The Drosophila castor gene is involved in postembryonic brain development

castor (cas) encodes a zink finger protein expressed in a subset of Drosophila embryonic neuroglioblasts where it controls neuronal differentiation. We show here that cas is expressed at larval and pupal stages in brain cell clusters where it participates in the elaboration of the adult structures. In particular using the MARCM system (mosaic analysis with a repressible cell marker), we show that cas is required postembryonically for correct axon pathfinding of the central complex (CX) and mushroom body (MB) neurons. The linotte (lio) gene encodes a transmembrane protein expressed at larval/pupal stage in a glial structure, the TIFR, and interacts with the no-bridge (nob) gene. We show that cas interacts genetically with lio and nob. These interactions do not involve direct transcription regulation but probably cellular communication processes.