Parkinson's disease (PD) is the second most common neurodegenerative disorder. To understand genetic factors influencing PD, we have conducted a genetic screen in Drosophila to identify genetic modifiers of alpha-synuclein and have identified several highly conserved genes. To understand how ageing affects the risk of neurodegeneration, we are currently conducting experiments in a short-living killifish to identify single-cell gene expression changes during brain ageing.