Although we did not pursue this observation further, it is worthy to note that a serine/threonine kinase PKN (also known as protein kinase C-related kinase 1), which is involved in the pathogenesis of Alzheimer's disease and amyotrophic lateral sclerosis,33, 34 interacts with and phosphorylates cdr2.13 This evidence concerns the gene MARK2 and Alzheimer disease.