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

Abstract

The intricate but still precise pattern of brain circuitry is unquestionably the most complex feature of both vertebrates and invertebrates. How that complex circuitry develops has been the subject of intense study for over a century. Neurons, being the excitable residents 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 neurons experience many different trans-cellular cues in their journey to their final target, which can be attractive or repellent. Glial cells constitute one class of cells that promote axonal outgrowth, either through cell-cell adhesion or by secreting diffusible signals. Olfactory system of Drosophila represents an ideal system for the study of axonal guidance. There are about 1500 olfactory receptor neurons (ORNs), which are subdivided into 50 classes according to the olfactory receptor they express. Olfactory receptor neurons, expressing the same olfactory receptor converge into the same synaptic subunit on brain, which are called glomeruli. There are many mechanisms identified in the formation of this accurate pattern of olfactory system, but still many steps remain unknown. Towards this end, the recently identified cell adhesion molecule Unzipped was found to be expressed by a subset of ORNs and glia in the Drosophila olfactory system. Results of this study implicate that, Unzipped is necessary for midline crossing of all olfactory receptor neurons, and also for proper targeting of some ORNs to the brain. Therefore, it is claimed that Unzipped is an important factor in mediating neuron-glia interaction in the olfactory system of Drosophila.