Evidence that nitric oxide regulates cell-cycle progression in the developing chick neuroepithelium.

In all developing epithelia, the nuclei continually migrate between the apical and basal sides of the cell during the cell cycle, with S phase occurring basally and mitosis occurring apically. The purpose and mechanism of this nuclear migration are unknown. Here, we show that nitric oxide (NO) is endogenously produced in the developing chicken neural tube, where it apparently regulates cell-cycle progression. We provide evidence that high NO levels promote entry into S phase basally, whereas low levels of NO facilitate entry into mitosis apically.