Supplementary Figure S4 shows the characterization of AAV9 vector injection in SNpc of mouse brain. Double immunofluorescence for Hb and the specific DA marker tyrosine hydroxylase (TH) revealed that AAV9 vectors were efficiently transduced in DA neurons in the ipsilateral side (Supplementary Figures S4d and e). Furthermore, double immunofluorescence for tagged α- and β-globin demonstrated their co-localization in DA cells, confirming the efficiency of co-infection (Supplementary Figure S4g). This evidence concerns the gene GSTM1 and coinfection.