Binding pattern of ferritin-labeled lectins (RCAI and WGA) during neural tube closure in the bantam embryo

Cell surface sugar residues in neurulating ectoderms of bantam chick embryos of stage 4-11 were examined using ferritin-labeled Ricinus communis (RCAI) and Wheat germ agglutinin (WGA). RCAI binding sites densely covered the apical surfaces of the basal plate cells during the neural plate stage (1,322.8 +/- 28.8 ferritin particles/micron 2). As neural tube formation advanced, the number of receptors decreased as a result of an increase in the extent of the sparsely covered regions. The decrease in receptors for WGA occurred in a similar manner but more rapidly. By the stage of development at which the opposite sides of the neural ridges meet at the dorsal midline, the receptors for WGA were reduced to about half. After this period, the two lectin receptors did not show significant changes. This result suggests that sugar residues or the sugar-chain skeleton on basal plate cells are altered during neurulation.