THE CELL-CYCLE OF THE PSEUDOSTRATIFIED VENTRICULAR EPITHELIUM OF THE EMBRYONIC MURINE CEREBRAL WALL

Neurons destined for the cerebral neocortex are formed in the pseudost ratified ventricular epithelium (PVE) lining the ventricular cavity of the developing cerebral wall. The present study, based upon cumulativ e S-phase labeling with bromodeoxyuridine, is an analysis of cell cycl e parameters of the PVE. It is undertaken in the dorsomedial cerebral wall of mouse embryos from the eleventh to the seventeenth gestational day (E11-E17, day of conception = E0) corresponding to the complete p eriod of neuronogenesis. The growth fraction (fraction of cells in the population which is proliferating) is virtually 1.0 from E11 through E16. The length of the cell cycle increases from 8.1 to 18.4 hr, which corresponds to a sequence of 11 integer cell cycles over the course o f neuronal cytogenesis in mice. The increase in the length of the cell cycle is due essentially to a fourfold increase in the length of G1 p hase which is the only phase of the cell cycle which varies systematic ally. Thus, the G1 phase is most likely to be the phase of the cell cy cle which is modulated by extrinsically and intrinsically acting mecha nisms involved in the regulation of neuronal cytogenesis.