GBA1 and Parkinson disease: Novel susceptibility genes associated with an increased risk of developing PD have also been identified, including NR4A2 (Nurr1, nuclear receptor superfamily protein), SNCAIP (synphilin-1), APOE (apolipoprotein E), MAPT (tau protein), GBA (b-glucocerebrosidase), and COMT (catechol-O-methyl transferase) [13,14,15].