Researchers have some new clues into the maddening mystery of multiple sclerosis—a disease that robs neurons of their protective sheaths and wreaks havoc on the central nervous systems of 2.5 million people worldwide. While the disorder's effects are obvious—loss of balance and slurred speech—its cause has eluded doctors and scientists for decades. Despite evidence suggesting a genetic component, only one gene has been definitively linked to MS in the past 30 years.
Now, scientists have uncovered a second gene that appears to increase the risk of developing MS by 20 percent. The findings were reported in two separate studies, published Sunday in Nature Genetics and the New England Journal of Medicine. "The exciting thing is that we've been able to find something after so long," says Jonathan Haines, director of Vanderbilt's Center for Human Genetics Research and a lead author on both studies. But, as with most diseases, how strong a role any one gene plays, or even whether genes will prove to be the main cause, remains to be seen.
"It's very important research for identifying a gene that we had no idea was associated with MS," says Moses Rodriguez, a scientist at the Mayo Clinic, who was not involved in either of the studies. Beyond that, he cautions, several questions have yet to be answered, and any benefits in the way of treatment or diagnostics are a long way off.
The new suspect is IL7-R, a protein that shepherds the immune system's warrior cells—known as T lymphocytes—into battle. People who express one version of the gene are more likely to develop MS, according to the studies—though researchers have yet to figure out why. "The variant is found in healthy populations as well, so it's not a clear cause-and-effect relationship," says Rodriguez.
Scientists have also looked to the environment for potential causes of MS. Suspects include an unidentified virus that preys on genetically weak immune systems, vitamin D deficiency and smoking. "This paper doesn't answer the genes versus infection question one way or the other," says Rodriguez. "The answer is that we still don't have the answer."
In a third paper, published in the journal Nature on Thursday, Lawrence Steinman and his colleagues showed that Cryab, a protein found in the human eye, protects brain cells during the early stages of MS. As the disease progresses, however, the immune system destroys this protein. "Giving Cryab as a therapy could be a future treatment to slow the progression of MS," Steinman says. His study also leaves the question of what causes MS unanswered.
While this flurry of MS news offers some hope to patients and their families, the hard truth is that the case is a long way from being solved. "The reality is that you could develop a treatment for this disease without really knowing its true origins," says Rodriguez.