Magazine article Newsweek

The Mice That Roared ... and Killed and Raped, Due to a Genetic Defect

Magazine article Newsweek

The Mice That Roared ... and Killed and Raped, Due to a Genetic Defect

Article excerpt

Ted and Valina Dawson of Johns Hopkins University were doing the kind of scientific gruntwork the recruiters don't warn about: breeding mice. They started with five special mice lacking the gene needed to make nitric oxide (NO), a little molecule best known as an air pollutant but recently found to exist in the brain, too, where it carries chemical signals from neuron to neuron. The Dawsons were studying NO's role in brain damage caused by stroke. But last year, when they arrived at their lab on workday mornings, they often found that one or two mice were dead. At first the scientists suspected heart attacks. But when they looked closely they saw that the dead had not gone gentle into the good mousy night: they had been killed by cage mates. The mutant mice were sexual aggressors, too: when put into cages with females, "the females would cower, sit and scream for hours," says Hopkins neuroscientist Randy Nelson. "But still the males kept mounting them."

The researchers bagged the stroke research. With Hopkins's Solomon Snyder, they designed experiments to examine how the lack of NO turned animals that were downright mousy into serial killers and rapists. They shipped a normal male mouse into a cage with a mutant male; the mutant relentlessly launched three times more attacks than did a normal male facing an intruder, the scientists reported last week in the journal Nature. The attacks didn't stop even when the victim "surrendered" by lying on its back. The scientists then caged a mutant male with a female who was not in estrus; normal males gave up, but the mutant mounted the screaming female for hours. Earlier studies also found "knockout" mutations (so called because a gene is KO'd) that make mice hyperaggressive. But "the extent of the behavioral change we see here," says Snyder, "is totally unprecedented. …

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