CDK5R1 and early-onset autosomal dominant Alzheimer disease: Cdk5 hyperactivation, associated to p35 overexpression and production of p25, a proteolytic fragment containing the C-terminal portion of p35 [12], has been implicated in some neurodegenerative disorders, such as Alzheimer's disease (OMIM: 104300) [13], Parkinson's disease (OMIM: 168600) [14] and amyotrophic lateral sclerosis (OMIM: 105400) [15].