Investigation of FAD (dominantly inherited familial AD) reveals mutation of the APP (Amyloid-Precursor Protein) gene and PSEN (Presenilin) that cleaves the protein and forms Aβ from APP, and tau is responsible for frontotemporal dementia [19], which supports another hypothesis apart from toxic protein aggregate formation that helps us to understand the neurodegeneration mechanism [20]. This evidence concerns the gene APP and frontotemporal dementia.