Developing follicles of the spotted ray Torpedo marmorata express different glycoside residues in relation to granulosa differentiation and vitelline envelope formation M. Prisco, L. Ricchiari, R. Uliano, A. Pisacane, A. Liguoro and P. Andreuccetti Department of Evolutionary and Comparative Biology, University of Naples Federico II, Naples, Italy Offprint requests to: Dr. Prisco Marina, c/o Dipartimento di Biologia Evolutiva e Comparata, Via Mezzocannone n.8, 80134 Napoli, Italy. Fax: 00390812535035. e-mail: piero.andreuccetti@unina.it
Summary. Lectins constitute a class of proteins/glycoproteins
that specifically bind to terminal glycoside residues. The present
investigation aimed to identify lectin-binding sites in developing
follicles of Torpedo marmorata. Using eleven lectins (WGA, GSI-A4,
GSI-B4, PSA, UEA-I, PNA, MPA, Con-A, DBA, LCA, BPA, SBA), we
demonstrated that the biochemical nature and the distribution
of carbohydrate residues significantly change during oogenesis
in the granulosa cells and the vitelline envelope. In fact, a
progressive appearance of surface glycoproteins bearing terminated
ß-GlcNAc O-linked side chains was observed in the granulosa
during the differentiation of pyriform-like cells from the small
ones via intermediate cells simultaneously with a significant
reduction of the D-Gal chains present in their nucleus. Glycoproteins
bearing ß-GlcNAc O-linked side chains were first evident
on the surface of small cells in contact with the oocyte, then
on the intermediate ones, and finally on pyriform-like cells.
The distribution pattern of such glycoproteins over the differentiated
granulosa cells remained unchanged during the subsequent stages
of the oocyte growth so granulosa cells preserved the same sugar
distribution pattern. Furthermore, a progressive loss of D-Gal
residues was evident in the nucleus of granulosa cells. In fact,
staining for D-Gal was intense in the nucleus of small follicle
cells and progressively reduced till disappearing in differentiated
pyriform-like cells. Conversely, the small follicle cells located
under the basal lamina were devoid of ß-GlcNAc residues,
and the nuclear content in D-Gal remained unchanged. This finding
strongly suggests that surface glycoproteins containing ß-GlcNAc
residues, and the nuclear content in D-Gal might be related to
the differentiation of pyriform-like cells. Key words: Lectin, Pyriform-like cells, Granulosa,
Vitelline envelope, Cartilaginous fish |