Moens, C; IBN #9816905 The enormous functional complexity of the vertebrate nervous system is built upon events that occur during early embryogenesis when an initially homogeneous field of cells, the neural plate, is divided and subdivided into progressively more sharply restricted domains. Within the hindbrain, these domains are overtly segmental in character, containing re-iterated sets of neurons and being separated by morphologically and molecularly distinct boundaries. These hindbrain segments, or rhombomeres, acquire their distinct anterior-posterior identities through the action of the hox genes, which also pattern the body segments of invertebrate animals. As such, the vertebrate hindbrain has an archetypal significance as being patterned by mechanisms that are conserved across animal phyla. This project proposes to study the mechanism by which vertebrates establish anterior-posterior pattern within the hindbrain, and thereby co-opt the hox gens into their segmental body plan. The zebrafish is used as a model system, because its relatively simple nervous system allows the identification of individual neurons at particular anterior-posterior levels within the hindbrain. Thus, it is possible to study the specification and patterning of individual neurons both experimentally, by transplanting them to different anterior-posterior levels, and genetically, by studying mutants in which their organization is disrupted through gene deletions. Using this combination of experimental embryology, molecular biology and genetics, the experiments outlined in this proposal will address when and how individual neurons become committed to their region-specific identities, and what role candidate signalling molecules and candidate signalling sources play in this process.
