Diagram depicting a working hypothesis for the roles of DCC and netrin and integrin in the migration of neural precursors from the SVZ to the center of the olfactory bulb. Netrin-1 secreted from mitral cells attracts DCC- or neogenin-expressing migrating cells, or both, to the olfactory bulb. Slit proteins from the septum inhibit migration out of the RMS into the septum or surrounding tissues by their repulsive activity. Integrins and laminins provide the traction for the motive force, and PSA-N-CAM provides the cellular milieu where the cells can move easily and maintenance of chains. Theshort arrow indicates the differentiation of neural precursors to granule cells; the long arrow marks the periglomerular cells. EPL, External plexiform layer;GCL, granule cell layer; GL, glomerular layer; MCL, mitral cell layer; ONL, olfactory nerve layer.