The chromosome 22q11.2 region contains some excellent candidate genes for PD: COMT (or Catechol-O-Methyltransferase), a key regulator of synaptic dopamine levels and a target of inhibitory drugs for the treatment of wearing-off phenomena in PD patients (Muller 2015); SEPT5, a vesicle- and membrane-associated protein playing a significant role in inhibiting exocytosis, as well as a parkin substrate (Son et al. 2005; Marttinen et al. 2015); DGCR8 that encodes a complex subunit involved in the biogenesis of microRNAs, including miR-185 which is predicted to target LRRK2 (Ogaki and Ross 2014). This evidence concerns the gene PRKN and Parkinson disease.