Cyclin-dependent kinase 5 (CDK5) has been implicated as one of the major protein kinases involved in the abnormal hyperphosphorylation of tau in AD [2], the activity of CDK5 has been shown to be higher in the prefrontal cortex of AD brains [3], and CDK5 has been described to be associated with all stages of neurofibrillary pathology in AD brains [4]. The gene discussed is CDK5; the disease is Alzheimer disease.