Telomeres are regions of repetitive DNA bound with a set of specialized proteins required to protect chromosomes from fusing with each other and from eliciting DNA damage response. Dysfunctional telomere maintenance can lead to premature cellular senescence, premature organismal aging and cancer predisposition. In the last few years the evidence has emerged indicating a link between dysfunctional maintenance of telomeres and defective DNA damage response. The objective of this project was to explore further this link by examining effects of some DNA damage response proteins on telomeres that have not been examined before and examining DNA damage response in cells in which telomeres are dysfunctional as a result of alterations in genes not directly involved in DNA damage response. We have developed a method, termed IQ-FISH, for accurate identification of average telomere length in interphase cells from individuals with defective DNA damage response. By applying IQ-FISH we could successfully measure telomere lengths in cell lines from patients that are heterozygous (+/-) and cell lines from patients or animals that are homozygous (-/-) with respect to mutations in these genes. We then analysed telomere length and function, as well as DNA damage response, in lymphoblastoid cell lines originating from BRCA1 and BRCA2 carriers (+/-) and also a single fibroblast cell line from a patient with bi-allelic mutations in BRCA2 (-/-). In addition we have analysed a mouse embryonic stem cell line in which Brca1 was deleted (Brca1-/-) by gene targeting. Our results show lack of correlation between DNA damage response and telomere maintenance in heterozygous cell lines (with the exception of one BRCA1+/- cell line) but a clear positive correlation in the case of cell lines with homozygous mutations. Finally, as a model for telomere dysfunction we have chosen cell lines from Dyskeratosis Congenita (DC) patients. DC is a rare progressive congenital disorder which results in premature aging. DC is primarily a disorder of dysfunctional telomere maintenance and we used cell lines from patients with mutations in DKC1, a gene encoding a protein termed Dyskerin which forms a part of the telomerase enzyme complex. Our results indicate that DC cells with dysfunctional DKC1 may have a dysfunctional DNA damage response.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:571796 |
| Date | January 2012 |
| Creators | Ojani, Maryam |
| Contributors | Slijepcevic, P. |
| Publisher | Brunel University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://bura.brunel.ac.uk/handle/2438/7441 |
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