Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Brain may ’hard-wire’ sexuality before birth

22.10.2003


Refuting 30 years of scientific theory that solely credits hormones for brain development, UCLA scientists have identified 54 genes that may explain the different organization of male and female brains. Published in the October edition of the journal Molecular Brain Research, the UCLA discovery suggests that sexual identity is hard-wired into the brain before birth and may offer physicians a tool for gender assignment of babies born with ambiguous genitalia.



"Our findings may help answer an important question -- why do we feel male or female?" said Dr. Eric Vilain, assistant professor of human genetics and urology at the David Geffen School of Medicine at UCLA and a pediatrician at UCLA’s Mattel Children’s Hospital. "Sexual identity is rooted in every person’s biology before birth and springs from a variation in our individual genome."

Since the 1970s, scientists have believed that estrogen and testosterone were wholly responsible for sexually organizing the brain. In other words, a fetal brain simply needed to produce more testosterone to become male. Recent evidence, however, indicates that hormones cannot explain everything about the sexual differences between male and female brains.


Vilain and his colleagues explored whether genetic influences could explain the variations between male and female brains. Using two genetic testing methods, they compared the production of genes in male and female brains in embryonic mice -- long before the animals developed sex organs.

To their surprise, the researchers found 54 genes produced in different amounts in male and female mouse brains, prior to hormonal influence. Eighteen of the genes were produced at higher levels in the male brains; 36 were produced at higher levels in the female brains.

"We didn’t expect to find genetic differences between the sexes’ brains," Vilain said. "But we discovered that the male and female brains differed in many measurable ways, including anatomy and function."

In one intriguing example, the two hemispheres of the brain appeared more symmetrical in females than in males. According to Vilain, the symmetry may improve communication between both sides of the brain, leading to enhanced verbal expressiveness in females. "This anatomical difference may explain why women can sometimes articulate their feelings more easily than men," he said.

Overall, the UCLA team’s findings counter the theory that only hormones are responsible for organizing the brain.

"Our research implies that genes account for some of the differences between male and female brains," Vilain said. "We believe that one’s genes, hormones and environment exert a combined influence on sexual brain development."

The scientists will pursue further studies to distinguish specific roles in the brain’s sexual maturation for each of the 54 different genes they identified. What their research reveals may provide insight into how the brain determines gender identity.

"Our findings may explain why we feel male or female, regardless of our actual anatomy," Vilain said. "These discoveries lend credence to the idea that being transgender -- feeling that one has been born into the body of the wrong sex -- is a state of mind.

"From previous studies, we know that transgender persons possess normal hormonal levels," he said. "Their gender identity likely will be explained by some of the genes we discovered."

Vilain’s findings on the brain’s sex genes may also ease the plight of parents of intersex infants, and help their physicians to assign gender with greater accuracy. Mild cases of malformed genitalia occur in 1 percent of all births -- about 3 million cases. More severe cases -- where doctors can’t inform parents whether they had a boy or girl -- occur in one in 3,000 births.

"If physicians could predict the gender of newborns with ambiguous genitalia at birth, we would make less mistakes in gender assignment," Vilain said.

Lastly, Vilain proposes that the UCLA findings may help to explain the origin of homosexuality.

"It’s quite possible that sexual identity and physical attraction is ’hard-wired’ by the brain," he said. "If we accept this concept, we must dismiss the myth that homosexuality is a ’choice’ and examine our civil legal system accordingly."


The UCLA study was supported by the National Institute of Child Health and Human Development, the National Science Foundation and with start-up funds from the UCLA Department of Urology. Vilain’s co-authors included Phoebe Dewing, Steve Horvath and Tao Shi, all of UCLA.

Elaine Schmidt | EurekAlert!
Further information:
http://www.ucla.edu/

More articles from Life Sciences:

nachricht Research team of the HAW Hamburg reanimated ancestral microbe from the depth of the earth
01.03.2017 | Hochschule für Angewandte Wissenschaften Hamburg

nachricht Researchers Imitate Molecular Crowding in Cells
01.03.2017 | Universität Basel

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

Im Focus: Safe glide at total engine failure with ELA-inside

On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded after a glide flight with an Airbus A320 in ditching on the Hudson River. All 155 people on board were saved.

On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded...

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

A better way to measure the stiffness of cancer cells

01.03.2017 | Health and Medicine

Exploring the mysteries of supercooled water

01.03.2017 | Physics and Astronomy

Research team of the HAW Hamburg reanimated ancestral microbe from the depth of the earth

01.03.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>