Growth cone guidance: First steps towards a deeper understanding

Growth cones, the hand-like structures at the tip of growing neurites, poss ess remarkable abilities to detect directional cues. On their way to their targets they traverse a dense jungle of many different cells, expressing a variety of different molecular guidance cues. Proper reading and integratio n of these cues is essential for precise wiring of different parts of the p eripheral and central nervous systems. Guidance cues have been classified a ccording to the response they elicit as either attractive or repulsive. Rec ent work, however, suggests that this might not represent an absolute disti nction and that the internal state of the growth cone can dictate whether i t detects a cue as repulsive or attractive. This article reviews some new e xperimental approaches to understanding growth cone signal transduction mec hanisms induced by extracellular guidance cues.