The diversity of neuronal cell types in vertebrates derives from regional differences along the anterior-posterior (A/P) as well as the dorsal-ventral (D/V) axes of the developing nervous system. Previous work has shown that A/P properties are extremely labile during the initial phases of regionalization. In order to investigate the corresponding stages of neural regionalization along the D/V axis, this investigator initiated a series of experiments examining the early phases of D/V neural patterning using the amphibian Xenopus as a model system. Preliminary data suggest a model in which D/V pattern in the prospective spinal cord region is fixed at relatively early stages in contrast to the anterior brain region in which D/V pattern remains labile for a prolonged period of time. Using tissue manipulations in conjunction with molecular approaches, this proposal will test and extend this model by systematically examining the tissue interactions governing the early stages of D/V neural patterning. These experiments will not only provide a framework for linking gene expression with biological processes mediating D/V patterning events but will also contribute to an understanding of the unique properties of embryonic neuronal tissue, particularly its enormous plasticity.
