Bio-engineered mice made with ease

SAN FRANCISCO — They're being bred now by the millions, the mutants, created to carry the ghastliest of diseases for the benefit of the human race.

Since researchers published the mouse's entire genetic makeup in map form three years ago, increasingly exotic rodents are being created with relative ease.

There's the Schwarzenegger mouse — injected with muscle-building genes. The marathon mouse, which never seems to tire. Researchers recently engineered some mice to be extremely addicted to nicotine, and others to be immune to scrapie, a close cousin to the brain-wasting mad cow disease. And scientists are in hot pursuit of a Methuselah mouse, able to cheat death long after its natural brethren meet their maker.

Millions of these and other mutant mice are routinely created now, by injecting disease-causing genes or "knocking out" genes in mouse embryos. Their decreasing cost and increasing availability is helping researchers in pursuit of all manner of disease cures.

Top researchers in the Parkinson's disease field, for example, were more excited by the dopamine-free "knock-out" mouse that Duke University researchers invented than the actual study they unveiled this week, which suggests that the club drug Ecstasy reversed Parkinson's-like effects in these particular bio-engineered mice.

Researchers first genetically engineered a mouse in 1980. But until recently, such creations were mostly scientific novelties.

That changed drastically after President Clinton announced the mapping of the human genome in 2000. That's because mice and men are nearly genetically identical, each possessing just a few hundred different genes out of a possible 25,000 or so. Cancer in mice is a lot like human cancer, for instance. Mice have become powerful, living research tools.

The number of mutant research mice has grown so dramatically in recent years that companies are now profiting by housing and breeding scientists' creations.

"Space is precious," said Terrence Fisher of Charles River Laboratories in Wilmington, Mass., the nation's largest mutant mouse house. The publicly traded company breeds and cares for scientists' creations and markets their inventions to other researchers, shipping an estimated 7 million mice worldwide annually.

"The novelty of being simply able to do this has worn off and clearly these mice are tools that are accelerating research," Fisher said.