Filters
Availability
Publication Year
Resource Type
Faculty
School/Institute
Publication Search Results
Sort
Results per page
1 - 10 of 125
-
(2008)Journal ArticleAbstract OBJECTIVE: to determine the effects of a 15-week high intensity intermittent exercise (HIIE) program on subcutaneous and trunk fat and insulin resistance of young women. DESIGN AND PROCEDURES: subjects were randomly assigned to one of three groups: HIIE (n = 15), steady state exercise (SSE; n=15), or control (CONT; n=15). HIIE and SSE groups underwent a 15-week exercise intervention. SUBJECTS: forty-five women with a mean BMI of 23.2 + 2.0 kg/m2 and age of 20.2 + 2.0 years. RESULTS: both exercise groups demonstrated a significant improvement, P < 0.05, in cardiovascular fitness. However, only the HIIE group had a significant reduction in total body mass (TBM), fat mass (FM), trunk fat, and fasting plasma insulin levels. There was significant fat loss, P < 0.05, in legs compared to arms in the HIIE group only. Lean compared to overweight women lost less fat after HIIE. Decreases in leptin concentrations were negatively correlated with increases in (r = -.57, P < 0.05) and positively correlated with decreases in TBM (r = .47; P < 0.0001). There was no significant change in adiponectin levels after training. CONCLUSIONS: HIIE three times per week for 15 weeks compared to the same frequency of SSE exercise was associated with significant reductions in total body fat, subcutaneous leg and trunk fat, and insulin resistance in young women. Keywords: intermittent sprinting, body fat, insulin
-
(2010)Recorded/Rendered Creative WorkABSTRACT Pancreatic stellate cells (PSCs) produce the stromal reaction of pancreatic cancer (PC) and their interaction with cancer cells facilitates cancer progression. This study investigated the role of human PSCs (hPSCs) in the metastatic process and tumor angiogenesis using an in vivo (orthotopic model) and in vitro (cultured PSC and PC cells) approach. A gender mismatch study [injection of male hPSCs + female PC cells into the pancreas of female mice] was conducted to determine whether hPSCs accompany cancer cells to metastatic sites. Metastatic nodules were examined by fluorescent in situ hybridization for the presence of the y chromosome. Angiogenesis was assessed by i) immunostaining tumors for CD31, an endothelial cell marker; and ii) in vitro quantifying human microvascular endothelial cell (HMEC-1) tube formation upon exposure to conditioned media from hPSCs. Transendothelial migration was assessed by examining the movement of fluorescently labeled hPSCs through an endothelial cell monolayer. Human PSCs i) were found in multiple metastatic sites in each mouse injected with male hPSCs + female PC cells; ii) increased CD31 expression in primary tumors from mice injected with MiaPaCa-2 and hPSCs and stimulated tube formation by HMEC-1 in vitro; iii) exhibited transendothelial migration which was stimulated by cancer cells. Human PSCs accompany cancer cells to metastatic sites, stimulate angiogenesis and have the capacity to intravasate/extravasate to and from blood vessels.
-
(2015)ThesisParkinson’s disease (PD) is a neurodegenerative disorder that manifests as a result of degeneration of the nigrostriatal system. While L-Dopa still remains the most effective symptomatic treatment, its benefits are limited as it is associated with the development of L-Dopa-induced dyskinesias (LIDs). Furthermore, there is currently no treatment that has proved effective in halting the nigrostriatal degeneration, thus alternative therapeutic targets are needed. To identify such targets, we first established the MPTP mouse model of PD to allow for the investigation of both pathological and behavioural outcomes. In contrast to previous studies, we demonstrated no significant effect of MPTP on motor function at 1 week and 3 months post-MPTP, despite stereological quantification showing a decrease in dopamine cells with increasing MPTP dose, suggesting the MPTP model is more appropriate for identifying effects on cell survival. A screen of novel therapeutic agents and genetic modifications in mice in the MPTP model revealed the growth factor activin A and the kainate receptor subunits GluK1 and GluK3 as the most promising neuroprotective targets. We showed activin A increased survival of dopamine neurons at 1 and 8 weeks following MPTP. Interestingly, animals receiving activin A did not have a corresponding increase in dopamine levels and striatal terminal protection. This nigral protective effect of activin A was replicated in the 6-OHDA model of PD. Animals receiving activin A also had lower numbers of astrocytes and microglia following MPTP and LPS, suggesting that activin A’s neuroprotective effects may be driven by its anti-inflammatory properties. In addition, activin A was shown to increase the efficacy of low doses of L-Dopa in 6-OHDA-lesioned mice, suggesting activin A may act as an L-DOPA-sparing agent. We also showed that blocking GluK1 or GluK3, through the use of selective antagonists or knockout animals, increased survival of dopaminergic neurons following MPTP, however there was no corresponding increase in dopamine levels and striatal terminal protection. Our results indicate that activin A, GluK1 and GluK3 are potential neuroprotective targets for PD.
