APP and Alzheimer disease: To this end, Piedrahita and co-workers showed that AAV-mediated shRNA knock-down of the cycline dependent kinase 5 (CDK5) in a mice transgenic for PS1, APP and Tau resulted in significant reduction of phosphorylated Tau and reduced levels of neurofibrillary tangles implying the CDK5 might also be a possible therapeutic target in some forms of AD [124].