APP and Alzheimer disease: Genetic factors of AD vary depending on the subtype of the disease, such as the presence of the ε4 variant of the apolipoprotein E (APOE) gene that is associated with the more common sporadic form of AD (sAD) that manifests in those over the age of 65, or mutations in the amyloid precursor protein (APP) and presenilin (PSEN) genes that bring about the early onset of Alzheimer’s [3,4,5,6].