Galactosides in glycoconjugates of Xenopus laevis testis shown by lectin histochemistry.

The implication of galactosides and other glycoconjugates on spermatogenesis has been previously reported. Glycans show such a complex structure that it makes them very difficult to analyze. Lectin histochemistry is a helpful tool for the study of glycan composition. Lectin histochemistry can be combined with deglycosylation pretreatments to explore the glycan type to which carbohydrates are linked. The aim of the present work was the localization of galactose (Gal)-containing glycoconjugates in the testis of Xenopus laevis, a species widely used in cell, molecular and developmental biology. Gal specific lectins BPL, PNA, BSI-B4, MAA-I, and RCA-I, were used in combination with deglycosylation procedures. Except for BPL, all the lectins were reactive for several testicular tissues. Some of the lectins showed a different reactivity depending on the stage of spermatogenic development, suggesting that cell glycoconjugates are modified during spermatogenesis. The surface of primary spermatocytes was strongly labeled with lectins from peanut (PNA) and castor bean (RCA-I), which agrees with the presence of galactosyl-glycolipids reported in the cell membrane of mammalian spermatocytes. The acrosome was unexpectedly negative to all the lectins tested, whereas the acrosome of mammals and other amphibians has shown a high expression of glycoconjugates, including galactosides. The results obtained after deglycosylation by β-elimination or incubation with PNGase F, which respectively remove O- and N-linked oligosaccharides, allowed us to elucidate the nature of the labeled glycans. The strong expression of galactosides at the cell surface of spermatocytes and spermatids suggests the involvement of these glycans in cell adhesion mechanisms during spermatogenesis.