs13376333 and rs1131820 in the KCNN3 gene and atrial fibrillation in the Chinese Han population

Modulation of SK Channels: Insight Into Therapeutics of Atrial Fibrillation

Atrial fibrillation (AF) is the most prevalent cardiac arrhythmia in the world. Although much technological progress in the treatment of AF has been made, there is an urgent need for better treatment of AF due to its high rates of morbidity and mortality. The anti-arrhythmic drugs currently approved for marketing have significant limitations and side effects such as life-threatening ventricular arrhythmias and hypotension. The small conductance Ca²⁺-activated K⁺ channels (SK channels) are dependent on intracellular Ca²⁺ concentrations, which tightly integrate with membrane potential. Given the predominant expression in the atria of many species, including humans, they are now emerging as a therapeutic target for treating AF. This review aimed to illustrate the characteristics and function of SK channels. Moreover, it discussed the regulation of SK channels and their potential as a therapeutic target of AF.

The regulation of the small-conductance calcium-activated potassium current and the mechanisms of sex dimorphism in J wave syndrome

Apamin-sensitive small-conductance calcium-activated potassium (SK) current (I_KAS) plays an important role in cardiac repolarization under a variety of physiological and pathological conditions. The regulation of cardiac I_KAS relies on SK channel expression, intracellular Ca²⁺, and interaction between SK channel and intracellular Ca²⁺. I_KAS activation participates in multiple types of arrhythmias, including atrial fibrillation, ventricular tachyarrhythmias, and automaticity and conduction abnormality. Recently, sex dimorphisms in autonomic control have been noticed in I_KAS activation, resulting in sex-differentiated action potential morphology and arrhythmogenesis. This review provides an update on the Ca²⁺-dependent regulation of cardiac I_KAS and the role of I_KAS on arrhythmias, with a special focus on sex differences in I_KAS activation. We propose that sex dimorphism in autonomic control of I_KAS may play a role in J wave syndrome.

Annotation of susceptibility SNPs associated with atrial fibrillation

OBJECTIVE

Genome-wide association studies (GWAS) and the candidate gene based association studies have identified a panel of variants associated with atrial fibrillation (AF), however, most of the identified single nucleotide polymorphisms (SNPs) were found located within intergenic or intronic genomic regions, and whether the positive SNPs have a real biological function is unknown, and the real disease causing gene need to be studied.

RESULTS

The current results of the genetic studies including common variants identified by GWAS (338 index SNPs) and candidate gene based association studies (40 SNPs) were summarized.

CONCLUSION

Our study suggests the relationship between genetic variants and possible targeted genes, and provides insight into potential genetic pathways underlying AF incidence and development. The results may provide an encyclopedia of AF susceptibility SNPs and shed light on the functional mechanisms of AF variants identified through genetic studies.

METHODS

We summarized AF susceptibility SNPs identified by GWAS and candidate gene based association studies, and give a comprehensive functional annotation of all these AF susceptibility loci. by genomic annotation, microRNA binding prediction, promoter activity analysis, enhancer activity analysis, transcription factors binding activity prediction, expression quantitative trait loci (eQTL) analysis, long-range transcriptional regulatory function analysis, gene ontology and pathway enrichment analysis.

Genotype-phenotype associations in atrial fibrillation: meta-analysis

PURPOSE

Genome-wide association studies have identified several single-nucleotide polymorphisms (SNPs) associated with atrial fibrillation (AF). The relationship between SNPs and the incidence of stroke, heart failure, and the recurrence rate of AF after cardioversion has been reported. This meta-analysis focuses on the genotype-phenotype associations in AF.

METHODS

We searched PubMed/Medline and Embase for literature providing the phenotypic parameters and genotypes of RS10033464, RS13376333, RS2106261, RS2200733, and RS7193343. We selected literature published in English and reviewed the full text of included studies to perform a meta-analysis.

RESULTS

Fifteen papers, and 7034 patients with AF, were included. The mean risk gene frequency of the investigated variants was between 12 and 43%. The mean age of patients was between 50 and 70 and 70-80% of them were male. The stroke and heart failure frequencies in AF patients with RS2200733 were 10 and 7%, respectively. There was no significant difference in left ventricular ejection fraction and left ventricular end-diastolic diameter for all risk genotypes. For the AF recurrence after cardioversion treatment with direct current electric conversion, catheter ablation therapy, and anti-arrhythmic drugs. The early AF recurrence rate was 46% in RS10033464 and RS13376333 patients, and the late AF recurrence rate was 53% in RS2200733 patients.

