DNA methylation may help form memories

Once cells in an embryo have differentiated sufficiently, DNA methyltransferase (DNMT) attaches methyl groups to select regions of DNA to permanently switch off targeted genes. Researchers at the University of Alabama, Birmingham, propose that brain cells have adapted this technique as a means to store memories (Neuron 2007, 53, 857). Neurobiologists Courtney A. Miller and J. David Sweatt began a study by conditioning rats with a series of mild shocks in a training chamber. The researchers found that blocking DNMT activity interfered with the animals' ability to form memories of fear associated with the chamber. Conversely, formation of fear-related memories in conditioned but otherwise untreated animals increased production of DNMT messenger RNA. Fear conditioning also increased methylation, and hence deactivation, of a memory-suppressor gene and demethylation, and hence activation, of a memory-promoting gene. These modifications were all rapid and reversible, the researchers say, which suggests that "changes in DNA methylation in the adult nervous system are not necessarily permanent."