The use of ancient DNA has provided insight into the reason why individuals of northern European descent are more susceptible to multiple sclerosis compared to other lineages. This can be attributed to the genetic inheritance of horse-riding nomads who migrated into the area approximately 5,000 years ago.

The results are the product of a large-scale study that compared current DNA with that extracted from the teeth and bones of ancient humans. This has enabled scientists to track the movement of prehistoric populations and identify genes associated with diseases.

On Wednesday, researchers discovered that the Yamnaya people, a group from the Bronze Age who migrated from the steppes of present-day Ukraine and Russia to north-western Europe, brought with them gene variations that are currently linked to a higher risk of developing multiple sclerosis.

However, the Yamnaya people thrived and their genetic variations spread extensively. These genes likely provided protection for the nomadic herders against infections transmitted by their livestock. This was determined by a study published in the journal Nature.

“We were met with unexpected results,” stated William Barrie, the co-author of the study and a genetics researcher at the University of Cambridge. “These variations were providing individuals with some sort of advantage.”

This discovery is part of a unique collection of genetic data, containing thousands of samples from ancient humans in Europe and western Asia. The project was led by Eske Willerslev from Cambridge and the University of Copenhagen, who was a pioneer in the field of studying ancient DNA. Other studies have also identified early relatives of humans, such as Neanderthals.

The initial action of utilizing the updated gene database to investigate MS was a rational decision. This is due to the fact that although MS can affect any group, it is most prevalent among individuals of European descent, particularly those from northern Europe. Researchers have been unable to provide an explanation for this trend.

The potentially disabling disease occurs when immune system cells mistakenly attack the protective coating on nerve fibres, gradually eroding them. It causes varying symptoms – numbness and tingling in one person, impaired walking and vision loss in another – that often wax and wane.

The exact cause of MS is unknown, but it is believed that certain infections may activate the condition in individuals who have a genetic predisposition. There have been over 230 identified genetic variations that can heighten the likelihood of developing MS.

The scientists initially analyzed genetic material from approximately 1,600 early Eurasian individuals, uncovering significant changes in the population of northern Europe. Initially, Middle Eastern farmers began to replace hunter-gatherers, followed by the arrival of the Yamnaya people around 5,000 years ago. These nomads traveled with horses and wagons while tending to their herds of cattle and sheep.

The researchers analyzed ancient DNA and compared it to a gene bank of approximately 400,000 individuals in the UK. They found that genetic variations associated with multiple sclerosis were more common in the northern regions where the Yamnaya people migrated, rather than in southern Europe.

According to Willerslev, the Yamnaya quickly supplanted traditional farmers in what is currently Denmark, making them the most direct predecessors of present-day Danes. Scandinavian countries have notably high rates of multiple sclerosis.

How can genetic variations, initially thought to have enhanced immunity in ancient times, contribute to an autoimmune disorder? According to Astrid Iversen from Oxford University, variations in exposure to animal pathogens in modern humans may disrupt the balance of the immune system.

According to genetic expert Samira Asgari, who provided commentary on the research, the results now provide a possible explanation for the division of multiple sclerosis cases in Europe between north and south. However, further research is necessary to verify this connection.

Source: theguardian.com