P25 is a subunit of the Cyclin-dependent kinase 5 (CDK5) that is elevated in human AD patients (Patrick et al., 1999) and has been linked to amyloid and tau pathology as well as severe neurodegeneration and memory impairment (Cruz et al., 2003, 2006; Fischer et al., 2005). This evidence concerns the gene CDK5 and Alzheimer disease.