Identification of the role of a novel cell adhesion molecule, unzipped, in mediating neuron-glia interactions in Drosophila

The intricate but still precise pattern of brain circuitry is unquestionably the mostcomplex feature of both vertebrates and invertebrates. How that complex circuitry developshas been the subject of intense study for over a century. Neurons, being the excitableresidents of the nervous system, are guided to their destinations in a tightly regulated manner,in order to conduct the sensory inputs to the correct targets. Growth cones of the neuronsexperience many different trans-cellular cues in their journey to their final target, which canbe attractive or repellent. Glial cells constitute one class of cells that promote axonaloutgrowth, either through cell-cell adhesion or by secreting diffusible signals. Olfactorysystem of Drosophila represents an ideal system for the study of axonal guidance. There areabout 1500 olfactory receptor neurons (ORNs), which are subdivided into 50 classesaccording to the olfactory receptor they express. Olfactory receptor neurons, expressing thesame olfactory receptor converge into the same synaptic subunit on brain, which are calledglomeruli. There are many mechanisms identified in the formation of this accurate patternof olfactory system, but still many steps remain unknown. Towards this end, the recentlyidentified cell adhesion molecule Unzipped was found to be expressed by a subset of ORNsand glia in the Drosophila olfactory system. Results of this study implicate that, Unzippedis necessary for midline crossing of all olfactory receptor neurons, and also for propertargeting of some ORNs to the brain. Therefore, it is claimed that Unzipped is an importantfactor in mediating neuron-glia interaction in the olfactory system of Drosophila.