9357246 Hardin Understanding how single cells and sheets of cells move, and what controls their movements, is fundamental for understanding early embryonic development. A particularly striking series of morphogenetic movements occurs during gastrulation, when massive tissue movements and cell migrations transform the early embryo from a hollow ball or disc to a three-layered embryo possessing all of the basic structures of the emerging organism. Because the movements of gastrulation are so complex and dramatic, we have turned to a seemingly simple system, the sea urchin embryo, in order to discover general rules that all embryos use during gastrulation. In particular, we want to answer the following questions: (1) What motile behavior(s) underlie epithelial cell rearrangement during gastrulation, and how are such behaviors coordinated to produce invaginations? (2) How do such rearrangements rely on attachments of epithelial cells to the apical extracellular matrix, or apical lamina, and to the basal lamina? In order to answer these questions, our laboratory is seeking to use novel approaches to unite classical techniques, computer-enhanced imaging, and molecular biology. In particular, we will use computer-assisted videomicroscopy and low-level fluorescence imaging to study the motility of cells as they rearrange during gastrulation. Using the imaging techniques as an analysis tool, we will use blocking antibodies and competitive peptides, either expressed from cDNA clones or synthesized directly, to examine the effects of perturbing the attachment of cells to the extracellular matrix on motility in rearranging epithelia. In addition, we will use the technique of chromophore- assisted laser inactivation of protein function (CALI) to perturb these attachments at a highly local level to examine very specific regions of interest during gastrulation. As an embryo develops, the fairly featureless fertilized egg must be transformed into an animal with a recognizable body plan and many highly organized structures. This NSF Young Investigator Award supports studies on the forces that shape embryos. In particular, we are interested in gastrulation, when cells move in dramatic ways to reshape the embryo, producing the basic body plan of the animal. We are studying a simple system, the sea urchin embryo, with the hope that by understanding this simple organism, we will eventually understand much more complex one. ***
