Characterisation of Alzheimer’s disease risk genes and their behavioural phenotypes in Drosophila melanogaster

Abstract

Alzheimer’s disease (AD) is the most prevalent form of dementia worldwide. The pathology of the disease is complex and difficult to target therapeutically. Genome- wide association studies (GWAS) and epigenome-wide association studies (EWAS) are being increasingly used to identify single nucleotide polymorphisms (SNPs) and differentially methylated positions (DMPs) respectively that occur more frequently in individuals with AD. However, translation of these findings to rodent models is challenging due to high costs and false positive rates. Drosophila melanogaster, commonly known as the fruit fly, is a highly genetically tractable model organism that allows quick and efficient screening of risk genes by identifying mutant phenotypes, including those relevant to AD. This project aimed to use Drosophila to screen fly orthologues of GWAS and EWAS hits for AD-associated phenotypes, to identify candidate genes that are potentially involved in AD pathogenesis. Firstly, bioinformatic analysis of GWAS and EWAS hits was performed, and Drosophila orthologues of human hits were identified. The GAL4-UAS system, which allows tissue-specific genetic manipulation in Drosophila, was used to express RNAi against 11 Drosophila orthologues of novel AD risk genes identified in GWAS and EWAS and screen for AD-associated behavioural phenotypes. Eye neurodegeneration, locomotor ability, lifespan, sleep and circadian rhythms and memory of flies with candidate gene knockdown was assessed. RT-qPCR was used to assess the efficacy of RNAi-mediated knockdown for selected candidate genes. Preliminary data from a courtship assay was used to assess the hearing of flies with knockdown of Ctl2, an Alzheimer’s and Parkinson’s disease risk gene also implicated in autoimmune hearing loss. Expression of RNAi against six Drosophila orthologues of novel AD genes screened induced AD-associated phenotypes in one or more assays, including Ctl2 (SLC44A2), Kuz (ADAM10), Frl (FMNL1), MTA1-like (MTA3), Ppt2 (PPT2) and Kdm2 (KDM2B). This demonstrates that these genes may be involved in AD pathology and should be further validated in Drosophila and rodent models.

Date of Award	20 Jun 2023
Original language	English
Awarding Institution	University of Bristol
Supervisor	James J L Hodge (Supervisor) & Shamik Dasgupta (Supervisor)