The generation of cellular diversity in the cerebral cortex.

We have used retroviral vectors to study cell lineage in the embryonic rat cerebral cortex both in vivo and in dissociated cell culture. We provide evidence that during the late phase of corticogenesis, most precursor cells of the ventricular zone are specified for the production of a single cell type, either neurons or one of the glial cell types. Although specified, the precursor cells that generate neurons can apparently generate both pyramidal and non-pyramidal cells. Earlier stages of development are dominated by a different type of precursor cell with a number of properties that lead us to believe that it is the founding, multipotential precursor cell of the cerebral cortex. We discuss a possible model of cell lineage which unifies these various observations.