CELL MOTILITY AND CELL INTERACTIONS DURING NEURULATION

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The broad objective of the proposed research is to describe the embryonic cell motility that shapes the early nervous system. The specific goals are to describe the types of neural cell motility that generate the movements of the neural plate of the African clawed frog, Xenopus laevis, and to learn what cell interactions pattern and control these motile behaviors, as well as the expression of selected regional neural markers. These goals will be achieved by using new technology that allows direct recording of the cell motility and cell contact interactions in explanted tissues, where the mechanical relationships between cell behaviors and change in tissue form can be determined. We will label Xenopus cells with fluorescein dextran amine or DiI (vital, fluorescent dyes) and graft them into albino hosts. Three types of explants of the neural plate will then be made at selected stages, each allowing expression of one, two, or three basic morphogenetic processes that function in shaping the nervous system. The motility of the labeled cells will be imaged and recorded using low-light, fluorescence microscopy, image processing and optical memory disc recording. Specific types of motility will be defined in terms of their spatial and temporal patterns of expression. Local tissue interactions controlling these events will be discovered by microsurgically changing tissue relationships and monitoring marker expression by specific antibodies or by in situ hybridization to localize specific gene products. These results will resolve the fundamental, force-producing, motile behaviors of individual cells that generate the forces shaping the nervous system and show how they are coordinated and related to regionalization of the nervous system. In resolving the cytomechanics of neurulation, these studies will contribute to genetic and molecular analyses and be of use in understanding the proximal, cytomechanical causes of neural tube defects.