For example, although the substitutions G328E and R275W in the human PARK2 gene have both been identified in individuals with Parkinson disease (West et al., 2002; Lücking et al., 2000), only the R275W form results in progressive degeneration of dopaminergic neurons when expressed in transgenic flies (Wang et al., 2007). Here, PRKN is linked to Parkinson disease.