Cathepsin Z is a lysosomal cysteine protease that is upregulated in LSDs and neurodegenerative diseases.46–48 We performed IHC to examine the levels of cathepsin Z in hippocampal, thalamic, and cortical tissues of Grn−/− mice injected with rAAV2/1 expressing GFP, hGRN2, hGRN4, and hPGRN (n = 5; one section/mouse) (Figure 3B). Here, CTSB is linked to neurodegenerative disease.