APEX1 and Alzheimer disease: The present study explores the relationships between the quantitative analysis of mRNA transcripts for the BER genes encoding APE1, Polβ, OGG1 and PARP1 and CSF biomarkers of AD and clinical signs of cognitive decline in blood from a clinical cohort (n = 166) as well as in a second cohort of postmortem samples of different brain parts (hippocampus, cerebellum, entorhinal cortex and frontal cortex) from AD patients (n =42) and HC (n = 9).