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Multiple sclerosis findings could help pinpoint cause
By Kathleen Fackelmann, USA TODAY
Gene hunters from the USA and Europe have located two genes that appear to increase the risk of developing multiple sclerosis, studies released Sunday show.
The findings are widely expected to help scientists figure out what causes MS, a baffling disease of the central nervous system that afflicts about 350,000 people in the USA. The hope is that new knowledge will lead to the development of more targeted treatments, says Jonathan Haines, director of the Center for Human Genetics Research at Vanderbilt University in Nashville.
"We've been trying to identify the genetic basis of MS for a long time," Haines says. Researchers discovered one gene in the 1970s called HLA (human leukocyte antigen) that raises the risk of developing MS, and they knew that other genes probably play a role, he says.
But the intense search to find them has been disappointing — until now.
In the July 29 online edition of Nature Genetics, Haines and his colleagues pored over previous studies to identify genes that appeared to have a role in the disease. They then collected blood from more than 10,000 people, MS patients and healthy subjects alike.
The DNA was extracted from the samples, and researchers homed in on suspect genes. They found that a variation in the interleukin 7 receptor gene increased the risk of developing MS by 20% to 30%.
A second study in Nature Genetics confirmed that finding.
A person who inherits this gene variation, however, isn't guaranteed to get MS, Haines says. To actually get the disease, people probably need to inherit other genes that put them at higher risk, says study co-author Margaret Pericak-Vance of the University of Miami School of Medicine. In addition, the disease might require a trigger — such as exposure to a virus, says John Richert of the National Multiple Sclerosis Society in New York.
David Hafler of the Harvard Medical School and an international consortium of researchers also identified the interleukin 7 receptor gene as a risk factor for MS. But Hafler's team identified a second gene that might play a role: the interleukin 2 receptor gene. Hafler's team gathered DNA from about 12,000 people, both MS patients and healthy subjects.
The team reports in the July 29 online edition of The New England Journal of Medicine that two variations of the interleukin 2 receptor gene raise the risk of developing MS by about 20%.
The interleukin genes are thought to help regulate specialized immune cells called T-cells, Hafler says. Researchers have long speculated that MS is an autoimmune disease that occurs when immune cells mistakenly attack the coating, or myelin, that protects nerve fibers. If that's true, drug developers might be able to craft a compound that could block or stop the attack, Richert says.
People who have MS often experience attacks of weakness and tremors. Over time — especially if the current lineup of drugs stop working — they can develop permanent disability. "Some people end up in a wheelchair," Haines says.
Although researchers are now racing to find better drug compounds, that effort might take years, Richert says.
"I don't expect a cure here," says Martha Crowninshield, a former venture capitalist who donated $1 million to finance the research that led to the The New England Journal of Medicine results. Still, Crowninshield, who has the disease, says she believes additional research into the interleukin genes "will accelerate the process of finding therapies."