THE TGF-BETA SIGNALING PATHWAY IS ESSENTIAL FOR DROSOPHILA OOGENESIS

We examine roles of signaling by secreted ligands of the TGF-beta fami ly during Drosophila oogenesis, One family member, the DPP ligand enco ded by the decapentaplegic (dpp) gene, is required for patterning of a nterior eggshell structures, This requirement presumably reflects the expression pattern of dpp in an anterior subset of somatic follicle ce lls: the centripetally migrating and the nurse cell-associated follicl e cells, Similar requirements are also revealed by mutations in the sa xophone (sax)-encoded receptor, consistent with the idea that DPP sign aling is, at least in part, mediated by the SAX receptor, A loss of ge rmline sax function results in a block in oogenesis associated with eg g chamber degeneration and a failure of the transfer of nurse cell con tents to the oocyte, indicating that TGF-beta signaling is required fo r these events, Some phenotypes of sax mutations during oogenesis sugg est that SAX responds to at least one other TGF-beta ligand as well in the posterior follicle cells.