PRKN and Parkinson disease: Given that PINK1 and Parkin have been observed to be mutated in familial forms of PD, one would expect that impaired mitophagy might be a general theme in the pathogenesis of PD; however PINK1- and Parkin-knockout mice do not display neurodegeneration (Palacino et al., 2004; Gautier et al., 2008).