Genes to Remember

By boosting levels of a single protein in mouse brains, researchers have made the animals better at memory and learning tests. They say the finding, reported in tomorrow's Nature, could be used to breed smarter animals. It may also someday lead to new drugs to boost ailing memories in people.

The study focussed on the receptor for a neurotransmitter called NMDA (N-methyl-D-aspartate). Studies have shown that the NMDA receptor appears to operate in brain cells as a "coincidence detector": It springs into action when two neurons fire at the same time, creating an association between them, and has therefore long been suspected to play a role in learning. Researchers also knew that the composition of the receptor, which is made up of four subunits, is different in children than in adults, says Princeton University neurobiologist Joe Tsien; in children, who generally have better memories and seem to learn faster, the receptor contains more of the subunit called NR2B.

To see if they could breed mice with childlike memories, Tsien and his colleagues genetically engineered a strain to produce abnormal amounts of NR2B. Mice of the strain they created--dubbed "Doogie" after the brilliant teenager in a U.S. comedy series called "Doogie Howser, M.D."--remember objects shown to them days before, which ordinary mice had forgotten. They were also quicker at finding a submerged platform in a pool of water, a standard intelligence test. "They look normal. They behave normally," says Tsien. "But ... they outperform their [normal] brothers and sisters every time." Tsien says the finding shows that it's possible to breed smarter animals; in theory, the same could even be done in humans.

Neurophysiologist Tim Bliss of the National Institute for Medical Research in London, U.K., says that knowing the NR2B subunit's role could help find drugs--perhaps NR2B mimics--for people with memory impairments. But he says better memory may not lead to smarter people. "There is no doubting that they are making smarter mice," says Bliss. "But I suspect that memory plays a much smaller part in the intelligence of humans than it does in mice."

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