Originally published as Genetics Published Articles Ahead of Print on February 3, 2008.

Genetics, Vol. 178, 1283-1293, March 2008, Copyright © 2008
doi:10.1534/genetics.106.065912

Conditional Switches for Extracellular Matrix Patterning in Drosophila melanogaster

Arvinder Khokhar, Nan Chen, Ji-Ping Yuan, Yishi Li, Gary N. Landis, Gregory Beaulieu, Harminder Kaur and John Tower1

Molecular and Computational Biology Program, Department of Biological Sciences, University of Southern California, Los Angeles, California 90089-2910

1 Corresponding author: Molecular and Computational Biology Program, 1050 Childs Way, Room 201, University Park, Los Angeles, CA 90089-2910.
E-mail: jtower{at}usc.edu

An F1 mutagenesis strategy was developed to identify conditional mutations affecting extracellular matrix (ECM) patterning. Tubulogenesis requires coordinated movement of epithelial cells and deposition of a multilayered ECM. In the Drosophila ovary, an epithelium of follicle cells creates the eggshells, including the paired tubular dorsal appendages (DAs) that act as breathing tubes for the embryo. A P-element mutagenesis strategy allowed for conditional overexpression of hundreds of genes in follicle cells. Conditional phenotypes were scored at the level of individual mutant (F1) female flies. ECM pattern regulators were readily identified including MAPK signaling gene ets domain lacking (fused DAs), Wnt pathway genes frizzled 3 and osa (long DAs), Hh pathway gene debra (branched DAs), and transcription factor genes sima/HIF-1{alpha}, ush, lilli, Tfb1, broad, and foxo. In moving cells the [Ca2+]/calcineurin pathway can regulate adhesion to ECM while adherens junctions link cells together. Accordingly, thin eggshell and DA phenotypes were identified for the calcineurin regulator calreticulin and the adherens junction component arc. Finally a tubulogenesis defect phenotype was identified for the gene pterodactyl, homologous to the mammalian serine/threonine receptor-associated protein (STRAP) that integrates the TGF-β and PI3K/AKT signaling pathways. Because phenotypes can be scored in each mutant fly before and after gene induction, this F1 conditional mutagenesis strategy should allow for increased scale in screens for mutations affecting repeated (reiterated) events in adult animals, including gametogenesis, movement, behavior, and learning.