DNA damage in spermatozoa is a crucial contributor to spontaneous abortion, severe
genetic disease in the offspring and infertility. The chromatin of spermatozoa is highly
compacted, transcriptionally and translationally silent, hence lacking DNA damage response
(DDR). DDR foci follow within seconds after a DNA double strand break (DSB) and correlate
to an abortive topoisomerase-IIb activity during spermiogenesis.
When comparing the DSB frequencies at the two most fragile genomic loci (fragile sites
FRA3B, FRA16D) in human and murine spermatozoa with lymphocytes, significantly
increased DSB levels were detected in spermatozoa in both species. This corroborates that
spermatozoa are more prone to DSBs than somatic cells. When comparing the DSB
frequencies at FRA3B/FRA16D in spermatozoa of smokers with non-smokers, two-fold
increases were found, probably caused by cigarette smoke components triggering abortive
topoisomerase-II¿ activity. The phosphorylated DDR proteins H2AX and ATM were
identified in human spermatozoa and murine spermatids using multicolour immunostaining
with laser-scanning confocal microscopy (LSCM) and Western blots. Based on significantly
increased DDR foci in spermatozoa of smoking men, but lacking DDR foci in response to in
vitro challenge with H2O2, an abortive topoisomerase-IIb activity is the likely cause of DDR
foci in spermatozoa. As DDR foci are susceptible to cigarette smoke, they can potentially be
used as a novel biomarker. When comparing paternal spermatozoa, and lymphocytes as
well as maternal and cord lymphocytes from 39 families for DSBs (via high-throughput
LSCM pH2AX detection) and DNA fragmentation (Comet assay), significant increases were
found in newborns of mothers exposed to environmental tobacco smoke and smoking
fathers. When challenging lymphocytes and spermatozoa to different genotoxicants,
significantly increased DNA damage in newborns compared to adults was found. This
confirms an exceptional vulnerability in newborns, believed to cause increased susceptibly
to disease in later life, including cancer. / European Union¿s 6th Framework project Newborns and
genotoxic exposure risk (NewGeneris), British Council¿s United Kingdom Indian Education Research Initiative (UKIER)
| Identifer | oai:union.ndltd.org:BRADFORD/oai:bradscholars.brad.ac.uk:10454/5332 |
| Date | January 2011 |
| Creators | Laubenthal, Julian |
| Contributors | Anderson, Diana, Gdula, Michal R. |
| Publisher | University of Bradford, Genetic and Reproductive Toxicology Laboratory, Division of Biomedical Sciences, School of Life Sciences. |
| Source Sets | Bradford Scholars |
| Language | English |
| Detected Language | English |
| Type | Thesis, doctoral, PhD |
| Rights | <a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/"><img alt="Creative Commons License" style="border-width:0" src="http://i.creativecommons.org/l/by-nc-nd/3.0/88x31.png" /></a><br />The University of Bradford theses are licenced under a <a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/">Creative Commons Licence</a>. |
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