03 July 2012

Gene therapy for memory rejuvenation

"Memory enzyme" found
Increased activity of one of the DNA methylases involved in the regulation of genes prevents age-related memory loss

Kirill Stasevich, Compulenta

Memory loss can be reversed–at least in mice. Researchers from the University of Heidelberg (Germany) experimented with the enzyme Dnmt3a2, one of the DNA methyltransferases (or DNA methylases). These proteins control the activity of genes by attaching methyl groups to the nitrogenous bases in DNA (cytosine is usually the modified base). Scientists sent additional copies of the Dnmt3a2 gene to the cells of the hippocampus, which is responsible for memory in the brain. The gene was sewn to the neutralized virus, and the viral particle delivered it to the neurons.

During the experiment, mice performed a memory test. At first, a certain object was shown to the animals, and a day later it was shown again and another, unfamiliar one. The young mice remembered well what they had seen before, and next time they paid more attention to a new thing. The old ones studied both to the same extent: poor memory provided them, so to speak, with constant freshness of impressions. But the picture changed if elderly rodents were injected with a virus with a DNA methylase gene. After this procedure, the memory of such animals, apparently, was dramatically rejuvenated – and elderly mice spent 70% of their time on a new subject. That is, they suddenly began to remember well what they had seen yesterday.

The reverse experiment was also performed: using the same technique, the researchers suppressed the synthesis of DNA methylase in the hippocampus in young mice. And as a result, the memory of animals deteriorated greatly: the young began to behave in the same way as the old. The details of the mechanism, as usual, are still unknown, but it can be assumed that the enzyme controls a whole "bundle" of genes responsible for specific age-related changes in neurons.

As for the practical application of the results, for a person, such a method – the introduction of additional copies of the gene into the cells of the hippocampus – is unlikely to work, that is, we need to look for a substance that would stimulate our own DNA methylase gene (or at least simply increase the activity of the enzyme). There is no such medicine yet, but progress, as they say, does not stand still, and it is already clear in which direction to look.

The results of the study are published in the journal Nature Neuroscience (Oliveira et al., Rescue of aging-associated decline in Dnmt3a2 expression restores cognitive abilities).

Prepared based on the materials of NewScientist: Rusty memories rejuvenated in elderly mice.

Portal "Eternal youth" http://vechnayamolodost.ru03.07.2012

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