It has been a medical mystery for 67 years, ever since the British geneticist Anthony Allison established that carriers of one mutated copy of the gene that causes sickle-cell anaemia are protected from malaria1. The finding wasn’t trivial: in equatorial Africa, where Allison did his work, up to 40% of people are carriers of this mutated gene. Since then, scientific sleuths have wondered how exactly the gene protects them. With a paper published today in Science2, the answer — or a large part of it — seems to be at hand.
Michael Lanzer and his colleagues at Heidelberg University in Germany and the Biomedical Research Center Pietro Annigoni in Ouagadougou, Burkina Faso, used powerful electron microscopy techniques to compare healthy red blood cells both with 'normal' cells infected with the malaria parasite Plasmodium falciparum and with infected cells from people carrying the mutated “S” gene that causes sickle-cell disease, as well as another mutation, dubbed “C,” which occurs at the same spot. Both mutations lead to the substitution of a single amino acid in the hemoglobin molecule, causing the haemoglobin to aggregate abnormally inside the cell. In people with two copies of the S mutation, they deform into a half-moon shape — the 'sickle cells' that give the disease its name..