The most widely used transgenic models express mutant forms of the amyloid precursor protein (APP) gene, with or without presenilin-1/2 (PSEN1/2), which are associated with autosomal-dominant, early-onset AD, or, alternatively, MAPT mutations, which cause familial frontotemporal dementia (FTD). Here, PSEN1 is linked to frontotemporal dementia.