Dorsal and ventral cell types can arise from common neural tube progenitors

To challenge the developmental potential of dorsal neural tube cells and test whether single neuroepithelial cells can give rise to the full range of neural tube derivatives, we grated a notochord lateral to the closing neural folds. This results in juxtaposition of dorsal and ventral cell types, by inducing floor plate cells and motor neurons dorsally. Clonal analysis with the vital dye lysinated rhodamine dextran showed that both "dorsal" and "ventral" neural tube derivatives can arise from a single precursor. Cells as diverse as sensory ganglion cells, presumptive pigment cells, roof plate cells, motor neurons, and floor plate cells were observed in the same clone. The presence of such diversity within single clones indicates that the responses to dorsal and ventral signals are not mutually exclusive; even in the early neural tube, neuroepithelial cells are not restricted to form only dorsal or ventral neural tube derivatives.