GENETIC-ANALYSIS OF AXON GUIDANCE AND MAPPING IN THE ZEBRAFISH

Systematic genetic screens have been powerful tools in identifying gen es responsible for axon guidance in fruitflies and nematodes. This app roach has now been extended to the study of axon guidance and the form ation of topographic neuronal connections in the vertebrate brain. A s ystematic genetic screen was used to identify genes responsible for pr ecise axon pathfinding and targeting in the retinotectal system of the zebrafish (Danio rerio). Over 30 genes were found that affect either: (1) retinal axon pathfinding to the contralateral tectal lobe; or (2) the topographic connection between the eye and the tectum. The zebraf ish retinotectal mutants represent a new resource for the study of axo n guidance in the vertebrate brain.