June 09, 2005
Prairie Vole Shyness Controlled By Microsatellite DNA

Regulatory regions for vasopression receptor regulation cause changes in the social behavior of male prairie voles.

ATLANTA - Why are some people shy while others are outgoing? A study in the current issue of Science demonstrates for the first time that social behavior may be shaped by differences in the length of seemingly non-functional DNA, sometimes referred to as junk DNA. The finding by researchers at the Yerkes National Primate Research Center of Emory University and the Atlanta-based Center for Behavioral Neuroscience (CBN) has implications for understanding human social behavior and disorders, such as autism.

In the study, Yerkes and former CBN graduate student Elizabeth A.D. Hammock, PhD, and Yerkes and CBN researcher Larry J. Young, PhD, also of the Department of Psychiatry and Behavioral Sciences at Emory University's School of Medicine, examined whether the junk DNA, more formally known as microsatellite DNA, associated with the vasopressin receptor gene affects social behavior in male prairie voles, a rodent species. Previous studies, including Dr. Young's gene-manipulation study reported in Nature's June 17, 2004, issue, have shown the vasopressin receptor gene regulates social behaviors in many species.

The researchers bred two groups of prairie voles with short and long versions of the junk DNA. By comparing the behavior of male offspring after they matured, they discovered microsatellite length affects gene expression patterns in the brain. In the prairie voles, males with long microsatellites had higher levels of vasopressin receptors in brain areas involved in social behavior and parental care, particularly the olfactory bulb and lateral septum. These males spent more time investigating social odors and approached strangers more quickly. They also were more likely to form bonds with mates, and they spent more time nurturing their offspring.

I picture women who want their men to stay faithful some day surreptitiously injecting gene therapy into neck arteries of sleeping boyfriends or husbands to reprogram their microsatellite DNA to longer lengths around the vasopressin gene. And here's the twist: If the guy discovers he has been reprogrammed by his woman he'll be so attached to her that he won't want to leave her because of it.

"This is the first study to demonstrate a link between microsatellite length, gene expression patterns in the brain and social behavior across several species," said Young. "Because a significant portion of the human genome consists of junk DNA and due to the way microsatellite DNA expands and contracts over time, microsatellites may represent a previously unknown factor in social diversity."

Hammock and Young's finding extends beyond social diversity in rodents to that in apes and humans. Chimpanzees and bonobos, humans' closest relatives, have the vasopressin receptor gene, yet only the bonobo, which has been called the most empathetic ape, has a microsatellite similar to that of humans. According to Yerkes researcher Frans de Waal, PhD, "That this specific microsatellite is missing from the chimpanzee's DNA may mean the last common ancestor of humans and apes was socially more like the bonobo and less like the relatively aggressive and dominance-oriented chimpanzee."

The researchers' finding also has set a clear course for the next step. They want to build upon previous studies that identified a microsatellite sequence in the human vasopressin receptor that varies in length. "The variability in the microsatellite could account for some of the diversity in human social personality traits," explains Hammock. "For example, it may help explain why some people are naturally gregarious while others are shy." In particular, Young wants his research team to expound upon studies that have identified a link with autism.

Research in prairie voles has provided evidence about vasopressin effects on pair bonding in prairie voles that led to the discovery that pair bonding in humans involves some of the same brain areas as are seen in prairie voles. It is not far fetched to take the discovery of vasopressin receptor microsatellite DNA's role behavior in prairie voles as a reason to look for similar DNA in humans playing a regulatory role in human behavior.

Male voles with the longer microsatellite DNA were friendler to strangers and more nurturing toward their young.

The researchers first showed in cell cultures that the vole vasopressin receptor microsatellites could modify gene expression. Next, they bred two strains of a monogamous species, the prairie vole one with a long version of the microsatellites and the other with a short version. Adult male offspring with the long version had more vasopressin receptors in brain areas involved in social behavior and parenting (olfactory bulb and lateral septum). They also checked out female odors and greeted strangers more readily and were more apt to form pair bonds and nurture their young.

"If you think of brain circuits as locked rooms, the vasopressin receptor as a lock on the door, and vasopressin as the key that fits it, only those circuits that have the receptors can be 'opened' or influenced by the hormone," added Hammock. "An animal's response to vasopressin thus depends upon which rooms have the locks and our research shows that the distribution of the receptors is determined by the length of the microsatellites."

