Over the last decade, considerable progress has been made in defining mechanisms that control the generation of distinct types of neurons at different positions of the brain, whereas molecules that influence the generation of distinct neurons over time have remained unidentified. By examining the sequential generation of motor neurons and serotonergic neurons from the same pool of progenitor cells in the brainstem, the researchers were able to identify several 'transcription factors' - DNA binding proteins that regulate the expression of a particular set of genes - that control the time at which these neurons are generated. An unexpected finding was that all these factors had been implicated earlier in the spatial control of neural fate determination. "Identifying new roles to this bunch of old proteins is intriguing" says Dr. Ericson, "since it helps to demystify the time aspect of neural development and further indicates that the temporal and spatial control of neuronal differentiation must be tightly linked. It is important to stress, however, that so far we have examined only two well defined neurons in the brainstem, and it will also be necessary to examine other parts of the nervous system before we can tell if this mechanism may reflect a general principle in the establishment of neuronal cell diversity"
Genes & Development