Lewy bodies containing α-Synuclein are a neuropathological hallmark of PD, and missense mutations in α-Synuclein (A30P, E46K, H50Q, G51D, A53E, A53T), as well as α-Synuclein gene duplications and triplications, appear to cause PD. Moreover, polymorphisms in regulatory elements of the α-Synuclein gene predispose individuals to PD and are linked to an early onset of the disease. The non-Aβ-amyloid component (NAC) region of α-synuclein is relatively hydrophobic and aggregation-prone in human α-Synuclein but not in mouse α-Synuclein nor in the corresponding homologous region of human β-synuclein. Yet, β-synuclein is more homologous to α-synuclein in the N-terminal sequences (74%) than γ-synuclein (67%).