Surface glycoproteins bearing α‐GalNAc terminated chains accompany pyriform cell differentiation in lizards

Abstract

The present investigation demonstrates that in squamate reptiles, as already reported for Podarcis sicula (Andreuccetti et al., 2001), the differentiation of pyriform cells from small, stem follicle cells is characterized by the progressive appearance on the cell surface of glycoproteins bearing alpha-GalNAc terminated O-linked side chains. Using a lectin panel (WGA, GSI-A4, GSI-B4, PSA UEA-I, PNA, Con-A, DBA, LCA, BPA, SBA), we demonstrated that, during previtellogenesis, the pattern of distribution of DBA binding sites over the follicular epithelium dramatically changes. In fact, binding sites first appear in follicular epithelium at the time that small cells begin to differentiate; in such follicles, labeling is evident on the cell surfaces of small and intermediate cells. Later on, as the differentiation progresses, the binding sites also become evident on the cell surface of pyriform cells. Once differentiated, the pattern of the distribution of DBA binding sites over the follicular epithelium does not change. By contrast, during the phase of intermediate and pyriform cell regression, DBA binding sites gradually decrease, so that the monolayered follicular epithelium of vitellogenic follicles, constituted only by small cells, shows no binding sites for DBA. It is noteworthy that binding sites for DBA are present on small cells located in contact with the oocyte membrane, but not on those located under the basal lamina or among pyriform cells, and therefore not engaged in the differentiation into pyriform cells. This finding demonstrates that, in squamates, the pattern of distribution of alpha-N-GalNAc containing glycoproteins significantly changes during previtellogenesis, and that these modifications are probably related to the differentiation of small stem cells into highly specialized pyriforms.

Embryotoxic activity and differential binding of plant-derived carbohydrate-recognizing proteins towards the sea urchin embryo cells

“…An increasing number of plant lectins have been fully characterized in terms of three-dimensional folding and detailed requirements for glycan recognition [20]. Such information greatly helps the investigation of their action upon cells or organisms as signalling molecules [21] as well as making them valuable tools for the detection and characterization of glycan moieties naturally occurring on cell surfaces during the cells life cycle or under pathological conditions [22,23]. In this study, these two strategies were assessed using a set of well-characterized lectins whose monosaccharide specificities are glucose/mannose (ConBr and CFL), ␣-galactose (jacalin), galactose/N-acetylgalactosamine (VML and abrin) and N-acetylglucosamine/N-acetylneuraminic acid (WGA).…”

The Maturation of Oocyte Follicular Epithelium of Podarcis s. sicula Is Promoted by d-Aspartic Acid

“…In P. sicula (Andreuccetti et al 2001) and in other squamate reptiles (Del Carmen et al 1996;Uliano et al 2001), the gradual modification of surface glycoprotein distribution over the follicular epithelium of oocytes depends on the stage of oocyte growth. In the lizard Ctenosaura pectinata, the zona pellucida has been reported to consist of a polysaccharide-protein complex, which exhibits positive periodic acid-Schiff (PAS) reaction and hyaluronidase labile metachromasia and alcianophilia (Del Carmen et al 1996).…”