Protective gene variant linked to Crohn's disease

US and Canadian scientists have identified a gene involved in Crohn's disease, an inflammatory bowel condition. The team discovered that a version of gene involved in the body's inflammation response is linked to a decreased risk of Crohn's disease. The researcher say that this means the gene, which makes a protein called the interleukin-23 (IL-23) receptor, appears to have a protective effect. The findings, published online in Science Express, could lead to new drugs that might allow better management of the condition.

Crohn's disease and ulcerative colitis, collectively called inflammatory bowel disease (IBD) cause abdominal pain, diarrhoea and gastrointestinal bleeding. Both conditions run in families, and previous studies have linked Crohn's disease to mutations in a gene called CARD 15. However, not all Crohn's patients have mutations in this gene, prompting the researchers to scan the genome looking for other genes that might be involved. They analysed DNA samples from over 1000 people, and discovered that healthy people are four times more likely to have the protective IL-23 variant than people with Crohn's disease.

'We know that the IL-23 receptor plays an important role in activating inflammation, including in organs of the digestive tract, therefore it could be an extremely important target for improving the management of Crohn's disease and ulcerative colitis', said team leader Judy Cho. But she cautioned that 'the IL-23 pathway may serve a useful purpose in protecting us from other diseases, so when seeking to block or manipulate its activity with drugs or other means, we need to take this balancing act into consideration'.

In the UK, a large-scale study looking for genes involved in several common conditions, including Crohn's disease, is nearing completion. Professor Chris Mathew, who is involved in the Wellcome Trust Case Control Consortium (WTCCC), told BBC News Online that the new Science study suggests that the IL-23 receptor gene plays a 'key role' in the inflammatory response. The WTCCC is studying over 19,000 DNA samples to identify genetic 'signposts' for tuberculosis susceptibility, heart disease, type 1 and type 2 diabetes, rheumatoid arthritis, Crohn's disease and ulcerative colitis, bipolar disorder and high blood pressure.