Migrating neurons cross a reelin-rich territory to form an organized tissue out of embryonic cortical slices

In this study,we show that the radial migration of neuronal precursors out of cerebral cortex of embryonic brain slices cultured for 4-7days gives ris e to an organized tissue that forms de novo off developing slices. In our i n vitro preparations, migrating neuronal precursors overshot the marginal z one, as did the elongation of radial glial processes out of the slices. The se cells detached from radial glia at a distance from the cortex and differ entiated into pyramidal and nonpyramidal profiles that expressed different neuronal markers. Glial precursors were shown to proliferate in the slice a nd in the neotissue, and to differentiate into astrocytes. We show that cel ls expressing reelin in the marginal zone of embryonic cortical slices pers ist after a week in culture, which implies that neuronal migration is not n ecessarily hindered by the presumed stop signals provided by reelin in the marginal zone. Furthermore, our results provide a new model for in vitro st udies of migration and differentiation during cortical development.