Monday, February 25, 2008

Barenaked Mice

Nude mice are the result of a spontaneous mutation first observed in Scotland in 1962. These bizarre creatures have no hair, so they look pink and wrinkled, like elderly aliens.

They are also athymic, which means the thymus is absent. The thymus is the organ responsible for the development of T cells, those all-important soldiers of the immune system. Nude mice are soldier-deficient and are unable to defend themselves against infectious disease. At first, the most remarkable result of being athymic was that they died young. Later on, once researchers figured out how to keep germs out of their cages, the nude mice survived just fine.

What good is a nude mouse? You can study how the immune system works. That is important in itself. But the real starring role for nude mice is in xenotransplantation. Because they don't have the cells they need to reject foreign tissue, they will accept grafts from unrelated mice, and from cats and chickens (they grow feathers!) and lizards and frogs...and humans. Big deal, you say, a mouse with feathers.

It is a big deal. Nude mice will accept grafts of human cancer cells so we can study how to treat human cancers. Because they accept grafts of human cells, they can be used to study viruses that are difficult or impossible to grow in other animal models or in lab dishes, like hepatitis C virus and the human papilloma virus, which causes cervical cancer.

Why am I writing about nude mice? In a blatant attempt to increase traffic to my blog.

Someone may be looking for something a little more titillating and a little less immunological. I have been frustrated in many attempts to research nude mice. When I Google "nude mouse," I get a lot of "Our All-Nude site is just a mouseclick away..." Imagine my results when I try to find a photo of a nude mouse, or a story about nude mouse models for human diseases. You guessed it, photos of nude models with just the click of a mouse.

Turnabout is fair play.

To those who came to my blog looking for photos of nude models of the human variety: Thanks for visiting. I hope you learned something.

Thursday, February 21, 2008

What if Morgan Spurlock were a mouse?

If you give a mouse a Big Mac, does he get fat? If the Morgan Spurlock documentary “Super Size Me” is any indication, it’s highly likely.

So here’s a scientific study that answers that question, although that was a small part of the study. A group of scientists the Max-Planck-Institute for Evolutionary Anthropology in Leipzig, Germany used mice to study the differences between humans and chimpanzees. More specifically, they looked at the effect of diet on gene expression. The paper is here.

They took four groups of genetically identical mice and fed each group a different diet.

One group got the Mouse Diet: standard mouse chow.

A second group got the Chimpanzee Diet: fruits, vegetables, and yogurt usually fed to chimpanzees at the Institute.

The third group got the Scientist Diet: the food served in the Institute’s cafeteria.

A fourth group got the Morgan Spurlock Diet: straight from McDonald’s.

The most scientifically significant result had to do with gene expression. Each human, mouse, or chimp has a genome, a set of genes with the DNA blueprint that dictates which proteins that animal will make. The thing is, not all of the genes are used all of the time in every cell. You don’t want your heart to grow a mustache, for example, or your earlobes to be made of bone. The key is to make the right proteins at the right time in the right place. That’s gene expression.

Humans and chimps and mice have different genomes, different blueprints. But they’re not really all that different. What adds to the differences between species is the way the genes are expressed. The mystery is what causes these differences in gene expression.

The researchers at the Max-Planck Institute hypothesized that diet could affect how genes are expressed. What they found was that the livers of mice fed different diets expressed the genes in their livers differently. What was really cool was that 117 genes expressed differently in mice fed the chimp diet vs. the human diets were the same genes that are expressed differently in chimpanzees vs. humans. That means that diet affects how we express genes and is part of what makes humans different from chimps.

Notice that I said “human diets.” For the most part, the Scientist Diet and the Morgan Spurlock Diet produced the same results. (I wonder what they serve at that cafeteria.)

There were two differences. One was that, although gene expression in the livers of mice fed both human diets was pretty much the same, the Scientist Diet didn’t affect gene expression in the brain. The Morgan Spurlock Diet did. Fast food changes your brain. Scary.

The other difference was that after two weeks on the Morgan Spurlock Diet, the body weights of the mice were significantly greater.


Monday, February 11, 2008

Jet-Set Mice

Last month, 7,000 lab mice got the royal treatment after the truck they were riding in was in an accident in Wyoming. The mice were en route from The Jackson Laboratory in Bar Harbor, Maine (The Mouse Capital of the World) to laboratories on the West Coast. Since the mice were so valuable, officials decided to box them up, 20 to a crate and fly them in three Lear jets to their destination. I wonder if they were served champagne.

Reports vary on their monetary value, from $100,000 to $6,300,000. Apparently some of the mice were worth $900 each. That's a lot of money for a lab mouse. Your standard C57BL/6 (or, as it is more commonly known, "Black 6") mouse costs about $15. Some reporter did the math, assuming they were all worth $900 (900 x 7,000 = 6,300,000). In reality, very few scientists could afford to use $900 mice. It's likely that just a few of the mice were that expensive. Hence, the revised figure of $100,000 to $250,000. Maybe they were served Miller Lite.

Thursday, February 7, 2008

The Original Sminthia

It started in a barn.

Forced to retire from her teaching job because of pernicious anemia, Abbie Lathrop made a career switch in 1900, at the age of 32. She became a purveyor of “fancy mice.”

The Victorian fad of Fancy Mice was in full swing. The mice were not particularly fancy, but they were fancied. In other words, the Victorians fancied their mice. They bred them for their beautiful or unusual appearance or behavior. (Remember The Spinning Mice?) They entered them in competitions, like Prize Poodles at the Westminster Kennel Club dog show.

Abbie thought she would cash in on the craze, so she began breeding mice in her Granby, Massachusetts barn. Among her “Creams,” “Tans,” and “Silver Fawns,” she noticed something unusual. Some of her mice had cancer.

She struck up a collaboration with Dr. Leo Loeb, with whom she authored ten scholarly papers. Here’s a quote from one of them:

In 1907 we published some observations made on the mouse farm of Miss Lathrop, in Granby, Mass., which rendered it probable that the frequency of tumors in mice at certain places was in all probability due, not to infection, but to hereditary transmission in certain families.

The rest, as they say, is histology…

Read the paper here. All 28 pages of it.