Three genes inherited from Neanderthals reduce the risk of severe Covid-19 by 22 percent, a new study has found.
The genes are close to each other on chromosome 12, and this large piece of genetic material includes 75,000 individual pieces of DNA.
The researchers compared the DNA of 2,200 Covid-19 patients from around the world with the genes of three Neanderthals who lived 50,000, 70,000 and 120,000 years ago.
They found that people with Neanderthal versions of the OAS1, OAS2 and OAS3 genes were less likely to develop severe symptoms after coronavirus infection.
These genes produce enzymes that specifically target invading RNA viruses, and the Neanderthal version is believed to be more potent.
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Previous research has found eight genetic locations spread across five chromosomes (3, 6, 12, 19 and 21) that are ‘associated with the risk of requiring intensive care after SARS-CoV-2 infection’. However, the new analysis shows that only those found on chromosomes 3 and 12 come from Neanderthals (photo). Chromosome 12 contains three genes that help fight Covi and reduce the risk of serious infection by 22%
Professor Hugo Zeberg and Dr. Svante Pääbo of the Karolinska Institutet in Stockholm and the Max Planck Institute for Evolutionary Anthropology in Leipzig, respectively, conducted the study.
Previous research has found eight genetic locations spread across five chromosomes (3, 6, 12, 19 and 21) that are ‘associated with the risk of requiring intensive care after SARS-CoV-2 infection’.
However, the new analysis shows that only those found on chromosomes 3 and 12 originate from cross-species encounters between Homo sapiens and Neanderthals.
The researchers compared the DNA of 2,200 Covid-19 patients from around the world with the genomes of three Neanderthals who lived 50,000, 70,000 and 120,000 years ago. They found that people with Neanderthal versions of the OAS1, OAS2 and OAS3 genes were less likely to develop severe symptoms after infection with the coronavirus
The chromosome 3 gene has been the subject of previous research by the same team of experts.
He revealed that the Neanderthal version, which is present in about one in eight people today, actually doubles the risk of needing intensive care if a person catches Covid.
But the stretch of Neanderthal DNA on chromosome 12 is more common.
It was present in about one in ten humans who lived more than 20,000 years ago and then increased to about 15 percent up to 10,000 years ago.
The researchers estimate that it continued to become more dominant, with about a third of the people who lived between 3,000 and 1,000 years ago.
In the photo, the percentage of people in Eurasia with genes fighting Covid on chromosome 12 over time. It is now over 30 percent, but experts say it often reaches and exceeds 50 percent in some populations
In the photo, a world map showing the percentage of people who have the Neanderthal versions of the OAS1, OAS2 and OAS3 genes (red parts of the pie charts). Due to the ancient migratory patterns of Neanderthals and the fact that they sparsely inhabited Africa before they became extinct, very little Neanderthal DNA is seen in people living in sub-Saharan Africa today.
“Interestingly, the current allele frequency in Eurasia is around 30 percent, suggesting that the Neanderthal haplotype may have increased in frequency relatively recently,” wrote the researchers in their article.
They add: ‘It is present in the populations of Eurasia and the Americas on carrier frequencies that frequently reach and exceed 50 percent.’
Dr. Pääbo says it is “impressive” that two variants of the Neanderthal can have drastically different impacts on the human immune response to SARS-CoV-2 infection.
“It shows that our Neanderthal heritage is a double-edged sword when it comes to our response to SARS-CoV-2,” adds Professor Zeberg.
The researchers believe that the location of Neanderthal DNA on chromosome 12 is critical, as it includes three genes (OAS1, OAS2 and OAS3) that play a critical role in fighting infections.
Specifically, they help to produce enzymes that target and destroy invasive RNA, such as SARS-CoV-2, which causes Covid-19.
The new research, published in the journal PNAS, also found that the Neanderthal variant produces more enzymes that fight viruses than the ancestral alternative to Homo sapiens.
“It can be speculated that when modern humans found new RNA viruses outside Africa, the increased enzymatic activity of ancestral variants that they acquired through genetic interactions with Neanderthals may have been advantageous,” wrote the researchers.
‘Interestingly, there is evidence that the OAS haplotype similar to the Neanderthal may have recently increased in frequency in Eurasia, suggesting that selection may have positively affected the OAS locus derived from the Neanderthal in the last millennium.’
Due to the ancient migratory patterns of Neanderthals and the fact that they sparsely inhabited Africa before they became extinct, very little Neanderthal DNA is seen in people living in sub-Saharan Africa today.
In fact, the researchers say that the Covid-fighting Neanderthal genes are ‘almost completely absent’ in these populations.
“In the Americas, it occurs at lower frequencies in some populations of African ancestors, probably due to the gene flow of populations of European or Native American ancestors,” they add in the article.
The latest study supports previous findings by a separate team of researchers from Canada, who also came to the conclusion that the OAS1 gene reduces the risk of serious illness, hospitalization and death by Covid-19.
Although they did not examine the origin of the gene, they found five genes that increase the chances of serious infection.
Four of these genes – TYK2 and DPP9 on chromosome 19; IFNAR on chromosome 21 and OAS on chromosome 12 – were also studied by the last study.