Fig. 9. Model for the dual role of Cux2 in spinal cord neurogenesis.

Cux2 activity stimulates the cell-cycle progression of neural progenitors in the spinal cord vz. In so doing, Cux2 initiates a neuroblast gene expression program that includes the bHLH factor Neurod, and subsequently directs these populations to exit the cell cycle by inducing p27^Kip1 in the iz. Cux2 activity in neural progenitors also biases their fate to mature interneurons (IN) in the mz, thereby acting as a cell-fate selector in nascent neurons.