Brunel University Research Archive (BURA)

Relationship between DNA damage response and telomere maintenance

2013-05-20T15:11:26Z

Title: Relationship between DNA damage response and telomere maintenance Authors: Ojani, Maryam Abstract: 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. Description: This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.

Friedreich ataxia: Investigating the relationships between mismatch repair gene expression, FXN gene expression and GAA repeat instability in human and mouse cells and tissues

2013-05-20T14:59:14Z

Title: Friedreich ataxia: Investigating the relationships between mismatch repair gene expression, FXN gene expression and GAA repeat instability in human and mouse cells and tissues Authors: Ezzatizade, Vahid Abstract: Friedreich ataxia (FRDA) is the most common inherited ataxia disorder, caused by a GAA repeat expansion mutation within the first intron of the FXN gene. The subsequent deficiency of frataxin protein leads to neurological disability, increased risk of diabetes mellitus, cardiomyopathy and premature death. The exact FRDA disease mechanism is not yet clear, despite some understanding of epigenetic, transcriptional and DNA repair system effects that lead to frataxin reduction. Previous studies have shown that mismatch repair (MMR) genes can affect other trinucleotide repeat disorders by destabilisation of the repeats. Furthermore, it has been proposed that frataxin deficiency might lead to cell malignancy by an as yet undefined mode of action. Therefore, the principle aim of this thesis was to use human and genetically altered mouse cells and tissues to understand the effects of MMR proteins on GAA repeat instability and FXN transcription, and also to identify potential changes in MMR transcription that might cause malignancy in FXN-defective human cells. Firstly, by using FXN and MMR genetically altered mice, MMR proteins were shown to be involved in both intergenerational and somatic GAA repeat instability, although their effects in the two systems were different. Thus, Msh2 or Msh3 were both found to protect against intergenerational transmission of GAA contractions, while loss of Msh2 or Msh3 reduced somatic GAA repeat expansions and increased levels of FXN transcription in brain and cerebellum tissues. Loss of Msh6 induced both intergenerational GAA repeat expansions and contractions, while the frequency of somatic GAA repeat expansions was reduced. Curiously, the level of FXN transcription was also reduced in Msh6-deficient brain and cerebellum tissues. On the other hand, Pms2 was found to protect against both intergenerational and somatic GAA repeat expansions, with loss of Pms2 causing increased GAA repeat expansions and decreased levels of FXN transcription in brain and cerebellum tissues. Finally, loss of Mlh1 led to a reduced frequency of both intergenerational and somatic GAA repeat expansions, but the level of FXN transcription was also reduced in brain and cerebellum tissues. Furthermore, upregulation of MMR mRNA expression was detected in human FRDA fibroblast cells, but downregulation was seen in FRDA cerebellum tissues, suggesting tissue-dependent control of FXN and MMR expression. In summary, these studies indicate that the MMR system can affect GAA repeat expansion instability and FXN transcription through different mechanisms of action. Furthermore, frataxin deficiency can also affect the levels of MMR mRNA expression in a tissue-dependent manner. These findings will assist future investigations aimed at identifying novel FRDA therapies. Description: This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.

Exposure variability and behaviour of indoor and outdoor air pollutants in primary schools in the United Kingdom

2013-05-21T09:17:37Z

Title: Exposure variability and behaviour of indoor and outdoor air pollutants in primary schools in the United Kingdom Authors: Zeka, A; Jones, BJ; Anopa, Y; Koulkova, A Abstract: Background and Aims: Current evidence suggests that exposure to common indoor air pollutants is associated with adverse health effects in children. This study was conducted to examine air quality in four primary schools in southern England, in order to establish daily, weekly and seasonal variability of pollutant concentrations within and between the schools, and to understand the behaviour of common indoor and outdoor air pollutants. Methods: Four primary schools were selected for the study, in urban, suburban and rural environments with diverse size and socioeconomic backgrounds. Air quality monitoring was conducted in three rounds (autumn, winter, summer) during the academic year 2009-2010. Each round involved monitoring continuously for one week in four locations of typical children’s exposure: generally three indoors and one outdoors. Measurements were carried out for particulate matter count for size range 0.5-5.0μm (PM0.5-5.0), carbon dioxide (CO2), carbon monoxide (CO), and nitrogen dioxide (NO2). Results: Findings revealed great variability in PM0.5-5.0 concentrations during the week and between rounds of measurements within each school, and between schools. CO concentrations were greatly variable for the suburban and rural schools. Little variability was seen for NO2 concentrations. CO2 levels differed during the day and between days and rounds in each school, and between schools, depending on the daily activity patterns of children and practice of ventilation. Linear regression models predicted indoor levels for PM0.5-5.0, CO and NO2, based on contribution of outdoor concentrations to the same pollutant, ventilation measured by CO2 concentrations and weather variables. Conclusions: Study findings showed variability in pollutant exposure levels between locations, days and seasons in each school, and between all four schools. These differences related to school building design and location, ventilation practices and children’s daily activities. These findings support the need for developing methodology for personal exposure assessment to air pollutants among school children. Description: Copyright @ 2011 ISEE

A multi-proxy palaeonenvironmental reconstruction from sediment cores, offshore Iran - Natural hazards and climatic change within the Late Holocene

2013-05-17T14:20:14Z

Title: A multi-proxy palaeonenvironmental reconstruction from sediment cores, offshore Iran - Natural hazards and climatic change within the Late Holocene Authors: Miller, Charlotte Sarah Abstract: During the last millennia, North African and Arabian palaeoclimatic records indicate a number of important climatic transitions. As a direct consequence, terrestrial ecosystems experiences significant changes. Although palaeoenvironmental records do exist in proximity to the north-western Arabian Sea, they remain sparse and provide little insight into environmental and climatic change of this region during the Late Holocene (the dating here is from 2300 cal. yr BP to present). Additionally, the north-western Arabian Sea is prone to natural disasters including recent cyclones and tsunamis such as the Makran tsunami, 1945 and cyclone Gonu, 2007, which leave a signal in the sediment. This thesis presents the results of detailed pollen and dinoflagellate cyst analysis in concert with a range of sedimentological techniques from sediment cores recovered from southern Iran (Chabahar Bay, Sea of Oman, Iran 25° 20’N, 60° 30’E). The data reveal the patterns of vegetation and oceanographic response to climatic change during the Late Holocene in the north-western Arabian Sea. Zonation on pollen and dinoflagellate results divides the last 2300 years into three distinct climatic phases: a wet period (2300 – 1830 cal. yr BP), a dry period (1830 – 1500 cal. yr BP) and a wet period (1500 – 120 cal. yr BP). The wet period (2300 – 1830 cal. yr BP) corresponds with well-known phases of intensive agriculture, including the Sassanid Period. The dry period (1830 – 1500 cal. yr BP) corresponds well with the end of the Beysehir occupation phase in southern Turkey. Moreover, an abrupt event is preserved in a single core and is dated at AD < 1808. Palynological evidence constrains the source of the sediment to be inner-continental but not of coastal origin, with a fluvial flood being the most likely mechanism of transportation. Description: This thesis was submitted for the degree of Master of Philosophy and awarded by Brunel University.