Genetic link to transsexualism?

[rxpharm]

Here's an interesting article from BBC News Health:

Story link: Transsexual Gene Link Found

"There is a social stigma that transsexualism is simply a lifestyle choice, however our findings support a biological basis of how gender identity develops"
Professor Vincent Harley, researcher

Australian researchers have identified a significant link between a gene involved in testosterone action and male transsexualism.

DNA analysis from 112 male-to-female transsexual volunteers showed they were more likely to have a longer version of the androgen receptor gene.

The genetic difference may cause weaker testosterone signals, the team reported in Biological Psychiatry.

However, other genes are also likely to play a part, they stressed.

Increasingly, biological factors are being implicated in gender identity.

One study has shown that certain brain structures in male-to-female transsexual people are more "female like".

In the latest study, researchers looked for potential differences in three genes known to be involved in sex development - coding for the androgen receptor, the oestrogen receptor and an enzyme which converts testosterone to oestrogen.

Comparison of the DNA from the male to female transsexual participants with 258 controls showed a significant link with a long version of the androgen receptor gene and transsexualism.

Testosterone

It is known that longer versions of the androgen receptor gene are associated with less efficient testosterone signalling.

This reduced action of the male sex hormone may have an effect on gender development in the womb, the researchers speculated.

"We think that these genetic differences might reduce testosterone action and under masculinise the brain during foetal development," said researcher Lauren Hare from Prince Henry's Institute of Medical Research.

Co-author Professor Vincent Harley added: "There is a social stigma that transsexualism is simply a lifestyle choice, however our findings support a biological basis of how gender identity develops."

Although this is the largest genetic study of transsexualism to date, the researchers now plan to see if the results can be replicated in a larger population.

Terry Reed from the Gender Identity Research and Education Society said she was convinced of a biological basis to transsexualism.

"This study appears to reinforce earlier studies which have indicated that, in some trans people, there may be a genetic trigger to the development of an atypical gender identity.

"However, it may be just one of several routes and, although it seems extremely likely that a biological element will always be present in the aetiology of transsexualism, it's unlikely that developmental pathways will be the same in all individuals."

It would be interesting if they could study lbs to see if this genetic link is also present - but I doubt if there would ever be funding for such a study.

[SamplerDoc]

Wow, even a picture of the Gene

[Guest]

I'm trying to look up which Uni the researchers of this study are from. The news articles about this latest development do not seem to say so. At any rate, transsexual gene or not, the transgender community has to define itself on its own terms.

[jaymee]

They haven't managed to replicate Gooren's Zhou et al which is quoted a little too often.

I'm quite doubtful of this.

I'm with defining the community through other means rather than some DNA strand.

[mirimark]

Thanks for sharing this rxphram. I feel a little redemption here.
I've always wondered if its genetics or a psycilogical disorder that makes me feel this way.

I have realized a long time ago my body does not produce a lot of testosterone. I've always had very little body hair, I am under sized at 5'-7 130lbs and emotionally I'm not a Tough guy until I'm pinned in a corner and have to fight my way out.

I wonder if this article is really true ? I think yes, I believe it.

[rxpharm]

Another article this time, published in SFGate.com but quoting research published in Journal of Society of Biological Psychiatry.

For transsexuals, scientists say, difference is in the genes

Earlier this week, the Sydney Morning Herald reported the results of a new scientific-research project, the "largest-ever genetic study of transsexuals," in which "Australian researchers have discovered a DNA variation linked to male-to-female transsexualism." This genetic discovery "strengthens the view that there is a biological reason why some people feel they are living in the wrong body, in this case men who have a strong desire to live as [women]." In the research study, "112 Australian and American male-to-female transsexuals found they were more likely to have a genetic variation in a gene that could lead to a feminization of the brain during early development." Thus, the research project's findings (published in the journal Biological Psychiatry), have "confirmed that transsexual[ism is] not a lifestyle decision," as some commentators have suggested.

Some details about the research, which involved scientists at several institutions in Melbourne, Australia, and at the University of California, in Los Angeles, and has been described as "the largest genetic study of its kind" to date: In the study, researchers "measured the variation in the androgen receptor gene, which is involved in the functioning of the sex hormone testosterone. DNA samples from the transsexuals were compared with the samples from 250 typical men. Researchers discovered [that] the transsexuals were more likely than non-transsexuals to have a longer form of the gene." (Australian Associated Press in the Age)

Associate Professor Vincent Harley, the head of molecular genetics at Prince Henry's Institute for Medical Research at Monash University in Melbourne, was the project's lead researcher. Reporting on the research-project's results, Britain's New Scientist notes: "The biological bases for gender identity are largely unknown, 'but we could speculate that [effective] testosterone signaling is required for male gender identity,' says Vincent Harley....'This signaling is weakened in male-to-female transsexuals, leading to decreased masculinization of their brains.'" Commenting on the recent research study's results, Harley also noted: "There is a social stigma that transsexualism is simply a lifestyle choice. However, our findings support a biological basis of how gender identity develops...." Harley "said [that] researchers were recruiting transsexual people for another study and hoped to double the sample size and examine other genes." (Australian Associated Press in the Age)

Trudy Kennedy, the director of the Monash Gender Dysphoria Clinic in Melbourne, also took part in the research project. Speaking about the phenomenon of transsexualism, she observed: "People who come to our clinic describe how they knew they were different at a very early age, just three or four years old. This is something that people are born with...." Moreover, "Juliet Richters, an associate professor in sexual health at the University of [New South Wales], said much of the distress felt by transsexuals was caused by cruel treatment from others. 'A little more tolerance toward everyone who doesn't conform to gender norms would be a good thing,' she said." (Sydney Morning Herald)

The Australian Associated Press quotes Julie Peters, "a transgender person, [who] said she knew from as young as three or four years old she did not fit into being a boy." Peters told the news agency's reporter: "I have always had the personality of a girl...and even from a very young age...I was really mad at people for making me a boy....You are born with a predisposition to have a certain personality and then, depending on the culture you are brought up in[,] your personal situation[,] it becomes active in a particular way." (Australian Associated Press in the Age)

New Scientist also cites Andrew Sinclair, the director of early development and disease at Murdoch Children's Research Institute in Melbourne, who noted that the results of the recent genetic-research project support "the notion that transsexualism has a biological basis rather than being due to psychosocial factors in early childhood...." Sinclair added: "However, the finding does not explain all male-to-female transsexuals, suggesting that multiple genetic factors are involved." The British science publication reports: "While the genetic link was statistically significant, it was weak - 55% of the transsexuals had the long version of the gene, compared with 50% of normal men. [Lead researcher Vincent] Harley agrees that many more genes related to male-to-female transsexualism probably remain to be discovered."

Here is the link for this article: For Transsexuals, Scientists say the Difference is in the Genes

Abstract from Psychiatry Journal: Adrogen Receptor Repeat Length Polymorphism in MtF Transsexuals

Some interesting findings, would be even more interesting if Thai ts were also included in such a study.