Molecular determinants of the cardiac pacemaker automaticity

心脏起搏器自动性的分子决定因素

• 批准号: 8373469
• 负责人: Hee Cheol Cho
• 金额: $ 41.75万
• 依托单位: CEDARS-SINAI MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-07-03 至 2017-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8373469
• 关键词: Adult; Affect; Aging; Architecture; Arrhythmia; Artificial cardiac pacemaker; Biological Pacemakers; Boxing; Cardiac Myocytes; Cell Culture System; Cells; Clinical; Communication; Congenital Heart Defects; Data; Development; Devices; Disease; Drug Formulations; Electronics; Electrophysiology (science); Embryonic Development; Engineering; Gap Junctions; Gene Expression Regulation; Gene Targeting; Generations; Genes; Gold; Heart; Heart Block; In Vitro; Ion Channel; Knowledge; Lead; Link; Mediating; Modeling; Modification; Molecular; Morphogenesis; Muscle Cells; Myocardium; Neonatal; Nodal; North America; Outcome; Pacemakers; Pathologic; Pathway interactions; Phenotype; Physiology; Rattus; Regulation; Regulator Genes; Regulatory Pathway; Relative (related person); Shapes; Signal Transduction; Signaling Molecule; Sinoatrial Node; Small Interfering RNA; Somatic Cell; Source; Specific qualifier value; Structure; System; Testing; Tissues; Transcription factor genes; Transcriptional Regulation; Ventricular; base; cellular transduction; design; electronic pacemaker; genome wide association study; heart rhythm; in vivo; innovation; insight; knockout gene; monolayer; nodal myocyte; novel; overexpression; postnatal; programs; research study; three dimensional structure; tool; transcription factor; voltage

DESCRIPTION (provided by applicant): The sinoatrial node (SA node or SAN) is a finely-tuned structure that initiates and sets the rhythm of the heartbeat. Recent insights into embryonic development have pinpointed T-box (Tbx) transcription factors as key determinants of SA node development. Tbx18, in particular, has been shown to be indispensable for the specification of the SA node during development. However, little is known about Tbx-driven gene regulatory pathways which specify morphogenesis of the SA node, and how these pathways lead to automaticity in pacemaker cells. We seek to test the general hypothesis that re-expression of Tbx18 suffices to reprogram postnatal cardiomyocytes to pacemaker cells. We propose to reveal Tbx18-dictated gene regulatory pathways that give rise to de novo automaticity. In parallel, we will characterize the changes in electrophysiological pathways which confer automaticity on normally-quiescent ventricular myocytes, and compare the reprogrammed mechanisms of pacing to those which are operative in native SA nodal myocytes, as the gold standard for genuine pacemaker cells. The main impediment to understanding the gene regulatory pathways to automaticity is a lack of a system to study specific targets of SA nodal transcriptional regulatory pathways. This is because the rapid temporal and spatial changes during embryonic development make it difficult to study specific targets of transcriptional regulation. In contrast, our proposed studies in postnatal cardiomyocytes offer a milieu for relatively slow-changing (neonatal) or steady-state (adult) electrophysiology. AIMs 2 and 3 are designed to gain insights into the Tbx18-reprogrammed automaticity in single-cell, two-cell pacing unit, 2D monolayers, and 3D structures. Our cell culture systems could readily be applied for other transcription factor- or disease-mediated studies of cellular electrophysiology. Three scientific innovations are imminent from this study. One, data from AIMs 1 and 2 will provide insights into molecular determinants of automaticity as quiescent myocytes begin to beat spontaneously and autonomously upon Tbx18 re-expression. Two, outcomes of AIM 3 will provide important insights into the source-sink mismatch phenomenon in SAN physiology. Three, at the conclusion of the proposed studies, a candidate for a biological pacemaker could be identified as an alternative to electronic pacemaker devices. Furthermore, Genome wide association studies (GWAS) have identified and linked T-box transcription factor genes with congenital heart defects and conduction system abnormalities. Dysregulation of Tbx18-guided pathways may cause improper morphogenesis of conduction system and may lead to arrhythmias. Knowledge gained from AIMs 1, 2, and 3 will provide the first cause-effect explanations for clinical manifestations of these arrhythmias. PUBLIC HEALTH RELEVANCE: Abnormally slow or fast heart rhythms, known as cardiac arrhythmias, affect many in North America and the number of people affected by this disease is increasing steadily with our aging populace. A key to treating these pathologic conditions is a fundamental understanding of the cardiac rhythm generation. We propose a detailed mechanistic study to investigate the initiation and propagation of a heartbeat, which will lead to better understanding and treatment of cardiac arrhythmias.

描述(申请人提供)：窦房结(窦房结或窦房结)是一个微调的结构，启动和设定心跳的节奏。最近对胚胎发育的研究表明，T-box(TBX)转录因子是SA节点发育的关键决定因素。特别是，已经证明，在开发过程中，对于SA节点的规范而言，TBX18是不可或缺的。然而，关于TBX驱动的基因调控通路指定SA结节的形态发生，以及这些通路如何导致起搏细胞的自律性，人们知之甚少。我们试图验证这样的普遍假设，即重新表达TBX18足以将出生后的心肌细胞重新编程为起搏细胞。我们建议揭示由TBX18决定的基因调控途径，这些途径导致从头开始的自律性。同时，我们将描述赋予正常静止的心室肌细胞自律性的电生理通路的变化，并将起搏的重新编程机制与在天然SA结节肌细胞中操作的机制进行比较，以此作为真正起搏细胞的金标准。理解自动化的基因调控途径的主要障碍是缺乏一个系统来研究SA节点转录调控途径的特定靶标。这是因为胚胎发育过程中时间和空间的快速变化，使得研究转录调控的特定靶点变得困难。相反，我们提出的对出生后心肌细胞的研究为相对缓慢变化(新生儿)或稳定状态(成人)的电生理学提供了环境。AIMS 2和3旨在深入了解TBX18-在单细胞、两细胞起搏单元、2D单层和3D结构中的重新编程自动化。我们的细胞培养系统可以很容易地应用于其他转录因子或疾病介导的细胞电生理学研究。这项研究即将进行三项科学创新。其一，来自AIMS 1和2的数据将为静止的心肌细胞在TBX18重新表达后开始自发和自主跳动的分子决定因素提供洞察力。第二，AIM 3的结果将对SAN生理学中的源-汇失配现象提供重要的见解。第三，在拟议的研究结束时，可以确定生物起搏器的候选者作为电子起搏器设备的替代品。此外，基因组广泛关联研究(GWAS)已经发现T-box转录因子基因与先天性心脏病和传导系统异常有关。TBX18引导通路的失调可能导致传导系统的形态发生异常，并可能导致心律失常。从目标1、目标2和目标3获得的知识将为这些心律失常的临床表现提供第一个因果解释。 公共卫生相关性：异常缓慢或快速的心律失常，称为心律失常，影响着北美的许多人，而且随着人口老龄化，受这种疾病影响的人数正在稳步增加。治疗这些病理情况的关键是对心律的产生有一个基本的了解。我们建议进行详细的机制研究来研究心跳的启动和传播，这将导致对心律失常的更好的理解和治疗。