The Drosophila cystoblast differentiation factor, benign genial cell neoplasm, is related to DExH-box proteins and interacts genetically with bag-of-marbles

Selection of asymmetric cell fates can involve both intrinsic and extrinsic factors. Previously rye have identified the bag-of-marbles (bam) gene as a n intrinsic factor. for cystoblast fate in Drosophila germline cells and sh own that it requires active product from the benign gonial cell neoplasm (b gcn) gene. Here we present the cloning and characterization of bgcn. The pr edicted Bgcn protein is related to the DExH-box family of RNA-dependent hel icases but lacks critical residues for ATPase and helicase functions. Expre ssion of the bgcn gene is extremely limited in ovaries but, significantly, bgcn mRNA is expressed in a very limited number of germline cells, includin g the stern cells. Also, mutations in bgcn dominantly enhance a bam mutant phenotype, further corroborating the interdependence of these two genes' fu nctions. On the basis of known functions of DExH-box proteins, we propose t hat Bgcn and Bam may be involved in regulating translational events that ar e necessary for activation of the cystoblast differentiation program.