DNA from thousands of years ago reveals multiple sclerosis and schizophrenia
Multiple sclerosis, an autoimmune disease that affects millions of people, is a biological mystery. A new study has found a possible solution to this problem in the skeletal remains of a vanished tribe of nomads from Western Asia.
Many researchers suspect that multiple sclerosis is caused by the Epstein-Barr virus, which causes the immune system to attack nerves and can make it difficult for patients to walk or talk. But a virus may not be the complete explanation, since almost everyone gets it at some point in their lives.
A new study of the skeletal remains of a vanished tribe of nomads who grazed cattle on the Western Asian steppes 5,000 years ago may help uncover the true cause of the disease, scientists report. It turns out that the nomads carried genetic mutations that most likely protected them from pathogens carried by their animals, but which also made their immune systems more sensitive. These genes are thought to have made the descendants of the nomads prone to a rampant immune response. They hope to trace the genetic roots not only of multiple sclerosis, but also of diabetes, schizophrenia and many other modern diseases.
“We are taking the genomics of ancient man to a whole new level,” says geneticist Eske Willerslev.
For more than a decade, researchers have been extracting DNA from ancient human bones. By comparing preserved DNA remains with genetic material from living people, scientists have been able to trace some of the most significant human migrations around the world. The researchers were then able to link thousands of genetic variants in the database to an increased risk of developing a wide range of diseases.
One analysis found that Western European hunter-gatherers, for example, carried many variants that increase the risk of high cholesterol , high blood pressure and diabetes. Another showed that ancient farmers in the Middle East carried a large number of variants associated with anxiety and other mood disorders.
These findings do not necessarily mean that these ancient people suffered from similar diseases. Diabetes, for example, is becoming increasingly common in the modern world, partly due to the cheap, high-sugar foods that make up an increasingly large part of our diet. In earlier centuries, high-risk genes for diabetes may not have been able to cause the disease.
Dr. Willerslev and his colleagues found that in some cases these genetic variants gave ancient peoples a survival advantage.
Some of the skeletons contained DNA not only from humans, but also from pathogenic viruses and bacteria. Many of these pathogens did not appear among hunter-gatherers or even early farmers in Europe. But the remains contained genetic signatures of a number of pathogens, including the one that caused the plague.
“They made a really compelling case,” genomics specialist Yasin Swilmi praised the work. “I will be shocked if further experimental testing does not will confirm their conclusions.”
Oxford University multiple sclerosis expert Dr Lars Fugger, who collaborated with Dr Willerslev on the new research, said the disease may not have become common until recent decades. In today's environment, with fewer infectious diseases than in past centuries, a strong immune system is more likely to fail by attacking its own body, he said.
Understanding the evolutionary roots of multiple sclerosis could help researchers develop better effective treatments for this disease. Currently, the only treatments for this diagnosis are drugs that suppress the immune system. To Dr. Fugger, these drugs seem like blunt instruments against a delicately balanced part of our biology.
“Instead of just turning it off, we should just try to figure out in more detail how unbalanced it is, and then try to recalibrate it,” says Dr. Fugger. he.
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