Custom-Made Mice Have Served Men for Decades

BAR HARBOR, Maine -- Ralph Waldo Emerson is reputed to have said that if a man makes a better mousetrap "though he build his house in the woods, the world will make a beaten path to his door."

Gary A. Churchill hopes this is also true if a man builds a better mouse.

Actually, it's already true.

Biologists have been beating a path to this town on Mount Desert Island since 1933, when the Jackson Laboratory began selling inbred mice for genetic research.

Today, the laboratory offers about 3,000 strains. Individual animals in each strain are essentially all the same at the genetic level -- an endless stream of identical twins, except for the genes determining sex. Many have traits that mimic human ailments -- diabetes, hypertension, osteoporosis and Alzheimer's disease. Others have the tendency to develop problems such as obesity, cancer or infection when subjected to the "right" environmental conditions.

In most cases, these traits (and hundreds more) arose through chance mutations in single animals. They caught the eye of a scientist, who in turn "captured" the trait by mating the animal with its siblings, and then those offspring with one another. After 25 generations, such animals are all identical and -- if things go as planned -- all carry the gene or genes responsible for the trait of interest.

In recent decades, genetic technology has also allowed scientists to knock out or, in some cases, add genes to animals. Of the lab's 3,000 strains, about one-third are genetically engineered.

The usefulness of these animals is hard to overstate. They help biologists understand basic physiology. They help identify genetic defects that lead to disease. The benefits or risks of experimental drugs are often easier to detect when tried on animals that are the same.

Mice became workhorses of medical research in the decades after World War I. They were cheap and easy to raise, prolific, reached maturity quickly and were all around more practical than larger animals such as dogs.

At the time, the mouse's genetic malleability was well known and the source of popular entertainment.

Clubs of "mouse fanciers" in the early years of the 20th century bred animals to have exotic coat colors and strange behaviors. (A type of "waltzing mice" from that period turned out to have an inner ear defect.) This briefly fueled even a fashion fad. Full-length mouse coats, made of 400 skins, sold for about $350 in the 1930s.

A main source of early mice for research was a farm in the western Massachusetts town of Granby run by a retired school teacher named Abbie E.C. Lathrop. She began breeding in 1903.