GBA1 and Parkinson disease: Many genes contribute to the pathogenesis of PD, including α-synuclein (SNCN), leucine-rich repeat kinase 2 (LRRK2), glucocerebrosidase (GBA), vacuolar protein sorting associated protein 35 (VPS35), phosphatase homolog-induced kinase (PINK1) and Parkinson protein 7 (PAPK7) [3, 4].