Directional guidance of neuronal migration in the olfactory system by the protein Slit

Although cell migration is crucial for neural development, molecular mechan isms guiding neuronal migration have remained unclear. Here we report that the secreted protein Slit repels neuronal precursors migrating from the ant erior subventricular zone in the telencephalon to the olfactory bulb. Our r esults provide a direct demonstration of a molecular cue whose concentratio n gradient guides the direction of migrating neurons. They also support a c ommon guidance mechanism for axon projection and neuronal migration and sug gest that Slit may provide a molecular tool with potential therapeutic appl ications in controlling and directing cell migration.