Developmental changes in carbohydrate antigens in embryonic rat lens

The functions of glycosphingolipids, especially those containing the alpha-galactosyl epitope, were investigated during the development and differentiation of rat lens. Glycosphingolipids in embryonic lens tissue were mainly composed of neolacto-series glycosphingolipids and sialic acid-containing ganglio-series gangliosides GM3 and GD3. These glycosphingolipids and gangliosides were widely expressed on cell membranes in the lens vesicle and the elongating lens fibers. In particular, the expression of neolacto-series glycosphingolipids with the alpha-galactosyl epitope was found to be associated with the differentiation and interaction of lens fibers. Glycoproteins with the alpha-galactosyl epitope was also involved in the elongation of lens fibers. The expression of the glycoproteins was highly specific in elongating lens fibers when these were examined in head sections obtained at various embryonic stages. Thus, the alpha-galactosyl epitope on glycosphingolipids and glycoproteins appears to be associated with the differentiation and elongation of lens fibers in the rat. Evolution-related changes in the expression of carbohydrate antigens are also discussed in relation to the development and cell-to-cell interaction of lens fibers in mammals.