In AD, the DNA methylation of genes such as amyloid precursor protein, PSEN1, MAPT, apolipoprotein E, presenilin-1, beta-secretase 1 precursor, or apolipoprotein E, Sorbin SH3 domain containing 3 (Sorbs3) and BDNF was found to be altered in three parts of the brain. The gene discussed is APOE; the disease is Alzheimer disease.