Circadian clock regulation of myocardial ion channel expression and function

总结： 该提案的总体目标是：1）定义基因组和转录组机制， 心肌细胞时钟调节有助于心脏兴奋性的离子通道;和2）破坏心肌细胞的生物钟。 心肌细胞时钟将昼夜节律基因表达的变化与电生理特性联系起来 心房和心室的心肌细胞。这些成果将解决我们对以下问题的理解方面的重大差距： 心肌生物钟如何调节心脏关键离子通道的表达， 心脏时钟功能导致心律失常的脆弱性。 调节昼夜节律的机制，即分子钟，几乎存在于体内所有类型的细胞中。一 分子钟的关键功能是将一天中的时间与大规模转录程序联系起来， 迄今为止，我们的实验室已经使用了一种诱导型心肌细胞特异性小鼠模型来敲除 核心时钟基因Bmal 1（iCSΔ Bmal 1）。这些研究表明，心肌生物钟的破坏是 足以降低心室K+和Na+通道基因表达，破坏电流水平，破坏心脏 兴奋性，并增加心律失常的易感性。这些研究确立了心肌细胞在 时钟，独立于中央时钟，在调节不同家族的离子通道基因的表达 影响正常兴奋性所需的离子平衡。该项目的一个目标是利用大规模 基因组学和转录组学方法与我们的小鼠模型系统，以确定生物钟依赖 控制心房和心室组织中的时间基因表达。 为了解决异常的生物钟功能，我们的实验室使用了不同的生物钟中断模型，例如 作为慢性相位提前或时间限制喂养，以测试昼夜节律中断和心律失常之间的联系 小鼠模型的脆弱性。我们发现，干扰光照或进食时间线索足以 诱发正常小鼠心律病理改变，加速心脏性猝死， 心律失常易感性的遗传小鼠模型。这些研究支持了我们的假设，即白天的中断- 通过环境因素引起的夜间节律导致心肌生物钟功能改变， 包括修饰离子通道表达、心脏兴奋性和心律失常脆弱性。 本研究旨在验证以下假说：1）心房肌细胞的分子钟 而心室心肌细胞是指导日常染色质可及性和转录输出所必需的 包括关键离子通道和离子通道调节基因的表达。2)长期破坏 使用改变的进食时间的心肌细胞时钟足以引起心脏时钟的失调 导致心脏离子通道表达和电流失衡，导致兴奋性改变， 增加心律失常的脆弱性。

Summary: The overall objectives of this proposal are to 1) define the genomic and transcriptomic mechanisms by which the cardiomyocyte clock regulates ion channels that contribute to cardiac excitability; and 2) disrupt the cardiomyocyte clock to link changes in circadian-ordered gene expression with electrophysiological properties of atrial and ventricular cardiomyocytes. The outcomes will address significant gaps in our understanding for how the myocardial circadian clock regulates the expression of key cardiac ion channels and how abnormal cardiac clock function contributes to arrhythmia vulnerability. The mechanism regulating circadian timing, the molecular clock, exists in virtually all cell types in the body. A critical function of the molecular clock is to link time of day with a large-scale transcriptional program to support cellular homeostasis To date, our labs have used an inducible cardiomyocyte specific mouse model to knock out the core clock gene, Bmal1 (iCSΔBmal1). These studies showed that disruption of the myocardial clock is sufficient to decrease ventricular K+ and Na+ channel gene expression, disrupt current levels, disrupt cardiac excitability, and increase arrhythmia susceptibility. These studies establish a critical role for the cardiomyocyte clock, independent of the central clock, in regulating the expression of different families of ion channel genes that impact the ionic balance needed for normal excitability. One goal of this project is to utilize large scale genomic and transcriptomic approaches with our mouse model system to define the circadian clock dependent control of temporal gene expression in both atrial and ventricular tissues. To address abnormal circadian clock function, our lab has used different models of circadian disruption, such as chronic phase advance or time restricted feeding to test links between circadian disruption and arrhythmia vulnerability in mouse models. We have found that disrupting either light or feeding time cues is sufficient to induce pathological changes in cardiac rhythms in normal mice and to accelerate sudden cardiac death in a genetic mouse model of arrhythmia susceptibility. These studies support our premise that disruption of day- night rhythms through environmental factors leads to altered myocardial clock function with outcomes that include modified ion channel expression, cardiac excitability and arrhythmia vulnerability. The aims of this proposal are designed to test the following hypotheses: 1) The molecular clocks in both atrial and ventricular cardiomyocytes are necessary to direct daily chromatin accessibility and transcriptional output including expression of key ion channel and ion channel regulatory genes. 2) Chronic disruption of the cardiomyocyte clock using altered time of feeding is sufficient to cause dysregulation of the cardiac clock resulting in an imbalance in cardiac ion channel expression and currents leading to altered excitability and increased arrhythmia vulnerability.