The largest-ever gene study of MS has identified 29 new genetic variants associated with the disease, confirmed 23 previously known genetic links, and suggested five more genes that may contribute to the disease.
Scientists regard the findings, recently published in the journal Nature, as significant for two reasons: Because many of the genes linked to MS are involved in regulating the immune system-- specifically, the development of T cells -- this boosts speculation that the disease is primarily an autoimmune disorder. It also gives researchers new targets for future treatment strategies.
For the study, scientists compared DNA from nearly 10,000 people with MS with DNA from more than 17,000 unrelated, healthy individuals. The researchers were affiliated with the International Multiple Sclerosis Genetics Consortium and the Wellcome Trust Case Control Consortium.
They said the newly-found links point to the idea that T-cells -- a type of white blood cell responsible for mounting an immune response -- and chemicals called interleukins play a key role in the development of the disease.
Drugs that target the immune system include rituximab, sold under the brand name Rituxan® by Roche and Biogen to fight leukemia, Tysabri® from Biogen and Elan, Lemtrada, sold as Campath® by Sanofi's unit Genzyme for cancer, and Abbott and Biogen's Zenapax® or daclizumab. Mid-stage trial data for daclizumab recently showed the drug on a par with other new medicines for MS, but some of the side-effects were worrisome.
In a second study reported in the Public Library of Science journal PLoS Genetics, researchers found that many of the genes linked to MS are also linked to other autoimmune diseases such as Crohn's disease and Type 1 diabetes. This also points to potential new uses for existing drugs in development, they said.
"We have known for some time that many devastating diseases of the immune system must have common genetic causes," said Chris Cotsapas of Yale University in theUnited States, who led the PLoS study. "Now we have the outline of a map that tells us where we can look for common treatments."
Experts think both genetic and environmental factors are equally important in determining who is likely to develop MS, and taken together, the known genetic variants probably explain about 20 percent of the genetic links, they said.
Previous research has suggested a link between Vitamin D deficiency and an increased risk of MS. Compston's team said that along with the many genes which play a role in the immune system, they had also found two involved in the metabolism of Vitamin D -- which mostly comes from sunlight -- lending weight to a possible link between genes and the environment.
In 2007 only three genes were linked to MS.