2024-01-12 20:30:11
Multiple sclerosis is an autoimmune disease that occurs more frequently in people from northern Europe, and whose prevalence has increased over the past fifty years. This increase in cases indicates that its triggering is due to a poorly understood combination of environmental and genetic factors.
A series of studies published in the journal Nature suggests that migrations of populations practicing pastoralism that occurred five thousand years ago would have contributed to increasing the genetic risk of multiple sclerosis in Northern Europe. This additional risk would have been offset by protection against diseases transmitted by animals (zoonoses).
Eske Willerslev (Universities of Cambridge and Copenhagen) and his colleagues relied on more than 1,600 prehistoric human genomes covering the European population for 34,000 years. These data refine the history of migratory waves: after the arrival from Africa, 45,000 years ago, of the first hunter-gatherers A wise man, Neolithic farmers from the Near East in turn ventured into Western Europe eleven thousand years ago. Then, around five thousand years ago, the nomadic shepherds of the steppe from the Danube to the Urals in turn made their way towards the Sunset.
Inflammatory diseases in the Bronze Age
The latter, representatives of the so-called “Yamna” culture, would have brought in their genetic baggage mutations favoring the occurrence of multiple sclerosis. The researchers relied on “genome-wide association studies” (GWAS), which compare numerous modern genomes to establish relationships between physiological and/or behavioral traits and genetic mutations. No fewer than 233 genetic variants have been identified in association with multiple sclerosis, notably the HLA-DRB1*15:01 variant, carriers of which are three times more likely to develop the disease.
Today, the highest proportion of carriers of this mutation are found in Finland, Sweden and Iceland. In ancient populations, the Yamnayas present more of this genetic profile. The steppe genetic heritage, more present in the north, would therefore partly explain the gradient in the prevalence of multiple sclerosis with southern Europe, which is half as affected.
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Population geneticist at the Pasteur Institute, Lluis Quintana-Murci judges these results “very interesting”. Especially since they agree with his work, recently published in Cellon the appearance of genetic profiles linked to inflammatory diseases in the Bronze Age, around 4,500 years ago. “These mutations simultaneously protect against more serious diseases, likely infectious diseases – a phenomenon called ‘antagonistic pleiotropy’”, he indicates. Like sickle cell disease, which protects African populations from malaria.
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