Abstract

Alzheimer’s disease (AD) and Parkinson’s disease (PD) are the first and second most common age-related neurodegenerative disorders and both diseases are characterised by the formation of protein aggregates in neurons. In the case of PD, α-synuclein accumulates and misfolds into Lewy bodies and Lewy neurites, whereas in AD, amyloid-β forms extracellular plaques and tau forms neurofibrillary tangles. Despite overall distinct aetiologies and symptomology, there is evidence that α-synuclein and amyloid-β neuropathologies can co-exist, leading to Parkinson’s disease dementia (PDD) and dementia with Lewy bodies (DLB). Across the PD, PDD, DLB and AD spectrum, both mitochondrial and lysosomal-autophagy dysfunction have been widely implicated in contributing to the neuronal dysfunction and death. Yet, the mechanisms by which these aggregating proteins contribute to dysfunction of mitochondria and lysosomes are not understood.

To investigate the molecular mechanisms underpinning the effect of α-synuclein and amyloid-β, we are using a correlative light and electron microscopy (CLEM) and genetic CRISPR-interference (CRISPRi) screening approach in an i³ cortical neuron model. CLEM will enable the detailed study of mitochondrial and lysosomal ultrastructure and in the presence and absence of pre-formed fibrils of α-synuclein or amyloid-β oligomers. We are also conducting genetic screening using CRISPRi technology to identify genes influencing the aggregation of α-synuclein and its effects on mitochondrial function. We have identified a shift in mitochondrial network morphology as well as a reduction in lysosomal abundance in α-synuclein-treated cells. We have also demonstrated the functionality of CRISPRi for gene knockdown and its maintenance over the course of a month in culture. This study is expected to provide mechanistic insight into how aggregating proteins exert their deleterious effects in neurons and potentially identify novel targets for therapeutics.