Drosophila as a model for epithelial tube formation

Abstract

Summary Epithelial tubular organs are essential for life in higher organisms and include the pancreas and other secretory organs that function as biological factories for the synthesis and delivery of secreted enzymes, hormones and nutrients essential for tissue homeostasis and viability. The lungs, which are necessary for gas exchange, vocalization and maintaining blood pH, are organized as highly branched tubular epithelia. Tubular organs include arteries, veins and lymphatics, high-speed passageways for delivery and uptake of nutrients, liquids, gases and immune cells. The kidneys and components of the reproductive system are also epithelial tubes. Both the heart and central nervous system of many vertebrates begin as epithelial tubes. Thus, it is not surprising that defects in tube formation and maintenance underlie many human diseases. Accordingly, a thorough understanding how tubes form and are maintained is essential to developing better diagnostics and therapeutics. Among the best-characterized tubular organs are the Drosophila salivary gland and trachea, organs whose relative simplicity have allowed for in depth analysis of gene function, yielding key mechanistic insight into tube initiation, remodeling and maintenance. Here, we review our current understanding of salivary gland and trachea formation – highlighting recent discoveries into how these organs attain their final form and function.

A cellular process that includes asymmetric cytokinesis remodels the dorsal tracheal branches in Drosophila larvae

“…We have previously studied how the coordinated action of cell signaling and cell migration leads to dorsal branch formation during embryogenesis [reviewed by Affolter and Caussinus (2008); Maruyama and Andrew (2012)]. Here, we investigate dorsal branch remodeling during larval development, a dynamic cellular process that includes mitosis, unlike the rearrangement of the embryonic dorsal branches.…”

Tubulogenesis

“…Less common are 'seamless' tubes with no cellular junctions in the circumference of the lumen. Examples of such seamless tubes include the sinusoidal blood vessels in the mammalian kidney (Bär et al, 1984), the C. elegans kidney cell (Buechner, 2002) and the Drosophila tracheal system (Maruyama and Andrew, 2012). Importantly, an organ can contain multiple tube types and junctional organizations (Buechner, 2002;Herwig et al, 2011;Lubarsky and Krasnow, 2003).…”

Cadherin 99C regulates apical expansion and cell rearrangement during epithelial tube elongation

“…the salivary gland, SG) or gas exchange (e.g. the trachea) (Maruyama and Andrew, 2012). These tubular organs form directly from already polarized ectodermal epithelia, which exhibit discrete subcellular localization of polarity complexes and other junctional proteins.…”

“…The SGs form from two primordia of ∼150 surface ectodermal cells found in the ventral region of parasegment two, the most posterior region of the head. Over a period of a few hours, the SG primordia invaginate, elongate and collectively migrate to form simple unbranched tubes (Maruyama and Andrew, 2012). The large cell size and simple structure, as well as the absence of cell division and cell death, make the Drosophila SG ideal for examining how changes in cell shape, adhesion and position affect tube morphology.…”