Genes, such as NOS1 (nitric oxide synthase 1), SNCA (alpha-synuclein), PINK1 (PTEN-induced putative kinase 1), Parkin, UCH-L1 (ubiquitin C-terminal hydrolase L1), DJ-1 (PARK7), NR4A2 (nuclear receptor subfamily 4, group A, member 2), and LRRK2 (leucine-rich repeat kinase 2) have all been found to be mutated in PD [10,11,12,13], although only 1% of PD cases have SNCA mutations [14]. This evidence concerns the gene NR4A2 and Parkinson disease.