In some familial forms of AD, APP duplication, mutations in APP, or mutations in components of γ-secretase such as Presenilin 1 (PSEN1) or Presenilin 2 (PSEN2) result in increased production of Aβ (Scheuner et al., 1996; Murayama et al., 1999). The gene discussed is PSEN2; the disease is Alzheimer disease.