GBA1 and Parkinson disease: Heterozygous mutations in the glucocerebrosidase gene (GBA) encoding the lysosomal enzyme GCase represent the strongest common genetic risk factor for PD (Sidransky et al., 2009) and have also been associated with other related Lewy body disorders (Goker-Alpan et al., 2006); however, the underlying molecular mechanisms are still poorly understood.