Dysfunctional mitochondria are also related to monogenic forms of PD: genetic methods have identified variants in mitophagy regulatory genes—e.g., PINK1 (PTEN-induced putative protein kinase 1), Parkin (PRKN, parkin RBR E3 ubiquitin protein ligase) and DJ-1 (protein deglycase DJ-1)—as hereditary factors of PD etiology, being associated with early-onset autosomal recessive PD (age less than 45 years) through alterations in mitophagy [233,234]. Here, PRKN is linked to Parkinson disease.