-
(2018)ThesisThe mammary gland is a unique model to study regulation of stem cell homeostasis and differentiation due to its postnatal development. Embedded within the bilayered mammary epithelium are populations of mammary stem cells (MaSCs), which give rise to inner luminal and outer basal/myoepithelial cells. Developmental transcription factors (TFs) control stem cell self-renewal and differentiation. TFs driving luminal differentiation are well studied, however the regulators of MaSC maintenance and myoepithelial differentiation of basal cells are poorly understood. The helix-loop-helix (HLH) TF Inhibitor of Differentiation 4 (ID4) is exclusive to basal cells and is essential for appropriate mammary gland development. ID proteins lack DNA binding domains, and function by binding to and inhibiting basic HLH (bHLH) TFs. The overarching aims of this thesis were to i) isolate and characterise mammary epithelial cells expressing ID4, and ii) integrate multi-omic approaches to define the cis-regulatory mechanism through which ID4 controls cell fate. I found that selecting for cells with high ID4 expression enriched for basal cells with stem cell characteristics. Moreover, basal cells with low ID4 expression exhibited a differentiated myoepithelial phenotype. ID4 was required to inhibit expression of genes involved in muscle contraction, and to activate genes involved in cell growth, metabolism and cell cycle, suggesting that ID4 blocks myoepithelial specialisation and maintains proliferation of MaSCs. ID4 was found to interact with ubiquitously expressed bHLH TFs, E2A, HEB, and ITF-2 (E-proteins) using an unbiased proteomics approach. E-proteins co-regulated a large subset of ID4 target genes. This was unexpected, due to the typical role of ID proteins in antagonising E-protein activity. Motif enrichment revealed E-protein binding motifs in the promoters of genes co-regulated by both ID4 and E-proteins. This raises the possibility of a novel mechanism for ID4 in acting as a chromatin-bound co-factor for E-proteins, rather than simply sequestering E-proteins in the nucleoplasm. Chromatin Immunoprecipitation followed by DNA-Sequencing (ChIP-Seq) experiments will directly test this hypothesis. I discovered that ID4 dictates the MaSC fate by inhibiting myoepithelial differentiation, potentially by cooperating with E-proteins at the level of chromatin. Lessons learnt from the mammary gland may have broader implications in the regulation of adult stem cells by HLH TFs.
-
(2018)ThesisEstrogen receptor positive (ER+) breast cancer constitutes 70% of all breast cancers and anti-ER therapies such as aromatase inhibitors and tamoxifen represent the main therapeutic strategies in the treatment of this disease. Unfortunately, up to 30% of all primary ER+ tumours will ultimately develop endocrine-resistance and progress on ER-targeted therapies resulting in disease-related morbidity. As a result, there is an urgent medical need for novel therapeutic strategies capable of managing endocrine-resistant breast cancer. Androgen receptor (AR) is expressed in up to 90% of ER+ breast cancers. AR functions as a tumour suppressor in primary ER+ breast cancer and high AR positivity is strongly associated with a favourable patient outcome in the ER+ setting. However, the role of AR in endocrine-resistant breast tumours is highly controversial with data supporting both oncogenic and tumour suppressive functions reported in the literature. Here I have used different modulatory approaches on in vitro and in vivo preclinical models to dissect the functions of AR and determine the best approach to target AR in endocrine-resistant breast cancer. I use an siRNA-mediated approach to knock down AR in cell line models and discover that the basal expression of AR contributes to endocrine-resistance and that loss of AR restores classical ER signalling and reverses endocrine-resistance. However, inhibiting the transcriptional activity of AR with enzalutamide does not recapitulate this effect, suggesting that it is the non-canonical activity of AR which contributes to endocrine-resistance. In contrast, I show that activation of AR by either 5-α dihydrotestosterone (DHT) or selective AR modulator enobosarm in vitro and in patient derived (PDX) models of endocrine-resistance results in significant growth suppression. Mechanistically, this growth-inhibitory effect of AR activation is associated with downregulation of ER signalling. Moreover, I identify AR-regulated genes from the global gene expression of an ER+AR+ endocrine-resistant PDX model treated with DHT and establish a highly prognostic AR gene signature based on primary ER+ patients in the METABRIC dataset. This suggests that activity of AR is tumour-suppressive independent of endocrine-sensitivity. In summary, I demonstrate that activation, not antagonism, is the optimal AR-targeted therapeutic strategy in the management of endocrine-resistant breast cancer.
