9418678 Fleming One mutation in Drosophila melanogaster which exhibits neuronal hyperplasia with concomitant reduction in hypodermal structures has been named Notch. Serrate, another gene mutation, appears to play an important developmental role in interacting with the Notch gene product to mediate cell- to- cell signaling during the development of tissues other than the early embryonic neuroblast, where the product of another gene, Delta, seems to interact with Notch. Since Ser-null alleles cause larval death, it has not been possible to identify which tissues require Ser for viability or the possible role of Ser post-embryonically. New approaches will be utilized to answer the questions: (1.) What is the essential role played by Serrate during development? (2.) Where and when is the Serrate protein expressed during development? (3.) What is the nature of the class of dominant Serrate mutations that interact strongly with null Delta alleles? %%% Experiments are proposed to investigate the function of the Serrate gene product in the fruit fly, Drosophila melanogaster. A number of genetic loci have been isolated on the basis of a common mutant phenotype and studies have suggested that most of these genes products are interactive in a manner necessary for the differentiation of neuro-ectoderm. The function of one of them, Serrate, will be examined in relation to its function in embryonic development and in the manner in which it interacts with products of other related gene loci. ***
