LRRK2 and Parkinson disease: It has been demonstrated in patients with SNCA mutations whose brains showed the aggregation of α-synuclein, represented as the occurrence of Lewy bodies and the loss of DA neurons, that the PARK1/PARK4 gene for the expression of α-synuclein is related to the abnormal pathological aggregation of insoluble α-synuclein fibril.42,43 The most frequent genetic cause of PD is a mutation in the leucine-rich repeat kinase 2 gene (LRRK2), known as PARK8.