For example, mutations in genetic variants such as α-synuclein (SNCA), microtubule-associated protein tau, the glucocerebrosidase gene, Parkin (PARK2), PTEN-induced kinase 1 (PINK1), and multidrug resistance protein 1 are implicated in diseases like Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD) [64, 78]. The gene discussed is ABCB1; the disease is Parkinson disease.