Cellular Mechanisms of Cardiac Trabeculae Formation

描述（由申请方提供）：本研究的总体目的是检查小梁形成过程中心肌细胞定向迁移的细胞机制。结构畸形是导致先天性心脏病的主要因素。影响心室小梁形成的情况，无论是小梁形成不足还是小梁形成过度（如左心室致密化不全），都会导致心脏功能不良和临床结局不良。心脏小梁是心肌细胞（CM）脊，其突出到内衬有内皮细胞的心脏内腔中。它们有助于心脏传导系统和乳头肌;因此它们对心脏功能不可或缺。定向细胞迀移 是心脏小梁形态发生的主要因素。虽然先前的研究已经确定了促进小梁形成的信号通路，但CM向心室腔迁移以形成小梁的潜在细胞机制仍然难以捉摸。我们最近产生的遗传工具，以检查平面细胞极性途径（PCP），一个已知的途径，促进定向细胞迁移，在斑马鱼心脏小梁形成的作用。我们的指导性假设是CM通过定向延伸它们的板状伪足向心室腔迁移。此外，neuregulin-ErbB 2和PCP途径协同作用，调节迁移CM中板状伪足的形成和定向，以促进小梁形成。为了验证我们的假设，我们提出：1）检查迁移的心肌细胞是否形成板状伪足以及板状伪足是否具有定向排列; 2）检查在小梁形成过程中介导心肌细胞定向迁移的分子机制; 3）检查神经调节蛋白-ErbB 2信号是否可能通过促进板状伪足形成而成为定向迁移的上游调节因子。将对发育中的斑马鱼心脏进行高分辨率的体内成像，以捕获促进小梁形成的细胞事件。将进行具有缺陷PCP信号传导的CM的克隆1分析，以检查PCP途径在通过定向其板状伪足来调节CM定向迁移中的作用。此外，神经调节蛋白-ErbB 2途径作为PCP途径的上游调节剂的潜在作用将通过使用药理学抑制剂的功能丧失研究来检查。了解心脏小梁形成的细胞机制将对明确心脏小梁形成畸形所致先天性心脏病的病因和潜在的治疗靶点产生深远的影响。

DESCRIPTION (provided by applicant): The overall objective of this proposed study is to examine the cellular mechanisms underlying directional cardiomyocyte migration during trabeculation. Structural malformation is a major contributing factor towards congenital heart diseases. Conditions that affect ventricular trabeculation, either by hypotrabeculation or hypertrabeculation (such as left ventricular noncompaction) result in poor cardiac function and poor clinical outcome. Cardiac trabeculae are cardiomyocyte (CM) ridges that protrude into the lumen of the heart lined with endocardial cells. They contribute to the cardiac conduction system and papillary muscles; thus they are indispensable for cardiac function. Directional cell migration is a major contributing factor to cardiac trabeculae morphogenesis. Although previous studies have identified signaling pathways that facilitate trabeculae formation, the underlying cellular mechanism by which the CMs migrate towards the ventricular lumen to form trabeculae remains elusive. We have recently generated genetic tools to examine the role of planar cell polarity pathway (PCP), a known pathway that facilitates directional cell migration, during cardiac trabeculation in the zebrafish. Our guiding hypothesis is that CMs migrate towards the ventricular lumen by directionally extending their lamellipodia. Furthermore, the neuregulin-ErbB2 and the PCP pathways work synergistically to regulate the formation and directional orientation of lamellipodia in migrating CMs to promote trabeculae formation. To test our hypothesis, we propose: 1) To examine whether migrating cardiomyocytes form lamellipodia and whether lamellipodia have directional alignment in vivo, 2) To examine the molecular mechanisms that mediate directional migration of cardiomyocytes during trabeculae formation, 3) To examine whether neuregulin-ErbB2 signaling may be an upstream regulator of directional migration by promoting lamellipodia formation. High resolution, in vivo imaging of the developing zebrafish heart will be carried out to capture the cellular events facilitating trabeculation. Clonl analysis of CMs with defective PCP signaling will be carried out to examine the role of the PCP pathway in regulating CM directional migration by orienting their lamellipodia. Furthermore, the potential role of neuregulin- ErbB2 pathway as an upstream regulator of the PCP pathway will be examined by loss of function studies using pharmacological inhibitors. Understanding the cellular mechanisms underlying cardiac trabeculation will have profound impact on identifying the etiology and potential therapeutic targets for congenital heart diseases caused by malformation of cardiac trabeculation.