Sema3C and Netrin-1 differentially affect axon growth in the hippocampal formation

The interaction between outgrowing neurons and their targets is a central e lement in the development of the afferent and efferent connections of the h ippocampal system. This requires that axonal growth cones recognize specifi c guidance cues in the appropriate target area. At present, little is known about the mechanisms that determine the lamina-specific termination of hip pocampal afferents. In order to understand the role of different guidance f actors, we analyzed the effects of Sema3C and Netrin-1 on explants from the entorhinal cortex, dentate gyrus, cornu ammonis regions CAI and CA3 and me dial septum in a collagen coculture assay. Our observations suggest that bo th semaphorins and netrin play important roles in the neuron-target interac tions in the hippocampal system. Sema3C is involved in the control of the i ngrowth of the septohippocampal projection. We also show that netrin-1 is i nvolved in attracting commissural neurons from dentate gyrus/hilus and CA3 to their target area in the contralateral hippocampus.