Investigating collective myocardial cell movement during heart tube formation

项目摘要 器官的形成受到组织间通讯的重要调控。成熟心灵的架构 是一系列形态发生事件的结果，从原始的心管开始， 心的其余部分建立的基础。建造原始心管的过程始于 随着心肌细胞从前侧板两侧位置的集体运动 中胚层到中线，这是一个在所有脊椎动物中保守的称为心脏融合的过程。遗传 分析表明，相邻的内胚层对于这些运动是至关重要的。然而，信号 或者内胚层与心肌层通讯的分子仍然是未知的。此外，委员会认为， 脊椎动物心肌细胞响应这些信号的分子机制， 集体向中线移动也知之甚少。为了阐明这些机制， 来自密西西比大学的本科生和研究生将参加一个多维度的 在组织、分子、细胞和生物力学水平上检查心脏融合的方法。我们有 发现血小板衍生生长因子受体α（Pdgfra）的突变导致心脏融合 斑马鱼和小鼠都存在缺陷。心肌运动似乎是对局部心肌收缩的反应， PDGF配体pdgf-aa的来源，我们发现其表达于内胚层内侧相邻的 PDGFRA在心肌中的表达。此外，我们的初步数据显示，PI3K的破坏 斑马鱼中的信号传导也导致心脏融合缺陷。心肌细胞会出现突起 并在心脏融合过程中显示细胞形状的异质性变化。这些数据表明， 假设来自内胚层的旁分泌PDGF信号激活Pdgfra介导的PI3K信号， 心肌以产生内侧定向的迁移突起，其产生不对称的生物力学 促进内侧运动的心肌张力。我们将用组织来检验这个假设- 特定的遗传技术来确定pdgfra和pdgf-aa功能的组织（目的1） 作为确定Pdgfra下游的PI3K信号传导和迁移突起是否被激活， （目标2）。此外，我们将使用微流变学和微激光烧蚀结合PDGFRA 突变体，以检查由PDGF信号传导控制的心肌中的生物力学特性（Aim 3）。总之，这些研究很可能阐明了 心肌细胞感知并响应其局部环境，并在长期内识别出 在发育和疾病中构成心脏形态发生基础的基本原则。 此外，该提案将有助于建立一个将学生研究交织在一起的研究项目 发现组织间的基本分子机制的机会 器官形态发生过程中的通讯。

Project Summary Organ formation is critically regulated by inter-tissue communication. The architecture of the mature heart is a result of sequential morphogenetic events, starting with the primitive heart tube, which is the foundation upon which the rest of the heart is built. The process of building the primitive heart tube starts with the collective movement of myocardial cells from bilateral locations in the anterior lateral plate mesoderm to the midline, a process called cardiac fusion which is conserved in all vertebrates. Genetic analysis has revealed that the adjacent endoderm is critical for these movements. However, the signals or molecules by which the endoderm communicates to the myocardium remain unknown. Furthermore, the molecular mechanism by which myocardial cells in vertebrates respond to these signals and collectively move towards the midline is also poorly understood. To elucidate these mechanisms, undergraduate and graduate students from the University of Mississippi will take a multi-dimensional approach examining cardiac fusion at the tissue, molecular, cellular and biomechanical level. We have found that mutations in the Platelet-derived growth factor receptor alpha (Pdgfra) leads to cardiac fusion defects in both zebrafish and mice. Myocardial movement appears to occur in response to a localized source of the PDGF ligand pdgf-aa, which we found is expressed in the endoderm medially adjacent to pdgfra expression in the myocardium. Furthermore, our preliminary data reveals that disruption of PI3K signaling in zebrafish also causes cardiac fusion defects. And that myocardial cells exhibit protrusions and display heterogenous changes in cell shape during cardiac fusion. Together, this data suggests the hypothesis that paracrine PDGF signals from the endoderm activates Pdgfra-mediated PI3K signaling in the myocardium to create medial oriented migratory protrusions which create asymmetric biomechanical tension in the myocardium facilitating medial movement. We will test this hypothesis by using tissue- specific genetic techniques to determine the tissues in which pdgfra and pdgf-aa function (Aim 1) as well as determine whether PI3K signaling and migratory protrusions are activated downstream of Pdgfra (Aim2). Additionally, we will use micro-rheology and micro-laser ablation in combination with pdgfra mutants to examine the biomechanical properties in the myocardium controlled by PDGF signaling (Aim 3). In summary, these studies are likely to elucidate the molecular mechanisms that underlie how myocardial cells sense and respond to their local environment and in the long-term identify the fundamental principles that underlie cardiac morphogenesis in both development and disease. Furthermore, this proposal will help to establish a research program that intertwines student research opportunities with the discovery of fundamental molecular mechanisms underlying inter-tissue communication during organ morphogenesis.