Virginia, USA
— What makes a man behave like a man and a woman
a woman? The answer may be partly in your genes.
Researchers at the University of Virginia Health System
<http://www.healthsystem.virginia.edu/>
have discovered a new twist on the role that estrogens
play in the development of behavioral differences between
males and females.
In laboratory tests on
mice, the researchers found evidence that an estrogen
receptor in the hypothalamus called ER (regulates
defeminization, a process by which males lose the ability
to display female-type behavior in adulthood.
Defeminization is believed by many experts to be the main
neurological process that differentiates males and
females before birth. The discovery is detailed in the
March 10 edition of the Proceedings of the National
Academies of Sciences <http://www.pnas.org/>.
"Our hypothesis is that
neonatal males are exposed to the steroid estradiol (a
form of natural estrogen) produced by their testes.
Estradiol binds to the estrogen receptor (ER) and this
acts to turn on, or turn off, other genes which sculpt
the neural architecture required for adult function,"
said the study's main author, Emilie Rissman, PhD, a
professor of biochemistry and molecular genetics at U.Va.
and a specialist in the genetics of mammalian behavior.
"We'd like to find out
what the genes are, where precisely they reside in the
brain, when in development this happens, and what the
cellular targets are of these genes," Rissman said.
Interestingly, male fetuses are exposed to estrogen in
their normal development and females are not because
ovaries don't fully develop until puberty.
This newly described role
for ER could be important in research on behavioral
differences between men and women, Rissman said, such as
in the areas of aggression, nurturing, and cognition. The
discovery could also help scientists find out why some
diseases target men and women differently, Rissman said,
including depression, Alzheimer's and multiple sclerosis
to name just a few. Lupus, for instance, is nine times
more prevalent in women than men. Depression is more
likely to affect women as well. "The more we know about
how these sex differences may be established in the brain
and periphery, the more likely it is we will discover
cures," Rissman said.
