PRKN and Parkinson disease: Loss of parkin function causes a rare form of Parkinson’s disease (PD), and in Drosophila, it causes developmental deficiencies, decreased lifespan, deficits in motivated behavior, and selective degeneration of protocerebral posterior lateral region 1 (PPL1) dopaminergic neurons that are functionally homologous to the mammalian substantia nigra [6,7,8,9,10,11].