Specification of neuronal fates in the ventral neural tube

The generation of distinct classes of neurons at defined positions is a fun damental step in the development of the vertebrate central nervous system. Recent work has begun to reveal the extracellular signals and transcription al mediators that direct the pattern of generation of distinct neuronal sub types in the neural tube. This work has provided a framework to understand the patterning of the ventral neural tube and is permitting molecular analy ses of the assembly of functional neuronal circuits.