Coordinate regulation of motor neuron subtype identity and pan-neuronal properties by the bHLH repressor Olig2

Within the developing vertebrate nervous system, the mechanisms that coordi nate neuronal subtype identity with generic features of neuronal differenti ation are poorly defined. We show here that a bHLH protein, Olig2, is expre ssed selectively by motor neuron progenitors and has a key role in specifyi ng the subtype identity and pan-neuronal properties of developing motor neu rons. The role of Olig2 in the specification of motor neuron subtype identi ty depends on regulatory interactions with progenitor homeodomain proteins, whereas its role in promoting pan-neuronal properties is associated with e xpression of another bHLH protein, Ngn2. Both aspects of Olig2 function app ear to depend an its activity as a transcriptional repressor. Together, the se studies show that Olig2 has a critical role in integrating diverse featu res of motor neuron differentiation in the developing spinal cord.