Human evolution: resisting malaria (Introduction)

by David Turell , Wednesday, September 16, 2020, 20:53 (1317 days ago) @ David Turell

A new blood type in Africa does it:

https://medicalxpress.com/news/2020-09-dantu-blood-group-malariaand-humans.html

"The secret of how the Dantu genetic blood variant helps to protect against malaria has been revealed for the first time by scientists at the Wellcome Sanger Institute, the University of Cambridge and the KEMRI-Wellcome Trust Research Programme, Kenya. The team found that red blood cells in people with the rare Dantu blood variant have a higher surface tension that prevents them from being invaded by the world's deadliest malaria parasite, Plasmodium falciparum.

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"In 2017, researchers discovered that the rare Dantu blood variant, which is found regularly only in parts of East Africa, provides some degree of protection against severe malaria. The intention behind this new study was to explain why.

"Red blood cell samples were collected from 42 healthy children in Kilifi, Kenya, who had either one, two or zero copies of the Dantu gene. The researchers then observed the ability of parasites to invade the cells in the laboratory, using multiple tools including time-lapse video microscopy to identify the specific step at which invasion was impaired.

"Analysis of the characteristics of the red blood cell samples indicated that the Dantu variant created cells with a higher surface tension—like a drum with a tighter skin. At a certain tension, malaria parasites were no longer able to enter the cell, halting their lifecycle and preventing their ability to multiply in the blood.

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"The Dantu variant actually slightly increases the tension of the red blood cell surface. It's like the parasite still has the key to the lock, but the door is too heavy for it to open."

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"The Dantu blood group has a novel 'chimeric' protein that is expressed on the surface of red blood cells, and alters the balance of other surface proteins. In Kilifi, a town on the Kenyan coast, 10 percent of the population have one copy of the Dantu gene, which confers up to 40 percent protection against malaria. One percent of the population have two copies, conferring up to 70 percent protection. By contrast, the best malaria vaccines currently provide 35 percent protection.

"Because humans have evolved alongside malaria for tens of thousands of years, some people in the worst affected areas have developed genetic resistance to the disease. The most famous example is sickle cell trait, which confers 80 percent resistance to malaria, but can cause serious illness in those with two copies of the gene. There is currently no evidence that the Dantu variant is accompanied by other health complications.

"Dr. Alejandro Marin-Menendez, of the Wellcome Sanger Institute, said: "The fact that we see the most protective adaptations in areas where malaria is most prevalent tells us a lot about how these parasites have influenced human evolution. Malaria is still an incredibly destructive disease, but evolutionary adaptations like sickle cell trait and the Dantu variant may partially explain why the mortality rate is much lower than the rate of infection. We've been fighting malaria parasites for as long as we've been human, so there may be other adaptations and mechanisms yet to be discovered.'"

Comment: Another way malaria is blocked in this case by surface tension of the cells. A beneficial mutation is an existing species.