Multiple sclerosis is an autoimmune disease that occurs more frequently in people from northern Europe, and its prevalence has increased over the past 50 years. This increase in cases suggests that it is caused by a poorly understood combination of environmental and genetic factors.
A series of published studies In the magazine nature It suggests that the migration of herding populations that occurred 5,000 years ago may have contributed to an increased genetic risk of MS in northern Europe. This additional risk could have been compensated for by protection against diseases transmitted by animals (zoonosis).
Eske Willerslev (Universities of Cambridge and Copenhagen) and colleagues relied on more than 1,600 prehistoric human genomes covering the European population for 34,000 years. These data refine the dating of migration waves: after the first hunter-gatherers arrived from Africa, 45,000 years ago. Homo sapiensNeolithic farmers from the Near East, in turn, ventured into Western Europe eleven thousand years ago. Then, about five thousand years ago, nomadic steppe herders made their way from the Danube to the Ural Mountains toward sunset.
Inflammatory diseases in the Bronze Age
The latter, who are representatives of the so-called “Yemeni” culture, brought their own genetic mutations favoring the occurrence of multiple sclerosis. The researchers relied on “genome-wide association studies” (GWAS), which compare several modern genomes to establish relationships between physiological and/or behavioral traits and genetic mutations. At least 233 genetic variants associated with MS have been identified, in particular the HLA-DRB1*15:01 variant, carriers of which are three times more likely to develop the disease.
Today, the highest percentage of carriers of this mutation are found in Finland, Sweden and Iceland. In ancient populations, the Yamnaya presented more of this genetic profile. Thus, the steppe genetic heritage, which is more prevalent in the north, partly explains the gradient in the prevalence of MS in southern Europe, which accounts for half the number of people affected.
Population geneticist at the Pasteur Institute, Luis Quintana Murci Judge these results “so interesting”. Especially since they agree with his work recently published in cellabout the emergence of genetic profiles associated with inflammatory diseases in the Bronze Age, about 4,500 years ago. “These mutations simultaneously protect against more serious, potentially infectious diseases – a phenomenon called ‘hostile pleiotropy’.”Indicates. Such as sickle cell disease, which protects African populations from malaria.
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