Neuronal CDK7 in hippocampus is related to aging and Alzheimer disease

Despite their supposedly terminally-differentiated quiescent status, many neurons in Alzheimer disease display an ectopic re-expression of cell-cycle related proteins. In the highly regulated process of cell cycle, cyclin-dependent kinase 7 (Cdk7) plays a crucial role as a Cdk-activating kinase and activates all of the major Cdk-cyclin substrates. In this study, we demonstrate that Cdk7 immunoreactivity is significantly elevated in susceptible hippocampal neurons of Alzheimer disease patients in comparison with age-matched controls. Notably, the expression of Cdk7 is age-dependent, with decreased levels between the ages of 54 and 65 years and after the age of 78. While the Cdk7 levels in Alzheimer disease patients are higher than controls within each age group, the difference is greatest between ages 54–65 where disease susceptibility and/or progression is likely more related to genetic factors.