CDK5 and early-onset autosomal dominant Alzheimer disease: Cyclin-dependent kinase 5 (Cdk5) has been linked to multiple NDDs, including Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS) and Parkinson's disease (PD) (Nguyen et al., 2001; Patrick et al., 1999; Qu et al., 2007).