Because increased lysosomal biogenesis, linked to activation of TFEB-driven expression of lysosomal genes (4, 9, 12, 13), occurs in multiple mouse models of neurological MPS, including those of MPS IIIC (4, 9, 12, 14, 46–50), NEU1 activity showed a trend opposite to that of other lysosomal enzymes and proteins. Here, TFEB is linked to mucopolysaccharidosis type 3C.