Figure 1

Acquisition of neurogenic potential in midbrain floorplate cells. From analysis of gene expression, the midbrain DA neuron progenitor domain can be subdivided into medial (DA^M) and lateral (DA^L) domains. Left, at early embryonic stages, medial DA progenitor cells resemble floorplate cells expressing high levels of Shh (pale gray). Right, downregulation of Shh (striped pale grey) in the medial progenitor domain at later stages in embryogenesis promotes neurogenesis from the medial progenitor domain.