[Recent advances in the studies on Alzheimer's diseases]

Recent progress on the molecular mechanisms on Alzheimer's disease has been made through discoveries of genes involved in the pathogenesis of Alzheimer's disease. Amyloid precursor protein (APP), presenilin I (PS 1) and presenilin II (PS 2) genes have been identified as the causative genes for early-onset familial Alzheimer's disease. Apolipoprotein E gene, which was originally identified as the gene for late-onset familial Alzheimer's disease, has now been established as a genetic risk factor for not only early-onset but also late-onset sporadic Alzheimer's disease. Recent studies suggest that mutations in APP, PS 1 or PS 2 result in increased production of amyloid beta protein (A beta), a major constituent of senile plaques. Apolipoprotein E 4, which is a risk factor for Alzheimer's disease, has also been reported to be associated with increased density of senile plaques. Although these data suggest that accumulation of A beta is an essential step in the pathogenesis of Alzheimer's disease, it still remains to be elucidated whether such process is causative for Alzheimer's disease. Recently another gene on chromosome 12 has been suggested to be involved in the development of late-onset Alzheimer's disease, and identification of the gene on chromosome 12 may bring a new insight into the pathogenesis of Alzheimer's disease.