Before I came to graduate school, I was pretty uncomfortable generally regarding the idea of mice being used as a model system. I could understand why they were being used on a surface-level: they are mammals, so they’re sort of similar to humans, so they react to diseases or illnesses like humans. That’s fine. But I still didn’t like the idea of it. I thought the idea of working with mice was disgusting and would be traumatic, both for the scientists and the animals involved in mouse-model studies.
Somehow, for my first rotation in school (the first 5 weeks I was here, I did a trial-run in a lab to see if I liked it), I wound up in a mouse lab. And I don’t mean a lab that works with mice, I mean a lab that bases every project it starts and finishes on mice. There was work on cancer in mice, toxicity of substances in mice, environmental impact of mice as an invasive species; you name it, they were working on it in mice.
While I was interested in the cancer side of all of that, what I really learned working with these animals is that a lot of my preconceived notions about mouse work was wrong. Not only that, but other people in my program actually gave me the stink-eye for working with mice! I was shocked, when I would talk about my labs work (which, granted, involved a lot of dissections and dosing animals and the likes, but we’re scientists! I figured this would be run-of-the-mill, that maybe they would support me and we could have a conversation) they would look at me like I was a monster.
So I’m here to talk about mice. Because no one wants to, and no one asked, and that’s exactly why it needs to be addressed.
Mice Are a Genetic Model System
You’ve probably heard this before if you’re into medical literature- “model system”. A model system is just an animal used in place of a human to look at something that happens in humans. These are sometimes called “model organisms”, too.
They include things like mice, worms, flies, and yeast.
We use these for a number of reasons, and the big picture is usually that we want to study something that is too difficult or impossible to study in humans. For starters, all of these have faster reproduction times than people. Mice are only pregnant for 3 weeks, unlike a humans’ 9 months. Flies can go through an entire lifetime in a month and a half, whereas humans can take up to 100-something years to live a lifetime.
Another big reason to use these systems is that we understand them super well. They are easy to take care of (and generally inexpensive), and we know how to make sure that they are kept happy and organized while they are part of an experiment. We also know a lot about their biology, like how their organs work relative to ours, or what it looks like when they get sick and how to treat them. We also know a lot about their DNA. For all of the model systems that get used to look at human diseases or illnesses, we have their entire genome sequenced, so we know most of what there is to know about their DNA. This makes them a lot easier to study, because it’s like having a big master key to look back at if we start to see something that we’re not expecting.
Mice Have Done A Lot of Good
Since we know so much about them, we’ve gotten to do a lot of really spectacular things with mice. In the last 10 years alone, nine out of the fourteen Nobel Prizes that were awarded in medicine were based on studies that used mice as a model. If you go back further, you can see more and more of the list of Nobel Prizes in medicine have been mouse-centric for decades.
Of these studies, there are a lot of big-ticket human diseases that mice are helping eliminate. Several from the past years have had to do with things like cell survival and respiration, which are both directly related to most types of cancer. There has also been work done in mice about the ends of chromosomes (called telomeres), which have a direct correlation with aging.
Mice have also been used to help develop vaccines, such as to bacterial gut infections or malaria.
Lab Mice are NOT Pet Mice
Mice that people buy as pets are apparently called “fancy mice“, which is very cute and my first reason why lab mice and pet mice are very different. They’ve actually even gotten their own sub-species, the domesticated pet mouse is called Mus musculus domestica, while lab mice are simply Mus musculus.
Lab mice also generally get left alone to do their own thing. They don’t interact with people much, and they interact with themselves a lot more (not dissimilar to what they would do in the wild, in some respects). They live in very standard and well-kept cages, with a constant supply of food and water. They are also very closely monitored for any signs of illness or disease, with vets on-site in the buildings they are housed in. The nice thing about having lots of standardized care for lab animals is that, while it is weird to think that living things are just parts of an experiment, the life they live is an extremely comfortable one.
And, while the idea of just taking some of the lab mice home and taking care of them like pets can be tempting, since they’re not used to people, they are not particularly friendly. As someone who’s gotten too close too many times to nips from lab mice, I’ve wanted to actually interact with lab mice less and less. In addition, taking lab mice out of a lab setting would actually probably only be detrimental. As animals that have always been in such a controlled environment, many lab mice tend to have stunted immune systems that keep them from being able to survive at all outside of a lab setting.
So those are the things to know about lab mice. They have done a lot of good, and while they are nothing short of a challenge to work with, they are worth their weight in gold when it comes to bettering human health and well-being.
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