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Title: Investigating the role of Viperin in beta-cell function and inflammation
Author: Tebeka, Nchimunya
ISNI:       0000 0005 0291 732X
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2020
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Background: In type 1 diabetes, insulin-producing pancreatic beta-cells are destroyed by an autoimmune response. There are various cellular mechanisms, genes and environmental factors that may influence the autoimmune destruction of beta-cells. Previous studies have shown high induction of Viperin (a viral-response protein of the innate immune system) in isolated human islets exposed to inflammatory cytokines and viruses. Viperin has also been shown to be present in the blood cells of pre-type 1 diabetic subjects. Based on this knowledge, we hypothesised on a possible role of Viperin in beta-cell apoptosis and dysfunction in the development and progression of type 1 diabetes. Methods: This research aimed to investigate the role of Viperin in immune-mediated beta-cell apoptosis by using a combination of both in vitro and ex vivo models of beta-cell inflammation. In the INS1-rat beta-cell line, induction of Viperin mRNA expression levels was assessed, and apoptosis was determined after establishing siRNA knock-down of Viperin. Beta-cell apoptosis was also studied in isolated mouse islets of Viperin knock-out mice. RT-qPCR and mRNA sequencing were applied to investigate the influence of Viperin on mechanisms controlling beta-cell function and survival Results: The research findings show that in the INS1 beta-cell line and isolated mouse pancreatic islets, Viperin mRNA expression is highly induced within a few hours of exposure to inflammatory cytokines, and expression levels start to decrease over time. Viperin expression was also induced in mouse islets after systemic infection with a chimpanzee adenovirus. Interestingly, apoptosis starts to peak when Viperin levels are decreasing, suggesting that the two events may be linked. In the absence of Viperin, cytokine-induced beta-cell apoptosis is increased, implying that Viperin expression plays a protective role in beta-cells. To investigate this further, RT-qPCR was used to quantify downstream markers of cytokine signalling in the presence and absence of Viperin and results showed that Viperin influenced the expression pattern of these markers under normal and cytokine-stimulated conditions. As part of these studies, we opted to run total mRNA sequencing to take an unbiased approach to identify both individual genes, along with gene networks and pathways, that are influenced by viperin. These results indicated that Viperin seems to affect a wide array of genes involved in various cellular pathways such as cell development, immune response and homeostatic regulation. Conclusion: Viperin expression plays a protective role against cytokine-mediated beta-cell apoptosis. Viperin also influences the expression pattern of numerous genes and key regulatory markers that mediates various cellular functions in beta-cells.
Supervisor: Christian, Helen ; Cantley, James Sponsor: Rhodes Scholarships ; Diabetes Research and Wellness Foundation (DRWF)
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Molecular biology ; Metabolism ; Physiology ; Immunology