Ionising radiation-induced DNA damage response in marine mussels, Mytilus edulis

Alamri, Ohoud (2012) Ionising radiation-induced DNA damage response in marine mussels, Mytilus edulis. Doctoral thesis (DPhil), University of Sussex.

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Abstract

The effects of ionising radiation (IR) present in aquatic environments have been
observed principally in vertebrate species but the potential biological impacts for
aquatic invertebrate species are less clear. It is important to determine the influence of
IR as a pollutant causing DNA damage in invertebrates at the molecular level since this
may serve as an early warning of future population level repercussions.

In this study, the biological effects of the IR as an environemntal contaminant at
the molecular level was investigated by studying the induction of DNA damage,
measured as mRNA expression of DNA repair genes and comet damage, in
experimentally- and environmentally-exposed mussels, M. edulis. The experimental
exposure consisted of different IR doses (1, 2, 10 and 50 Gy) and sampling at different
post-exposure time points (1hr, 4 and 7 days). The environmental exposure was
investigated using mussels collected from a contaminated site (Ravenglass Estuary) and
a reference site (Brighton Marina). Two new molecular biomarkers were developed and
employed. The first involves Rad51, a key protein in resynthesis, catalyzing and
transferring of strands between broken sequences and its homologues in double strand
break (DSBs) damage. The second biomarker involved a cell cycle checkpoint protein,
check point kinase 1 (Chk1). To explore the activation of Rad51 and Chk1 mRNA
activity as a result of exposure to IR, Rad51 and Chk1 mRNA in M. edulis were
partially isolated and characterized and a quantitative assay developed to measure their
expression using real-time PCR. Experimental exposure of M. edulis to IR (1, 2, 10 and
50 Gy) resulted in a statistically significant increase in the levels of Rad51 transcripts.
Chk1 mRNA expression levels, initially investigated in the experimental group, were
altered following exposure to IR. In the samples collected from the environment, Rad51
mRNA expression levels were increased in Ravenglass M. edulis gonad samples
compared with the reference samples from Brighton Marina. In contrast, Chk1
transcripts decreased in Ravenglass M. edulis gonad samples compared to Brighton
samples. The observed effects, and the potential role of both Rad51 and Chk1 in the IR
DNA damage response of mussels are discussed.

Item Type: Thesis (Doctoral)
Schools and Departments: School of Life Sciences > Biology and Environmental Science
Subjects: Q Science > QC Physics > QC0474 Radiation physics (General)
Q Science > QH Natural history > QH0301 Biology > QH0426 Genetics
Q Science > QL Zoology > QL0360 Invertebrates > QL0403 Mollusca
Depositing User: Library Cataloguing
Date Deposited: 23 Feb 2012 13:36
Last Modified: 25 Aug 2015 13:03
URI: http://sro.sussex.ac.uk/id/eprint/38114

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