For instance, the existence of several different promoters has already been described for genes linked to Alzheimer’s disease (AD), such as the apolipoprotein E gene APOE (the main AD genetic risk factor8) and the presenilin-2 gene PSEN2 (one of the catalytic moieties in the gamma secretase complex involved in amyloid precursor protein (APP) cleavage and generation of amyloid beta peptide (Aß), which accumulates outside the cell9,10). Here, APOE is linked to Alzheimer disease.