GBA1 and Parkinson disease: GBA1 mutations are also the most frequent genetic risk factors for Parkinson's disease (Brockmann and Berg, 2014; Klein and Westenberger, 2012), and decreased GCase enzyme activity is linked to α-synuclein accumulation and Parkinson's disease pathogenesis (Almeida, 2012; Mazzulli et al., 2016; Schapira, 2015).