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Fundamental research

26 - 06 - 2018

Studying Down syndrome to understand Alzheimer's

To better understand the origin of Alzheimer's disease, researchers are trying to discover the common genetic damage between the disease and Down syndrome, in a mouse model.
Down syndrome or trisomy 21 (presence in one person of three copies of chromosome 21 instead of two in each cell) is the highest risk factor for an early form of Alzheimer's disease.
As early as age 20, all people with Down's Syndrome have an accumulation of beta-amyloid proteins in their brains. By age 40, neurofibrils of tau protein in neurons can be found, and around the age of 60, two-thirds of down syndrome patients develop dementia.
The triplication of the APP gene present on chromosome 21 is sufficient to develop early Alzheimer's disease even in the absence of Down syndrome. But the effect of the triplication of the other 600 genes on this chromosome regarding
Alzheimer's disease remains unknown.
In an attempt to answer this question, researchers have used a mouse model of Down syndrome and Alzheimer's disease. They were able to discover that even in the absence of APP triplication, the early accumulation of beta-amyloid protein appears in trisomy 21. It is correlated with the appearance of an insoluble form of this protein (beta-amyloid 42 instead of 40).
This study strongly encourages the search for genes on chromosome 21 responsible for the appearance of this insoluble form. These could be involved in the origin of Alzheimer's disease.