One of the earliest success stories to arise from genome-wide association has involved Crohn’s disease, a painful intestinal disorder. Crohn’s has a strong genetic component–someone with a sibling with the disease has a 30 percent increased risk of developing it. Several risk genes have already been uncovered, including a gene involved in inflammation.
The Wellcome study identified additional Crohn’s genes, two of which were quite a surprise to scientists. They code for proteins involved in autophagy, a process by which a cell clears bacteria and other waste. “We had no reason to suspect autophagy to play a role [in Crohn’s] before these results came out,” says Miles Parkes, a gastroenterologist at the University of Cambridge, who confirmed the findings in a companion paper published today in Nature Genetics. “Now we know this pathway is very important to disease–it’s another triumph for the hypothesis-free approach.”
In another unexpected finding, scientists identified a gene that increases risk for type 1 diabetes and Crohn’s disease, which are both autoimmune diseases. Scientists hope the newly discovered link between the two diseases will speed development of new treatments. “The pathways that lead to Crohn’s disease are increasingly well understood and we hope that progress in treating Crohn’s disease may give us clues on how to treat type 1 diabetes in the future,” said John Todd, a researcher at the University of Cambridge, in a statement released by the Wellcome Trust. Todd led a companion study confirming the diabetes results published today in Nature Genetics.
Results from the Wellcome Trust follow those from several other studies released over the past few months, identifying genes linked to Crohn’s, diabetes, and cancer. Additional studies involving large-scale genome tests are under way in the United States. They will likely identify new genetic variants and confirm those that have already been discovered.
In fact, according to the Wellcome study, even larger numbers of participants may be needed to identify genetic markers for diseases linked to a greater number of genes, each exerting a small effect, such as bipolar disorder, or disorders that do not seem to arise from a small number of genetic factors, such as hypertension.