|
Middle age weight problems
A special fat-fighting cell present in mice is giving researchers new avenues to treat the human obesity epidemic.
The treadmills in a fitness centre can look a lot like mice on their exercise wheels – running fast but going nowhere. Many people hit the gym to lose extra pounds and we may get help to battle the bulge from research in mice. Mice can become obese for the same reasons that humans do; genetics and overeating. But mice have a secret weapon, brown fat; that prevents excess accumulation of body fat
Brown fat generates heat, meaning that calories are lost to the environment before they can be stored as white fat. The human body contains some brown fat but only small amounts in adults. Researchers are studying mice to find out how to turn on the production of brown fat cells in humans as a possible therapy for obesity.
One gene that may reactivate the production of brown fat in humans was identified first in mice and is called PRDM16. This gene can trigger brown fat cell development from white fat precursor cells. The researchers engineered fat precursor cells with PRDM16 and then implanted them as a way to prevent obesity. One day this could be a viable option to liposuction and the dreaded treadmill.
Color Vision
Mice have dichromatic vision while humans have trichromatic, or three color vision, and researchers are using this difference to study the evolution of color vision.
What is the difference between fuchsia and magenta? Perhaps only a few designers and fashionistas can tell – and now a couple of genetically engineered mice. Humans and primates have trichromatic vision; in other words, we can see red, green and blue and every variation in between. Mice and most other mammals only have dichromatic vision; they cannot see in the red spectrum because they are missing the light sensing cell for the red spectrum in their eyes.
If researchers add the human red photoreceptor gene to mice they develop sight for the full palette of colors in the same way humans do. These results tell scientists that the evolutionary event that lead to trichromatic vision wasn’t a huge change in brain chemistry or organization but instead a simple addition of one red photoreceptor gene. It also tells researchers that the mouse and human brain are very flexible to new sense receptors; these mice got an instant upgrade in their sensory experience.
Hearing Loss
Chemotherapeutic drugs can lead to human hearing loss, especially in childhood cancer patients; new research using mice can study the factors controlling hearing loss and how to prevent it.
Mice research is paving the way for therapeutics of both childhood and age-related hearing loss. Kids with cancer can lose their hearing because of the chemotherapy drugs used to treat them and adults can go deaf from long-term exposure to loud noise. Scientists have bred mouse models of hearing loss in humans that allow researchers to study the effects of drug and gene therapy strategies in combating human deafness.
Scientists have identified 17 families of mice with mutations in different genes affecting hearing. These genes have counterparts in humans and, when working properly, they contribute to different parts of the ear cells to promote hearing for both mice and humans. How can you tell if a mouse is deaf? Researchers measured brain activity after noise and watched the auditory and sensory receptors to see if the mice had heard/processed the noise. The goal of developing a mouse model for hearing loss is to mimic human deafness and to give scientists a way to rapidly test different strategies to cure deafness.
Depression
Scientists can breed different types of mice that are permanently cheerful or prone to depression and these genetic factors that control mood may be similar in human depression patients.
Approximately 8% of Canadians will suffer from depression at some point in their lives and their treatment will often be antidepressant drugs like Prozac. Many of these people suffering from depression may be more susceptible to developing this mental condition due to their combination of genetic factors.
Scientists are using mice as models to discover which genes are involved in mental illness and depression. Depressed mice aren’t that different than unhappy people; they are less social, are withdrawn and respond well to human antidepressants. A recently discovered protein is present at lower levels in both depressed humans and mice, called p11; meaning that these depressed mice and human may have a genetic predisposition to depression. p11 regulates a key brain chemical called serotonin that acts as the brain’s own antidepressant and is also the target of most available therapeutics.
A second group of researchers have developed a mouse with the opposite disposition - a permanently cheerful mouse; these depression-resistant mice are missing a gene called TREK-1. TREK-1 is also responsible for regulating the release of serotonin in the brain suggesting that serotonin is a key biochemical pathway in depression. Understanding the underlying genetic causes of depression will help pharmaceutical companies develop more targeted and effective antidepressant therapies.
A Heart
The genes that control heart development must be turned on and off at the right time and place during development, mouse models are used to study how the genes controlling human heart development are regulated.
Mice have all the body organs that humans have – hearts, lungs and kidneys to name a few. Scientists can study how human organs organize and develop by studying the genes that are expressed during mouse development.
The MORGEN project (Mammalian Organogenesis – Regulation by Gene Expression Networks) is determining which genes are turned on and off in the mouse genome during heart development. Many of these genes in mice are identical to those found in humans and using an organism as similar to humans as mice will give scientists a very clear picture of how the heart develops.
This project will provide researchers with a clear picture of some of the regulatory switches that tell a body where and when to start heart formation during embryonic development. The MORGEN project will also allow researchers to understand the genetic mistakes that happen in some of the heart defects that occur during human development.
Bullying/Aggressiveness
The playground bully is no longer the result of poor parenting – mouse research is telling us that there may be genetic factors controlling aggressiveness in both mice and humans.
We can learn a lot from mice because scientists have found that the majority of genetic pathways are identical between mice and humans. Researchers at UBC have identified a fierce mouse that is extremely aggressive. For example, these mice attack all new cage mates and will even be aggressive to other mice that they can see in other cages. These mice also have abnormal brain development and a mutated copy of the Nr2e1 gene. The human copy of Nr2e1 can replace the mouse one that is missing in these mouse bullies and the mouse is no longer mean.
The genetic basis for aggressiveness in mice indicates that this behavior can be inherited in a predictable pattern without too much influence by the environment. The human Nr2e1 gene may have a similar function in humans, affecting our behaviour. However, our aggressive behavior is probably much more complex than just one gene.
A Love of Cheese
Gouda, Asiago, Stilton….the list of incredible varieties of cheeses is longer than any deli counter. Humans and mice share a passion for any type of cheese.
Some of you may think that a chunk of cheddar is enough to trap those pesky housemates but perhaps trying a few more tasty varieties, like an aromatic blue cheese, will help catch some of the more discerning mice.
|
