We humans have more in common with mice -- at least genetically speaking -- than you might think, which is why they are such good substitutes for us in medical research, new studies have confirmed.
Several recently published studies suggest the systems that regulate gene activity in mice - research's favorite lab animal -- are in large part the same as in humans.
The studies were a result of a project known as Mouse ENCODE, an offshoot of the human ENCODE effort cataloging the elements of the humane genome that control cell function.
More than 100 mouse cell and tissue types were analyzed and compared to their corresponding features in humans, the researchers said.
The effort identified around 6,600 genes whose expression falls within a comparatively narrow range in both humans and mice, they said.
That suggests humans and mice share 70 percent of their protein-coding gene sequences, but because of evolutionary divergence the molecular mechanisms that regulate how those genes work are different roughly 75 percent of the time, the Mouse ENCODE researchers found.
That means that mice are good but not perfect models for medical research on human conditions, they said.
Mice -- cheap to breed and handle in labs, and not presenting the same level of ethical concerns as research with non-human primates such as chimpanzees -- are one of the most commonly used models for studying human biology, creating models of human diseases and testing experimental drugs and new therapies.
"They're great model organisms, don't get me wrong, but there are definitely profound differences," says Michael Snyder, the chair of genetics at Stanford and co-author of the main paper. "At the end of the day, a mouse is a mouse and a human is a human, and pinning down where those differences occur is important."
The database created by the Mouse ENCODE project will be of great use to scientists looking to use mice to learn more about humans, although there remains a great deal to be learned, Snyder says.
"If this were an opera, we'd have a few bars of a few pieces," he says. "We're not seeing the whole show yet."
Certain systems and processes in mice, such as metabolism, the immune system and stress responses are very different compared to those same things in humans, a finding that will help scientists determine when and in what cell types and tissues the mouse is an appropriate model to study human biology and disease, and may help to explain some of its limitations, the researchers explain.
"The mouse has long been a mainstay of biological research models," said Eric Green, director of the National Human Genome Research Institute. "These results provide a wealth of information about how the mouse genome works, and a foundation on which scientists can build to further understand both mouse and human biology."
