Two recent studies from Europe have shown that three genetic variants may be responsible for about 20% of the risk of developing Alzheimer’s. This discovery not only could help scientists refine tests that let you know if you are at risk, they may lead to advances in treating the disease as well. That could change the lives of the more than 16 million people worldwide and their families who suffer from Alzheimer’s.
These two studies also demonstrate advances in exploring the human genome for information. One examined more than 16,000 genomes, representing the largest such study so far. Of the 550 genetic variants that have been linked to Alzheimer’s, these projects present only the second time in history when a variant has been confirmed by more than one research group. We’re getting better at searching through our DNA, and it’s going to have a profound impact on how we live our lives.
Cardiff University in Wales was the larger of the two projects, studying 16,000 genomes and discovering 2 variants linked to Alzheimer’s (CLU and PICALM). The University of Lille in France studied more than 3000 genomes to discover 2 variants as well (CLU and CR1). Each group examined about 500,000 sites on each set of DNA, a small fraction of the total, but a large number until complete genome sequencing becomes cheaply available. The journal Nature Genetics published both papers (here and here) in the same September 6 issue, highlighting the groups’ unique verification of the CLU variant.
Of the three new variants, one may affect neural synapses, and the other two dampen inflammation in the brain. Inflammation has long been associated as a symptom of Alzheimer’s, but scientists now wonder if it plays a primary role. If so, it may inform a new treatment for the disease, or perhaps provide early diagnosis opportunities.
Of course, for those of you who know Alzheimer’s studies know that the most important genetic variant is still APOE4. This variant, discovered at Duke University in 1993, is thought to multiply a person’s risk for Alzheimer’s by 10-30 times. Cardiff’s project repeated the confirmation of APOE4 as a precursor to the main body of its study. The new variants, though very important, should be seen as refining the genetic risk already established by the presence of APOE4.
Of course, competing with APOE4 was never the point. These new variants show that even a complex disease like Alzheimer’s can be largely influenced by one gene, and perhaps completely defined by a few more. After all, just three genetic variants are responsible for controlling the wide range of dog fur. Genetic research, augmented by the ability to partially examine thousands of genomes, may find that complex illnesses could have relatively simple treatments.