Transsexual gene link identified
The researchers focused on three genes
Australian researchers have identified a significant link between a gene involved in testosterone action and male-to-female 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.
news.bbc.co.uk/2/hi/health/7689007.stm
Suicide linked to brain changes
The researchers looked at brain tissue
The brains of people who commit suicide are chemically different to those who die from other causes, a Canadian study has suggested.
Researchers analysed brain tissue from 20 dead people and, in those who killed themselves, they found a higher rate of a process that affects behaviour.
Writing in Biological Psychiatry, they said it appeared environmental factors played a part in the changes.
And they said the discovery opened up a new avenue of research.
This is exciting new evidence that genetic and environmental factors may interact to produce specific and long-lasting modifications in brain circuits
John Krystal, Biological Psychiatry editor
The researchers, from the University of Western Ontario, Carleton University and University of Ottawa, analysed tissue from 10 people who had a serious depressive disorder and had committed suicide and 10 who had died suddenly from other causes, such as a heart attack.
They found that the DNA in the suicide group was being chemically modified by a process normally involved in regulating cell development, called methylation.
It is methylation which shuts down the unwanted genes in a cell - so the necessary genes are expressed to make a cell a skin cell rather than, for example, a heart cell.
The rate of methylation in the suicide brains was almost 10 times that of the other group, and the gene that was being shut down was a chemical message receptor that plays a major role in regulating behaviour.
In the paper, the researchers suggest this reprogramming could contribute to the "protracted and recurrent nature of major depressive disorder".
Previous research has suggested that changes to the methylation process can be caused by a combination of genetic and environmental factors called epigenetics.
news.bbc.co.uk/2/hi/health/7689522.stm