Investigating the role of Alzheimer’s risk genes PLCγ2 and PLD3 in glial engulfment using drosophila

Storer, Freya 2022. Investigating the role of Alzheimer’s risk genes PLCγ2 and PLD3 in glial engulfment using drosophila. PhD Thesis, Cardiff University. Item availability restricted.

Preview	PDF - Accepted Post-Print Version Download (29MB) | Preview
	PDF (Cardiff University Electronic Publication Form) - Supplemental Material Restricted to Repository staff only Download (209kB)

Abstract

Microglial dysfunction is likely to play an important role in the pathogenesis of Alzheimer’s disease (AD).Dysregulated glial cells can excessively eliminate neuronal synapses of AD-affected brains and this loss correlates strongly with cognitive decline. Phagocytosis by glia is also important for the efficient clearance of amyloid beta (Aβ) aggregates, which characteristically accumulate during AD progression. Failure to clear aggregates can also negatively impact neuronal survival. Genome-Wide Association Studies (GWAS) and Meta-analyses have identified multiple genetic variants associated with AD progression risk, some of which are enriched in microglia. However, little is known about the function of risk genes in microglia and how they may promote disease. The present project aims to investigate a potential role for these genes in glial engulfment pathways using Drosophila melanogaster as a model. My first aim was to complete a reverse candidate knockdown (KD) screen using a robust injury-induced engulfment system. Here, maxillary palps are surgically removed, causing GFP-labelled neurons to degenerate, thereby triggering glial engulfment of neuronal debris, a process which takes up to 5 days. A significant change in the rate at day 1 was recorded as a hit. Knocking down small wing (sl) and phospholipase D family member 3 (Pld3) saw a significant delay in the rate of engulfment after day 1 and further investigation over multiple time points confirmed a significant partial delay over time. sl and Pld3 are likely to affect glial engulfment through changes in Phosphatidylinositol 4,5-bisphosphate (PIP2) levels, which were found to be significantly decreased in glia after antennal injury. Inversely, Phosphatidylinositol (3,4,5)-trisphosphate (PIP3) levels appeared significantly increased in response to injury. Individual gene KD in PIP reporters saw stark changes in general PIP levels as well as a change in the response after injury, suggesting that the phospholipid pathway has an important part to play in engulfment function. Finally, epistatic experiments revealed that knocking down PTEN in sl KD flies led to a rescue of the engulfment deficit observed in our initial data. Overall, the present project has identified new elements to be considered in existing pathways known to regulate glial engulfment and sheds light on how AD risk variants could be involved in microglial dysfunction in dementia.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Medicine
Date of First Compliant Deposit:	18 October 2022
Last Modified:	17 Oct 2023 01:30
URI:	https://orca.cardiff.ac.uk/id/eprint/153448

Actions (repository staff only)

Edit Item