Originally published as Genetics Published Articles Ahead of Print on January 26, 2009.

Genetics, Vol. 181, 1281-1290, April 2009, Copyright © 2009
doi:10.1534/genetics.108.099531

Drosophila convoluted/dALS Is an Essential Gene Required for Tracheal Tube Morphogenesis and Apical Matrix Organization

Lianna E. Swanson^*, Marcus Yu^*, Kevin S. Nelson^*, Patrick Laprise^,1, Ulrich Tepass and Greg J. Beitel^*,2

^* Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, Illinois 60208 and Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario M5S 3G5, Canada

² Corresponding author: Hogan Hall, Room 2-100, Northwestern University, Evanston, IL 60208.
E-mail: beitel{at}northwestern.edu

Insulin-like growth factors (IGFs) control cell and organism growth through evolutionarily conserved signaling pathways. The mammalian acid-labile subunit (ALS) is a secreted protein that complexes with IGFs to modulate their activity. Recent work has shown that a Drosophila homolog of ALS, dALS, can also complex with and modulate the activity of a Drosophila IGF. Here we report the first mutations in the gene encoding dALS. Unexpectedly, we find that these mutations are allelic to a previously described mutation in convoluted (conv), a gene required for epithelial morphogenesis. In conv mutants, the tubes of the Drosophila tracheal system become abnormally elongated without altering tracheal cell number. conv null mutations cause larval lethality, but do not disrupt several processes required for tracheal tube size control, including septate junction formation, deposition of a lumenal/apical extracellular matrix, and lumenal secretion of Vermiform and Serpentine, two putative matrix-modifying proteins. Clearance of lumenal matrix and subcellular localization of clathrin also appear normal in conv mutants. However, we show that Conv/dALS is required for the dynamic organization of the transient lumenal matrix and normal structure of the cuticle that lines the tracheal lumen. These and other data suggest that the Conv/dALS-dependent tube size control mechanism is distinct from other known processes involved in tracheal tube size regulation. Moreover, we present evidence indicating that Conv/dALS has a novel, IGF-signaling independent function in tracheal morphogenesis.

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Online ISSN: 1943-2361  Print ISSN: 0016-6731
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