Male agression not only testosterone
- From: "Lance" <lachenicht@xxxxxxxxxx>
- Date: 8 Mar 2006 15:46:57 -0800
Sex Chromosome Genes Influence Aggression And Maternal Behavior, Say
Researchers
It has been well documented that, across human cultures and in most
mammals, males are usually more aggressive and less nurturing than
females. It's simple to blame male hormones, like testosterone, for
male behavior such as aggression. But maybe it's in our genes, too.
Indeed such social behavior also has a genetic basis, according to new
research on mice by neuroscientists at the University of Virginia
Health System. "The differences in sex chromosomes, XX versus XY, are
also responsible for differences in adult behavior," explained Emilie
Rissman, PhD, a professor of biochemistry and molecular genetics at
UVa, who studied aggression and maternal behavior in genetically
engineered mice. "Sex chromosome genes may not be the whole story
that determines how aggressive or motherly we are, but they are a
partof it."
Rissman's work is published in the Feb. 22 issue of The Journal of
Neuroscience, found online at www.jneurosci.org. Co-authors on the
paper are scientists at the University of California Los Angeles and
the National Institute for Medical Research in London, England.
Using mouse models, Rissman and the research team uncoupled the
testis-determining gene Sry on the male Y chromosome from other sex
chromosome genes. The presence of Sry leads to the development of the
testes and high levels of androgens in males, which is partly
responsible for aggression. Sry was deleted from the Y chromosome and
replaced by a transgenic copy.
In their experiments, the researchers compared mice with or without the
Sry gene (either males with testes or ovary-bearing females) to mice
with the XX versus XY sex chromosomes. They tested how long it took for
mice to become aggressive when another mouse was placed in their home
territory. The researchers also clocked the time it took to exhibit
spontaneous parental behavior by retrieving a pup.
The researchers found that the sex chromosome complement, as well as
gonadal sex differences, influences behavior. Gonadal male mice (those
with Sry with either the XX or XY sex complement) behaved most
aggressively. But females with the Y chromosome were aggressive as
well. Females with the XX complement were not aggressive, but in
contrast they exhibited high levels of maternal behavior by picking up
pups and building nests.
"We know that hormones are important for development of sex
differences in brain and behavior," Rissman said. "But this is
another component of the sex difference that needs to be examined."
In all probability, Rissman said, genes and hormones interact with each
other, especially in males, because they have testosterone and the Y
chromosome. "It is our hope that these data could lead to the
discovery of new genetic bases for aggression and parental behavior in
other animals, including humans."
Full Text from ScienceDaily
http://www.sciencedaily.com/releases/2006/03/060306214707.htm
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