Cell Surface Changes Occurring During Sea Urchin Embryonic Development Monitored by Quantitative Agglutination with Plant Lectins

Plant lectins have been widely used to investigate the nature and functional significance of carbohydrate-containing cell surface receptor sites on normal, embryonic and tumor cells. In the present study, evidence is presented, using a quantitative electronic particle counter assay to measure agglutination, which indicated that carbohydrate-containing lectin-binding sites change during sea urchin embryonic development. Sea urchin embryo cells are 26 ± 5 % more agglutinable with ConA at early developmental stages (day 1) than at later ones with a marked decline in agglutinability between day 2 and 3. Agglutinability with Ricinus communis agglutinin (RCA) may also be greater in young embryos. Normal embryonic sea urchin cells are not agglutinated with wheat germ agglutinin (WGA) unless the cells are trypsinized. The results suggest that changes in the amount, mobility or distribution of Con A-binding (containing α-d-mannose-like or α-d-glucose-like residues) and RCA-binding (containing β-d-galactose or β-N-acetyl-d-galactosamine-like residues) receptor sites occur with differentiation in sea urchin embryos, while WGA-binding receptor sites (containing N-acetyl-d-glucosamine-like residues) are displayed in a state which precludes agglutination at all developmental stages studied. The results are discussed with respect to the cell types present during sea urchin embryo development and provide quantitative evidence for the contention that specific changes in carbohydrate-containing cell surface sites occur with differentiation and maturation.