Distribution of lectin binding sites in Xenopus laevis egg jelly

Diversity of sialic acids and sialoglycoproteins in gametes and at fertilization

Sialic acids are a family of 9-carbon monosaccharides with particular physicochemical properties. They modulate the biological functions of the molecules that carry them and are involved in several steps of the reproductive process. Sialoglycoproteins participate in the balance between species recognition and specificity, and the mechanisms of these aspects remain an issue in gametes formation and binding in metazoan reproduction. Sialoglycoproteins form a specific coat at the gametes surface and specific polysialylated chains are present on marine species oocytes. Spermatozoa are submitted to critical sialic acid changes in the female reproductive tract facilitating their migration, their survival through the modulation of the female innate immune response, and the final oocyte-binding event. To decipher the role of sialic acids in gametes and at fertilization, the dynamical changes of enzymes involved in their synthesis and removal have to be further considered.

Identification and role of carbohydrates on the surface of gametes in the zebra mussel, Dreissena polymorpha

The objective of this study is to identify surface carbohydrates on zebra mussel, Dreissena polymorpha, eggs and sperm and to analyze their potential role in fertilization. The lectins WGA, Con A, LcH, LTA, SBA, PNA, and GSII were tested for affinity to both eggs and sperm. WGA, Con A, and LcH uniformly labeled eggs. LTA, SBA, PNA, and GSII did not. WGA labeled the entire sperm surface including the unreacted acrosome. Labeling by Con A, LcH, LTA, SBA, PNA, and GSII was restricted to the inner acrosomal region of acrosome-reacted sperm. GSII labeling suggests the presence of N-acetyl-d-glucosamine (GlcNAc) only in the inner acrosomal membrane and not on eggs. GlcNAc blocked sperm-egg binding. GSII labeling was associated with a ring-like structure at the site of sperm entry intimately associated with sperm-egg binding. Nonfertilizing sperm were detached from the egg surface along with the GSII basal ring about 15 min postinsemination in a process blocked by trypsin inhibitors.

Expression pattern of glycoconjugates in the Bidderian and ovarian follicles of the Brazilian toad Bufo ictericus analyzed by lectin histochemistry

The Bidder's organ and ovary of the Brazilian toad Bufo ictericus were studied by light microscopy, using hematoxylin-eosin (HE) and periodic acid Schiff (PAS) staining. The expression and distribution of carbohydrate moieties was analyzed by lectin histochemistry, using 8 lectins with different carbohydrate specificities: Ulex europaeus (UEA I), Lens culinaris (LCA), Erythrina cristagalli (ECA), Arachis hypogaea (PNA), Ricinus communis (RCA I), Aleuria aurantia (AAA), Triticum vulgaris (WGA), and Glycine maximum (SBA). The results showed that the Bidderian zona pellucida presented alpha-mannose, alpha-L-fucose, beta-D-galactose, N-acetyl-D-glucosamine, and alpha/beta-N-acetyl-galactosamine residues. The Bidderian follicular cells showed the presence of beta-D-galactose and N-acetyl-D-glucosamine. In the extracellular matrix, alpha-mannose and alpha/beta-N-acetyl-galactosamine residues were detected. The ovarian zona pellucida showed alpha-L-fucose, N-acetyl-D-glucosamine, alpha/beta-N-acetyl-galactosamine residues, and alpha-mannose and N-acetyl-D-glucosamine residues were detected in the follicular cells. Thus, the zona pellucida in both organs contains N-acetyl-D-glucosamine, and alpha/beta-N-acetyl-galactosamine residues. alpha-L-fucose residues were detected in the zona pellucida of both organs, using different lectins. Considering that beta-D-galactose residue was absent from ovary but present in the Bidder's organ, this sugar residue may play an important role in follicle development, blocking the Bidderian follicles and preventing further development of the Bidder's organ into a functional ovary.

