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 during development of the nervous system. It remains elusive how specification of neuronal identity coordinates with acquisition of pan-neuronal properties. 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 Ngn2 are specifically coexpressed in motoneuron progenitors. Misexpression studies in chick demonstrate the specific, combinatorial actions of Olig2 and Ngn2 in motoneuron generation. Our results further revealed crossregulatory interactions between bHLH and homeodomain transcription factors in the specification of motoneurons. We suggest that distinct classes of transcription factors collaborate to generate motoneurons in the ventral neural tube.