It’s expression and proteolytic activity are strongly upregulated in mouse brain, with a preference for glial cells and aged neurons, particularly in a transgenic mouse model of Alzheimer’s disease (AD) in which cathepsin X upregulation in microglial cells surrounding amyloid plaques has been observed (Wendt et al., 2007; Hafner et al., 2013). This evidence concerns the gene CTSZ and Alzheimer disease.