Ancient DNA helps explain why northern Europeans have a higher risk of multiple sclerosis than other ancestries: the disease is a genetic legacy of horse-riding cattle herders who swept into the region about 5,000 years ago.
The findings come from a major project to compare modern DNA with that removed from ancient people’s teeth and bones – allowing scientists to trace prehistoric migration and disease-linked genes that co-tagged.
When a Bronze Age people called the Yamnaya moved from the steppes of what are now Ukraine and Russia into northwestern Europe, they carried gene variants known today to increase people’s risk of multiple sclerosis, researchers reported Wednesday.
Yet the Yamnaya flourished and spread those variants widely. Those genes probably also protected the nomadic herders from infections carried by their cattle and sheep, the research concluded published in the journal Nature.
“What we found surprised everyone,” said study co-author William Barrie, a genetics researcher at the University of Cambridge. “These variants gave these people an advantage of some kind.”
This is one of several findings from a first-of-its-kind gene bank of thousands of samples from early humans in Europe and western Asia, a project led by Eske Willerslev of Cambridge and the University of Copenhagen that helped to pioneering study of ancient DNA. . Similar research has even traced earlier cousins of humans such as Neanderthals.
Using the new gene bank to explore MS was a logical first step. This is because, while MS can affect any population, it is most common among white descendants of Northern Europeans and scientists have not been able to explain why.
The potentially disabling disease occurs when immune system cells mistakenly attack the protective coating on nerve fibers and gradually erode it. It causes different symptoms – numbness and tingling in one person, impaired walking and vision loss in another – that often wax and wane.
It is not clear what causes MS, although a leading theory is that certain infections can cause it in people who are genetically susceptible. More than 230 genetic variants have been found that can increase someone’s risk.
The researchers first examined DNA from about 1,600 ancient Eurasians and mapped some major shifts in Northern Europe’s population. First, farmers from the Middle East began to supplant hunter-gatherers and then, nearly 5,000 years ago, the Yamnaya began to move in – traveling by horse and wagon while tending cattle and sheep.
The research team compared the ancient DNA with about 400,000 modern-day people stored in a British gene bank to see that the MS-linked genetic variations persisted in the north, the direction the Yamnaya moved, rather than in the south Europe.
In what is now Denmark, the Yamnaya quickly replaced ancient farmers, making them the closest ancestors of modern Danes, Willerslev said. MS rates are particularly high in Scandinavian countries.
Why would gene variants thought to have strengthened ancient immunity later play a role in an autoimmune disease? Differences in how modern humans are exposed to animal germs may play a role, throwing the immune system off balance, said study co-author Astrid Iversen of Oxford University.
The findings ultimately provide an explanation for the north-south MS divide in Europe, but more work is needed to confirm the link, said geneticist Samira Asgari of New York’s Mount Sinai School of Medicine, who is not at the research was not involved, warned. an accompanying comment.
