Distribution of lectin‐binding glycosidic residues in the hamster follicular oocytes and their modifications in the zona pellucida after ovulation

Abstract

In the present study, we have employed a battery of colloidal gold-tagged lectins as probes in conjunction with quantitative analysis to demonstrate the distribution and changes of carbohydrate residues in the hamster zona pellucida (ZP) during ovarian follicular development and during transit of the oocyte through the oviduct after ovulation. High-resolution lectin-gold cytochemistry performed on thin sections of LR White-embedded ovaries revealed a moderate to strong reactivity to WGA, PNA, DSA, AAA, and MAA over the entire thickness of the ZP of ovarian oocytes at different stages of follicular development. Labeling intensity over the ZP progressively increased as follicles matured in the ovary. In parallel, there was an association of labeling by gold particles with cortical granules, stacks of Golgi saccules, and complex structures called vesicular aggregates in the oocyte proper especially during the late stages of follicular growth. In contrary, labeling with each of HPA, DBA, and BSAIB(4) was absent in the ovary but was found to be localized over Golgi complexes and secretory granules in the non-ciliated secretory cells of the oviduct. When ovulated oocytes were labeled with each of HPA, WGA, RCA-I, PNA, DSA, BSAIB(4), AAA, MAA, and DBA, the ZP and several organelles in the oocyte proper presented a differential distribution of lectin-binding sites. Quantitative analysis was also performed on labeling by lectin-gold complexes that bind specifically to the ZP of mature follicular and ovulated oocytes. Quantitative evaluation revealed heterogeneous labeling between the inner and the outer zone of the ZP. A significant increase in the labeling densities in both inner and outer ZP was noted when tissue sections of ovulated oocytes were labeled with RCA-I or AAA. Tissue sections of ovaries labeled with WGA demonstrated a significant increase in the density of labeling in the outer layer of the ZP. Labeling by PNA, DSA, and MAA, however, showed a significant decrease in both the inner and outer portions of the ZP. Together, these results suggest that in the hamster, glycoproteins carrying specific sugar residues are added to the ZP of ovarian follicles during the early stages of folliculogenesis and are processed through a common secretory machinery, and that there is a significant change in both the sugar moieties and distribution of glycoproteins in the ZP following ovulation. Our results also showed that the hamster oviduct plays an important role in contributing certain glycoproteins to the ZP suggesting that the sugar moieties of these oviductal glycoproteins may have functional significance in fertilization.

Topographical localisation of glucidic residues and their variations in the canine zona pellucida during folliculogenesis

“…The results obtained from our study agree with previous histochemical investigations (Roux & Kan 1991, Avile´s et al 1994, 1998, 2003, Parillo & Verini Supplizi 1999, El-Mestrah & Kan 2001, 2002 regarding the asymmetric distribution of some glycomolecules through the ZP. It has been suggested (ElMestrah & Kan 2002) that the different topographical localisation of the various lectin reactive-sites on the zona matrix indicates a different possible role of the glucidic determinants in the process of sperm-zona binding.…”

“…It has been hypothesized that these aggregates seen in the ooplasm and follicular cells are implicated in the synthesis and final secretion of glycosylated ZP proteins as intermediary vehicles (Avile´s et al 1994, El-Mestrah & Kan 2001. This allows us to suggest that both the oocyte and the surrounding granulosa cells are involved in the synthesis and secretion of the glycocomponents of the canine ZP in agreement with the findings of other Authors (Barber et al 2001, Blackmore et al 2004.…”

aura/mid1ip1Lregulates the cytoskeleton at the zebrafish egg-to-embryo transition

“…These observations suggest that aura is required for FMA reorganization. The size and the large number of vesicles observed in aura mutants suggested that they are unreleased CGs (Becker and Hart, 1999), which we confirmed using the glycoconjugate-binding dyes Maclura pomifera agglutinin (MPA) and wheat germ agglutinin (WGA) (Becker and Hart, 1999;El-Mestrah and Kan, 2001;Bembenek et al, 2007). Quantification of CG densities in mature, extruded eggs from wild-type and aura mutant females indicates that initial CG densities are not significantly different ( paired t-test, P=0.56).…”

Texture of the zona pellucida of the mature pig oocyte. The mammalian egg envelope revisited

“…The staining of ovarian sections with lectins for sugar distribution revealed heterogeneities in the ZP (layers of different affinities) of eutherians [50,51] and marsupials [52]. So glycosylation may change, particularly at the onset and/or the end of ZP secretion, inducing stronger lectin binding in the outer and/or inner faces of the ZP.…”