Previous study suggests that Wnt signaling pathway may be associated with schizophrenia, and expression of Wnt-related proteins is altered following APPs treatment, for example, the expression of β-catenin and glycogen synthase kinase-3 (GSK-3) protein are increased in rat medial prefrontal cortex and striatum after APPs administration (Alimohamad et al., 2005a). Here, CTSB is linked to schizophrenia.