GBA1 and Parkinson disease: Genes involved in monogenic cases of PD include SNCA, which codes for the α-synuclein protein, leucine-rich repeat kinase 2 (LRRK2), glucosidase beta acid (GBA), phosphatase and tensin homolog (PTEN)-induced putative kinase 1 (PINK1), parkin RBR E3 ubiquitin-protein ligase (PRKN), and cytoplasmic protein sorting 35 (VPS35).