Genetic and molecular analyses of motoneuron development

Motoneurons have distinct identities and muscle targets. Recent classical a nd molecular genetic studies in flies and vertebrates have begun to elucida te how motoneuron identities and target specificities are established. Many of the same molecules participate in the guidance of both vertebrate and f ly motor axons. It is less clear, however, whether the same molecular mecha nisms establish vertebrate and fly motoneuron identities.