PRKN and Parkinson disease: Parkin loss-of-function mutant flies were found to have advanced mitochondrial aging, structural mitochondrial damage, and a consequential selective loss of dopaminergic neurons (Cackovic et al., 2018), leading to motor deficits assessed by a climbing assay (Chambers et al., 2013; Cackovic et al., 2018), as well as non-motor PD phenotypes including memory deficits (Julienne et al., 2017).