Gene link to transsexualism

Male-to-female transsexualism may in some cases be linked to a particular gene variant, according to a study published in the journal 'Biological Psychiatry' today. It is thought that the gene variant, discovered by researchers based at Prince Henry's Institute in Melbourne and collaborators in Australia and the USA, may reduce the binding of testosterone to cells, potentially resulting in 'under masculinisation' of the brain during fetal development, say the researchers.

In the hunt for associated gene variants, the researchers analysed DNA from 112 male-to-female transsexual volunteers and compared this to DNA taken from 258 people with normal 'gender identity' - their sense of being either male or female. Although the gene identified is carried by everyone, the researchers found that a long version of the gene was slightly more common in transsexual men. Out of the group studied, 55 per cent of the transsexual men carried the long gene variant, compared to 50 per cent of the men with normal gender identity. The gene variant wasn't carried by all the transexual men studied, suggesting that other environmental and genetic factors also play a part.

It is hoped that the discovery may help to break down the belief that transexualism is caused by psychological factors in early childhood, say the researchers. 'There is a social stigma that transsexualism is simply a lifestyle choice, however our findings support a biological basis of how gender identity develops,' said study leader Associate Professor Vincent Harley, Head of Molecular Genetics at Prince Henry's Institute.

However, there is some concern that the 'medicalisation' of transexualism may have the opposite affect, leading to further discrimination and prejudice. 'Such treatments could include preventative strategies like pre-natal screening and the discarding of `affected' embryos and fetuses,' medical ethicist Dr Leslie Cannold told The Age newspaper.

Professor Harley disagrees: 'I don't think this will ever become a diagnostic thing given the complexity of the interaction between the environment and genes,' he told The Age.

The group is planning future studies to analyse the significance of the gene among different populations using larger groups of volunteers.