Emerging evidence has shown that the level of BACE1 protein is aberrantly increased in the brains of AD patients as well as in different AD transgenic mouse models, whereas the level of BACE1 mRNA tends to be constant (Holsinger et al., 2002; Preece et al., 2003; Yang et al., 2003; Li et al., 2004; O’connor et al., 2008; Kim et al., 2018). Here, BACE1 is linked to Alzheimer disease.