Ancient DNA reveals genetic roots of multiple sclerosis and other diseases

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Scientists have compiled the largest database of ancient DNA based on the bones and teeth of nearly 5,000 humans who lived in western Europe and parts of central Asia from 34,000 years ago to medieval times.

Analysis of this exceptionally detailed set of ancient genetic information suggests that genes that may once have protected prehistoric hunter-gatherers or Bronze Age herders from harmful pathogens may today increase the risk of neurodegenerative diseases such as multiple sclerosis and Alzheimer’s in Europeans.

The ambitious five-year project involving a team of 175 international experts combined previously known ancient genomes with newly sequenced DNA from hundreds of skeletal specimens from museums and other institutions across Europe. Together, these data form the largest bank of ancient genes in the world, according to scientists involved in the project.

The researchers were able to use the database to chart the spread of genes (and diseases) over time as populations migrated and interbred, revealing how specific and dramatic changes in the environment, such as the change of a style from hunter-gatherer life to agriculture, favored certain genetics. variants.

By comparing ancient DNA with modern samples, researchers gained new biological understanding of debilitating disorders and current physical traits. Initial results of the project were published Wednesday in four articles in the scientific journal Nature.

“What’s notable about this data set is that we can now see what happened in the past, we can see what are the genetic variants that change frequency in the past due to natural selection. And that allows us to get a very, very detailed picture,” Rasmus Nielsen, a professor of integrative biology and geneticist at the University of California, Berkeley, who helped lead the project, said at a news conference this week.

Researchers sequenced DNA from human remains in museum collections across Europe.  - The Danish National Museum

Researchers sequenced DNA from human remains in museum collections across Europe. – The Danish National Museum

How Bronze Age shepherds are linked to MS

One of the key findings from the first batch of research, based on more than 1,600 genomes in the database, was related to multiple sclerosis, often called MS, an autoimmune disease of the nervous system that affects approximately 2.5 million. people all over the world. It is a complex condition made up of multiple environmental and genetic factors with many potential symptoms, including problems with vision, arm or leg movement, sensation, and balance.

Northern Europeans are among the most prone to the disease, the study noted, but the reasons are poorly understood.

The researchers used the database to explore the genetic origins of multiple sclerosis. They found that genetic risk for the condition correlates with the proportion of ancestry from a group of ancient pastoralists who introduced domesticated animals to Europe about 5,000 years ago.

These nomadic cattle and sheep herders, known as Yamnaya, originate from the Pontic Steppe, which stretches from southeastern Europe to Kazakhstan. It is believed that they were the first horsemen, which made them very mobile.

When they moved west toward Europe, they brought specific genetic variants that researchers believe evolved to protect nomads against pathogens carried by domesticated animals, according to the study.

These genetic variants may have subsequently been beneficial to European populations as they shifted from hunting and gathering to agriculture.

And because the Yamnaya moved primarily to northern Europe, the team concluded that the higher proportion of pastoral ancestry in today’s northern Europeans could be partly responsible for the higher prevalence of the disease there.

“These results surprised us all. “They provide a major advance in our understanding of the evolution of MS and other autoimmune diseases,” William Barrie, a postdoctoral researcher in the department of zoology at the University of Cambridge and co-author of one of the papers, said in a statement. “Showing how our ancestors’ lifestyles impacted modern disease risk simply highlights how recipients we are of ancient immune systems in a modern world.”

Today, the protective benefits of these genetic variants are no longer as useful, said co-author Astrid Iversen, a professor of virology and immunology at the University of Oxford.

“We now lead very different lives to our ancestors in terms of hygiene, diet and medical treatment options, and this, combined with our evolutionary history, means we may be more susceptible to certain diseases than our ancestors, including diseases autoimmune diseases like MS,” Iversen said in a statement.

link with Alzheimer’s

The researchers also mapped the origins of a genetic variant, APOE ε4, known to increase Alzheimer’s disease risk. The gene was linked to the earliest hunter-gatherer populations that once inhabited prehistoric Europe, one of the four studies found.

“Hunter-gatherer DNA is present at higher levels in northeastern Europe, meaning the region has an elevated genetic risk of developing Alzheimer’s disease,” Barrie said.

Similarly, ancient genetic information sheds light on the evolutionary history of traits such as height and lactose tolerance.

In a commentary accompanying the research, Samira Asgari, assistant professor of genetics and genomic sciences at the Icahn School of Medicine at Mount Sinai in New York, said it was crucial to extend these types of studies beyond Europe to other regions to ” “Better understand how differences in population history might have contributed to the risk of autoimmune diseases such as multiple sclerosis.”

“Although human biology is shared, each population has a unique history, and focusing on a single population limits opportunities for discoveries that can provide insights that advance medicine,” wrote Asgari, who was not involved in the four studies.

The new database provides “the most comprehensive views of a region’s genetic history to date,” said Tony Capra, associate professor of epidemiology and biostatistics at the Bakar Computational Health Sciences Institute at the University of California, San Francisco. Francisco.

“This has allowed the authors to fill in missing details in our understanding of who lived where and when, as well as how natural selection shaped the traits of modern individuals,” he said.

However, Capra cautioned that “there is rarely a simple answer to why one population may have one genetic variant and another may not.”

“The evolutionary history of our species makes many contributions to our current health and traits,” Capra, who was not involved in the research, said by email.

“However, then as now, all of these genetic effects are modulated by the environment. And for most traits, including MS, the genetic effects are the result of multiple genetic variants,” he said. “Ultimately, we cannot say that MS came from Bronze Age populations, but the movements and environments of these populations contribute to differences in MS risk today.”

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