13 december 2010

Two genes linked to common gynaecological disease

Source: Wellcome Trust

Science | Health

Strand of DNA

Two genetic variants have been identified that increase the risk of developing endometriosis, a common gynaecological disease. The study provides clues to the origin of this often very painful condition, which has a significant impact on the quality of life of many women.

The research was carried out at the University of Oxford, the Queensland Institute of Medical Research, Australia, and Brigham and Women's Hospital and Harvard Medical School in the USA. The findings are published in the journal Nature Genetics.

Endometriosis is a common gynaecological disease affecting an estimated 6–10% of all women in their reproductive years – an estimated 170 million women worldwide. In some cases, endometriosis will only cause minor symptoms and go undiagnosed. But in more severe cases, debilitating symptoms can have a profound effect on the woman’s life.

The condition is characterised by the growth of cells similar to those lining the womb on organs in the pelvis, such as the ovaries and bowel. These deposits can result in pelvic pain as well as infertility in some women, but why the deposits arise in the first place is as yet largely unknown.

A diagnosis can only be made reliably by looking into the pelvis with a laparoscope, which explains why it is common for years to pass before the diagnosis is made. Current treatments are limited to surgery and hormonal drugs that have numerous side-effects.

‘Endometriosis can be a painful and distressing condition that affects a significant number of women in their reproductive years,’ explains Dr Krina Zondervan of the Wellcome Trust Centre for Human Genetics and the Nuffield Department of Obstetrics and Gynaecology at Oxford University.

Endometriosis can be a painful and distressing condition that affects a significant number of women in their reproductive years

Dr Krina Zondervan

The researchers compared the genomes of over 5,500 women from the UK, Australia and the US who had been surgically diagnosed with endometriosis, with almost 10,000 healthy volunteers. They identified two new genetic variants that increase the risk of developing the disease, particularly moderate-severe forms.

‘We've known for some time that endometriosis is heritable, but until now we have been unable to find any robust genetic variants that influence a woman’s risk of developing the disease,’ says Dr Zondervan, who led the Wellcome Trust-funded study.

The first is a variant on chromosome 7 believed to be involved in regulating nearby genes, probably those involved in the development of the womb and its lining.

The second variant was found on chromosome 1, close to the gene WNT4. This is important for hormone metabolism and the development of the female reproductive tract, especially the ovaries, making it an important biological candidate for involvement in endometriosis.

‘Our study is a breakthrough because it provides the first strong evidence that variations in DNA make some women more likely to develop endometriosis,’ says Dr Zondervan. ‘We now need to understand the effect of these variations on cells and molecules in the body.’

Dr Stephen Kennedy, head of the Nuffield Department of Obstetrics and Gynaecology and joint senior author on the paper, adds: ‘We have great confidence that the results of this study will help towards developing less invasive methods of diagnosis and more effective treatments for endometriosis.’