Changes in peanut lectin binding sites on the neuroectoderm during neural tube formation in the bantam chick embryo.

Cell surface carbohydrates in the neurulating ectoderm of bantam chick embryos of stage 6-11 were examined using the fluorescein isothiocyanate-labeled and ferritin-labeled peanut lectin, Arachis hypogaea agglutinin (PNA), which is Gal beta 1----3GalNAc specific. Weak fluorescence showing PNA binding sites was seen on the apical surfaces of neural plate cells. On the surfaces of neural tube cells the fluorescence was more intense and appeared as a band. When using ferritin particles as a quantitative EM marker, only a few PNA binding sites covering the apical surfaces of the basal plate cells during the neural plate stage were seen (274.3 +/- 18.67 ferritin particles/micron 2). As neural tube formation advanced, the number of the ferritin labeled PNA binding sites increased as was to be expected from the fluorescent label experiment. At the neural ridge contact stage there were 2.5 times more binding sites than at the neural plate stage. After this period, the lectin binding sites showed no significant changes. These results were the inverse of those for RCAI or WGA lectins previously reported by us. These observations suggest that sugar residues or the sugar-chain skeletons on the neuroectoderm are altered during neurulation.