One of the fundamental questions in developmental biology is how cells communicate with each other in determining cell fate and pattern formation. Inductive signal transduction that utilizes diffusible extracellular signaling molecules plays an important role in this process. For instance, two secreted molecules Hedgehog (Hh) and the transforming growth factor (TGF-B) homologue Decapentaplegic (Dpp) are essential for patterning the Drosophila eye, which provides a model system for a molecular and genetic dissection of the signaling hierarchy mediated by secreted molecules. Dr. Lai has recently identified a potential key component, Delayed furrow (Defu), of the Hh signaling pathway. Mutations in the delayed furrow gene slow down progression of the morphogenetic furrow in eye imaginal discs, and this phenotype is enhanced by hedgehog mutations. A long term objective of this research is to elucidate basic mechanisms and principles of neural morphogenesis. The immediate goal is to test a hypothesis that Defu protein participates with Hedgehog to provide cells with positional information for pattern formation, by utilizing a combination of genetic, molecular and cellular approaches. Specific experimental aims are: 1) To characterize null phenotypes of defu in eye morphogenesis; 2) To molecularly clone and characterize the defu gene; 3) To reveal mechanisms by which Defu participates with Hh in neural morphogenesis.