Inflammatory bowel disease is a spectrum of chronic relapsing inflammatory disorders of the gastrointestinal tract affecting as many as 1,000,000 individuals in the United States.
Dr Katherine Siminovitch and colleagues report variants in 2 neighboring genes on chromosome 5 associated with susceptibility to Crohn's disease.
These genes encode related proteins whose function is to transport small molecules across cell membranes. The genes are expressed in the cells lining the intestine, the principal tissue affected in individuals with Crohn's disease.
The variant in one of the genes results in a protein with altered transport properties.
The other variant alters a binding site for a factor that controls expression levels of the second gene.
In a second study, Dr Stefan Schreiber and colleagues describe a different gene on chromosome 10 associated with susceptibility to both ulcerative colitis and Crohn's disease.
This gene encodes a protein involved in maintaining the integrity of cellular sheets like the one that forms the lining of the intestine.