Mutant Mice Aid Hunt for Cures

[Guest guest]

August 17, 2005 latimes.com

http://www.latimes.com/business/la-fi-mice17aug17,1,232198.story

Mutant Mice Aid Hunt for Cures

Bioengineered rodents with altered genes are being created by the

millions to help researchers in pursuit of treatments for diseases.

From Associated Press

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, which is injected with muscle-

building genes, and 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 by

injecting disease-causing genes or by " knocking out " genes in mouse

embryos. Their decreasing cost and increasing availability are

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 month, which suggested that the club drug Ecstasy reversed

Parkinson's-like effects in these particular bioengineered 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 identical genetically, 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 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.

Many animal rights groups oppose all animal experimentation as cruel,

but lab scientists who work with bioengineered mice point out that

the Food and Drug Administration requires that all drugs be tested on

animals before people.

Nearly all the genetically engineered mice in circulation today have

but one gene added, subtracted or altered. The problem with that

model is that many diseases such as diabetes and cancer are caused by

multiple gene malfunctions.

" Eventually, that's where engineered mice are going, " said Mendell

Rimer, a University of Texas neuroscientist who tends to about 500

mice in his Austin lab. " That's a more realistic disease model. "

Rimer's genetically engineered mice are among the most advanced and

offer a glimpse of the breakthroughs to come.

He spent 2 1/2 years engineering mice with muscles that lose

connection to their nerve cells.

He's done this by splicing into mice a cancer gene that creates a

protein that " disassembles " the connections. But he's also taken his

work one step further than the usual cut-and-paste work.

Rimer is able to turn on the mutant gene by feeding the genetically

engineered mouse an antibiotic. He can turn it off by stopping the

antibiotic treatment. This way, he can observe the progression and

regression of the mutation he made, giving him unparalleled insight

into how nerves communicate with muscle.

" We can control the timing of the defect that we induce in these

mice, " Rimer said. " This type of complexity is where genetic

engineering is heading. "