How can an APP gene defect increase amyloid beta deposition in the brain?

A defect in the APP (amyloid precursor protein) gene can contribute to the development of Alzheimer disease by altering how the body processes this protein.12

Normally, amyloid precursor protein is a standard component of nerve cells. However, a genetic defect in the APP gene—which is located on chromosome 21—is thought to result in the abnormal cleavage of this protein. This irregular processing leads to an increase in the production and subsequent deposition of amyloid beta protein in the brain. These amyloid beta proteins then clump together to form the core of neuritic plaques, which are characteristic tissue lesions associated with the destruction of healthy brain tissue in patients with Alzheimer disease.3214