Black Death may have caused convergent evolution in the immune systems of two distinct populations

February 4, 2014 by Marcia Malory, Medical Xpress report
Europeans/Romanians and Rroma/Gipsy share the same location, though the latter originated in North India. Credit: PNAS

(Medical Xpress)—Throughout human history, our immune systems have evolved in response to infectious diseases. People with genes that provide resistance to specific pathogens are more likely to survive infection and transmit those genes to future generations than people without these resistant genes. To gain a better understanding of how disease affects the evolution of our immune systems, Mihai Netea of Radboud University Nijmegen Medical Centre in the Netherlands and his colleagues studied two genetically distinct ethnic groups, European Romanians and Rroma, both of which lived in Romania during the time of the Black Death, or Black Plague. The researchers found that both groups harbor genes that provide resistance to the plague, and that these genes do not exist in populations from North India, the original home of the Rroma. This indicates that the immune systems of European Romanians and Rroma evolved convergently in response to the disease. The study appears in the Proceedings of the National Academy of Sciences.

The Rroma left North India and settled in Europe 1,000 years ago. By the 14th century, when the Black Death devastated Europe, both Rroma and European Romanians had established themselves in Romania. However, the two populations had not interbred much and therefore, their genomes remained distinct. Because of this, the researchers thought studying the two groups would provide valuable information about the evolution of genetic responses to disease. They hypothesized that the extreme evolutionary pressure caused by the plague would have led to convergent evolution in the immune systems of both populations.

To test their hypothesis, Netea and his colleagues studied the genomes of 100 Rroma, 100 people of European Romanian descent and 500 people of North Indian descent, whose ancestors had remained in India after the Rroma migration. The plague never affected India, so it would not have caused any changes to the immune systems of the North Indians.

After examining 200,000 single-nucleotide polymorphisms in all three groups, the scientists found that despite their different ancestries, the Rroma and the European Romanians shared 20 gene variants that the Northwest Indians did not possess. Among these shared gene variants was the gene cluster TLR2, which contains the genes TLR1, TLR6 and TLR10. These code for toll-like receptors, proteins that help defend against dangerous bacteria. When the researches exposed cells engineered to express TLR2 to the plague bacterium, Yersinia pestis, and to its ancestor, Yersinia pseudotuberculosis, the cells exhibited a heightened immune response.

The researchers think genetic adaptations caused by exposure to diseases earlier in history could have caused autoimmune diseases in modern populations.

Explore further: Researchers find ancient plague DNA in teeth

More information: Convergent evolution in European and Rroma populations reveals pressure exerted by plague on Toll-like receptors, Hafid Laayouni, PNAS, DOI: 10.1073/pnas.1317723111

Abstract
Recent historical periods in Europe have been characterized by severe epidemic events such as plague, smallpox, or influenza that shaped the immune system of modern populations. This study aims to identify signals of convergent evolution of the immune system, based on the peculiar demographic history in which two populations with different genetic ancestry, Europeans and Rroma (Gypsies), have lived in the same geographic area and have been exposed to similar environments, including infections, during the last millennium. We identified several genes under evolutionary pressure in European/Romanian and Rroma/Gipsy populations, but not in a Northwest Indian population, the geographic origin of the Rroma. Genes in the immune system were highly represented among those under strong evolutionary pressures in Europeans, and infections are likely to have played an important role. For example, Toll-like receptor 1 (TLR1)/TLR6/TLR10 gene cluster showed a strong signal of adaptive selection. Their gene products are functional receptors for Yersinia pestis, the agent of plague, as shown by overexpression studies showing induction of proinflammatory cytokines such as TNF, IL-1β, and IL-6 as one possible infection that may have exerted evolutionary pressures. Immunogenetic analysis showed that TLR1, TLR6, and TLR10 single-nucleotide polymorphisms modulate Y. pestis–induced cytokine responses. Other infections may also have played an important role. Thus, reconstruction of evolutionary history of European populations has identified several immune pathways, among them TLR1/TLR6/TLR10, as being shaped by convergent evolution in two human populations with different origins under the same infectious environment.

Related Stories

Researchers find ancient plague DNA in teeth

January 27, 2014
An international team of scientists has discovered that two of the world's most devastating plagues – the plague of Justinian and the Black Death, each responsible for killing as many as half the people in Europe—were ...

New research paper says we are still at risk of the plague

March 15, 2013
Today archaeologists unearthed a 'Black Death' grave in London, containing more than a dozen skeletons of people suspected to have died from the plague. The victims are thought to have died during the 14th century and archaeologists ...

US approves new treatment for ancient plague

April 27, 2012
Hardly anyone succumbs to the bubonic plague these days, but US health authorities on Friday approved a new treatment for it and other forms of the potentially deadly bacterial infection.

Researchers discover origin of the Black Death

August 30, 2011
(Medical Xpress) -- The bacteria responsible for causing the 1348 Black Death, identified as one of the most cataclysmic events in human history, has been identified by a McMaster researcher.

Scientists discover new mechanism regulating the immune response

June 28, 2013
Scientists at an Academy of Finland Centre of Excellence have discovered a new mechanism regulating the immune response that can leave a person susceptible to autoimmune diseases.

Bubonic plague claims 32 lives in Madagascar (Update)

December 20, 2013
Bubonic plague, which wiped out a third of Europe's population in the Middle Ages, has reared its ugly head in the African island state of Madagascar where 32 people have died in a fresh outbreak of the so-called Black Death ...

Recommended for you

Two new breast cancer genes emerge from Lynch syndrome gene study

January 18, 2018
Researchers at Columbia University Irving Medical Center and NewYork-Presbyterian have identified two new breast cancer genes. Having one of the genes—MSH6 and PMS2—approximately doubles a woman's risk of developing breast ...

A centuries-old math equation used to solve a modern-day genetics challenge

January 18, 2018
Researchers developed a new mathematical tool to validate and improve methods used by medical professionals to interpret results from clinical genetic tests. The work was published this month in Genetics in Medicine.

Peers' genes may help friends stay in school, new study finds

January 18, 2018
While there's scientific evidence to suggest that your genes have something to do with how far you'll go in school, new research by a team from Stanford and elsewhere says the DNA of your classmates also plays a role.

Epigenetics study helps focus search for autism risk factors

January 16, 2018
Scientists have long tried to pin down the causes of autism spectrum disorder. Recent studies have expanded the search for genetic links from identifying genes toward epigenetics, the study of factors that control gene expression ...

Group recreates DNA of man who died in 1827 despite having no body to work with

January 16, 2018
An international team of researchers led by a group with deCODE Genetics, a biopharmaceutical company in Iceland, has partly recreated the DNA of a man who died in 1827, despite having no body to take tissue samples from. ...

The surprising role of gene architecture in cell fate decisions

January 16, 2018
Scientists read the code of life—the genome—as a sequence of letters, but now researchers have also started exploring its three-dimensional organisation. In a paper published in Nature Genetics, an interdisciplinary research ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.