Single cell analyzes of cell behavior In Drosophila tracheal morphogenesis

在动物形态发生过程中，细胞运动和黏附的协调对于组织的协调运动是必不可少的。果蝇的气管网络是由管状外胚层上皮细胞的分枝、迁移和融合形成的。气管尖端细胞位于每个将要融合的分支的末端。尖端细胞延伸丝状伪足以寻找靶点，然后将它们的细胞形状改变为无缝的环，以允许管腔通过。细胞黏附分子DE-钙粘附素是气管形成所必需的，并在接触部位聚集形成一个标志管腔进入部位的环，对融合是必不可少的。部分枝条顶端细胞中脱钙粘附素的表达依赖于蜗牛，这是一种在所有顶端细胞中表达的锌指基因。这种蜗牛突变体的尖端细胞无法相互粘连，继续通过延长长丝状伪足来寻找替代目标。我们提出的证据表明，蜗牛正向调节DE-钙粘素基因的转录，猎枪。DE-钙粘蛋白的过表达挽救了蜗牛突变体中一个融合点的缺陷，显示了DE-钙粘蛋白在靶标识别和鉴定蜗牛作为细胞黏附和运动的关键调节因子中的重要作用。这些研究证明，气管系统是研究细胞运动和形态发生过程中黏附的理想工具。为了便于研究活体动物的气管形成，我们开发了GFP表达载体，使我们能够观察活体胚胎中气管细胞的迁移。

Coordination of cell motility and adhesion is essential for concerted movement of tissues during animal morphogenesis. The Drosophila tracheal network is formed by branching, migration and fusion of tubular ectodermal epithelia. The tracheal tip cell is located at the end of each branch that are going to fuse. Tip cells extend filopodia to search for targets and later change their cell shape to that of a seamless ring to allow passage of lumen. The cell adhesion molecule DE-cadherin is required for tracheal formation, and accumulates at the site of contact to form a ring that marks the site of lumen entry, and is essential for the fusion. DE-cadherin expression in tip cells of a subset of branches is dependent on escargot, a zinc finger gene expressed in all tip cells. Such escargot mutant tip cells failed to adhere to each other and continued to search for alternative targets by extending long filopodia. We present evidence indicating escargot positively regulates transcription of the DE-cadherin gene, shotgun. Overexpression of DE-cadherin rescued the defect in one of the fusion points in escargot mutants, demonstrating an essential role of DE-cadherin in target recognition and identifying escargot as a key regulator of cell adhesion and motility in tracheal morphogenesis.These studies has proven that tracheal system is ideal for study of cell motility and adhesion during morphogenesis. To facilitate the study of tracheal formation in live animals, we have developed gfp expression vector that enabled us to observe tracheal cell migration in living embryos.