11/11/2002 • Genes play a part, but violence may be viral

11/11/2002 • Genes play a part, but violence may be viral

By TOM SIEGFRIED
The Dallas Morning News
ORLANDO, Fla.

Harvard Medical School

This interesting article states: “Those genes are found in nerve cells (or neurons) that produce the brain chemicals dopamine and serotonin. When active, the genes tell the neurons to pump more of the chemicals into the fly’s nervous system. When the genes are turned off, dopamine and serotonin production falls off”.

“Some flies are genetically engineered with a “gene switch” that depends on temperature. Turn up the heat, and you turn off the genes. In this case, Harvard researcher Selby Chen and collaborators engineered flies who fight away when the temperature is a pleasant 77 degrees Fahrenheit. But when the scientists heat up the lab to a toasty 86, the flies equipped with a genetic switch in the dopamine and serotonin neurons throw in the towel. (Ordinary flies are happy to keep on fighting in the heat.) The apparent implication is that dopamine and serotonin genes play an important role in aggressive violence”.

Genes play a part, but violence may be viral

http://www.dallasnews.com/health/columnists/tsiegfried/stories/111102dnlivtomcol.13af7.html

By TOM SIEGFRIED
The Dallas Morning News
ORLANDO, Fla.

Harvard Medical School

This interesting article states: “Those genes are found in nerve cells (or neurons) that produce the brain chemicals dopamine and serotonin. When active, the genes tell the neurons to pump more of the chemicals into the fly’s nervous system. When the genes are turned off, dopamine and serotonin production falls off”.

“Some flies are genetically engineered with a “gene switch” that depends on temperature. Turn up the heat, and you turn off the genes. In this case, Harvard researcher Selby Chen and collaborators engineered flies who fight away when the temperature is a pleasant 77 degrees Fahrenheit. But when the scientists heat up the lab to a toasty 86, the flies equipped with a genetic switch in the dopamine and serotonin neurons throw in the towel. (Ordinary flies are happy to keep on fighting in the heat.) The apparent implication is that dopamine and serotonin genes play an important role in aggressive violence”.

It’s not exactly something you’d try to market for Pay-Per-View, but fruit flies sometimes stage some pretty fierce fights. Put two males in a laboratory ring and, under the right conditions, they’ll battle it out for the flyweight championship.

The scientists who serve as the fans at such fights aren’t interested in seeing flies bash their brains out, but rather are trying to understand something about brains in general.

It’s the brain, after all, that controls behavior, whether fighting or fleeing, speaking or thinking. Figuring out what goes on in a brain that tells it to fight might help reduce the risk of unnecessary violence in the world.

In the case of the flies, new research shows, violent aggression involves brain chemicals produced by specific genes. Turning off those genes induces the flies to stop throwing punches and return to their corners, Harvard Medical School scientists reported in Orlando, Fla., last week at the annual meeting of the Society for Neuroscience.

Those genes are found in nerve cells (or neurons) that produce the brain chemicals dopamine and serotonin. When active, the genes tell the neurons to pump more of the chemicals into the fly’s nervous system. When the genes are turned off, dopamine and serotonin production falls off.

Usually there’s not much you can do to manipulate genes quickly enough to stop a fight in mid-round. But fruit fly researchers have developed a neat trick for immediate gene control with a system that’s as simple as adjusting a thermostat. Some flies are genetically engineered with a “gene switch” that depends on temperature. Turn up the heat, and you turn off the genes.

In this case, Harvard researcher Selby Chen and collaborators engineered flies who fight away when the temperature is a pleasant 77 degrees Fahrenheit. But when the scientists heat up the lab to a toasty 86, the flies equipped with a genetic switch in the dopamine and serotonin neurons throw in the towel. (Ordinary flies are happy to keep on fighting in the heat.)

The apparent implication is that dopamine and serotonin genes play an important role in aggressive violence. But genes cannot be the whole story of violence in the animal kingdom.

Consider baboons, for instance. In the wild they are normally peaceful and live in harmony with their fellow primates. But after associating with humans for a while, baboons turn nasty. They attack each other rather viciously, in fact, sinking their fangs into the most sensitive of body regions. Females try to bite the tails off of other females.

“They just rip into each other,” says Timothy Smock of the University of Colorado at Boulder. “You wonder if they had guns, would they blow each other away. I’m quite convinced that they would.”

Dr. Smock and collaborator David Langoi, a veterinarian at the Institute for Primate Research in Nairobi, Kenya, have studied the brains of both peaceful and violent baboons. In the violent ones, a brain region called the superior temporal gyrus seems enlarged on the left side. In peaceful baboons that region seemed larger on the right side of the brain. For some reason, the violent baboons’ brains become modified in a way that promotes aggression.

Dr. Smock, who presented the findings at last week’s neuroscience meeting, does not know what causes the brain differences. But he has a suggestion that might be worth exploring. Maybe, he says, the aggression is the result of a virus. Perhaps there’s a virus for violence that somehow the baboons acquire from people.

“It’s total speculation,” Dr. Smock said in an interview. “But I’m hoping it’s a virus, because if we can find a virus that causes excessive violence, think about the implications for the type of insanity we’ve seen in the last 50 years. … The implications could be immense. ”

For one thing, a viral cause of violence would open a whole new avenue of understanding aggressive behavior. Much current research tries to draw conclusions about violence from studies of rats or mice. But such aggression, Dr. Smock points out, is typically not as senseless as the common human variety, but rather is directed toward specific goals involving territory or mates.

“We could possibly have a model for violence in people that’s different from simple aggression seen in rodents,” he said.

So far, though, there is no real evidence for the virus idea (although baboons do appear to acquire other diseases from humans, such as tuberculosis). And the preliminary findings are based on studies of only 10 baboon brains (five violent, five peaceful).

“We need to do a lot more work,” Dr. Smock acknowledged. For one thing, more intricate examination of the baboon brains is needed to determine whether some underlying defect is causing the enlarged regions seen on the surface.

Nevertheless, the idea of a violence virus is intriguing. Violent aggression may just turn out not to be only a societal sickness, but a medical one as well.

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