deCODE genetics in Reykjavik screened the whole genomes of nearly 1,800 Icelanders and found a rare change in the APP gene, the same gene that produces the plaques found in Alzheimer's brains.
The variant, called A673T, sat right next to the site where enzymes cut APP into the fragments that form amyloid plaques. In lab tests it cut the plaque-forming fragment by about 40 percent, and elderly carriers without the disease scored better on cognitive tests than non-carriers of the same age.
It was the first time a change in APP itself had been shown to lower disease risk rather than raise it, and it strengthened the case that amyloid buildup drives the disease rather than merely accompanying it. Drugs that block the same enzyme step have since been tested, so far without success.
Read the original study
One gene, cutting amyloid instead of making it.
Source
- Jonsson, T., Atwal, J. K., Steinberg, S., Snaedal, J., Jonsson, P. V., Bjornsson, S., Stefansson, H., Sulem, P., Gudbjartsson, D., Maloney, J., Hoyte, K., Gustafson, A., Liu, Y., Lu, Y., Bhangale, T., Graham, R. R., Huttenlocher, J., Bjornsdottir, G., Andreassen, O. A., . . . Stefansson, K. (2012). A mutation in APP protects against Alzheimer's disease and age-related cognitive decline. Nature, 488(7409), 96–9. https://doi.org/10.1038/nature11283