Saudi Cultural Missions Theses & Dissertations
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Item Restricted An Assessment of miRNA Manipulation on Senescence and Ageing Phenotypes in vitro and in vivo(2023-06-19) Manni, Emad Mohammed O; Harries, Lorna WAgeing has been widely described as a progressive functional deterioration of tissues that causes diminished organ function and increased mortality risk. It has been established that the proportion of senescent cells in tissues rises with age in many organs and in agerelated illnesses, suggesting that cellular senescence plays a significant role in the functional decline related to ageing. Correspondingly, it has previously been shown in animal models that eliminating senescent cells might mitigate the deleterious consequences of ageing. As a key regulator of several cellular mechanisms, there are microRNAs (miRNAs) known to be associated with senescence. However, miRNAs that may directly trigger or reverse senescence remain to be elucidated. Here, the first goal of thesis was to identify the miRNA profile of proliferating, senescent, and rescued senescent endothelial cells to determine miRNAs that may be causal or influential of cellular senescence. I found that miR-361-5p not only associated with senescence but also reduced the load of senescent cells in vitro in human endothelial cells upon induction in late passage cells. Secondly, C. elegans was used to examine the role of miR-361-5p targeted genes on ageing in vivo. I found that 56% of genes which were dysregulated in vitro adversely affected healthspan and/or lifespan in vivo. Finally, a previous finding from our lab (Holly et al., 2015) identified three miRNAs-associated with human ageing and senescence in human primary fibroblasts of which miR-15b-5p may reduce senescence markers and secretory phenotypes (SASP) in the human dermal fibroblast cells. This thesis presents new miRNAs (miR-361-5p and miR-15b-5p) which may be involved in the aetiology of senescence and may be used in future in ageing intervention.2 0Item Restricted Function of a microRNA gene containing an intron in Solanum lycopersicum(2023-05-09) Bawazeer, Afrah; Dalmay, TamasMicroRNAs (miRNAs) are short single stranded RNA molecules. They are ~21 nucleotide long that are derived from long hairpin structures that result in post transcriptional gene silencing. MiRNA molecules are incorporated into a protein complex called RISC (RNA-induced silencing complex) and take this complex to target mRNA for degradation or inhibition of translation. It has been shown that miRNA molecules and other short RNA molecules intrinsically linked to the regulation of many genes that control the development, growth, and differentiation of plants. In this study, we have characterised a novel tomato miRNAtop14. This miRNA is unusual as its primary transcript (pri-miRNA) contains a ~700nt intron, which is spliced out. MiRNA top 14 has been found to be conserved within the economically important Solanaceae family and among other agriculturally relevant members of the Solanales order, like in sweet potato, while its peculiar intron-split pri-miRNA structure is exclusively kept in the more closely related genera Solanum, Capsicum and Nicotiana. A mRNA cleaved by this miRNA was identified; the mRNA coding for LOW PHOSPHATE ROOT (LPR), a protein, which is involved in the arrest of root growth under phosphate starvation conditions in Arabidopsis. Interestingly, although LPR is widely conserved in plants, included in all the ones harbouring miRNAtop14, LPR cleavage was found to occur only in the three genera where the intron-split pri-miRNA structure is conserved. The current study indicates that MIRs encoded by less canonical loci should be included in future miRNA searches, since they may be producing mature miRNAs with a function, as seen in this investigation. Furthermore, our results suggest that thismiRNA (top14) seems to be involved in plant growth and development as our experiments have indicated that the deletion of MIRtop14 seems to affect the root development. Moreover, as it is mentioned above, during the working on this project the experiments have found a target for top14 so called LOW PHOSPHATE ROOT1 (LPR1) in roots and the analyses by Northern blot have shown a high expression level of this miRNA in roots. Finally, the discovery of this miRNA and the study of it so far have opened up numerous avenues of possible investigation. Further study would indicate how this miRNA functions in the plant.3 0Item Restricted Effect of the inflammatory mediator TNF-α on colorectal cancer epithelial cells development and metastasis, role of dietary carcinogens and miRNA(ICL, 2023-05-01) Alotaibi, Aminah Ghazi; Gooderham, Nigel; Li, JiaColorectal cancer (CRC) is the third most common cancer world-wide and second leading cause of mortality. The majority of CRC cancer cases result from epigenetic and genetic alterations that promote development and metastasis of the disease. Exposure to environmental and dietary carcinogens are strongly associated with CRC. Also, inflammatory mediators are known as a major risk factor for CRC, however the underlying mechanisms are still understudied. Upregulation of pro-inflammatory mediators and dysregulation of miRNAs in the tumour microenvironment (TME) have been observed in CRC. Tumour necrosis factor alpha (TNF-α) is a pleiotropic cytokine thought to play numerous roles in tumour progression including epigenetic gene regulation, activation of tumour promoting signalling pathways, thus presence of TNF- in CRC tumour microenvironment may be key to promoting CRC progression. I hypothesise that the presence of TNF- α in the TME could regulate miRNAs and enzyme expression to induce DNA damage caused by dietary carcinogens, thereby stimulating changes that promote CRC development and metastasis. The present study investigated this hypothesis through a mechanistic approach with in vitro cell line culture. Effects of TNF-α on phenotypic changes were observed and the potential involvement of miRNAs were determined. The results showed that TNF-α enhances dietary carcinogen-induced DNA damage through activation of JNK signalling pathway. Also, TNF-α induced metastatic phenotype cell proliferation and migration through miRNA regulation. Moreover TNF-α regulated expression of CYP450 enzymes through miRNA regulation, which can promote chemical carcinogen genotoxicity. Taken together, the data indicated that CRC progression and metastasis may be related to epigenetic and inflammatory mediators active at the tumour site. Understanding these molecular mechanisms could provide better prevention and therapeutic strategies.26 0