Many organs including the mammalian lung and vascular system consist of branched tubular networks that transport essential gases or fluids, but the genetic programs that control the development of these complex three-dimensional structures are not well understood. The Drosophila melanogaster tracheal (respiratory) system is a network of interconnected epithelial tubes that transports oxygen and other gases in the body and provides a paradigm of branching morphogenesis. It develops by sequential sprouting of primary, secondary, and terminal branches from an epithelial sac of approximately 80 cells in each body segment of the embryo. Mapping of the cell movements and shape changes during the sprouting process has revealed that distinct mechanisms of epithelial migration and tube formation are used at each stage of branching. Genetic dissection of the process has identified a general program in which a fibroblast growth factor (FGF) and fibroblast growth factor receptor (FGFR) are used repeatedly to control branch budding and outgrowth. At each stage of branching, the mechanisms controlling FGF expression and the downstream signal transduction pathway change, altering the pattern and structure of the branches that form. During terminal branching, FGF expression is regulated by hypoxia, ensuring that tracheal structure matches cellular oxygen need. A branch diversification program operates in parallel to the general budding program: Regional signals locally modify the general program, conferring specific structural features and other properties on individual branches, such as their substrate outgrowth preferences, differences in tube size and shape, and the ability to fuse to other branches to interconnect the network.

中文翻译：

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果蝇气管系统的分支形态发生。

许多器官，包括哺乳动物的肺和血管系统，都由分支管网组成，这些管网输送必需的气体或流体，但是控制这些复杂的三维结构发展的遗传程序尚不清楚。果蝇黑腹气管（呼吸）系统是相互连接的上皮管网络，可在体内输送氧气和其他气体，并提供分支形态发生的范例。它通过在胚胎的每个身体部分中从大约80个细胞的上皮囊中依次萌发初级，次级和末端分支而发育。在萌芽过程中细胞运动和形状变化的图谱揭示了在分支的每个阶段都使用了上皮迁移和管形成的独特机制。该过程的遗传解剖学已经确定了一个通用程序，其中反复使用成纤维细胞生长因子（FGF）和成纤维细胞生长因子受体（FGFR）来控制分支的出芽和生长。在分支的每个阶段，控制FGF表达和下游信号转导途径的机制都会改变，从而改变所形成分支的模式和结构。在末端分支过程中，FGF的表达受到缺氧的调节，从而确保气管结构与细胞需氧量相匹配。分支机构的多样化计划与一般的萌芽计划同时进行：区域性信号在本地修改一般程序，赋予个别分支机构特定的结构特征和其他属性，例如其基质生长偏好，管子尺寸和形状的差异，