The Drosophila cystoblast differentiation factor, benign gonial 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 we have identified the bag-of-marbles (bam) gene as an intrinsic factor for cystoblast fate in Drosophila germline cells and shown that it requires active product from the benign gonial cell neoplasm (bgcn) gene. Here we present the cloning and characterization of bgcn. The predicted Bgcn protein is related to the DExH-box family of RNA-dependent helicases but lacks critical residues for ATPase and helicase functions. Expression of the bgcn gene is extremely limited in ovaries but, significantly, bgcn mRNA is expressed in a very limited number of germline cells, including the stem cells. Also, mutations in bgcn dominantly enhance a barn mutant phenotype, further corroborating the interdependence of these two genes' functions. On the basis of known functions of DExH-box proteins, we propose that Bgcn and Bam may be involved in regulating translational events that are necessary for activation of the cystoblast differentiation program.