PSEN1 and Alzheimer disease: Next, to investigate if p21rac is also activated in the CNS of an animal model of AD, we examined the status of activated p21rac in the hippocampus of 5XFAD (B6SJL-Tg(APPSwFlLon,PSEN1*M146L*L286V)6799Vas/J) Tg mice.