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Abstract：
Branching morphogenesis and seamless tube formation in Drosophila melanogaster are essential for the development of vascular and tracheal systems, and instructive in studying complex branched structures such as human organs. Zipper is a myosin II\'s actin-binding heavy chain; hence, it is important for contracting actin, cell proliferation, and cell sheet adhesion for branching of the tracheal system in post-larval development of the D. melanogaster. Nevertheless, the specific role of Zipper in the larva is still in question. This paper intended to investigate the specific role of Zipper in branching morphogenesis and lumenogenesis in early developmental stages. It did so by checking the localization of the protein in the cytoplasm of the terminal cells and also by analyzing the morphology of zipper RNAi loss-of-function mutants in regard to branching and lumen formation in the terminal cells. A rescue experiment of RNAi mutants was also performed to check the sufficiency of Zipper in branching morphogenesis. Confocal imaging showed the localization of Zipper in the cytoplasm of the terminal cells, and respective quantitative analyses demonstrated that zipper RNAi terminal cells develop significantly fewer branches. Such a result hinted that Zipper is required for the regulation of branching in the terminal cells of D. melanogaster. Nevertheless, Zipper is not significantly involved in the formation of seamless tubes. One hypothesis is that Zipper\'s contractility at the lateral epidermis\' leading edge allows cell sheet movement and respective elongation; as a result of such an elongation, further branching may occur in the elongated region of the cell, hence defining branching morphogenesis in the terminal cells of the tracheal system.
摘要：
果蝇的分支形态发生和无缝管形成对于血管和气管系统的发育至关重要，对研究复杂的分支结构如人体器官具有指导意义。拉链是肌球蛋白II的肌动蛋白结合重链；因此，这对收缩肌动蛋白很重要，细胞增殖，和细胞片粘附在D.melanogaster幼虫发育中气管系统的分支。然而，拉链在幼虫中的具体作用仍然存在疑问。本文旨在研究拉链在早期发育阶段的分支形态发生和腔形成中的特定作用。通过检查蛋白质在末端细胞的细胞质中的定位以及通过分析拉链RNAi功能丧失突变体在末端细胞中的分支和管腔形成方面的形态来做到这一点。还进行了RNAi突变体的拯救实验以检查Zipper在分枝形态发生中的充分性。共聚焦成像显示拉链在末端细胞的细胞质中的定位，和各自的定量分析表明，拉链RNAi末端细胞产生的分支明显减少。这样的结果表明，拉链是调节黑腹D的末端细胞中的分支所必需的。然而，拉链不显著参与无缝管的形成。一种假设是，拉链在外侧表皮前缘的收缩性允许细胞片移动和各自的伸长；由于这种伸长，进一步的分支可能发生在细胞的细长区域，因此定义了气管系统末端细胞的分支形态发生。
