Cardiac Pacemaker Development

项目摘要/摘要 窦房结的心脏起搏细胞对于产生有节奏的心跳是必不可少的。尽管 这种特殊的心脏细胞类型的重要性，对它们的个体发育或机制知之甚少。 规范和差异化。 我们的初步数据显示，尽管初级心管最初表现出有节奏的跳动，但细胞 起搏不能分化为窦房结。相反，起搏器前体来自中胚层。 在已知的心源场之后，并在心跳时接管起搏功能。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的情况下在培养中分化 纸巾。它们表现出持续的有节奏的搏动频率，以及对起搏细胞特有的离子通道的敏感性 拦截者。此外，它们还具有控制其他心肌细胞群的能力。我们的全球核糖核酸图谱 已经确定了一组在起搏器前体中表达的独特的Wnt相关基因。 这些有些令人惊讶的发现导致了三个中心假设：(1)起搏器前体产生于 特定的中胚层群体与心场分离；(2)起搏细胞的命运先于心脏被诱导。 管状结构的形成；(3)Wnt相关信号对心电活动有抑制作用，起促进作用 在起搏器细胞规范期间。我们将通过实验来检验这些假设。 这一提议将为确定起搏器前体的胚胎起源(目标1)提供第一个基础， 特定中胚层亚群进入起搏细胞命运的能力(目标2)，以及新的分子 在短暂的时间窗口中指定和指导这种重要细胞类型的分化的机制 以及在胚胎中的特定位置(目标3)。

Project Summary/Abstract 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).