Abstract
Most organs of multicellular organisms are built from epithelial tubes. To exert their functions, tubes rely on apico-basal polarity, on junctions, which form a barrier to separate the inside from the outside, and on a proper lumen, required for gas or liquid transport. Here we identify apnoia (apn), a novel Drosophila gene required for tracheal tube elongation and lumen stability at larval stages. Larvae lacking Apn show abnormal tracheal inflation and twisted airway tubes, but no obvious defects in early steps of tracheal maturation. apn encodes a transmembrane protein, primarily expressed in the tracheae, which exerts its function by controlling the localization of Crumbs (Crb), an evolutionarily conserved apical determinant. Apn physically interacts with Crb to control its localization and maintenance at the apical membrane of developing airways. In apn mutant tracheal cells, Crb fails to localize apically and is trapped in retromer-positive vesicles. Consistent with the role of Crb in apical membrane growth, RNAi-mediated knockdown of Crb results in decreased apical surface growth of tracheal cells and impaired axial elongation of the dorsal trunk. We conclude that Apn is a novel regulator of tracheal tube expansion in larval tracheae, the function of which is mediated by Crb.
Highlights
Animal organs consist of epithelial tissues, which form the boundaries between internal and external environment [1,2,3]
Tubular organs, such as the fruitfly airways, comprise essential functional pipes through which gas and liquid are transported. They consist of highly polarized epithelial cells that form a barrier between air and the larval body
In this work we have discovered a new gene called apnoia, which is important for tracheal growth and inflation at larval stages
Summary
Animal organs consist of epithelial tissues, which form the boundaries between internal and external environment [1,2,3]. A fundamental feature of epithelial tubes and sheets is to keep the balance between the maintenance of structural integrity and tissue rigidity during organ growth and morphogenesis To understand how this balance is achieved during rapid, temporally regulated developmental transitions from juvenile to adult body shapes, several studies in various animal models have focused on elucidating how cell proliferation, cell polarity, cell shape changes and trafficking contribute to the formation of the tubular lumen length and diameter [4,5,6,7]. The correct coordination of these processes is crucial for normal organ function This is reflected in the fact that several human diseases are linked to defects in epithelial tube formation and maintenance, such as polycystic kidney disease or cystic fibrosis [8,9,10,11]
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