How does a one-dimensional genetic code specify a three- dimensional organism? How do blastula adhesion molecules specify the shape of the embryo? Glycoprotein molecules stored in yolk granules of sea urchin eggs and embryos appear to mediate the adhesion of cells into the orderly blastula structure. Multimeric adhesion molecules can be removed, noncytolytically, from the surface of dissociated blastula cells with 2.5% butanol. These cells are then incompetent to reaggregate until after the readdition of the butanol-solubilized adhesion complexes. These adhesion complexes are purified from the butanol extract by sedimentation as a 22S complex (No11 et al., Proc. Nat. Acad. Sci. USA 82, 8082, 1985). The adhesion complex appears to originate in yolk granules as a hexamer of 160- to 190-kDa proteins that are proteolytically cleaved as development proceeds. Similar, though smaller, glycoproteins appear to mediate the compaction of preimplantation mouse embryos (Hyafil et al., Cell 21, 927, 1980). The goals of this proposal are: (1) To determine whether all of these sea urchin adhesion molecules are stored in the egg, or whether some are synthesized during the formation of the blastulae. (2) To observe changes in the composition or numbers of the plasma membrane-derived adhesion complex during development, and the relationship between these changes and the adhesion of blastomeres. (3) To determine the functional domains of this adhesion complex, and the structural requirements for adhesion to the plasma membrane and to neighboring blastomeres. These studies involve the isolation and purification of cell surface and yolk-derived 22S adhesion complexes, and their various peptide fragments. The complexes will be identified by SDS-PAGE, radiolabeling, antibody specificity, and peptide mapping. Functional domains will be mapped by covalent modification of neighboring peptides with labeled transfer-linking molecules, by solubilization in lipid vesicles, and by competition during cell-cell adhesion by peptide fragments from the 22S complex and by Fabs to the 22S complex proteins.
| Hawkins, R L; Fan, J; Hille, M B (1995) Gastrulation in the sea urchin, Strongylocentrotus purpuratus, is disrupted by the small laminin peptides YIGSR and IKVAV. Cell Adhes Commun 3:163-77 |
