Immunochemical study of gangliosides at the cell surface of sea urchin embryos

Two main gangliosides (G-1 and G-2) were isolated from eggs and embryos S. intermedius. They contain glucose, N-glucolylneuraminic acids, phytosphyngosine, fatty acids and alpha-hydroxy fatty acids. Molar ratios and sequence of these components are the same for both gangliosides, but G-2 contains sulphate residue which is attached to the terminal neuraminic acid. To obtain specific antisera rabbits were immunized by G-1 or G-2, which were mixed with bovine serum albumin and Freund's adjuvant. Both gangliosides possessed electrophoretic and antigenic heterogeneity. G-1 and G-2 gangliosides have common and individual antigenic determinants. Glucosylceramide of gangliosides is immunologically inactive. Individual antigenic specificity of the gangliosides depends on the presence of N-glycolylneuraminic acid (G-1) and SO3H-group (G-2). Egg gangliosides were demonstrated by immunofluorescence throughout the cell surface. After fertilization of immunofluorescent label was concentrated on one pole of the embryo only. During the development of specific fluorescence was again uniformly distributed at the blastomer surface. The most intense fluorescence was observed in the junction areas of the blastomers.