Role of Potassium Channels in Fibrillatory Conduction

描述（由申请人提供）：这项工作的重点是原纤化的分子机制。它的动机是最近发现的两种不同的通道病与编码内向整流通道的KCNJ 2基因的功能获得性突变有关i）短QT综合征的变体SQTS 3，由增加心脏性猝死风险的突变（D172）引起;和ii）由KCNJ 2中的不同突变（V93 I）引起的新型家族性心房纤颤（AF）。我们的具体目标是：1。检验IK 1的外向成分在控制频率和负责纤颤的转子稳定性方面至关重要的假设。我们将使用计算机模拟的2D传播和实验在成年心脏和新生儿心肌细胞单层D172 N和V93 I突变小鼠，小鼠过表达野生型Kir2.1通道，和Kir2.1-AAA小鼠。我们还将确定改变[K+]o对折返和纤颤频率和稳定性的影响。人体心脏兴奋的模拟将帮助我们检查我们的结果的临床相关性。2.比较增加与减少IK 1在汇-源失配导致波破裂和再入机制中的作用。在单层中的模拟和实验将比较D172 N和V93 I突变与增加或减少Kir2.1通道的表达对兴奋性、曲率-速度关系和涡旋脱落的影响。我们将测试的假设，即Kir2.1的功能增益增加成功传播的临界曲率半径，从而波的入射，而功能损失具有相反的效果。3.确定空间梯度在野生型和突变型Kir2.1蛋白表达中的作用。我们假设IK 1密度梯度有助于不应性的分散，Kir2.1过表达放大了分散的致瘤效应。数值和生物学实验在野生型和基因改变的心肌细胞单层具有特定模式的IK 1密度分散将确定的作用Kir2.1通道梯度折返。此外，免疫组织化学，膜片钳和光学映射在成年人的心脏将确定是否Kir2.1梯度有助于在完整的小鼠心脏的波破碎和折返。总之，这些研究应该提供对SQTS 3和AF患者心律失常机制的见解，也可能在许多受特发性VF影响的患者中。

DESCRIPTION (provided by applicant): This work focuses on the molecular mechanisms of fibrillation. It is motivated by the recent discovery of two different channelopathies associated with gain-of-function mutations in the KCNJ2 gene that codes for the inward rectifier channel (Kir2.1) protein responsible for IK1: i) a variant of short QT syndrome, SQTS3, resulting from a mutation (D172) that increases risk of sudden cardiac death; and ii) a new type of familial atrial fibrillation (AF) that results from a different mutation (V93I) in KCNJ2. Our Specific Aims are: 1. To test the hypothesis that the outward component of IK1 is critical in controlling frequency and stability of rotors responsible for fibrillation. We will use computer simulations of 2D propagation and experiments in adult hearts and neonatal myocyte monolayers from D172N and V93I mutant mice, mice overexpressing wild-type Kir2.1 channels, and Kir2.1-AAA mice. We will also determine the effects of changing [K+]o on frequency and stability of reentry and fibrillation. Simulations of human cardiac excitation will help us check the clinical relevance of our results. 2. To compare the effects of increasing versus decreasing IK1 in the mechanism of sink-to-source mismatch leading to wavebreak and reentry. Simulations and experiments in monolayers will compare the effects of D172N and V93I mutations with those of increasing or decreasing the expression of Kir2.1 channels on excitability, curvature-velocity relationships and vortex-shedding. We will test the hypothesis that gain-of-function of Kir2.1 increases the critical radius of curvature for successful propagation and thus the incidence of wavebreaks, whereas loss-of function has the opposite effects. 3. To determine the role of spatial gradients in the expression of wildtype and mutant Kir2.1 proteins on wavebreak formation and reentry. We hypothesize that gradients in IK1 density contribute to dispersion of refractoriness, and Kir2.1 overexpression amplifies the arrhythmogenic effect of dispersion. Numerical and biological experiments in wildtype and genetically altered myocyte monolayers having specific patterns of IK1 density dispersion will ascertain the role of Kir2.1 channel gradients in reentry. Also, immunohistochemistry, patch clamping and optical mapping in adult hearts will determine whether Kir2.1 gradients contribute to wavebreak and reentry in the intact mouse heart. Altogether, these studies should provide insights into mechanisms of arrhythmias in SQTS3 and AF patients, and possibly also in many patients affected by idiopathic VF.