tap, a Drosophila bHLH gene expressed in chemosensory organs.

We have isolated a Drosophila bHLH gene, tap, that is expressed in a small subset of neurons when they undergo differentiation. In the peripheral nervous system, tap is expressed exclusively in one of the neurons that innervate each larval chemosensory organ, possibly controlling the specific properties of that neuron. Sequence comparisons suggest that tap is most closely related to two bHLH genes identified in several vertebrate species, neurogenin and neuroD, which are involved respectively in neural determination and in neuronal differentiation.