Sept. 28, 2009 - A gene variant common in whites is linked to Crohn's disease, an intriguing new study suggests.
Crohn's disease is an inflammatory bowel disease (IBD). In IBD, the delicate balance of the gut ecosystem is disrupted by an excessive inflammatory immune response.
People who carry the gene variant make less of an inflammation-dampening enzyme called CD39. This may tip the immune balance toward IBD, suggest David J. Friedman, MD, of Beth Israel Deaconess Medical Center, and colleagues.
"Our data indicate that CD39 [gene variants] are associated with inflammatory bowel disease in humans," the researchers conclude. Their report appears in the Sept. 29 issue of the Proceedings of the National Academy of Sciences.
The researchers fed mice a chemical that gives them IBD. Specially bred mice lacking the CD39 gene had worse IBD than mice with a normal version of the gene.
All humans have a CD39 gene. But some have a version of the gene linked to lower CD39 levels. Friedman and colleagues identified a genetic marker for low CD39 production. They then looked for this marker in 1,748 patients with Crohn's disease and in 2,936 people without IBD.
They found that the genetic marker was significantly more common in people with Crohn's disease. Moreover, people without IBD were more likely to carry two copies of the high-CD39 gene, while those with Crohn's disease were more likely to carry two copies of the low-CD39 gene.
Genetics are not destiny. Not everyone with the low-CD39 gene has or will have IBD. Even having two copies of the gene only increases a person's risk of Crohn's disease by 27%.
But since about 40% of whites of European ancestry carry at least one copy of the gene, its effects across the entire population should be quite large.
Moreover, the gene may affect more than IBD. It's also linked to kidney disease in people with diabetes and to blood clots in the arteries.
The researchers plan to perform more extensive studies of the role of the CD39 gene in IBD.