Investigation of novel epidermal growth factor receptor target genes implicated in Drosophila egg and wing development. Jacquelyn Gallo, Luke Dombert, Justin Hunter, Kristopher Krawchuk, Connor Zale, Lisa Kadlec. Department of Biology, Wilkes University, Wilkes-Barre, PA.
Signaling by the Drosophila epidermal growth factor receptor (Egfr) plays an important role in many aspects of development, including oogenesis, embryogenesis and proper development of both the eye and the wing. In the ovary, the Egfr pathway plays a key role in the establishment of the body axes during oogenesis. In the wing, Egfr signaling plays an important role in vein tissue specification. Microarray screens by our lab and others have been used to identify potential downstream transcriptional targets of the Egf receptor using the Drosophila ovary as a model system. Our initial work compared gene expression using fly ovaries in which the activity of the Egfr-pathway was reduced (grk HK36), normal (OreR), or constitutively active (CY2/Top). We are now employing a number of approaches to investigate the expression, biological function, and mechanism of action of several putative targets of interest. Target genes currently under investigation include several genes implicated in eggshell formation (e.g. Dec-1) and/or as part of chorion amplicons (e.g. CG18419 and yellow-G2), as well as a number of genes of unknown function (including CG13299, CG11381, CG13083 and CG14309). RT-PCR has confirmed the up-regulation of a number of targets, as originally seen by microarray. Several putative targets exhibit developmentally regulated expression in the ovary, and in some cases this expression has been shown to be altered in response to changes in levels of Egfr signaling. Screening of putative targets for biological function using UAS-RNAi suggests roles for several target genes of unknown function in eggshell production and/or integrity, wing morphogenesis, or both. A neutral red uptake assay indicates defects in vitelline membrane integrity in compromised eggshells. Additionally, we are using in situ hybridization to investigate target gene expression in wing imaginal discs, as well as to evaluate the effectiveness of our targeted RNA interference.