Cell and growth cone migrations establish the pattern of a developing nervous system. While several conserved proteins have been implicated in these processes in vertebrates and invertebrates, little is known about the molecular control of anteroposterior migrations. These migrations are the focus of the two specific aims of this proposal, which utilizes the nematode Caenorhabditis elegans. First, the investigator will use a genetic screen involving direct visualization of neurons and their axons in living animals to identify mutants with defects in anteroposterior axonal growth and pathfinding. The genes identified by these mutations will be characterized genetically and molecularly. Second, the investigator will clone and analyze the mig-11 gene, which is needed for the posteriorly directed migration of CAN cells and axons. The focus of action of the gene will be determined by mosaic analysis, GFP reporter fusions, in situ hybridization, and antibodies. Molecular and genetic interactions with mig-11 will be studied as well.