- Title
- Post-meiotic DNA damage in spermatoza and consequences to offspring
- Creator
- Xavier, Miguel João Garcia dos Santos
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2018
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Sexual reproduction is an essential component of mammalian life where genomic information is transmitted from both parents to their offspring through the gametes. From the fusion of the gametes, a single-celled zygote can arise and develop into a functional multicellular eukaryotic organism. As such, each gamete must transport all the inheritable information, while protecting it from becoming damaged. However, given the importance of this inheritable information, even small alterations can have devastating consequences to health of their offspring. Unfortunately, several biological processes and environmental factors promote alterations to the genetic and the epigenetic information inside the gametes. As a result, unresolved alteration may comprise the integrity of the gametes and give rise to de novo mutations in their offspring. Recent work has shown that the age of human fathers at the time of conception may be responsible for the introduction of numerous de novo mutations to the genome of their children. The initial study within this thesis aimed to build upon this body of work by validating that the offspring of aged mice carried a higher mutational load than those of younger mice. Regrettably, no conclusive evidence was found to suggest that parental age had any influence on the genetic composition of their progeny. In view of these findings, we hypothesize that the presence of an extremely efficient DNA repair mechanism in germ line cells and strong selective forces in the female reproductive track may have prevented the accumulation of de novo mutations in the developing embryos. This suggested that the Big Blue mouse strain used in our study is unsuitable to model the effects of parental age observed in human. A common feature of older fathers and infertile men is the production of oxidatively damaged spermatozoa. Much of this damage appears to be inflicted by oxidative stress during and post-testicular maturation, at a time when the spermatozoa have been shown to be mostly inert. Therefore, the absence of a fully functional DNA repair pathway in the mature spermatozoa may result in the accumulation of genetic alterations, which due to too much DNA damage and insufficient oocyte repair capacity after fertilisation may be translated into de novo mutations in their offspring. Herein, we provide for the first time evidence that oxidative DNA damage is not randomly distributed in mature human spermatozoa but occurs at specific areas of the genome. From the analysis of human spermatozoa with a novel DNA extraction technique and a newly designed bioinformatic pipeline, we identified approximately 9,000 genomic sites highly vulnerable to oxidative damage. Sites that lay outside protamine- and histone-bound regions, strongly associated with SINEs, LINEs, centromeres and telomeres domains. This data provided the impetus to assess the DNA damage present at these vulnerable regions in the spermatozoa of infertile patients. Excitingly, our studies revealed that not only was the DNA at these regions more heavily oxidised in infertile patients than in their healthy counterparts, but also highly fragmented. Taken together, the findings presented expand our understanding of male infertility, by establishing a link between the molecular consequences of oxidative stress and genomic integrity in human spermatozoa. Our ability to measure oxidative damage at vulnerable regions of the genome suggests that these regions may be used as markers to predict male infertility. Furthermore, we propose these techniques can be employed to quantify the risks associated with assisted reproductive technologies by examining the mutational burden at these regions in children of infertile patients.
- Subject
- reproduction; genomics; oxidative DNA damage; spermatozoa; transgenerational inheritance
- Identifier
- http://hdl.handle.net/1959.13/1385037
- Identifier
- uon:32163
- Rights
- Copyright 2018 Miguel João Garcia dos Santos Xavier
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 6 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 57 KB | Adobe Acrobat PDF | View Details Download |