PRKN and Parkinson disease: For PD we examined two models: Expression of wild-type human alpha-synuclein (SNCA) under control of Elav-Gal4 [14, 34] (elevated levels of wild-type SNCA in both flies and humans cause neurodegeneration [14,35]), and homozygous parkin mutant flies [36–40] (mutations in parkin underlie the most common cause of early onset PD [41]).