It’s no secret that mice are cool at Jackson Laboratory in Bar Harbor. But these days they’re super-cool — to about 385 degrees below zero, to be exact.

Since its founding more than seventy years ago, the world-renowned science facility has developed thousands of unique strains of mice — obese mice, diabetic mice, blind mice, and many more — not only for its own needs but also for other researchers all over the world. Today it offers more than 2,256 distinctive varieties, with 97 percent available only from Jackson Lab.

But rather than mailing out cartons of live mice every day — last year mice were a $46.3-million business for the lab — more of the shipments are going out as microscopic, eight-cell embryos in vacuum bottles filled with liquid nitrogen.

“We have a lot of people asking us for embryos to transfer into clean, pathogen-free host mice,” explains Dr. Larry Mobraaten, a senior staff scientist at the lab. “It’s a technique that produces completely uncontaminated mice, which is increasingly important in modern research.”

Mobraaten says the method is also handy for maintaining particular strains that may not currently be in demand. Maintaining a genetically pure breeding colony of mice costs about $1,500 a year, while keeping the strain “alive” as embryos in liquid nitrogen costs next to nothing after the initial harvesting and freezing is done. “We have so many strains, and not all of them are being used all the time,” he explains.

“This is a way to preserve them for the future.” As long as the temperature is maintained, the embryos remain viable “for centuries,” the scientist says. Liquid nitrogen storage also gives the lab the option of backing up a live strain as a safety measure. “If we lost a particular variety for whatever reason — say disease or fire — we could go back to the nitrogen tanks and rebuild the breed,” he explains. Mobraaten says the lab has been in the iced mice business on a small scale for some twenty years. “It was a way to trade strains with other repositories around the world, especially in Great Britain, because there’s no quarantine requirement for embryos the way there is with live mammals,” he notes.

Even today the lab fills only three or four orders a day for frozen embryos, “but we anticipate that need will grow as other laboratories upgrade their facilities to higher health standards,” Mobraaten says. “We’re organizing to do this on a mass-production basis eventually.”

Mobraaten says the usual shipment contains forty to fifty mice embryos at about ten dollars per embryo. This could turn into a cool new business for Maine’s premier research laboratory.

(Published May 2003)