Identification of gene expression changes in Drosophila models of mammalian prion diseases

Prion diseases are fatal transmissible neurodegenerative diseases of humans and other animals. These include acquired prion diseases, such as scrapie in sheep, bovine spongiform encephalopathy in cattle and variant Creutzfeldt-Jakob disease in humans. Genetic prion diseases also occur in humans, which are associated with mutations in the prion protein (PrP) gene, such as genetic CJD (gCJD) and fatal familial insomnia. Prion diseases are caused by the misfolding of the cellular isoform of PrP (PrPC) into the disease-associated isoform (PrPSc). Prion inoculated wild-type and PrP transgenic mice have been used to model acquired prion diseases. Mice transgenic for mutated forms of PrP have also been used to model different genetic prion diseases. Mouse models of different prion diseases have been used to investigate prion-induced gene expression changes. PrP transgenic Drosophila have also been developed as models of authentic prion diseases, which provide certain practical advantages over mouse models of prion diseases. In this thesis, I aimed to determine whether similarities in prion-induced gene expression changes were present between an ovine PrP transgenic Drosophila model of the acquired prion disease PG127 ovine scrapie and a hamster (E200K) PrP transgenic Drosophila model of gCJD, as well as between this Drosophila model of ovine scrapie and a mouse PrP transgenic Drosophila model of the acquired prion disease Rocky Mountain Laboratory (RML) mouse-adapted scrapie, at two timepoints. I also aimed to determine whether the expression of an epitope-tagged ribosomal protein (ribotag), that consisted of RpL10a tagged with GFP and 3X-FLAG, impacted the prion-induced gene expression changes in these Drosophila models of ovine scrapie and RML mouse-adapted scrapie. In addition, I aimed to determine whether the co-expression of the neurotoxic anti-PrP single-chain variable fragment (scFv) POM1 and PrP in neurons or other cell types in Drosophila caused a specific toxicity. RNA sequencing (RNAseq) analyses demonstrated that, while there were some similarities in altered gene expression between the Drosophila model of ovine scrapie and those of gCJD and RML mouse-adapted scrapie, there were substantial differences at the same timepoints. This included altered expressions of some of the genes involved in synapses, ribosomes and oxidative phosphorylation. RNAseq studies also demonstrated that the expression of the ribotag in Drosophila models of ovine scrapie and mouse-adapted scrapie did alter the prion-induced gene expression changes at both timepoints studied. Analyses of climbing assay data confirmed that Drosophila that co-expressed scFv POM1 and PrP from neurons or glia displayed a specific toxicity as measured by reductions in locomotor ability. Therefore, this thesis has advanced the knowledge of gene expression changes in Drosophila models of mammalian prion diseases, which includes the impact of ribotag expression, and has provided evidence that Drosophila that co-express scFv POM1 and PrP from neurons could be used in future studies to study PrPSc-PrPC neurotoxic signalling.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2023

Author dc:creator

• Smith, Andrew

Advisors dc:contributor.advisor

• Bujdoso, Raymond
• Blacklaws, Barbara

• Prion diseases
• Neurodegenerative
• Prions
• Gene expression
• Drosophila
• RNA sequencing

Licence

• https://www.repository.cam.ac.uk/bitstreams/eb808a50-cc34-41bc-8f82-416d0933a6b0/download
• https://creativecommons.org/licenses/by/4.0/

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.117812

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/383436