As animals age, the addition of methyl groups to DNA — a mechanism that controls gene expression — decreases in the brain. This reduction causes cognitive decline, researchers now show.

Hilmar Bading and his colleagues at the University of Heidelberg in Germany showed that a gene central to DNA methylation, Dnmt3a2, controls cognitive abilities in mice. When the researchers overexpressed Dnmt3a2 in the hippocampal brain area of elderly mice, the animals regained their cognitive skills in two long-term-memory tests. Reducing hippocampal expression of the gene caused young adult mice to perform poorly in the tests compared with controls of the same age.

Nature Neurosci. http://dx.doi.org/10.1038/nn.3151 (2012)