THE ROLE OF RETROTRANSPOSITION AND EXOSOMAL DNA IN RADIATION-INDUCED GENOMIC INSTABILITY

Radiation-induced genomic instability (RIGI) is characterized by an increased rate of genomic alterations including delayed mutations, chromosomal aberrations, and micronucleus formation in the descendants of irradiated cells many generations after the initial radiation insult. At present the mechanism of RIGI remains elusive, however it is possible that the random insertion nature of the LINE-1 retrotransposons could be a cause of RIGI. The work in this thesis has aimed investigate the role of retrotransposable elements in the mechanism of RIGI. Three different cell lines (HF19, Caco-2, and MCF7) were used to investigate if clinically relevant doses of 0.1 Gy and 2 Gy X-rays activated LINE-1 retrotransposition, and if this caused an instability within the genome. 48 hours post exposure to 0.1 Gy X-rays the HF19 fibroblast cell line showed an increase in LINE-1 levels, which correlated with an increase in micronuclei formation. While speculative, this is suggestive of an early activation of LINE-1 retrotransposition thereby indicating a possible link to radiation-induced damage. Recent studies show an abundance of retrotransposon sequences within the DNA of extracellular vesicles (EVs). EVs, including exosomes, have become of keen interest due to their widespread implications in intercellular communication, and have been suggested as a likely means of transmission for retrotransposons between cells. Therefore, the work in this thesis also aimed to characterize the exosomes released from sham and irradiated MCF7 cells. Furthermore, we aimed to extract and characterize exosomal DNA using whole-genome sequencing to identify any copy number variation by comparing exosomes excreted from sham and 2 Gy irradiated MCF7 cells. The results herein suggest that exosomes excreted from MCF7 cells following a 2 Gy X-ray dose have a different composition and DNA contents compared to those excreted from sham-irradiated cells, including high levels of LINE-1 found in exoDNA in irradiated populations. Additionally, results from the copy number variation (CNV) analysis show a genetic variation between the sham and irradiated exoDNA samples. In summary this study has contributed to the knowledge in the mechanism of RIGI and the role of exosomes in the IR response.

Grantor dc:publisher

Oxford Brookes University

Year dc:date

2019

Author dc:creator

• Almond, Brittany Lee

Contributors dc:contributor

• Kadhim, Munira

Statement dc:rights

• All rights reserved

Language dc:language

en

DOI dc:identifier

https://doi.org/10.24384/dfev-5464

OAI identifier oai:identifier

tle:1d97d7ff-f945-4e96-896f-85098022cafe:d6bd9758-527a-46cd-bfe2-c433766e8fca:1