Interkinetic nuclear movement in the vertebrate neuroepithelium: encounters with an old acquaintance.

The vertebrate neuroepithelium is a highly efficient structure with respect to the process of neurogenesis. The orthogonal arrangement of the nuclei with respect to the surface of the epithelium facilitates the dramatic increase in cell density necessary to produce a high number of neurons. Moreover, the spatial organization of the neuroepithelium reflects the segregation of cells that are transiently embarked upon distinct functions, thereby avoiding any interference between these populations in terms of their physiological activities. Two main regions can be distinguished: an apical neurogenetic zone, where lateral inhibitory signals and neurogenic gene expression can be observed, and a basally located pre-neurogenetic zone, which contains cells replicating their DNA and able to receive the signals that will modify their fate.