Chapter 9 Surface Antigens Involved in Interactions of Embryonic Sea Urchin Cells

Abstract

This chapter explores the specificity hypothesis, with the intent to show the way the cell surface might contribute to the process of gastrulation. It discusses two lines of research—namely, (1) data on the formation of cell–cell contacts is presented to demonstrate an array of age-specific and tissue-specific recognition capabilities available to embryonic cells, (2) immunochemical data shows age-specific and tissue-specific differences in cell surface antigens during the early development of the sea urchin. A species-specific pattern of cellular recognition is identified experimentally between the embryonic cells of Lytechinus variegatus and Tripneustes esculentus . Hybrid embryos, formed as a cross between these two species, are studied to determine their pattern of cellular recognition. Prior to gastrulation, hybrid cells adhered to the cells of maternal genotype only. After gastrulation had begun in the hybrid embryos, hybrid cells adhered to the cells of both maternal and paternal genotype. A serological study identified a similar pattern of cell surface antigen expression; paternal antigens are first observed on hybrid cell surfaces at the gastrula stage. The study further identified four classes of antigens present on embryonic cell surfaces—namely, (1) maternal antigens present on cleavage-stage cells, (2) embryonic antigens appearing at gastrulation and specified by embryonic templates, (3) ectoderm-specific antigens, and (4) endoderm-specific antigens.