Isolation of species-specific and stage-specific adhesion promoting component by disaggregation of intact sea urchin embryo cells

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 -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 -galactose and N-acetyl- -galactosamine by 10 min of incubation, but not by -glucose, -fucose, -mannose, -glucosamine, -mannosamine or N-acetyl- -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 -galactose-like and N-acetyl- -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.