Branching Morphogenesis of theDrosophilaTracheal System

Abstract

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.

Tracheal branching morphogenesis inDrosophila: new insights into cell behaviour and organ architecture

“…In Drosophila melanogaster, genetic studies have provided much insight into the regulatory networks that regulate the ordered formation of tracheal branches in the embryo, and into how the different branches coordinate their relative sizes, an issue that is of importance to the physical aspects of branched organ function (Affolter et al, 2003;Ghabrial et al, 2003;Uv et al, 2003). More recently, the development of live-imaging approaches in Drosophila have allowed researchers to take a deeper look at the behaviour of cells during the branching process, and have enabled events at the molecular level to be linked to the behaviour of individual cells or groups of cells.…”

Candidate regulators of mammary branching morphogenesis identified by genome‐wide transcript analysis

“…The development of the ductal network takes places through branching morphogenesis, a process by which a rudimentary ductal structure initiates, extends, bifurcates, and differentiates to give rise to the mature tubular organ (Affolter et al, 2003;Ghabrial et al, 2003). The iterative nature of ductal morphogenesis allows a large epithelial surface area to be generated in limited space, which is essential because these organs function in air/ fluid exchange and secretion.…”

Quantitative Genetic Analysis of Sleep inDrosophila melanogaster

“…escargot encodes a zinc-finger protein with a role in the fusion of tracheal tubes (Zelzer and Shilo 2000;Ghabrial et al 2003) and PNS development (Norga et al 2003). Line BG02419, which has the P-element insertion 1 kb from the 59-end of escargot, had significantly reduced sleep in both males and females (Table 3).…”