A number of previous studies reported that Rac1 expression level, Rac1 activity, and activities of its downstream components, such as PAK and cofilin, are reduced in brain tissues obtained from either AD patients (Zhao et al., 2006; Huang et al., 2013; Kim et al., 2013; Borin et al., 2018) or from APP(swe) Tg2576 mice (Petratos et al., 2008), which is contradictory to our findings. Here, RAC1 is linked to Alzheimer disease.