- Title
- Marsupial sperm antigens
- Creator
- Harris, Merrilee Sue
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 1998
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- The mechanisms and molecules mediating marsupial fertilisation and reproduction will only be elucidated with a detailed understanding of the molecular nature of marsupial gametes and their post-testicular maturation. This thesis presents the first pivotal steps in defining the antigenic nature and maturation of marsupial spermatozoa. Numerous monoclonal antibodies produced against tammar wallaby (Macropus eugenii) and brushtail possum (Trichosurus vulpecula) sperm antigens provided specific tools for characterising the cellular, biochemical and molecular nature of these gametes. Marsupial spermatozoa, like those of their eutherian counterparts, are comprised of a complex array of antigens. Many of these antigens were restricted to specific cellular regions and surface domains, whilst others were distributed widely in the cell. The epitopes recognised by the monoclonal antibodies also displayed differential characteristics. Some were species-specific, whilst others were shared only by other marsupial spermatozoa or a wide variety of species. Similarly some antibodies bound sperm-specific epitopes, whilst others were common to somatic tissues. Most sperm antigens arose in the marsupial testis, however others were added or modified during post-testicular maturation in the epididymis. The characterisation of sperm antigens with potential roles in sperm maturation, fertilisation events were facilitated by the WSA- 1 monoclonal antibody. This antibody recognised a species and tissue-specific epitope shared by an acrosomal matrix antigen and an epididymal maturation antigen on wallaby spermatozoa. The acrosomal antigen arose in the wallaby testis, persisting unaltered during epididymal maturation and shared some sequence homology with proacrosin. The proacrosin/acrosin zymogen mediates sperm binding to ZP2 and zona penetration in eutherian species. This antibody might therefore be used to investigate the importance of proacrosin in marsupial fertilisation. The WSA- 1 maturation antigen was added to the whole surface of wallaby spermatozoa during epididymal transit. Secretion by the epididymal epithelium commenced in the proximal head of the epididymis and persisted distally in the tract whereas the antigen first associated with the sperm surface in the proximal body of the epididymis. Cross-linking of the WSA-1 carbohydrate epitope on the sperm surface resulted in potent midpiece-midpiece agglutination of wallaby ejaculated spermatozoa. Investigations in eutherian species suggest that the WSA-1 maturation antigen may function in sperm storage or the acquisition of sperm motility and fertility in the wallaby epididymis. As such the WSA-1 antigen is likely to be involved capacitation and/or fertilisation events in the female tract and has great promise as an immunocontraceptive target antigen. Intracellular antigenic maturation accompanies the morphological maturation of marsupial spermatozoa during epididymal transit. The PSA-10 monoclonal antibody recognised midpiece fibre network antigen(s) that arose concomitantly with the epididymal development of this structure in both possum and wallaby spermatozoa. Thus the PSA-lO monoclonal antibody provides an important tool for following the development and fate of a cytoskeletal structure which is unique to marsupial spermatozoa. The PSA-10 antibody also recognised an antigen associated with the outer acrosomal membrane of possum spermatozoa. Initial detection of PSA-10 acrosomal immunoreactivity also accompanied major morphological folding and consolidation of the possum acrosome during epididymal transit. Evidence of the antigenic modification of the marsupial sperm nucleus during spermiogenesis was provided by the differential binding patterns of two monoclonal antibodies. The WSA-3 and PSA-1 monoclonal antibodies each bound sperm-specific nucleoproteins in the wallaby testis. The WSA - 3 antigen was first detected in stage 10 spermatids and accumulated in spermatids in stages of spermiogenesis characterised by considerable nuclear condensation and elongation. However the PSA- 1 nucleoprotein was first detected quite late in spermiogenesis on stage 13 spermatids. These marsupial sperm nucleoproteins may play a role in the protein transitions thought to mediate chromatin binding and condensation in the mammalian spermatid nucleus. The construction of a wallaby testis cDNA library as part of this investiagation provides an invaluable tool for the identification of of the nucleotide sequences encoding marsupial sperm proteins. Screening the cDNA library resulted in the cloning of a partial sequence for a marsupial heat shock protein. The highly conserved heat shock proteins have important roles in the cellular processing and cytoprotection of testicular polypeptides. The significant contributions to our fundamental knowledge of marsupial sperm antigens and their epididymal maturation in this study provide a strong foundation for future examinations of marsupial capacitation and fertilisation events. Some of the antigens identified may also have applications to the regulation of fertility in pest marsupial species.
- Subject
- marsupial fertilisation; reproduction; monoclonal antibodies; sperm maturation; WSA-1
- Identifier
- http://hdl.handle.net/1959.13/1418097
- Identifier
- uon:37295
- Rights
- Copyright 1998 Merrilee Sue Harris
- Language
- eng
- Full Text
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