London - Scientists have identified a defective gene that may cause inflammatory bowel disease (IBD).
Both IBD conditions, Crohn`s disease and ulcerative colitis, are believed to be caused mainly by the immune system`s over-reaction to gut bacteria.
However, studies of family members who show the disorders have indicated a strong genetic influence.
Research has already linked Crohn`s disease to mutations in a gene known as CARD 15. However, scientists already knew that other parts of the genetic puzzle were missing.
The new study points towards a gene involved in inflammation that may play a crucial role in IBD.
The gene, IL23R, produces part of a receptor protein at the core of the inflammation pathway. It responds to an inflammation-promoting signalling molecule or cytokine, released by immune system cells.
Several different variants of the IL23R gene were found to increase or decrease a person`s risk of developing IBD. The gene link was discovered by an international team of scientists who scanned the DNA of 547 people with Crohn`s disease and 548 healthy volunteers.
Researchers scoured nearly all 22,000 genes in the human genetic blueprint and tested more than 300,000 variations in the DNA code, the journal Science reported.
The leading researcher, Dr Judy Cho, from the Yale School of Medicine in Connecticut, in the United States, said: "This finding is particularly intriguing because we appear to have identified a gene variant that protects against development of IBD. It causes us to think about the genetics of health as well as about the genetics of the disease."
One mutation seems to protect from IBD, and will be a crucial target for drugs that might better manage Crohn`s disease and ulcerative colitis.
Together, Crohn`s disease and ulcerative colitis hit around 150,000 people in Britain. Symptoms include abdominal pain, bloody diarrhoea, fatigue and weight loss.