9603709 Wightman Dr. Bruce Wightman studies the mechanism of axon guidance in the developing nervous system. During the development of an animal, nerves get formed by the growth of axons. In order for the nervous system to function properly, these axons must "wire up" properly. This means that axons must have a mechanism for determining direction. They must be able to select one particular route over another. We have employed a moleculargenetic approach to identify two genes, fax-1 and unc-20, that are required foraxons to follow the correct route during development of the nematode Caenorhabditis elegans. Therefore, these genes may function as molecular "signs" that provide navigational information to growing axons. We are using molecular and genetic techniques to clone these two genes and determine how they provide directions to growing axons. An understanding of the mechanism of axon guidance will help us understand how nerve wiring occurs, and thus provide a clearer view of the biological basis of behavior.