Early specification of sensory neuron fate revealed by expression and function of neurogenins in the chick embryo

The generation of sensory and autonomic neurons from the neural crest requi res the functions of two classes of basic helix-loop-helix (bHLH) transcrip tion factors, the Neurogenins (NGNs) and MASH-1, respectively (Fode, C., Gr adwohl, G., Morin, X., Dierich, A., LeMeur, M., Goridis, C. and Guillemot, F. (1998) Neuron 20, 483-494; Guillemot, F., Lo, L.-C., Johnson, J. E., Aue rbach, A., Anderson, D. J. and Joyner, A. L. (1993) Cell 75, 463-476; Ma, Q ., Chen, Z. F., Barrantes, I. B., de la Pompa, J. L. and Anderson, D. J. (1 998 Neuron 20, 469-482). We have cloned two chick NGNs and found that they are expressed in a subset of neural crest cells early in their migration. E ctopic expression of the NGNs in vivo biases migrating neural crest cells t o localize in the sensory ganglia, and induces the expression of sensory ne uron-appropriate markers in non-sensory crest derivatives. Surprisingly, th e NGNs can also induce the expression of multiple pan-neuronal and sensory- specific markers in the dermomyotome, a mesodermal derivative. Taken togeth er, these data suggest that a subset of neural crest cells may already be s pecified for a sensory neuron fate early in migration, as a consequence of NGN expression.