The mechanisms of normal and abnormal tissue morphogenesis will be studied in cell cultures, chicken embryos and in a model collagen gel system. Polystyrene latex beads will be used as probes of cell-extracellular matrix interactions during morphogenesis of limb tissues in these systems. Heparin-coated beads have been found previously to be translocated into developing mesenchymal aggregates in high density cultures of chick limb precartilage cells. They are also subject to translocating forces generated in type I collagen gels in which fibronectin is nonuniformly distributed. Using beads coated with various cell surface macromolecules and monoclonal antibodies directed against specific domains of fibronectin, the cell surface and extracellular matrix determinants of translocation in the culture and gel systems will be studied. Cell aggregation and chondrogenesis will be assayed in high density cultures containing anti-fibronectin antibodies to analyze the matrix determinants of precartilage cell aggregation and differentiation. Beads with various surface coatings will be micro-injected into the somites and limb buds of chick embryos to assay selective translocation into chondrogenic or myogenic primordia of the limbs. Elvax resin containing anti-fibronectin monoclonal antibodies will be implanted in developing limbs with or without bead injections to assay the fibronectin domain dependence of potential bead translocation during limb development, as well as the role of specific fibronectin domains in chondrogenic and myogenic cell translocation and morphogenesis. The relevance of the collagen gel model to cell-matrix interactions in living tissues will be studied with additions of hyaluronic acid, chondroitin sulfate and type III collagen to gels containing varying amounts of type I collagen. In addition, the local organization of collagen fibrils during cell and bead translocation in collagen gels will be examined using polarizing microscopy, and the magnitude of the translocational force will be determined by measurement of the magnetic field strength necessary to oppose translocation of heparin-coated iron oxide spheres. These studies will provide insight into the molecular mechanisms of morphogenetic interaction during normal and abnormal embryonic development.
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