Genetic screen for modifiers of the rough eye phenotype resulting from overexpression of the Notch antagonist hairless in Drosophila.

Hairless was identified as antagonist in the Notch signaling pathway based on genetic interactions. Molecularly, Hairless inhibits Notch target gene activation by directly binding to the Notch signal transducer Su(H). Additional functional domains apart from the Su(H) binding domain, however, suggest additional roles for the Hairless protein. To further our understanding of Hairless functions, we have performed a genetic screen for modifiers of a rough eye phenotype caused by overexpression of Hairless during eye development. A number of enhancers were identified that comprise mutations in components of Notch- and EGFR-signaling pathways, some unknown genes and the gene rugose. Mutant alleles of rugose display manifold genetic interactions with mutants in Notch and EGFR signaling pathway components. Accordingly, the rugose eye phenotype is rescued by Hairless and enhanced by Delta. Molecularly, interactions might occur at the protein level because rugose appears not to be a direct transcriptional target of Notch.