Pathologically, PD is characterized by the selective loss of midbrain dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc) and the accumulation of intracellular inclusions called Lewy bodies (LBs) and Lewy neurites (LNs), which mainly consist of aggregated fibrillar α-synuclein (α-syn)2. This evidence concerns the gene SNCA and Parkinson disease.