WASHINGTON, June 30 (Xinhua) -- An international consortium of Crohn's disease researchers has combined data from three independent studies to identify 21 new genetic variants associated with the inflammatory bowel disorder, bringing the total number of risk factors to 32, according to a report available here on Monday.
The report was published in the latest online edition of the journal Nature Genetics.
Several of these new genetic factors are involved with the immune system's initial response to pathogens, supporting earlier evidence that disruptions in a process called autophagy may lead to the disorder's characteristic immune system over activity.
"This greatly increases our knowledge of the genetic architecture of Crohn's and gives us more detailed insight into the biological underpinnings of the disease," says Mark Daly of the Massachusetts General Hospital (MGH), the report's senior author. "Better understanding of the precise functions of these genes and the molecular effects of Crohn's-associated variants should lead us to novel strategies for therapies and, someday, prevention."
In 2007 three separate research teams, from North American and Europe, each published genome-wide association studies (GWAS) of Crohn's disease that, combined with earlier studies, brought the total number of Crohn's-associated gene sites to 11. However, those explained only a small proportion of the heritability of Crohn's.
Since the power of any GWAS is limited by the number of samples available for screening, the three teams combined their data through a process called meta-analysis, allowing the comparison of data from more than 3,200 Crohn's patients with more than 4,800 controls. That was supplemented by an analysis of new data from an additional 3,700 patients and matching controls.
Both of those analyses strongly confirmed the 11 previously-identified sites and found an additional 21 areas associated with susceptibility to Crohn's.
While the newly identified sites are not as strong as those found in earlier studies, they continue to build a picture of factors leading to the inappropriate immune-system activation that characterizes the disorder, said the authors.