DISTRIBUTION PATTERNS IN GLYCOCONJUGATE EXPRESSION DURING THE DEVELOPMENT OF THE RAT PALATE

The distribution of complex carbohydrate structures during the embryon ic development of the rat palate was analysed by examining lectin-bind ing patterns in serial paraffin and cryostat sections. With few except ions, the binding patterns showed a general increase in lectin recepto rs in the more developed stages of palatogenesis. High mannose oligosa ccharides were especially amplified during development. Terminal fucos e molecules were not expressed. In contrast, terminal sialic acid mole cules were ubiquitously distributed in epithelial and mesenchymal tiss ues. Non-sialylated terminal N-acetylglucosamine was specifically rest ricted to evolving bone matrix. Before palatal fusion, quantitative bu t not qualitative differences were detected between oral, nasal, and m edial-edge epithelial surfaces. The only exception was LCA, which spec ifically marked epithelial cells at the tip of palatal shelves. A very selective affinity for Jacalin was demonstrated in the oral epitheliu m of the palate after day 16, suggesting the presence of sialylated te rminal galactose-(beta-1,3)-N-acetylgalactosamine. PNA specifically ma rked the basal lamina of the oral side of palatal processes. The bindi ng patterns of DBA, GSL I-A, SBA, and WA indicated that the epithelium of the tongue is characterized by terminal alpha- and beta-galactose residues, whereas palatine cells possess only molecules with beta-anom ery. During palatogenesis, glycosaminoglycans patterns were significan tly modified. Our data suggest that alteration of complex carbohydrate structures may play a central role in modulating cell-cell and cell-m atrix interactions. The significance of these findings, however, remai ns to be elucidated.