Laboratory animals commonly used in biomedical research include a variety of species, among them fruit flies, zebra fish, rats, rabbits, dogs, cats and primates.

So, why has The Jackson Laboratory focused nearly exclusively on the breeding and distribution of laboratory mice?

Over the past 79 years, the Lab has bred countless millions of mice, with some 3,300 genetically engineered varieties now available for annual shipment to 16,000 researchers in 60 countries worldwide.

Mice are small, docile, relatively easy to care for, and are well suited for shipment over long distances. Eight to 10 mice can be cared for in the same space required by two rats. Mice also reproduce quickly. After only 19 days of gestation, mice can give birth to large litters of “pups.” By comparison, the gestation period for a Rhesus monkey is 164 days for a single offspring.

From a molecular genetics standpoint, the mouse genome includes more than 95 percent of the 25,000 genes contained in the human genome. Through careful breeding, scientists can manipulate mouse genetics to mimic the biomolecular mechanics of human diseases as diverse as breast and liver cancer and high blood pressure and obesity.

When scientists at The Jackson Laboratory create a “mouse model,” they don’t create a model; they create a mouse. By breeding strains of lab mice that replicate a wide range of human diseases, the Lab provides researchers in-house and worldwide with living raw materials that allow what Director Richard Woychik terms “experimental genetics.”

“You can’t do experimental genetics on people,” he said. “By doing experimental genetics with mice, we can do these powerful experiments to connect genes and the function of genes to human disorders.

“What we’ve come to appreciate over the last several years is that the mouse is just the ideal model organism. We have the entire sequence of the mouse genome. We have the entire sequence of the human genome, and we have the sequence of lots of different variants in the mouse and in the sequence of different individuals.”

For the vast majority of human genes, there is a functional copy in mice, he said.

“There’s been no instance in my own research experience where the gene I’m studying in the mouse doesn’t have a functionally similar gene in humans,” he said. “You basically have the same complement of genes.”

While the JAX® Mice & Services division of the Lab distributed 2.4 million mice last year and generated $80 million in revenue, that operation is only one aspect of the Laboratory’s mission, Woychik said.

“People need to understand that this is much, much more than a mouse distribution business. But the mouse distribution business is important, because we get letters from Nobel laureates who are saying ‘Keep up the good work. If you weren’t doing what you’re doing, we couldn’t do what we do.’ That’s all part of leading the search for tomorrow’s cures, and that’s what this organization is all about.”