APP and Alzheimer disease: Our informatics analysis results show that RTN4 was reduced in the brain of AD patients (Appendix S1, Figure S6), and our results showed that the protein level of RTN4B also significantly reduced in APP/PS1 mice compared to the WT control mice group, especially in the hippocampus of both 10‐month‐old and 20‐month‐old mice (Figure 2e,f).