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Neanderthal Genes May Increase the Risk of Severe COVID-19
Neanderthal Genes May Increase the Risk of Severe COVID-19
Written By: Paphapin Pairojtanachai
One’s environment, age, and health conditions are some of the most important factors that help determine one’s susceptibility to developing severe COVID-19. However, genetics also play a significant role: on September 30, a study was published in Nature, revealing the association between the coronavirus infection and the genetic heritage from Neanderthals. This research, done by the COVID-19 Host Genetics Initiative, reported that there is an area of DNA on human chromosome 3 that raises the risk of exhibiting serious COVID-19 symptoms. The researchers knew that since 50,000 years ago, when humans interbred with the Neanderthals, some genes were passed down until this day; indeed, the genetic variants on chromosome 3 are also “almost identical to that of a 50,000-year old Neanderthal from southern Europe.”
In genome-wide association studies (GWAS), which compared over 3,000 individuals who either had mild COVID-19 symptoms or had extreme symptoms and required hospitalization, the DNA region was labeled as a “COVID-19 danger zone”. This stretch of chromosome covers 49.4 thousand base pairs of DNA and contains 13 variants that form a block called a haplotype, meaning that the variants are almost always inherited together, so that if it is found that an individual has one of the 13, they are likely to have the other 12 variants as well. Hugo Zeberg, the evolutionary geneticist of the Max Planck Institute for Evolutionary Anthropology in Leipzig and the Karolinska Institute in Stockholm, along with Professor Svante Pääbo, who leads the Human Evolutionary Genomics Unit at the Okinawa Institute of Science and Technology (OIST), who are the authors of the research paper, are still trying to figure out which genes in the region contribute to the severity of COVID-19.
After comparing the dangerous haplotype with the genes of extinct human cousins, the scientists revealed that a 50,000 year-old Neanderthal from Croatia carried 11 of the 13 genetic variants. Two Neanderthals from Russia only carried three variants, and Denisovans, another archaic human species, did not carry these variants. Because the variants shared between present-day people and the Neanderthal from southern Europe span over such a long stretch of DNA, Zeberg and Pääbo concluded that these genes come from interbreeding between the two human groups.
Today, there are huge differences in the prevalence of the haplotype comprising the 13 variants in different parts of the world. Even though “most non-Africans carry some Neanderthal DNA as a relic of ancient interbreeding” and East Asians generally have the highest quantity of Neanderthal DNA, the haplotype seemed to have only been passed down in South Asia but not East Asia. For instance, approximately 63% of Bangladeshis have at least one copy (either from their father or their mother) of the genetic area. This could be due to the fact that the haplotype has been of an evolutionary advantage to the Bangladesh people, such as by allowing them to fight cholera. In contrast, it might have given East Asians an evolutionary disadvantage, leading to a decrease in frequency.
From this study, it is suggested that the Neanderthal DNA might have some responsibility for increasing mortality from coronavirus infection for up to three times. Nonetheless, one should keep in mind that, even without the Neanderthal gene, thousands of East Asians have died of COVID-19. As Mark Maslin, a professor at UCL, says, “We must avoid simplifying the causes and impact of Covid-19, as ultimately a person’s response to the disease is about contact and then the body’s immunity response, which is influenced by many environmental, health and genetic factors.”
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