AN N-LINKED CARBOHYDRATE-CONTAINING EXTRACELLULAR-MATRIX DETERMINANT PLAYS A KEY ROLE IN SEA-URCHIN GASTRULATION

During the process of gastrulation in the sea urchin embryo, the veget al plate invaginates to form the archenteron, a long narrow tube that extends across the blastocoel. Rearrangement of cells within the arche nteron is thought to be a key component of the process of archenteron elongation. While these cell rearrangements have been well described, the mechanism of the rearrangements and the coordination of the moveme nts of individual cells that results in the elongation of the archente ron are not well understood. We have identified a monoclonal antibody, called ECM 1, that recognizes an N-linked carbohydrate-containing epi tope on several high-molecular-weight basal lamina glycoproteins. In a n attempt to block the function of this determinant in development, th e ECM 1 antibody was injected into the blastocoel of living embryos an d the effects on morphogenesis were determined. Injection of intact EC M 1 IgG or monovalent Fab fragments blocks cell rearrangements during secondary invagination and cell movements during segmentation of the g ut. Clycopeptides derived from the glycoproteins recognized by ECM 1 a lso inhibit cell rearrangements during secondary invagination when inj ected into the blastocoel. The inhibitory activity of these peptides i s eliminated by digestion with N-glycosidase F or pronase, enzymes tha t also disrupt the ECM 1 determinant. ECM 1 recognizes a nonuniformly distributed determinant in the basal lamina and blastocoel matrix. Thi s determinant is stored in cytoplasmic granules in the unfertilized eg g and is deposited into the basal lamina by the blastula stage. The de terminant becomes concentrated in the basal lamina in the vegetal regi on of the embryo early in gastrulation. At the prism stage, the determ inant accumulates in the basal lamina and blastocoel matrix in the ven tral region of the embryo. These data indicate that the vegetally loca lized, N-linked carbohydrate-containing determinant recognized by ECM 1 plays an important role in cell movements during archenteron morphog enesis in the sea urchin embryo. (C) 1994 Academic Press, Inc.