Clonal organization in the postnatal mouse central nervous system is prefigured in the embryonic neuroepithelium

We have used the LaacZ clonal method of cell labeling of neuronal ancestors and report that the spatial organization of neuronal cells in the post-natal CNS shares striking similarities to that in the embryonic neuroepithelium, from the spinal cord to the diencephalon. The maintenance of the organization occurs despite massive cell divisions and morphogenetic movements. We deduce that the cellular and architectural organization in the mouse CNS results from a succession of patterns of oriented cell dispersion, a general arrest of cell dispersion in the neuroepithelium, and then well-documented radial neuronal migration. The arrest of cell dispersion in the neuroepithelium is consistent with the possibility that an important part of the cellular and architectural organization of the mature CNS requires conservation of spatial relationship between cells and supports the hypothesis of a transition from global and sparse to local and dense cell interactions occurring early within the neuroepithelium.