Analysis of the participation of N-acetylglucosamine in the different steps of sperm-zona pellucida interaction in hamster

Glycoproteins and lectin-like proteins mediate sperm-zona pellucida interaction. The present study analysed the participation of carbohydrates in the different stages of sperm interaction with the zona pellucida in hamster, by determining the effects of different monosaccharides. N-acetylglucosamine (GlcNAc, 1 mM) reduced sperm ability to bind to the zona pellucida. Surprisingly, spontaneous acrosome reaction (AR) was also inhibited by this sugar. In order to analyse the effect of GlcNAc on sperm-zona pellucida binding, independent of its effect on the AR, strontium (Sr) was used as a calcium (Ca) replacement in the sperm capacitation and co-incubation medium. Sr seemed to be able to replace Ca for sperm capacitation, at least when measured as the ability to bind to the zona pellucida, and undergo AR when Ca is provided. Moreover, sperm-zona pellucida binding could also take place in a Sr-modified medium. When binding assays were carried out in the Sr medium, GlcNAc also produced an inhibitory effect. This could be reproduced when sperm, but not oocytes, were pre-incubated with the monosaccharide. IVF assays were also carried out to analyse the participation of GlcNAc in the different steps of sperm-oocyte interaction. Taken together, the results support the involvement of the GlcNAc residues of the zona pellucida in the early steps of the interaction with sperm.

The urodele egg-coat as the apparatus adapted for the internal fertilization

Fertilization is a significant event for reproducing offspring. It is achieved under a species-specific environment, which influences the conditions to assure the successful fertilization in some cases. Several studies about the basic mechanism of fertilization suggest that the fertilization mechanism is modified among species to be suited for the fertilization environment. In amphibians, many anurans undergo external fertilization while most urodeles do internal fertilization. An amphibian egg is surrounded by egg-coats, which are composed of vitelline envelope and layered egg-jelly. They are significant as fields for the sperm-egg interaction at fertilization. The fertilization processes that take place in the egg-coats are supposed to be easily influenced by the fertilization environment, because they, especially egg-jelly, are exposed to the surroundings at fertilization. In the present article, we describe the fertilization system equipped in newt egg-coats. Newt sperm are stored in spermatheca that exists in cloaca of a female and directly inseminated on the surface of egg-jelly. Sperm motility and acrosome reaction are induced in the outermost portion of the egg-jelly. Motion of the moving sperm becomes vigorous in the egg-jelly and sperm are guided to vitelline envelope by the aid of egg-jelly structure. Most of the sperm passing through the egg-jelly, as the result, has been induced acrosome reaction and those sperm can bind to the vitelline envelope to contribute to the successful fertilization. This fertilization system has a distinct feature from the known system in species undergoing external fertilization. The feature of the system in the newt egg-jelly is discussed with the view to achieving the successful fertilization in the internal environment.

Profiling with structural elucidation of the neutral and anionic O-linked oligosaccharides in the egg jelly coat of Xenopus laevis by Fourier transform mass spectrometry

A strategic method with high speed and sensitivity is outlined for the analysis of mucin-type oligosaccharide from the jelly coat of Xenopus laevis. The method relies primarily on mass spectrometric techniques, in this case matrix-assisted laser desorption/ionization Fourier-transform mass spectrometry (MALDI-FTMS) and collision-induced dissociation (CID). Separation with isolation of the oligosaccharides was streamlined to couple well with mass spectrometry allowing the rapid determination of all detectable components from both neutral and anionic species. Partial structures of anionic components, composed primarily of sulfate esters, were obtained with CID. For neutral species, a method that allowed the complete structural determination using mass spectrometry was used. The method builds on the structure of small number of known compounds to determine unknown structures from the same biological source. In this example, a small number of oligosaccharides, elucidated previously by NMR, were used to develop a set of substructural motifs that were characterized by CID. The presence of the motifs in the CID spectra were then used to determine the structures of unknown compounds that were in abundances too small for NMR analysis.