Egg-Coat and Zona Pellucida Proteins of Chicken as a Typical Species of Aves

β1,4-Galactosyltransferase-I (GalTase-I) is one of the key molecules on the sperm surface of eutherian mammals that is likely to be involved in binding to the egg coat, the zona pellucida, to mediate sperm–egg interaction. In laboratory mice, the species for which most data are available, this protein functions as a receptor for the zona pellucida protein ZP3 of the oocyte and, upon binding, triggers the sperm acrosome reaction. In the present study, we investigated the presence and abundance of GalTase-I in epididymal sperm extracts of a marsupial, the brushtail possum, Trichosurus vulpecula. For this, spermatozoa were collected from cauda epididymides and the amount of β1,4-galactosyltransferase activity in washed sperm extracts was compared with that of porcine spermatozoa. Overall β1,4-galactosyltransferase enzyme activity was found to be more abundant in possum sperm extracts than those from porcine spermatozoa (P < 0.05). Immunoblots with an antibody to mouse GalTase-I revealed that the molecular weight of possum spermatozoa GalTase-I was 66 kDa, which is similar to the molecular weight of GalTase-I in spermatozoa from eutherian mammals. The molecular weight of GalTase-I was the same in sperm extracts collected from the caput and cauda epididymides. These results demonstrate that GalTase-I is indeed present in possum spermatozoa and thus it may be a gamete receptor molecule on the sperm surface of marsupials as well as those of eutherian mammals.

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The egg coat zona pellucida 3 glycoprotein – evolution of its putative sperm-binding region in Old World murine rodents (Rodentia: Muridae)

Reproduction Fertility and Development ◽

10.1071/rd16455 ◽

2017 ◽

Vol 29 (12) ◽

pp. 2376 ◽

Cited By ~ 1

Author(s):

Christine A. Swann ◽

Steven J. B. Cooper ◽

William G. Breed

Keyword(s):

Sexual Selection ◽

Zona Pellucida ◽

Laboratory Mouse ◽

Sequence Divergence ◽

Tail Length ◽

Good Evidence ◽

Sperm Binding ◽

Molecular Divergence ◽

Murine Rodents ◽

Egg Coat

In eutherian mammals, before fertilisation can occur the spermatozoon has to bind to, and penetrate, the egg coat, the zona pellucida (ZP). In the laboratory mouse there is good evidence that the primary sperm-binding site is a protein region encoded by Exon 7 of the ZP3 gene and it has been proposed that binding is species specific and evolves by sexual selection. In the present study we investigate these hypotheses by comparing Exon 6 and 7 sequences of ZP3 in 28 species of murine rodents of eight different divisions from Asia, Africa and Australasia, in which a diverse array of sperm morphologies occurs. We found considerable nucleotide (and corresponding amino acid) sequence divergence in Exon 7, but not in Exon 6, across these species, with evidence for positive selection at five codon positions. This molecular divergence does not appear to be due to reinforcement to reduce hybridisation, nor does it correlate with divergence in sperm head morphology or tail length, thus it is unlikely to be driven by inter-male sperm competition. Other forms of post-copulatory sexual selection therefore appear to have resulted in the molecular divergence of this region of ZP3 in this highly speciose group of mammals.

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Dicalcin, a zona pellucida protein that regulates fertilization competence of the egg coat in Xenopus laevis

The Journal of Physiological Sciences ◽

10.1007/s12576-015-0402-7 ◽

2015 ◽

Vol 65 (6) ◽

pp. 507-514 ◽

Cited By ~ 2

Author(s):

Naofumi Miwa

Keyword(s):

Xenopus Laevis ◽

Zona Pellucida ◽

Egg Coat

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Overexpressing sperm surface beta 1,4-galactosyltransferase in transgenic mice affects multiple aspects of sperm-egg interactions.

The Journal of Cell Biology ◽

10.1083/jcb.126.6.1573 ◽

1994 ◽

Vol 126 (6) ◽

pp. 1573-1583 ◽

Cited By ~ 47

Author(s):

A Youakim ◽

H J Hathaway ◽

D J Miller ◽

X Gong ◽

B D Shur

Keyword(s):