CONCLUSIONS

Pooled analysis showed a significantly high prevalence of stroke (10%) in RS2200733 AF patients. AF patients with the studied SNPs had preserved left ventricular systolic function (i.e., ejection fraction greater than 50%). AF patients with RS10033464 presented larger left atrium diameter (44 mm (95% CI 42.02-45.98)) than those with other SNPs. The late AF recurrence rate was highest in RS2200733 patients (53% (95% CI 0.43-0.64)). This study aids our understanding of the existing genetic findings and the function-altering "strongest" SNPs.

KCNN2 polymorphisms and cardiac tachyarrhythmias

Potassium calcium-activated channel subfamily N member 2 (KCNN2) encodes an integral membrane protein that forms small-conductance calcium-activated potassium (SK) channels. Recent studies in animal models show that SK channels are important in atrial and ventricular repolarization and arrhythmogenesis. However, the importance of SK channels in human arrhythmia remains unclear. The purpose of the present study was to test the association between genetic polymorphism of the SK2 channel and the occurrence of cardiac tachyarrhythmias in humans. We enrolled 327 Han Chinese, including 72 with clinically significant ventricular tachyarrhythmias (VTa) who had a history of aborted sudden cardiac death (SCD) or unexplained syncope, 98 with a history of atrial fibrillation (AF), and 144 normal controls. We genotyped 12 representative tag single nucleotide polymorphisms (SNPs) across a 141-kb genetic region containing the KCNN2 gene; these captured the full haplotype information. The rs13184658 and rs10076582 variants of KCNN2 were associated with VTa in both the additive and dominant models (odds ratio [OR] 2.89, 95% confidence interval [CI] = 1.505-5.545, P = 0.001; and OR 2.55, 95% CI = 1.428-4.566, P = 0.002, respectively). After adjustment for potential risk factors, the association remained significant. The population attributable risks of these 2 variants of VTa were 17.3% and 10.6%, respectively. One variant (rs13184658) showed weak but significant association with AF in a dominant model (OR 1.91, CI = 1.025-3.570], P = 0.042). There was a significant association between the KCNN2 variants and clinically significant VTa. These findings suggest an association between KCNN2 and VTa; it also appears that KCNN2 variants may be adjunctive markers for risk stratification in patients susceptible to SCD.

KCNN3 SNP rs13376333 on Chromosome 1q21 Confers Increased Risk of Atrial Fibrillation

To investigate the relationship between KCNN3 SNP (single-nucleotide polymorphism) rs13376333 and risk of atrial fibrillation (AF) and to provide evidence for prevention and treatment for AF.The PubMed, Embase, OVID, Cochrane library, CNKI, and Wan Fang databases were searched to identify studies on the relationship between KCNN3 SNP rs13376333 polymorphism and atrial fibrillation. Two authors performed independent article reviews and study quality assessment using the Newcastle-Ottawa Scale (NOS) checklist.Seven studies involving 24,339 individuals were included in the meta-analysis. The overall combined OR of rs13376333 polymorphism was observed for both lone AF (OR: 1.58 [95%CI: 1.37 to 1.82]; P < 0.001; I(2) = 47.0%) and total AF (OR: 1.33 [95%CI: 1.14 to 1.54]; P < 0.001; I(2) = 0). Further, when stratified by ethnicity, control sources, sample sizes, and genotyping method, similar results were observed in both subgroups. Sensitivity analysis revealed that the source of control was the source of the heterogeneity for lone AF. Omission of any single study had little effect on the combined risk estimate. No evidence of publication bias was found.This meta-analysis suggests that KCNN3 SNP rs13376333 polymorphism significantly increases the risk of lone AF and total AF, which suggests the rs13376333 polymorphism of the KCNN3 gene may play an important role in the pathogenesis of AF.

CASP3 genetic variants and susceptibility to atrial fibrillation in Chinese Han population

BACKGROUND

Caspase-3 plays an important role in the initiation and maintenance of atrial fibrillation (AF), but little is known about the role of CASP3 variants in the susceptibility to atrial fibrillation (AF). The purpose of this study was to comprehensively investigate the association between common genetic variants of CASP3 gene and AF in Chinese Han population.

METHODS AND RESULTS

We investigated the association of five variants in CASP3 and the risk of AF in 889 AF patients and 1015 controls. The genotype distribution of the rs4647602 was significantly different between patients with AF and controls (p<0.001), and the A allele frequency was significantly higher in AF patients than in controls (61.0% vs 53.2%; p<0.001). Compared with CC genotype carriers, subjects with AA genotype had significantly increased susceptibility to AF (OR=1.84, p<0.001). Multivariable logistic regression analysis showed that the rs4647602 polymorphism was significantly associated with risk of AF under dominant, recessive and additive genetic model (OR, 1.44-1.64; all p<0.001). There was no association between the other four SNPs (rs6948, rs2696056, rs4647602 and rs4647610) and risk of AF.

CONCLUSION

The rs4647602 polymorphism is independently associated with the risk of AF in Chinese Han population.