We examined mature CTSD in putamen isolated from GBA1 mutant (N370S/WT) PD, idiopathic PD and matched control brain (n = 3), and found the CTSD protein level and activity decreased in GBA1 mutant (N370S/WT) PD and idiopathic PD patients' putamen (Fig. 2 F—H), but did not reach significance. The gene discussed is CTSD; the disease is Parkinson disease.