Dr. Katherine Siminovitch from the Department of Medicine and her colleagues have isolated one of the genes that predisposes people to Crohn’s disease. This discovery will help diagnose and find better treatment for the disease, which affects approximately 150,000 Canadians.
Crohn’s disease is one of two kinds of inflammatory bowel diseases. It is hard to diagnose because the symptoms, which include abdominal pain, diarrhoea and weight loss, are similar to those of ulcerative colitis and irritable bowel syndrome. It is a chronic disease, which causes nutritional deficiencies, skin problems, eye and mouth inflammation and other complications, resulting in “multiple hospitalizations and surgeries for many affected people,” according to Siminovitch. Apart from surgery, the disease is also treated with drugs and nutritional supplements. Today there is no cure. Crohn’s disease can subside for a long time, but the symptoms can reappear.
How does one get Crohn’s disease? Dr. Siminovitch explains, “This disease is not caused by a single gene mutation, but rather by multiple gene defects.” One needs to have mutations in several specific genes in order to become susceptible to the disease. Development of the disease is then triggered by environmental factors.
“Our work on Crohn’s disease started 10 years ago,” said Dr. Siminovitch, “and involved a large family collection and chromosomal mapping studies which were completed in 2001. It then took us two more years to find the gene defect, and one more year to prove that the defect was important biologically.” The gene discovered lies on chromosome five.
They found that the difference between healthy and diseased individuals lies in a gene that codes for a transporter protein. Transporters are located in the cell membrane, and act as gates-they let substances in and out of the cell. Dr. Siminovitch said, “This transporter is found in many cells including blood cells, and the cells which line the gut wall.” Mutations in the gene prevent the transporter protein from functioning properly, which causes damage to the intestinal wall.
Dr. Siminovitch and her colleagues are now looking for compounds or proteins that will improve the faulty transporter’s functioning.
Dr. Siminovitch is a senior scientist at the Samuel Lunenfeld Research Institute at Mount Sinai Hospital. She is also one of the founding scientists at Ellipsis Biotherapeutics Corporation, a drug and diagnostics discovery company.

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