The journal 'Nature Genetics' contains details of the research, which was carried out at the Wellcome Trust Centre for Human Genetics and the Nuffield Department of Obstetrics and Gynaecology, University of Oxford; the Queensland Institute of Medical Research, Australia; and Brigham and Women's Hospital and Harvard Medical School, Boston, USA.
Endometriosis is a common gynaecological disease affecting an estimated 6 to 10 per cent of all women in their reproductive years - an estimated 170 million women worldwide. It 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 cause inflammation and adhesions; they result in pelvic pain and can cause infertility in some women. Why the deposits arise in the first place, and why they thrive outside the womb, is as yet largely unknown.
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 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.
Now, researchers from the International Endogene Consortium have compared the genomes of over 5,500 women surgically diagnosed with the disease from the UK, Australia and the US with almost 10,000 healthy volunteers. They have identified two new genetic variants that increase the risk of developing the disease, particularly moderate-severe stages.
"Endometriosis can be a painful and distressing condition that affects a significant number of women in their reproductive years," explains Dr Krina Zondervan, a Wellcome Trust Research Career Development Fellow at the University of Oxford and the study's principal investigator. "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."
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."
The study was funded by a grant from the Wellcome Trust as part of the Wellcome Trust Case Control Consortium 2 and builds on 15 years of collaborative work on the genetics of endometriosis between the research groups.
Painter, JN et al. Genome-wide association study identifies a locus at 7p15.2 associated with endometriosis. Nature Genetics; 12 December 2010.
The Wellcome Trust Centre for Human Genetics(opens in a new tab) was established to undertake research into the genetic basis of common diseases. The scientific objective of the Centre is to explore all aspects of the genetic susceptibility of disease. The Centre houses multidisciplinary research teams in human genetics, functional genomics, bioinformatics, statistical genetics and structural biology.
The Nuffield Department of Obstetrics and Gynaecology(opens in a new tab) is one of the largest academic clinical obstetric and gynaecology departments in the UK, encompassing interdisciplinary research across a wide range of important issues in human reproduction and applied basic science. It has a long-standing interest in researching the origins of endometriosis, its impact on women, and ways of improving diagnosis and treatment.
The Wellcome Trust is a global charitable foundation dedicated to achieving extraordinary improvements in human and animal health. It supports the brightest minds in biomedical research and the medical humanities. The Trust's breadth of support includes public engagement, education and the application of research to improve health. It is independent of both political and commercial interests.