Identifying novel players in misspecified cell elimination during development

El Gammal, Mennat 2024. Identifying novel players in misspecified cell elimination during development. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

While our cells carry the same genetic information, only a subset of genes is expressed in a certain cell type, determining its fate. Normal organ development heavily relies on the maintenance of correct gene expression patterns in the different cell types within it. Genetic mutations or epigenetic changes may cause misexpression of fate-determining factors in cells, disrupting proper patterning and compromising organ function. It is therefore important for a mechanism to be in place to detect and remove those harmful cells. However, little is known about the responsible molecular players. We induced aberrantly specified patches of cells by modifying the levels of the transcription factor Apterous (Ap) in Drosophila. This was done by misexpressing its negative regulator Drosophila LIM only (dLMO). Ap is expressed in the dorsal compartment of the imaginal wing disc, where it defines dorsal fate. First, we identified genes which are differentially expressed in misspecified cells using RNA-seq. We reasoned that if a gene is required for aberrant clone elimination, then its downregulation would rescue those clones, leading to wing defects. We then performed two rounds of RNAi verification screens, first scoring adult wing defects then quantifying clone areas in larval wing discs. We have tested 69 genes for their involvement in the elimination process and found that the downregulation of five genes resulted in significant rescue. We chose to focus on one candidate, Tau, a microtubuleassociated protein. We discovered that endogenous tau expression is minimal in the wing disc, making it challenging to detect changes in its expression pattern in the presence of aberrant cells. Overexpression of tau results in a marked increase in cell death in clones and wildtype tissue alike, indicating that its toxic effects are evident, even when apoptosis is blocked. Furthermore, tau downregulation does not fully inhibit apoptosis, nor does its complete knockout prevent it, suggesting that tau isn’t the main driver of this process. Our findings also demonstrate that tau downregulation disrupts the organisation of actin rings around misspecified clones, emphasising its impact on cytoskeletal dynamics. Additionally, our data suggest that tau functions broadly across different compartments, highlighting its general role in maintaining tissue integrity. These results offer new perspectives on the mechanisms of cell elimination and underline the relevance of studying tau in that context.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Biosciences
Subjects:	Q Science > Q Science (General)
Date of First Compliant Deposit:	9 January 2025
Last Modified:	09 Jan 2025 16:29
URI:	https://orca.cardiff.ac.uk/id/eprint/175169

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