-
(2019)ThesisThe skeleton is a multifunctional organ-system, providing structural support to the body and maintaining mineral homeostasis through endocrine interactions with distant organs. Balance between these functions is critical to skeletal health and is regulated by a network of cells distributed throughout bone tissue - the osteocyte network. Little is known of the genes with which the osteocyte network performs this specialised function. As a consequence, understanding of its contribution to skeletal disease is very limited. I hypothesised that defining gene expression in the osteocyte network would reveal genes important to its function and provide insights into skeletal disease. To test this, I developed techniques to perform transcriptome sequencing on the osteocyte network and analysed how gene expression is influenced by skeletal-site, age and sex. I established experimental and analytical strategies to identify a signature of genes enriched for expression in the osteocyte network and reveal molecular processes enabling its specialised function. These genes were examined for their association with skeletal dysplasia and clinically relevant skeletal traits. This work revealed that gene expression in osteocytes is highly conserved between skeletal sites, with the exception of a limited number of developmental transcription factors differentially active between adult bone types. Dynamic changes in the osteocyte transcriptome during skeletal maturation were also identified, including the sexually dimorphic regulation of genes associated with perilacunar-remodelling. An osteocyte transcriptome signature was defined - 830 genes enriched for expression within the osteocyte network. Enriched expression in the osteocyte network was the first evidence of skeletal involvement for the majority of signature genes, including novel genes with skeletally-restricted activity alongside known osteocyte markers. This work identified a range of signalling pathways significantly enriched in the osteocyte network, including neuron-like network formation pathways upregulated early in osteocytic differentiation. This osteocyte signature is enriched for gene-orthologs known to cause human skeletal dysplasias and influence bone mineral density. These discoveries identify the genes and molecular processes that define the osteocyte network and demonstrate that specific expression in the osteocyte network may be a powerful filter to identify genes that cause skeletal disease.
-
-
(2009)ThesisColorectal cancer (CRC) remains a significant burden in contemporary society due to an aging population, unhealthy dietary choices and an increasingly sedentary lifestyle. While the underlying defects for many hereditary forms of CRC have been determined, many genetic and epigenetic changes promoting common sporadic CRCs have yet to be identified. The Mutated in Colorectal Cancer (MCC) gene, identified in 1991, was initially thought to be responsible for the hereditary form of CRC, familial adenomatous polyposis, before the discovery of the susceptibility gene Adenomatous Polyposis Coli (APC), which then became the focus of intense research. Recent data, however, suggests that MCC may also be important in the development of CRC. I have investigated the mechanism of MCC gene silencing, the putative structure, and multiple functions of MCC. MCC was frequently silenced by promoter hypermethylation in CRC cell lines and primary tumours. MCC methylation showed strong molecular and clinicopathological associations with hallmarks of the serrated neoplasia pathway. Furthermore, MCC methylation was more frequent in serrated precursor lesions compared with adenomas, thus occurring early during carcinogenesis. MCC is highly conserved in complex multicellular organisms. Re-introduction of MCC in CRC cell lines resulted in partial G1 to S phase, and G2/M phase cell cycle blocks, potentially by upregulating cell cycle inhibitor gene transcription and interfering with the process of mitotic checkpoints and division, respectively. Changes in MCC levels also modulated NF?B pathway signalling, the pathway required for maintaining cell viability and proliferation in colonic epithelial cells. In particular, MCC overexpression suppressed both TNF? and LPS-induced NF?B activation, decreasing both the magnitude and rate of cellular responses. Overexpression also resulted in downregulation of proteins involved in canonical NF?B pathway signalling, while increasing the transcription of non-canonical NF?B genes. Therefore, MCC may direct activation of this pathway to a specific subset of NF?B-regulated genes. These data provide a molecular basis for the role of MCC as a tumour suppressor gene in CRC. MCC may have multiple functions, regulating cell cycle progression and modulating NF?B pathway signalling, either through direct involvement in pathway signalling cascades, or by providing a scaffold on which signalling events can occur.
