Of note, some of the lysosomal enzymes with elevated levels in MUT brain (GRN, HEXA, and GLB1 – M36; Figure 4) are also implicated in lysosomal storage disorders, where they generally have decreased, rather than increased, function or expression (Boles and Proia, 1995; Regier and Tifft, 1993; Smith et al., 2012; Ward et al., 2017). This evidence concerns the gene GLB1 and lysosomal storage disease.