Parkinson’s Disease. PD, the second most common neurodegenerative disease, is a movement disorder, associated to mutations in α-synuclein, LRRK2, parkin, and PINK1, and selectively affecting the substantia nigra dopaminergic (DA) neurons (Surmeier et al., 2017; McGregor and Nelson, 2019). The gene discussed is LRRK2; the disease is Parkinson disease.