THE DROSOPHILA PUTATIVE KINASE LINOTTE (DERAILED) PREVENTS CENTRAL BRAIN AXONS FROM CONVERGING ON A NEWLY DESCRIBED INTERHEMISPHERIC RING

The lio gene encodes a putative receptor tyrosine kinase, with unique motifs both in the extracellular and catalytic domains (Dura, J.-M., P reat, T., Tully, T., 1993. Identification of linotte, a new gene affec ting learning and memory in Drosophila melanogaster. J. Neurogenet. 9, 1-14). We show here that a complete deletion of lio activity causes s pecific structural defects in the adult brain. Gal4 enhancer-trap line s used as cell markers revealed that in lio mutants central brain axon s behave as if they were abnormally attracted by the midbrain area. Th e Lio protein is expressed in third instar larvae in a few cells at th e junction of the cerebral hemispheres. These glial cells form a newly described ring structure showing an invariable fibrous organization. In the wild-type this ring disappears at midpupation. Our results indi cate that the Lio putative kinase plays a major role in the modeling o f the adult brain by controlling the fate of the transient interhemisp heric ring. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved .