Cellular Mechanisms of Cardiac Trabeculae Formation

描述(由申请人提供)：这项拟议研究的总体目标是研究在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条件，无论是通过小梁减少还是过度小梁形成(如左心室致密化不全)，都会导致心功能不佳和临床结局不佳。心小梁是伸入心脏内腔的心肌细胞(CM)脊，内有心内膜细胞。它们有助于心脏传导系统和乳头肌；因此，它们对心脏功能是不可或缺的。定向细胞迁移 是心脏小梁形态发生的主要因素。尽管先前的研究已经确定了促进小梁形成的信号通路，但CMS向脑室腔迁移形成小梁的潜在细胞机制仍然不清楚。我们最近开发了基因工具来研究平面细胞极性途径(PCP)在斑马鱼心脏小梁形成过程中的作用，PCP是一种已知的促进细胞定向迁移的途径。我们的指导性假设是CMS通过定向延伸其片状脂膜而向脑室腔迁移。此外，NeuRegin-ErbB2和PCP途径协同作用，调节移行性CMS中片状脂膜的形成和定向，促进小梁形成。为了验证我们的假设，我们建议：1)检测迁移的心肌细胞是否形成板状脂，以及板状脂在体内是否具有定向排列；2)检测在小梁形成过程中介导心肌细胞定向迁移的分子机制；3)检测neuRegin-ErbB2信号是否可能通过促进板脂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活体成像，以捕捉促进小梁形成的细胞事件。我们将对PCP信号缺陷的CMS进行克隆分析，以研究PCP通路在调节CM定向迁移中的作用。此外，NeuRegin-ErbB2通路作为PCP通路上游调节因子的潜在作用将通过使用药理抑制剂的功能丧失研究来检验。了解心脏小梁形成的细胞机制将对确定心脏小梁畸形引起的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.