Fig. 9. Schematic diagram hypothesizing a dual function of reelin in the dentate gyrus. (A) Reelin (blue), synthesized by Cajal-Retzius cells (dark blue) in the marginal zone (m) provides a positional signal for radial glial fibers (green, arrow). The glial cell bodies are located in the secondary proliferation zone, the future hilus (h). (B) Glial cell processes have reached the pial surface, providing a scaffold for the migration of neurons (red). (C) Reelin provides a stop signal for migrating granule cells. Following migration, granule cells accumulate in a layer directly underneath the marginal zone. Alternatively, some radial glial cells may retract their long hilar process (soma translocation), thereby accumulating directly underneath the granular layer (right radial glial cell). Here they may divide and become neurons, inheriting the radial glial apical processes (Miyata et al., 2001).