Axon Guidance in the Drosophila Visual System

New York University Medical Center, New York NY

Investigators

Abstract

Treisman 9982093 The accurate transmission of information within the nervous system depends on the precise connections that neurons make with each other. To form these connections, axons must navigate over long distances to their target regions during development. Both long-range attractive or repulsive molecules, and short-range cues promoting selective adhesion, can guide axon outgrowth. The connections formed in the visual system are particularly intriguing, as they result in a precise mapping of the retina onto the brain, suggesting that each cell can sense its global position. Our understanding of the determinants of this positional information is far from complete. A genetic approach using the fruit fly Drosophila has the potential to identify new components mediating axon guidance, purely on the basis of their function. A genetic screen for mutations affecting the connections formed by photoreceptor axons in Drosophila has been initiated. The screen uses a mosaic approach that allows the identification of mutations in genes that are also required earlier in development. This screen is also rapid and favors the isolation of mutations that have defects specific to axon pathfinding. Mutations in two genes that control a pathfinding step specific to a particular photoreceptor have been identified. The proteins encoded by these genes will now be characterized in order to understand the basis for their functions in axon guidance. The screen will also be continued to obtain a more complete picture of the genetic requirements for the visual system projection pattern.