Immunofluorescent staining also showed that AAV-α-syn diminished PSAP in TH-positive neurons (Fig. 4C, D), while AAV-GFP did not (Supplementary Fig. 14C, D), which was in accordance with our result in DA neurons of PD patients (Fig. 1A, B) and PSAP downregulation in PD iPSC-derived DA neurons presenting α-syn accumulation6. Here, PSAP is linked to Parkinson disease.