Lost in space: misregulated positional cues create tripotent neural progenitors in cell culture

In a widely held view of vertebrate CNS development, neurons, astrocytes, and oligodendrocytes arise from a common tripotent progenitor cell. However, tripotent progenitors have never been detected in developing embryos. In this issue of Neuron, Gabay et al. show that tripotent progenitors can be created in vitro by deregulation of normal dorsoventral positional cues.