To follow the progression of the TH phenotype in MPS-IIIA, we also analysed 8-month-old MPS-IIIA mice in which the complete impairment in the lysosomal/autophagosome degradation pathway (Supplementary Fig. 3b, bʺ) apparently did not affect the number of TH+ cells in the SN/VTA complex (Supplementary Fig. 5a, b), suggesting an accelerated age-dependent TH+ cell loss. This evidence concerns the gene TH and mucopolysaccharidosis type 3A.