Continuity with ganglionic eminence modulates interkinetic nuclear migration in the neocortical pseudostratified ventricular epithelium

Cells of the pseudostratified ventricular epithelium (PVE) undergo interkin etic nuclear migration whereby position of cell soma with nucleus is system atically dependent upon cell cycle phase. We examined if the interkinetic n uclear migration in the neopallial PVE is influenced by tissue continuity w ith the ganglionic eminence (GE) of the basal forebrain in explants from em bryonic day 13 mice. We found that when continuity between the neopallial w all and the GE is intact, some neopallial PVE cells discontinue interkineti c nuclear migration following S-phase and upon entry into G2-phase, The som ata and nuclei of those cells shift outward from the S-phase zone toward th e subventricular and the intermediate zones, The outward migration of post- S-phase cells is observed only in the lateral region of the cerebral wall, which is closely adjacent to the GE, but not in the medial reson, and only when tissue continuity with GE is maintained. We suggest that the outward m oving PVE cells seed the secondary proliferative population (SPP) and that exit of the SPP seeding cells occurs in GB-phase, The phenomenon recapitula tes similar migratory behavior of neopallial PVE cells in vivo and appears to represent a "choice" between two opposing options available to post-S-ph ase cells of the PVE. The choice appears to be imposed by mechanisms depend ent upon continuity with the GE. We conclude that GE, and/or other adjacent basal forebrain structures, modulates interkinetic nuclear migration in th e neopallial PVE. (C) 2001 Academic Press.