Combinatorial roles of Olig2 and Neurogenin2 in the coordinated induction of pan-neuronal and subtype-specific properties of motoneurons

Distinct classes of neurons are generated at defined times and positions du ring development of the nervous system. It remains elusive how specificatio n of neuronal identity coordinates with acquisition of pan-neuronal propert ies. Here we show that basic helix-loop-helix (bHLH) transcription factors Olig2 and Neurogenin2 (Ngn2) play vital roles in the coordinated induction of pan-neuronal and subtype-specific properties of motoneurons. Olig2 and N gn2 are specifically coexpressed in motoneuron progenitors. Misexpression s tudies in chick demonstrate the specific, combinatorial actions of Olig2 an d Ngn2 in motoneuron generation. Our results further revealed crossregulato ry interactions between bHLH and homeodomain transcription factors in the s pecification of motoneurons. We suggest that distinct classes of transcript ion factors collaborate to generate motoneurons in the ventral neural tube.