Pathway selection by growth cones in the zebrafish central nervous system.

The accessibility and simplicity of the zebrafish embryo have led to a detailed characterization of pathfinding by identifiable growth cones in both the spinal cord and brain. These growth cones follow precise, cell-specific pathways to their targets. Analyses of pathfinding in mutant embryos and wild-type embryos following laser ablation or transplantation of specific cells demonstrate that growth cones accomplish this by interacting with specific cellular cues in their environment, many of which are likely to be redundant. These experiments suggest that a combination of separate pathway and directionality cues are required for pathfinding by growth cones. Growth cones distinguish different pathways by sensing specific pathway cues and know what direction they should extend on a pathway by sensing widely distributed directionality cues.