[ExI] differential gene expression

[hkhenson]

 From The Times

June 20, 2008

Scientists say genetic variations show that men think differently

Sexes preprogrammed with different skills

Mark Henderson, Science Editor

Women and men may genuinely think in different ways, according to
research that has found subtle genetic variations between their brains.

Hundreds of genes that are switched on and off differently in the male
and female brain have been identified, suggesting that many patterns of
behaviour regarded widely as typical of each sex could be founded on
nature as well as nurture.

Dozens of mental traits and skills are said to differ between men and
women. They include empathy, aggression, risk-taking, navigation and the
qualities that are valued most in a sexual partner.

The existence of such differences is now widely accepted, but natural
and social scientists have long disagreed about the extent to which they
are rooted in our underlying biology, or are learnt through male and
female social roles. Women are generally more accomplished than men at
empathising with other people, and usually score as more compassionate
on standard personality tests.

Men are more prone to aggression and risk-taking behaviour, and tend to
be proficient at understanding and devising systems, from car engines to
the offside law.

While there are no sex differences in general intelligence, women tend
to have stronger visual memories, while men are more proficient at
visualising objects when rotated in space. It has been suggested that
this may reflect the way most men like to navigate by reading maps,
while many women prefer to remember landmarks.

Such observations have led Professor Simon Baron-Cohen, of the
University of Cambridge, to suggest the existence of "empathising-type"
and "systemising-type" brains, the first of which is more common among
men and the second among women. Professor Baron-Cohen said: "This is a
very original study, testing which genes are expressed differently in
males and females across different primate species. It confirms the
supposition that genetic sex differences are expressed not just in the
secondary sexual characteristics in the body, but in the brain.

"Finding genes that are conserved across species points to the evolution
of these genetic sex differences, and finding them in the brain suggests
that they may in part influence the way the mind works, and in part
influence our behaviour."

Men and women also differ in their approach to finding sexual partners.
Men generally place a higher value on youth and good looks, while women
are often more attracted by status.

The new study, led by Elena Jazin, of the University of Uppsala in
Sweden, does not directly prove that any of these traits is related to
differences in gene activity, but it shows a contrasting genetic
architecture of male and female brains that could plausibly contribute.

While the two sexes have the same basic genes, many of these are more
active in the brains of only one sex. These gender-specific patterns of
gene expression could affect many aspects of behaviour, the researchers
said.

"The obvious question to follow is whether or not these signatures of
sex in the brain have physiological significance for brain physiology
and/or behaviour," they wrote in the journal Public Library of Science
Genetics.

"Our results suggest that variation in expression of genes in the brain
may be an important component of behavioural variation within as well as
between species." The differences could also explain sex variations in
mental health and neurological diseases: women, for instance, are more
at risk of depression and Alzheimer's.

"Knowledge about gender differences is important for many reasons," Dr
Jazin said. "For example, this information may be used in the future to
calculate medical dosages, as well as for other treatments of diseases
or damage to the brain."The scientists said that their work needed to be
followed up to examine whether any human behavioural or health
differences were related to the sex-specific gene expression profiles.