Cardiac Pacemaker Development

描述（由申请人提供）：窦房结的心脏起搏细胞对于产生节律性心跳至关重要。尽管这种特殊的心脏细胞类型的重要性，很少有人知道他们的个体发育或规范和分化的机制。我们的初步数据显示，虽然主心管最初显示有节奏的跳动，起搏它的细胞不分化成窦房结。相反，起搏器前体产生于已知心源性场后面的中胚层，并在心脏循环期间接管起搏功能。令人惊讶的是，起搏器前体中胚层可以在没有任何其他周围胚胎组织的培养中分化。它们表现出持续的节律性搏动率，以及对起搏细胞特异性离子通道阻滞剂的敏感性。此外，它们还具有调节其他心肌细胞群的能力。我们的全球RNA分析已经确定了一组独特的Wnt相关基因在起搏器前体中表达。这些有些令人惊讶的发现导致了三个中心假设：（1）起搏器前体来自与心脏领域分开的特定中胚层群体;（2）起搏器细胞命运在心管形成之前被诱导;和（3）Wnt相关信号传导，其对心脏领域具有抑制作用，在起搏器细胞特化期间充当促进信号。我们将用实验来检验这些假设。这一提议将为鉴定起搏器前体的胚胎起源（目标1）、特定中胚层亚群进入起搏器细胞命运的能力（目标2）以及在短暂的时间窗期间和胚胎中的确定位点指定和指导这种重要细胞类型分化的新分子机制（目标3）提供第一个基础。 公共卫生相关性：心脏起搏器对心脏功能和生存至关重要。有效治疗方法的选择有限，导致了冠心病的持续流行。这项拟议的研究将探索调节导致这种重要心脏组织产生的最早发育步骤的分子机制，并可能为未来的治疗方法提供基础。

DESCRIPTION (provided by applicant): Cardiac pacemaker cells of the Sinoatrial Node are essential for producing rhythmic heartbeats. Despite the importance of this specialized cardiac cell type, little is known about their ontogeny or mechanisms of specification and differentiation. Our preliminary data show that although the primary heart tube initially displays rhythmic beating, the cells pacing it do not differentiate into the Sinoatrial Node. Instead, pacemaker precursors arise from the mesoderm posterior to the known cardiogenic field and take over the pacing function during heart-looping. Surprisingly, the pacemaker precursor mesoderm can differentiate in culture without any other surrounding embryonic tissues. They display sustained rhythmic beat rates, and sensitivity to pacemaker cell specific ion channel blockers. Furthermore, they have the ability to pace other cardiomyocyte populations. Our global RNA profiling has identified a unique set of Wnt-related genes expressed in pacemaker precursors. These somewhat surprising findings lead to three central hypotheses: (1) the pacemaker precursors arise from a specific mesoderm population separate from the heart field; (2) pacemaker cell fate is induced prior to heart tube formation; and (3) Wnt-related signaling, which is inhibitory to the heart field, acts as a promoting signal during pacemaker cell specification. We will test these hypotheses experimentally. This proposal will provide the first basis for identifying the embryonic origin of pacemaker precursors (Aim 1), the ability of a specific mesoderm subpopulations to enter the pacemaker cell fate (Aim 2), and novel molecular mechanisms that specify and direct the differentiation this important cell type during a brief temporal window and at a defined site in the embryo (Aim 3). PUBLIC HEALTH RELEVANCE: The cardiac pacemaker is essential for cardiac function and survival. Limited options of effective treatments contribute to the continued prevalence of arrhythmic heart disease. The proposed study will explore the molecular mechanisms that regulate the earliest developmental steps leading to the generation of this essential cardiac tissue and may provide a basis for future therapeutic approaches.