"A couple of studies in recent years have suggested that identical twins are not identical," Kingsmore said. "We were kind of betting on the fact that [the twins in this study] wouldn't be identical."
Kingsmore and his colleagues looked at three pairs of identical twins in which one twin had MS and the other did not. The oldest twins were in their 50s, the youngest 19.
Three different genetic analyses allowed them to look not only at the genes the twins were born with, but also at gene expression and what's known as imprinting or epigenetics -- when genes change their activity over the course of a lifetime.
"It gives us a very good description of a genome that's not static," Kingsmore said. "We weren't just looking at what you were born with."
Still, the authors failed to find any genetic explanation for the discrepancy between the twins.
"At the end of the day, we looked under a rock and found no genetic differences in these three pairs of twins," Kingsmore said. "It was quite a surprise."
The authors feel they may have ruled out some genetic causes for the disease but, other than that, what triggers MS is still an unanswered question.
The group plans further genetic studies to see if anything was missed the first time around.
"We still don't have the answers, that's for sure, but this was only three pairs of twins," O'Looney pointed out. "Further work needs to take place."
"It's a big mystery," added Kingsmore. "There's an unknown or undiscovered environmental trigger that's really important."
There's more on MS at the National Multiple Sclerosis Society.
SOURCES: Stephen Kings
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