CDK5 and Alzheimer disease: Consistent with these observations, changes in the expression of markers of CCL (cyclins D [10] and B [3], [10], [11], CDK4 and p16 [2], CDC2 [12], Ki67 [4], p27 [13], BRCA1 [14], Polo-like kinases [15], CIP1-associated regulator of cyclin B [16], p25 - a cleavage product of p35 -the Cdk5 activator [17] and phosphorylated retinoblastoma (p130) protein [18]) have been noted in cortical neurons of postmortem brain specimens from persons with AD that are uncharacteristic of gene and protein expression in postmitotic cells.