A modular misexpression screen in Drosophila detecting tissue-specific phenotypes.

TLDR

Genetic screens in Drosophila have uncovered many genes essential for patterning and signal transduction, and traditionally these screens focus on loss‑of‑function mutations. The study develops a versatile misexpression screen in Drosophila, the first of its kind in higher eukaryotes, to link genes and function. The screen uses Gal4‑mediated transactivation of a mobile enhancer/promoter to target random endogenous genes for over‑ or misexpression in any desired spatial or temporal pattern, thereby revealing specific phenotypes or modulating existing mutant phenotypes. In the developing eye, 4 % of target inserts produced dominant phenotypes, including an insertion in a Ras GTPase‑activating protein whose overexpression was strongly enhanced by a Ras1 mutation, demonstrating that the screen identifies biologically relevant phenotypes and genetic interactions and offers a powerful tool for developmental genetics that can be adapted to other organisms.

Abstract

Genetic screens in Drosophila have lead to the discovery of many genes important for patterning and signal transduction in diverse organisms. Traditionally, the phenotypic effects of loss-of-function mutations are analyzed. As an alternative way to link genes and function, I have developed a versatile misexpression screen in Drosophila, the first such screen in higher eukaryotes. The screen identifies genes that, when over- or misexpressed in a pattern of interest, give a specific phenotype or modulate an existing mutant phenotype. It is based on Gal4 transactivation of a mobile enhancer and promoter that "targets" random endogenous genes for expression. The modular design of the screen allows directed expression in any temporal or spatial pattern. When activated in the developing eye, 4% of target inserts gave dominant phenotypes. One insertion was in the gene encoding Ras GTPase-activating protein; its overexpression phenotype was strongly enhanced by a mutation in Ras1. Thus, biologically relevant phenotypes and genetic interactions are identified using this method. The screen is a powerful new tool for developmental genetics; similar approaches can also be developed for other organisms.