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Back in mid-March, when most of us were hearing the words shelter in place for the first time, research labs across the country were busy with what they call sacking.

There are a lot of different terms that are used that I think people use to protect themselves from the reality of this, said Anneka Allman, a research technician at a University of Pennsylvania lab that works with hundreds of mice as part of cancer studies. Personally, I prefer to say we kill them, but the common term is sacking.

Sacking, because thats where the animals end up after theyre killed in a sack, in a freezer.

Research mice, you might imagine, generally are not long for this world. At her lab, Allman is usually the one to send them into the hereafter. Most of the mice born there even in normal times arent suitable for experiments for some reason or another so, straight to the sack.

Id say maybe we only actually use like a tenth of the mice that we breed, Allman said. Euthanizing these mice on a regular basis is just part of the job, and its not a fun part of the job, but it is a necessity.

Still, what happened back in March, on Friday the 13th, it was different it was a massacre.

We have a weekly lab meeting and we had it virtually, and we were like, OK, we need to figure out how to shut everything down she recalled.

They had some 500 cages of mice, and a looming stay-at-home order for most staff. You just cant take that many mice home with you, and many cant survive outside sterile settings. So most of the mice, they were going to get sacked.

It was just like piles and piles of cages just on top of each other empty cages, Allman said.

She personally euthanized hundreds of the mice.

Its actually very simple. You take their cages, take off the tops, put it in a machine called the Euthan-X which I have a lot of feelings about, but its essentially just a CO2 chamber, Allman said. And you turn the button on, and you wait for 20 minutes to half an hour, and they die.

Allman only worked that Friday before she was sent home for safety, but a skeleton crew stayed behind and sacking continued.

We did get an email about, I think, two weeks in that basically requested that we stop asking them to do it because of the emotional toll that it was having on them because of the masses that they had to kill, Allman said.

The animals deaths didnt hit her on that level. Before you get the wrong idea about Allman, know shes a self-described animal lover, a vegetarian; one of her pet cats scurried across her laptop during an interview. But she didnt mourn the euthanized mice, so much as the science the mice represented.

I had to kill mice that I had planned experiments for, that Im still upset theyre dead and not because of their lives, unfortunately for them, but because to do this research its going to be a lot. Its going to take a lot longer.

Untold thousands of mice were sacked in the early weeks of the United States pandemic response. The animals in Allmans lab, and in hundreds of labs like it, are the bedrock of research into human diseases.

Pick a disorder, an illness. Theres a mouse model for that, a mouse created specifically to study that disease.

Cat Lutz is director of the mouse repository at the Jackson Laboratory in Maine.

So whatever disease you can think of, you know, epilepsy, obesity, metabolic syndrome, anything that you can think of, we have a mouse model that you can genetically engineer to recapitulate that particular disease, Lutz said.

The Jackson Lab is a nonprofit where many labs get founder mice to start colonies of their own for research. It has about 11,000 strains of designer mice cryopreserved in its repository 80% of which dont exist anywhere else.

Mice first found their way into labs by way of so-called mouse fanciers.

They would keep mice as pets, and they would also select those mice that had spontaneous mutations, for example, coat color or ears or craniofacial features, long tails, kinky tails, maybe spotted mice or things like that, and they would start inbreeding them, Lutz said.

Mice breed very quickly and very often, so mutations tend to spring up fairly regularly. Fanciers were after aesthetic mutations, but scientists quickly found fanciers could provide mice with more utilitarian mutations. This mouse with a kinky tail, it can develop diabetes, or colon cancer, or this rare neurological disease.

Between mouse and humans, the gene conservation is incredibly high at the level of the coding sequence, so it was really quite translational, Lutz said.

Mice and people share about 98% of their genetic code.

The mutations that you would see in the mice would often translate to the mutations that you see in people, she said. They really have become the model animal for humans.

So if you can cure a cancer in a mouse, thats a step closer toward curing it in a person.

See the article here:
The great research mouse rescue amid the pandemic - WHYY