Zebrafish narrowminded suggests a genetic link between formation of neuralcrest and primary sensory neurons

In the developing vertebrate nervous system, both neural crest and sensory neurons form at the boundary between non-neural ectoderm and the neural pla te. From an in situ hybridization based expression analysis screen, we have identified a novel zebrafish mutation, narrowminded (nrd), which reduces t he number of early neural crest cells and eliminates Rohon-Beard (RB) senso ry neurons. Mosaic analysis has shown that the mutation acts cell autonomou sly suggesting that nrd is involved in either the reception or interpretati on of signals at the lateral neural plate boundary. Characterization of the mutant phenotype indicates that nrd is required for a primary wave of neur al crest cell formation during which progenitors generate both RE sensory n eurons and neural crest cells. Moreover, the early deficit in neural crest cells in nrd homozygotes is compensated later in development. Thus, we prop ose that a later wave can compensate for the loss of early neural crest cel ls but, interestingly, not the RE sensory neurons, We discuss the implicati ons of these findings for the possibility that RE sensory neurons and neura l crest cells share a common evolutionary origin.