'Smart gene' makes for brainy mice

Gap-43 is found early in the development of all animals

By BBC News Online science editor Dr David Whitehouse

Scientists have engineered mice that, in mazes at least, can run rings around ordinary rodents.

The research shows the importance of nerve growth in boosting brain performance.

Professor Aryeh Routtenberg, and colleagues from Northwestern University, US, used mice that had been modified so that their brains expressed enhanced levels of a protein that stimulates nerve fibre growth.

More nerve fibres in the brain meant that the mice were quicker at learning tasks such as hunting for food in a maze. The mice also remembered how to do the tasks much longer than the "wild type" mice.

Second gene

The gene for the protein is the second single gene that has been shown to significantly improve learning and memory. In September 1999, another US team showed that a gene called NR2B helped keep mouse brains "young", with lots of interconnections between the neurons.

The extra gene in the mice in this latest study produces a growth-associated protein called as GAP-43. It is found early in the development of all animals, when neurons are deciding where and how to grow. It acts on the ends of nerves, not only stimulating them to grow but also providing more resources for the brain's memory functions.

Mice that overproduced the GAP-43 protein performed better than the mice with normal GAP-43 levels in experiments designed to test the ability to remember the location of food in a maze.

In addition, when the interval between the tasks was lengthened the superiority of the altered mice was more pronounced.

Ethical questions

Professor Routtenberg said he would oppose moves to create a designer drug for people who want to be smarter, or who want their children to have an advantage in school.

"You get into ethical questions," he said.

"But I think that we are moving ever closer to finding an agent that will facilitate when we are learning."

Legitimate uses, in his opinion, would be in treating people with Alzheimer's, some with mental retardation and perhaps people suffering from age-related memory loss. He said there was evidence that GAP-43 was produced in lower amounts as people aged.

The research is reported in the Proceedings of the National Academy of Science.