Atrioventricular Junction Development

房室交界区发育

• 批准号: 9750008
• 负责人: Takashi Mikawa
• 金额: $ 39.63万
• 依托单位: UNIVERSITY OF CALIFORNIA, SAN FRANCISCO
• 依托单位国家: 美国
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-08-01 至 2021-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9750008
• 关键词: Ablation; Action Potentials; Adolescent; Biological; Biological Models; Birds; Blood Vessels; Blood flow; Cardiac; Cardiac Jelly; Cardiac development; Cell Differentiation process; Cells; Characteristics; Coronary; Cues; Defect; Development; Developmental Process; Electrophysiology (science); Embryo; Endocardium; Endoderm; Excision; Feedback; Fibroblasts; Future; Gene Activation; Genetic Models; Heart; Heart Atrium; Heart Valves; Human; Image; In Vitro; Individual; Intercellular Junctions; Investigation; Lead; Life; Liquid substance; Maps; Mesoderm; Modeling; Molecular; Monitor; Movement; Muscle Cells; Myocardial; Myocardium; Optics; Pathway interactions; Pattern; Physiologic pulse; Physiological; Play; Population; Publishing; Role; Signal Transduction; Specific qualifier value; Stem cells; Syndrome; Technology; Testing; Time; Transgenic Organisms; Tube; Ventricular; base; cardiogenesis; cell fate specification; congenital heart disorder; design; heart function; in vivo; insight; intercellular communication; novel; paracrine; prevent; recruit; transcription factor

Project Summary The atrioventricular junction (AVJ) plays vital roles for cardiac development and function. The AVJ myocytes provide a morphogenetic and electrophysiological boundary between the atrium and ventricle, instruct endocardial cushion formation, and recruit extra cardiac coronary stem cells to the heart. Defects in AVJ conduction delay, cushion formation, and/or extra cardiac cell entry to the heart, can all be prevalent and life threatening components of several congenital heart syndromes in humans. However, despite more than a century of investigation, the mechanisms that induce and specify the AVJ fate and function remain poorly understood. The current dogma assumes that the AVJ myocytes arise from the primary heart field and uniquely maintain molecular and physiological features of primitive heart tube myocardium. It is also postulated that a feedback loop encompassing Bmp2 and the transcription factors Tbx2/3 maintain this juvenile myocardial state, thus specifies AVJ fate. Contrary to these models, our preliminary studies show that: (i) AVJ myocytes are not derived from either the primary or secondary heart field; (ii) Slow conducting AVJ myocytes display specific electrophysiological and molecular characteristics distinct from primitive heart tube myocytes; (iii) Direct exposure of the AVJ to endoderm-derived fast conducting fate inducers up-regulate Cx40 in the AVJ myocytes and eliminate AVJ delay without suppressing either Bmp2 or Tbx2/3 expression; (iv) The AVJ can be converted to fast conducting by removal of the cardiac jelly that separates the AVJ myocytes from the endocardium; and finally (iv) AVJ myocytes pattern a pulsatile Ca2+ wave through the proepicardium from which extra cardiac coronary stem cells arise. Based on these surprising findings, this application proposes to experimentally test the following novel models for AVJ development and function: (i) Identity of AVJ myocytes is established within the newly identified Nkx2.5/ Isl1-negative tertiary heart rather than the Nkx2.5/Ist1-positive primary and secondary heart fields; (ii) The Bmp2-Tbx2/3 signaling axis acts as a morphogenetic cue, rather than a myocyte-autonomous cell fate determinant for slow conducting zone formation at the AVJ; and (iii) AVJ myocytes spatially pattern a novel pulsatile intercellular communication between proepicardial cells via a Ca2+ wave during oriented extension towards the heart. Using in vivo and in vitro approaches, this proposal will provide the first insight into the origin of the AVJ and the previously unrecognized roles of AVJ myocardiumn for proper heart development and function.

项目摘要 房室连接（AVJ）在心脏发育和功能中扮演至关重要的作用。 AVJ心肌细胞 在中庭和心室之间提供形态发生和电生理边界，指导 心内膜垫形成，并将额外的心脏冠状动脉干细胞募集到心脏。 AVJ中的缺陷 传导延迟，坐垫形成和/或心脏的额外心脏细胞进入心脏，都可以普遍存在，生命 威胁人类几种先天性心脏综合征的组成部分。但是，尽管不仅仅是 世纪的调查，诱导和指定AVJ命运和功能的机制仍然很差 理解。 当前的教条假设AVJ肌细胞来自主要心脏场并独特地维护 原始心管心肌的分子和生理特征。还假定反馈 循环包含BMP2和转录因子TBX2/3保持这种少年心肌状态，因此 指定AVJ命运。 与这些模型相反，我们的初步研究表明：（i）AVJ肌细胞并非来自任何一个 初级或继发性心脏场； （ii）缓慢进行AVJ肌细胞显示特定的电生理学和 分子特征与原始心管肌细胞不同； （iii）直接暴露于AVJ 内胚层衍生的快速传导命运诱导者在AVJ肌细胞中上调CX40并消除AVJ 延迟而不抑制BMP2或TBX2/3表达； （iv）AVJ可以转换为快速导电 通过去除将AVJ心肌细胞与心内膜区分开的心脏果冻；最后（iv）avj 心肌细胞模式通过胸膜膜的脉冲Ca2+波，从中额外的心脏冠状动脉茎 细胞出现。 基于这些令人惊讶的发现，该应用建议通过实验测试以下新型模型 对于AVJ的开发和功能：（i）在新确定的NKX2.5/中建立了AVJ肌细胞的身份 ISL1阴性三级心脏而不是NKX2.5/IST1阳性原发性和次要心脏场； （ii） BMP2-TBX2/3信号轴充当形态发生的提示，而不是心肌自主细胞命运 在AVJ处慢速导电区形成的决定因素； （iii）AVJ肌细胞在空间上模板 在定向延伸期间，通过CA2+波之间的脉冲性心膜细胞之间的脉冲间交流 朝向心脏。 使用体内和体外方法，该建议将为AVJ的起源提供首次见解 AVJ Mycardiumn先前无法识别的作用在适当的心脏发育和功能方面。