GBA1 and Parkinson disease: Specifically, total and oligomeric forms of aSyn have been found to be elevated in the brain of patients carrying GBA1 mutations (Mazzulli et al., 2011), the GCase protein has been found to be a component of aSyn-positive pathological inclusions in the brain of GBA1 mutation-positive PD patients (Goker-Alpan et al., 2010), direct associations between aSyn and GCase have been demonstrated (Yap et al., 2011), and GCase levels and activity are demonstrably lower in brain tissue of sporadic PD patients with aSyn pathology as compared to controls (Mazzulli et al., 2011; Murphy and Halliday, 2014).