SIMILARITY OF THE PRODUCT OF THE DROSOPHILA NEUROGENIC GENE BIG BRAIN TO TRANSMEMBRANE CHANNEL PROTEINS

CELLS in the neurogenic region of Drosophila embryos are initially bipotential; they can become either neuroblasts or epider-moblasts1,2. Cell-cell interaction seems to play an important part in this developmental decision3, which involves the function of a group of genes (the neurogenic genes). Loss-of-function mutations in any of the neurogenic genes result in nervous system hyperplasia and epidermal hypoplasia4,5. Of the six known zygotic neurogenic genes, big brain (bib) is unique in several aspects6-9. Most notably, all the other known neurogenic genes seem to fit into a cascade defined by genetic interactions, whereas bib does not show any detectable interaction with them9. To understand how bib functions, we have now cloned the bib genomic and complementary DNAs. The predicted bib product shows significant sequence similarity to a family of transmembrane proteins10-13, some of which form channels permeable to small molecules14,15. Together with genetic studies, our results indicate that the bib product may mediate intercellular communication in a pathway separate from the one involving the products of the other neurogenic genes. © 1990 Nature Publishing Group.