Alzheimer’s, Down Syndrome Link Explained

the Psychiatry Advisor take:

Researchers in California have discovered an explanation for why people with Down syndrome have a high risk of Alzheimer’s disease.

Lead researcher Huaxi Xu, PhD, of Sanford-Burnham Medical Research Institute in La Jolla, California, and colleagues found that the protein SNX27 regulates levels of beta amyloid plaques. That plaque is found in the brains of many Alzheimer's patients and is thought to contribute to the disease.

By age 40, almost everyone with Down syndrome will develop these plaques. By age 35, 25% of people with Down syndrome will develop Alzheimer’s symptoms, and 75% of them by age 65.

A previous post-mortem study found that people with Down syndrome had abnormally low levels of SNX27, a brain protein involved in complex molecular pathways. People with Down syndrome have a third — and extra — copy of a certain chromosome that produces a molecule that, in turn, reduces levels of SNX27.

Additionally, this previous research looked at mice with an extra copy of a chromosome similar to humans with Down syndrome. Tests demonstrated that the mice became learning deficient. When the mice were treated with gene therapy that delivered a gene that makes SNX27, the mice performed normally on a learning test.

The researchers are now working to find molecules that can increase production of SNX27.