Genetic analysis of the Drosophila ellipsoid body neuropil: Organization and development of the central complex

The central complex is an important center for higher-order brain function in insects. It is an intricate neuropil composed of four substructures, Eac h substructure contains repeated neuronal elements which are connected by p rocesses such that topography is maintained, Although the neuronal architec ture has been described in several insects and the behavioral role investig ated in various experiments, the exact function of this neuropil has proven elusive. To describe the architecture of the central complex, we study 15 enhancer-trap lines that label various ellipsoid body neuron types. We find evidence for restriction of gene expression that is correlated with specif ic neuronal types: such correlations suggest functional classifications as well. We show that some enhancer-trap patterns reveal a single ellipsoid bo dy neuron type, while others label multiple types. We describe the developm ent of the ellipsoid body neuropil in wild-type animals and propose develop mental mechanisms based on animals displaying structural mutations of this neuropil. The experiments performed here demonstrate the degree of resoluti on possible from the analysis of enhancer-trap lines and form a useful libr ary of tools for future structure/function studies of the ellipsoid body. ( C) 1999 John Wiley & Sons, Inc.