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In silico assessment of genetic variation in KCNA5 reveals multiple mechanisms of human atrial arrhythmogenesis.

ABSTRACT: A recent experimental study investigating patients with lone atrial fibrillation identified six novel mutations in the KCNA5 gene. The mutants exhibited both gain- and loss-of-function of the atrial specific ultra-rapid delayed rectifier K+ current, IKur. The aim of this study is to elucidate and quantify the functional impact of these KCNA5 mutations on atrial electrical activity. A multi-scale model of the human atria was updated to incorporate detailed experimental data on IKur from both wild-type and mutants. The effects of the mutations on human atrial action potential and rate dependence were investigated at the cellular level. In tissue, we assessed the effects of the mutations on the vulnerability to unidirectional conduction patterns and dynamics of re-entrant excitation waves. Gain-of-function mutations shortened the action potential duration in single cells, and stabilised and accelerated re-entrant excitation in tissue. Loss-of-function mutations had heterogeneous effects on action potential duration and promoted early-after-depolarisations following beta-adrenergic stimulation. In the tissue model, loss-of-function mutations facilitated breakdown of excitation waves at more physiological excitation rates than the wild-type, and the generation of early-after-depolarisations promoted unidirectional patterns of excitation. Gain- and loss-of-function IKur mutations produced multiple mechanisms of atrial arrhythmogenesis, with significant differences between the two groups of mutations. This study provides new insights into understanding the mechanisms by which mutant IKur contributes to atrial arrhythmias. In addition, as IKur is an atrial-specific channel and a number of IKur-selective blockers have been developed as anti-AF agents, this study also helps to understand some contradictory results on both pro- and anti-arrhythmic effects of blocking IKur.

SUBMITTER: Colman MA

PROVIDER: S-EPMC5493429 | biostudies-literature | 2017 Jun

REPOSITORIES: biostudies-literature

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In silico assessment of genetic variation in KCNA5 reveals multiple mechanisms of human atrial arrhythmogenesis.

Colman Michael A MA Ni Haibo H Liang Bo B Schmitt Nicole N Zhang Henggui H

PLoS computational biology 20170616 6

A recent experimental study investigating patients with lone atrial fibrillation identified six novel mutations in the KCNA5 gene. The mutants exhibited both gain- and loss-of-function of the atrial specific ultra-rapid delayed rectifier K+ current, IKur. The aim of this study is to elucidate and quantify the functional impact of these KCNA5 mutations on atrial electrical activity. A multi-scale model of the human atria was updated to incorporate detailed experimental data on IKur from both wild ...[more]

PMID: 28622331

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Project description:Electrical, structural, and Ca2+ -handling remodeling contribute to the perpetuation/progression of atrial fibrillation (AF). Recent evidence has suggested a role for spontaneous sarcoplasmic reticulum Ca2+ -release events in long-standing persistent AF, but the occurrence and mechanisms of sarcoplasmic reticulum Ca2+ -release events in paroxysmal AF (pAF) are unknown.Right-atrial appendages from control sinus rhythm patients or patients with pAF (last episode a median of 10-20 days preoperatively) were analyzed with simultaneous measurements of [Ca2+]i (fluo-3-acetoxymethyl ester) and membrane currents/action potentials (patch-clamp) in isolated atrial cardiomyocytes, and Western blot. Action potential duration, L-type Ca2+ current, and Na+ /Ca2+ -exchange current were unaltered in pAF, indicating the absence of AF-induced electrical remodeling. In contrast, there were increases in SR Ca2+ leak and incidence of delayed after-depolarizations in pAF. Ca2+ -transient amplitude and sarcoplasmic reticulum Ca2+ load (caffeine-induced Ca2+ -transient amplitude, integrated Na+/Ca2+ -exchange current) were larger in pAF. Ca2+ -transient decay was faster in pAF, but the decay of caffeine-induced Ca2+ transients was unaltered, suggesting increased SERCA2a function. In agreement, phosphorylation (inactivation) of the SERCA2a-inhibitor protein phospholamban was increased in pAF. Ryanodine receptor fractional phosphorylation was unaltered in pAF, whereas ryanodine receptor expression and single-channel open probability were increased. A novel computational model of the human atrial cardiomyocyte indicated that both ryanodine receptor dysregulation and enhanced SERCA2a activity promote increased sarcoplasmic reticulum Ca2+ leak and sarcoplasmic reticulum Ca2+ -release events, causing delayed after-depolarizations/triggered activity in pAF.Increased diastolic sarcoplasmic reticulum Ca2+ leak and related delayed after-depolarizations/triggered activity promote cellular arrhythmogenesis in pAF patients. Biochemical, functional, and modeling studies point to a combination of increased sarcoplasmic reticulum Ca2+ load related to phospholamban hyperphosphorylation and ryanodine receptor dysregulation as underlying mechanisms.

Project description:ObjectiveTo investigate the correlation between KCNA5 single nucleotide polymorphism (SNP) and idiopathic atrial fibrillation (IAF).MethodsA case-control study was conducted, including 282 cases of IAF patients and 300 cases of age and sex-matched normal controls; gene sequencing method was used to detect the distribution of KCNA5 SNP (rs3741930 and rs1056468) in the two groups. The IAF patients were divided into two groups based on the different genotypes of rs1056468 and rs3741930; differences in clinical parameters between the two groups of patients were compared.ResultsFor rs3741930, the CC, CT and TT genotype frequencies in the IAF group were 16.7%, 50.0%, and 33.3% respectively; C allele frequency in IAF group was 41.7%; in the normal control group, those were 10.0%, 49.3%, 40.7% and 34.7% respectively; CC genotype frequency and C allele frequency in IAF group were significantly higher compared with the control group (P=0.019, P=0.014). For rs1056468, the AA, AT and TT genotype frequencies in the IAF group were 44.3%, 48.6%, and 7.1% respectively; in 300 cases of normal controls, those were 38.7%, 50.7%, and 10.6% respectively; A allele frequency in IAF group was 68.6 %, and it was 64.0% in normal controls. There were no significant differences in genotype and allele frequencies between control and IAF groups (P>0.05). In IAF group, among different genotypes of rs1741930 and rs1056468, there were no significant differences in age, SBP, DBP, HR, LAD and LVEF (P>0.05). While the BMI in CC and CC+TT groups of rs3741930 locus were 26.9±2.3 Kg/m(2) and 24.8±2.5 Kg/m(2) respectively. There were statistical differences between the two groups (P=0.019). BMI in AA and AA+TT groups of rs1056468 locus were 24.9±2.7 Kg/m(2) and 26.4±2.4 Kg/m(2) respectively; There was statistically significant significance between the two groups (P=0.014).ConclusionThe single nucleotide polymorphism rs3741930 locus in KCNA5 gene was related to the risk of IAF; the population carrying C allele was more susceptible to IAF; the polymorphic loci, rs3741930 and rs1056468, were correlated with the BMI of IAF patients.

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In silico assessment of genetic variation in KCNA5 reveals multiple mechanisms of human atrial arrhythmogenesis.

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In silico assessment of genetic variation in KCNA5 reveals multiple mechanisms of human atrial arrhythmogenesis.

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