Carbohydrate Specificity of Sea Urchin Blastula Adhesion Component
The species-specific and developmental stage-specific aggregation-enhancing supernatant isolated from intact sea urchin (Strongylocentrotus purpuratus) blastula cells incubated in Ca2+?Mg2+-free sea water is a hemagglutinin. This material agglutinated trypsinized, fixed human type O and B (inhibited by d-galactose) erythrocytes, whereas control erythrocytes in Millipore-filtered sea water did not agglutinate. The blastula supernatant agglutinates both live and fixed S. purpuratus blastula cells. Fixed cells were chosen in these experiments so that a standardized, highly reproducible system could be produced by pooling batches of blastula cells. Dissociation supernatant (DS)-mediated agglutination of S. purpuratus blastula cells was blocked by d-galactose and N-acetyl-d-galactosamine by 10 min of incubation, but not by d-glucose, l-fucose, d-mannose, d-glucosamine, d-mannosamine or N-acetyl-d-mannosamine (all at 0.1 M concentration, the concentration chosen as a result of preliminary experiments). The results were consistently observed in scores of experiments and suggest that DS binds cells together via d-galactose-like and N-acetyl-d-galactosamine-like residues. We also found that aggregates of live blastula cells formed in the presence of DS gave rise, after 24 h incubation, to viable, swimming embryoids, suggesting that DS-mediated adhesion is physiologically meaningful.