Prairie voles with the long version have more receptors in circuits for social recognition, so release of vasopressin during social encounters facilitates social behavior. If such familial traits are adaptive in a given environment, they are passed along to future generations through natural selection.

Variability in vasopressin receptor microsatellite length could help account for differences in normal human personality traits, such as shyness, and perhaps influence disorders of sociability like autism and social anxiety disorders, suggest the researchers.

Will humans choose to biologically engineer their male offspring to be much more social? If future generations of men want to gossip endlessly about human relations this could be a problem for those of us with natural male brains. If due to rejuvenation therapies I live to see society dominated by highly social males I'm going to found a club of old style men who can hang around and talk about cars or airplanes or anything else for that matter. Or better yet, go through long periods of not talking at all.

Share |      Randall Parker, 2005 June 09 09:14 PM  Brain Genetics


Comments
Reed said at June 10, 2005 8:42 AM:

It's the death of the male!

Maybe increased socialness wouldn't neccesarily be a bad thing, but I doubt that they'll want to take it to an extreme. We still need soldiers, police officers, business leaders (imagine stockholders manipulating their CEOs to their own ends) and I doubt most women would want effiminate, talkative men all the time. I mean, naturally speaking, they are the other half of a hunter-gatherer system, they want masculine males.

Our culture right now seems to have this idea that femininity is the future, but I doubt that'll pan out until we're under an utterly socialist state. I mean, people will always find excuses to explore, right?

Randall Parker said at June 10, 2005 6:28 PM:

Reed,

Will women choose to have male babies that will grow up to have many feminine qualities? I don't know.

Lei said at June 11, 2005 4:22 AM:

You have a twisted idea of relationships. I married my husband not to reform him or change him but just to deal with him as he is. In any case, I find it surprising you'd rather not talk because you're very talkative on this blog!

Randall Parker said at June 11, 2005 6:56 AM:

Lei,

A lot of women want to change their husbands. Your husband should treasure you given your attitudes. Hope he does.

Talkativeness: But when a family member wants to chatter on to me about how cousin so-in-so dumped her boyfriend and the guy down the street has been married 4 times and so on then I can't stand it. If they just report the facts to me briefly I can stand it. But I do not want to hear about it for a half hour while I'm trying to read or write a blog post or do work.

A lot of women can talk about that stuff for hours and enjoy it. I've watched this (or tried to find an excuse to leave the room). Most men can't stand the relationship gossip unless there is some point to it or it is delivered quickly and rarely.

tara said at June 12, 2005 11:40 AM:

Randall,
It's odd to me that you perceive such significant social differences between yourself and the women around you. I believe comments such as, "Most men can't stand the relationship gossip unless there is some point to it or it is delivered quickly and rarely," represent a broad tendency to exaggerate male-female differences in sociability. My own experience has led me to the view that differences in stereotypically female-type social interest are minimized in like-groups of men and women. By "like groups" I mainly mean equally well-educated and intellectually oriented.

This is not to deny gender differences altogether of course; just to say that the differences are not terribly striking if class, general interest, and education variables are controlled. There seems to still be a far-reaching tendency for a gossip-preoccupied, supposedly average, woman to serve as a model for comparison to a supposedly average, but actually hyper-masculine, male when discussing gender differences.

Basically, I think what people see as gender difference is pulled from some deep crevice, located a bit lower than their cranial cavity. But that's just my humble opinion!

Randall Parker said at June 12, 2005 11:46 AM:

Tara,

It is odd to me that you do not see such differences between the sexes. Yes of course women are far more interested in gossip. Yes of course women spend far more time talking about relationships. Women think about people. Men think about things.

You say:

the differences are not terribly striking if class, general interest, and education variables are controlled.

Well I'm sure that male psychologists are closer to women in their interest in relationships than are male engineers. But if you control for interests and education you are already biasing your sample.

Lowell Getz said at June 24, 2005 9:27 PM:

I really did not mean to start all this when I first saw that prairie voles displalyed behavioral monogamy in my field study sites. But, interesting to see where it is going.

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