Molecular genetics of Alzheimer's disease: what have we learned?

Alzheimer's disease (AD), by fur the most common form of dementia in the el derly, is clinically characterized by gradual, progressive loss in cognitiv e functioning and changes in personality, ultimately leading to death. It i s now well established that genetic factors play an important role in AD. S o far three genes have been identified in which mutations cause autosomal-d ominant AD : the amyloid precursor protein (APP) gene on chromosome 21, the presenilin I (PSEN1) gene on chromosome 14, and the homologous presenilin 2 (PSEN2) gene on chromosome 1. A major susceptibility gene, the apolipopro tein E (APOE) gene, was identified on chromosome 19.