Modulating Morphogenesis: Genetic Regulation of Cardiac Cell Movement in Zebrafish

项目总结 器官发生依赖于集体细胞运动的仔细协调调节，在这个过程中，一群 细胞作为一个有凝聚力的实体运作，协调它们各自的轨迹，以到达共同的目的地。 例如，心脏发生在形态发生的多个阶段使用集体细胞运动， 包括心管的组装、小梁的突出和隔膜的构造。尽管 这些形态发生过程的重要性，我们还不清楚 管理发育中心脏的集体细胞行为。特别是，控制时间和路线的线索 心脏细胞的运动在很大程度上仍然是个谜。 在这里，我们的目标是破译在心脏导管过程中控制集体细胞运动的遗传途径。 在斑马鱼胚胎中组装。为了建造心管，两侧的心肌细胞群向 中线并通过一种称为心脏融合的过程进行合并。我们之前的研究已经提出了一个模型，在这个模型中 心肌、内胚层和细胞外基质(ECM)之间的相互作用促进心脏融合。 然而，对这些组织水平相互作用的阐明并没有回答关于 驱动细胞行为的分子机制。值得注意的是，我们还不知道哪些信号决定了方向 心肌细胞的运动轨迹或哪些线索控制心肌细胞的运动速度。因此，这是令人兴奋的 我们将研究两种新型的心肌细胞运动调节剂--血小板衍生生长因子 受体PDGFRA和跨膜蛋白Tem2-，准备解决这些悬而未决的问题。 首先，验证位于中间位置的PDGF配体在心肌细胞中激活PDGFRA从而激活PDGFRA的假设 控制心肌细胞运动的方向，我们将(A)使用延时分析来确定影响 PDGFRA对心肌细胞行为的影响，(B)使用组织特异性转基因来确定PDGFRA在哪里起作用 影响心脏融合，(C)测试PDGF配体是否作为心肌运动的方向性信号，(D) 确定在这种情况下作用于PDGFRA下游的效应器通路，以及(E)评估PDGFRA是否在 在小鼠心脏融合中的类似作用。其次，为了检验Tem2胞外区的假设 通过调节ECM来促进有效的心肌运动速度，我们将(A)采用延时 分析以确定tMem2对心肌细胞行为的影响，(B)确定tem2是否具有 对心肌运动的非自主影响，(C)测试Tem2是否通过以下方式调节心脏融合 调节ECM，以及(D)利用结构功能和蛋白质组学分析来确定 Tem2是其功能所必需的，以及哪些蛋白质与这些结构域相互作用。 总之，这些研究将揭示心管组装的基本机制，揭示 集体心脏细胞运动的调节，揭示了先天性心脏病的起源，以及 促进未来用于心脏修复的组织工程方法。

PROJECT SUMMARY Organogenesis relies upon the carefully coordinated regulation of collective cell movement, in which a group of cells operate as a cohesive entity, coordinating their individual trajectories to reach a common destination. Cardiogenesis, for example, employs collective cell movement during multiple phases of morphogenesis, including the assembly of the heart tube, the protrusion of trabeculae, and the construction of septae. Despite the importance of these morphogenetic processes, we do not yet understand the molecular mechanisms that govern collective cell behavior in the developing heart. In particular, the cues that control the timing and routes of cardiac cell movement remain largely mysterious. Here, we aim to decipher the genetic pathways that control collective cell movement during heart tube assembly in the zebrafish embryo. To build the heart tube, bilateral groups of cardiomyocytes move toward the midline and merge through a process called cardiac fusion. Our prior studies have suggested a model in which interactions between the myocardium, endoderm, and extracellular matrix (ECM) act to facilitate cardiac fusion. However, the elucidation of these tissue-level interactions has not answered key open questions regarding the molecular mechanisms that drive cell behavior. Notably, we do not yet know which signals dictate the direction of cardiomyocyte trajectories or which cues control the rate of cardiomyocyte mobility. It is therefore exciting that we will investigate two novel regulators of cardiomyocyte movement – the platelet-derived growth factor receptor Pdgfra and the transmembrane protein Tmem2 – that are poised to address these unresolved issues. First, to test the hypothesis that medially-located PDGF ligands activate Pdgfra in cardiomyocytes and thereby control the direction of cardiomyocyte movement, we will (a) employ time-lapse analysis to pinpoint the impact of pdgfra on myocardial cell behavior, (b) use tissue-specific transgenes to determine where pdgfra acts to influence cardiac fusion, (c) test whether PDGF ligands act as directional cues for myocardial movement, (d) identify effector pathways acting downstream of Pdgfra in this context, and (e) evaluate whether Pdgfra plays a comparable role during cardiac fusion in mouse. Second, to test the hypothesis that the Tmem2 ectodomain facilitates an efficient rate of myocardial motility through modulation of the ECM, we will (a) employ time-lapse analysis to determine the influence of tmem2 on myocardial cell behavior, (b) determine whether tmem2 has a non-autonomous effect on myocardial movement, (c) test whether Tmem2 regulates cardiac fusion by modulating the ECM, and (d) utilize structure-function and proteomic analyses to identify which domains of Tmem2 are required for its function and which proteins interact with these domains. Together, these studies will reveal essential mechanisms of heart tube assembly, uncover new paradigms for the regulation of collective cardiac cell movement, shed light on the origins of congenital heart disease, and facilitate future tissue engineering approaches for cardiac repair.