Transgenic Mice ◽

Zona Pellucida ◽

Transgenic Animals ◽

Wild Type ◽

Sperm Surface ◽

Receptor Aggregation ◽

Excess Surface ◽

Before And After ◽

Mechanistic Basis ◽

Egg Coat

Sperm surface beta 1,4-galactosyltransferase (GalTase) mediates fertilization in mice by binding to specific O-linked oligosaccharide ligands on the egg coat glycoprotein ZP3. Before binding the egg, sperm GalTase is masked by epididymally derived glycosides that are shed from the sperm surface during capacitation. After binding the egg, sperm-bound oligosaccharides on ZP3 induce the acrosome reaction by receptor aggregation, presumably involving GalTase. In this study, we asked how increasing the levels of sperm surface GalTase would affect sperm-egg interactions using transgenic mice that overexpress GalTase under the control of a heterologous promoter. GalTase expression was elevated in many tissues in adult transgenic animals, including testis. Sperm from transgenic males had approximately six times the wild-type level of surface GalTase protein, which was localized appropriately on the sperm head as revealed by indirect immunofluorescence. As expected, sperm from transgenic mice bound more radiolabeled ZP3 than did wild-type sperm. However, sperm from transgenic animals were relatively unable to bind eggs, as compared to sperm from wild-type animals. The mechanistic basis for the reduced egg-binding ability of transgenic sperm was attributed to alterations in two GalTase-dependent events. First, transgenic sperm that overexpress surface GalTase bound more epididymal glycoside substrates than did sperm from wild-type mice, thus masking GalTase and preventing it from interacting with its zona pellucida ligand. Second, those sperm from transgenic mice that were able to bind the zona pellucida were hypersensitive to ZP3, such that they underwent precocious acrosome reactions and bound to eggs more tenuously than did wild-type sperm. These results demonstrate that sperm-egg binding requires an optimal, rather than maximal, level of surface GalTase expression, since increasing this level decreases sperm reproductive efficiency both before and after egg binding. Although sperm GalTase is required for fertilization by serving as a receptor for the egg zona pellucida, excess surface GalTase is counterproductive to successful sperm-egg binding.

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Egg cortical granule N-acetylglucosaminidase is required for the mouse zona block to polyspermy.

The Journal of Cell Biology ◽

10.1083/jcb.123.6.1431 ◽

1993 ◽

Vol 123 (6) ◽

pp. 1431-1440 ◽

Cited By ~ 87

Author(s):

D J Miller ◽

X Gong ◽

G Decker ◽

B D Shur

Keyword(s):

Zona Pellucida ◽

Binding Sites ◽

Binding Activity ◽

Cortical Granule ◽

Cortical Granules ◽

Sperm Binding ◽

Competitive Inhibitors ◽

Glycosidase Inhibitor ◽

Egg Coat

The mammalian egg must be fertilized by only one sperm to prevent polyploidy. In most mammals studied to date, the primary block to polyspermy occurs at the zona pellucida, the mammalian egg coat, after exocytosis of the contents of the cortical granules into the perivitelline space. The exudate acts on the zona, causing it to lose its ability to bind sperm and to be penetrated by sperm previously bound to the zona. However, the cortical granule components responsible for the zona block have not been identified. Studies described herein demonstrate that N-acetylglucosaminidase is localized in cortical granules and is responsible for the loss in sperm-binding activity leading to the zona block to polyspermy. Before fertilization, sperm initially bind to the zona by an interaction between sperm surface GalTase and terminal N-acetylglucosamine residues on specific oligosaccharides of the zona glycoprotein ZP3 (Miller, D. J., M. B. Macek, and B. D. Shur. 1992. Nature (Lond.). 357:589-593). These GalTase-binding sites are lost from ZP3 after fertilization, an effect that can be duplicated by N-acetylglucosaminidase treatment. Therefore, N-acetylglucosaminidase, or a related glycosidase, may be present in cortical granules and be responsible for ZP3's loss of sperm-binding activity at fertilization. Of eight glycosidases assayed in exudates of ionophore-activated eggs, N-acetylglucosaminidase was 10-fold higher than any other activity. The enzyme was localized to cortical granules using immunoelectron microscopy. Approximately 70 or 90% of the enzyme was released from cortical granules after ionophore activation or in vivo fertilization, respectively. The isoform of N-acetylglucosaminidase found in cortical granules was identified as beta-hexosaminidase B, the beta, beta homodimer. Inhibition of N-acetylglucosaminidase released from activated eggs, with either competitive inhibitors or with specific antibodies, resulted in polyspermic binding to the zona pellucida. Another glycosidase inhibitor or nonimmune antibodies had no effect on sperm binding to activated eggs. Therefore, egg cortical granule N-acetylglucosaminidase is released at fertilization, where it inactivates the sperm GalTase-binding site, accounting for the block in sperm binding to the zona pellucida.

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