Immunocytochemical localization of the protein reactive to human β‐1, 4‐galactosyltransferase antibodies during chick embryonic skin differentiaion

Background: β‐1, 4‐Galactosyltransferase (GalTase) transfers galactose from UDP‐galactose to terminal N‐acetylglucosamine in glycoconjugates and is located both in the Golgi apparatus and in the plasma membrane. The cell surface GalTase is thought to be involved in cell‐to‐cell recognition and cell‐to‐extracellular matrix interaction. Methods: By the use of specific monoclonal antibodies against human GalTase, changes in cell surface localization of the protein reactive to the antibodies in chick embryonic skin during its differentiation in vivo and in vitro were detected immunohistochemically at both light‐ and electron microscopic levels. The distribution of glycoconjugates having terminal N‐acetylglucosamine residues was detected by staining with succinylated wheat germ agglutinin (s‐WGA). Results: Under the light microscope, intense immunostaining was observed in the keratinized epidermis, particularly in the intermediate layer. Marked changes in the localization of the staining were observed in vitamin A‐induced mucus‐secreting skin, in which keratinization was suppressed. The localization of the immunostaining was in parallel with that of glycoconjugates having terminal N‐acetylglucosamine residues. Immunoelectron microscopically the immunostaining was located on the cell surface and in the intercellular space of the desmosomes in the intermediate cells of the keratinized epidermis. However, the staining was not present on the cell surface but was detected on the limiting membrane of the mucous granules, in the mucous metaplastic epidermis. In contrast, the staining was always found in the Golgi apparatus in all of the cells. Conclusions: These results suggest that the protein reactive to human GalTase antibody may be involved in chick epidermal differentiation. © 1995 Wiley‐Liss, Inc.