PDF(Pubmed)
Abstract：
Genetic testing is crucial in inherited arrhythmogenic channelopathies; however, the clinical interpretation of genetic variants remains challenging. Incomplete penetrance, oligogenic, polygenic or multifactorial forms of channelopathies further complicate variant interpretation. We identified the KCNQ1/p.D446E variant in 2/63 patients with long QT syndrome, 30-fold more frequent than in public databases. We thus characterized the biophysical phenotypes of wildtype and mutant IKs co-expressing these alleles with the β-subunit minK in HEK293 cells. KCNQ1 p.446E homozygosity significantly shifted IKs voltage dependence to hyperpolarizing potentials in basal conditions (gain of function) but failed to shift voltage dependence to hyperpolarizing potentials (loss of function) in the presence of 8Br-cAMP, a protein kinase A activator. Basal IKs activation kinetics did not differ among genotypes, but in response to 8Br-cAMP, IKs 446 E/E (homozygous) activation kinetics were slower at the most positive potentials. Protein modeling predicted a slower transition of the 446E Kv7.1 tetrameric channel to the stabilized open state. In conclusion, biophysical and modelling evidence shows that the KCNQ1 p.D446E variant has complex functional consequences including both gain and loss of function, suggesting a contribution to the pathogenesis of arrhythmogenic phenotypes as a functional risk allele.
摘要：
基因检测对遗传性心律失常性信道病至关重要；然而，遗传变异的临床解释仍然具有挑战性.不完全外显率,寡基因,多基因或多因素形式的信道病进一步使变体解释复杂化。我们确定了KCNQ1/p。D446E变异在2/63例长QT综合征患者中，比公共数据库更频繁30倍。因此,我们表征了在HEK293细胞中与β亚基minK共表达这些等位基因的野生型和突变型IKs的生物物理表型。KCNQ1p.446E纯合性在基础条件下显着将IKs电压依赖性转移到超极化电位（功能获得），但在8Br-cAMP存在下未能将电压依赖性转移到超极化电位（功能丧失），蛋白激酶A激活剂。基础IKs激活动力学在基因型之间没有差异，但是为了回应8Br-cAMP，IKs446E/E(纯合)激活动力学在最正电位下较慢。蛋白质建模预测446EKv7.1四聚体通道向稳定的开放状态的转变较慢。总之,生物物理和建模证据表明，KCNQ1p.D446E变体具有复杂的功能后果，包括功能的获得和丧失，提示作为功能性风险等位基因对心律失常表型的发病机理有贡献。