-
(2019)ThesisAbstract Signal transducer and activator of transcription 3 (STAT3) is a transcription factor activated by multiple cytokines including IL-6, IL-10 and IL-21. Loss-of-function (LOF) mutations in STAT3 lead to the primary immunodeficiency autosomal-dominant hyper IgE syndrome (AD-HIES). This is a disease characterized by susceptibility to infection by pathogens such as C. albicans and S. aureus due to defective Th17 responses, and a failure to generate effective humoral immune responses. Interestingly, disease-causing mutations have been identified throughout all functional domains of STAT3 including the DNA binding, SH2 and transactivation domains. However, no phenotype-genotype correlations have been observed. The inability to generate an effective humoral immune response seen in these patients stems from the inability of B cells to respond to the cytokines IL-10 and IL-21. This unresponsiveness leads to reduced antigen specific antibodies, less IgG switching and significantly lower numbers of memory B cells. Interestingly, although the number of memory B cells is greatly reduced in AD-HIES patients, they are functionally responsive to IL-10 and IL-21. Further investigation into STAT3 signaling in healthy human naive and memory B cells has shown that memory B cells are more sensitive and respond more strongly to IL-21 stimulation. The first aim of this thesis is to elucidate the biochemistry behind various disease-causing STAT3 mutations in order to better understand how different mutations result in the same clinical and functional outcome. We sought to characterize which stage(s) of STAT3 signaling was impaired by a range of mutations and if this was consistent for mutations in different domains. This study reveals the mechanism underlying dysfunctional STAT3 signaling in AD-HIES and also identifies residues and regions of domains that are critical for normal STAT3 function. To further explore how naive and memory B cells respond differently to cytokines, we investigated the immune phenotype and cytokine responses of individuals with STAT3 LOF, STAT3 gain-of-function (GOF), ZNF341 LOF and STAT5B null mutations. Furthermore, we have used the techniques ATAC-seq and RNA-seq to further explore the accessibility of chromatin and the transcriptional profile of primary human naive and memory B cells. These approaches have revealed multiple differences in the accessibility of chromatin between these two subsets and the kinetics of gene induction by IL-21 stimulation. Such analyses provide new insight into the molecular changes involved in early naive and memory B cell activation. Thus, this thesis further advances our knowledge of STAT3 signalling at a biochemical, epigenetic and cellular level.
-
(2017)ThesisDNA cytosine methylation is an important epigenetic modification that plays a key role in demarcation of regulatory regions involved in controlling gene expression. In normal cells the bulk of the genome is methylated, whereas key regulatory regions, such as promoter CpG islands, are maintained in an unmethylated state. In cancer, while the majority of CpG islands remain unmethylated, a number of CpG islands undergo aberrant DNA hypermethylation. A widely studied, but still unresolved question to date is to understand what triggers the aberrant changes to the promoter CpG island methylation landscape in cancer. The recent discovery of DNA hydroxymethylation as a critical facilitator of DNA demethylation together with its widespread depletion in carcinogenesis has provided a new layer to this question suggesting a specific role for DNA hydroxymethylation in the aberrant changes to the DNA methylation landscape. In this study I analysed whole-genome bisulphite sequencing (WGBS), performed TET-assisted bisulphite sequencing (TAB-seq) and exploited several chromatin modification profiles (ChIP-seq) to elucidate the role of DNA hydroxymethylation and chromatin modifications in aberrant DNA methylation of promoter CpG islands in prostate cancer. In addition to the well-described hypermethylation of the entire CpG island, I observed a novel mode of aberrant methylation that entails an encroachment of methylation across 5’ and/or 3’ CpG island borders, resulting in smaller islands and new discreet CpG island borders. Importantly, I found that DNA hydroxymethylation showed distinct enrichment patterns across the different groups of promoter CpG islands, in concordance with their predisposition to hypermethylation in cancer. Integrative analysis of WGBS and ChiP-seq data revealed that in normal prostate epithelial cells, nucleosomes carrying H3K4me1 modification pre-mark borders of promoter CpG islands prone to aberrant hypermethylation in cancer, including the novel mode of DNA methylation encroachment. Significantly, I showed that depletion of histone H3K4me1 in the mouse model harboring a loss-of-function mutation of the gene encoding H3K4 methyltransferase KMT2D, resulted in a reduction of DNA methylation at the borders of promoters and expansion of the unmethylated regulatory regions. Overall, my work shows for the first time that there is a critical relationship between the organization of DNA hydroxymethylation, H3K4me1-marked nucleosomes and demarcation of DNA methylation borders at CpG island gene promoters in normal cells and their predisposition to DNA hypermethylation in cancer.