Biochemical Journal

Research article

O-glycan variability of egg-jelly mucins from Xenopus laevis: characterization of four phenotypes that differ by the terminal glycosylation of their mucins

Yann GUERARDEL, Ossarath KOL, Emmanuel MAES, Tony LEFEBVRE, Bénoni BOILLY, Monique DAVRIL, Gérard STRECKER


Eggs from Xenopus laevis are surrounded by several layers of jelly that are needed for proper fertilization. Jelly coat is composed of high-molecular-mass glycoconjugates to which are bound many globular proteins. O-glycans released from the jelly coat of X. laevis have been partially described in previous studies. In this study, we compared the glycosylation pattern of the egg jelly coat isolated from six specimens of X. laevis. The O-glycans were released from jelly coats by alkali/borohydride treatment. Structural characterization was performed through a combination of one- and two-dimensional 1H-NMR and methylation analysis. This allowed the description of a new family of sulphated O-glycans present in jelly coats of all X. laevis. However, the jelly O-glycans showed a low extent of polymorphism between specimens. This intra-specific variability was restricted to the terminal substitution of O-linked oligosaccharides. The differential expression of two glycosyltransferase [an α-(1 → 4) galactosyltransferase and an α-(1 → 3) fucosyltransferase] activities resulted in the characterization of four phenotypes of X. laevis. Furthermore, electrophoretic analysis suggested that the high-molecular-mass fraction of jelly coat was mostly composed of mucin-type glycoproteins. Blot analysis with lectins confirmed that the glycan variability was borne by these mucin-type components. However, fertilization assays suggested that the glycan polymorphism had no repercussion on egg fertilizability.

  • amphibian
  • fertilization
  • glycosyltransferase
  • NMR