British researchers have announced the discovery of a new blood group, which, they say, solves a mystery half a century old.
The new group is known as MAL, based on a newly identified protein. It provides the genetic background for the AnWj blood group antigen, discovered in 1972. Only a small number of people have ever been found to have the inherited AnWj-negative phenotype, the researchers say.
The genetic basis of the AnWj blood has been proved by researchers working with NHS Blood and Transplant in the UK and at the University of Bristol.
Their work, reported in Blood, shows that AnWj positive people – the vast majority – express the full-length Mal protein on their red cells. This was not found in AnWj-negative people, of whom there were five in the study, including an Arab-Israeli family.
Louise Tilley, senior research scientist at NHS Blood and Transplant, said she had spent 20 years of her career seeking to solve the mystery of AnWj.
She said: “It represents a huge achievement, and the culmination of a long team effort, to finally establish this new blood group system and be able to offer the best care to rare, but important, patients. The work was difficult because the genetic cases are very rare. We would not have achieved this without exome sequencing, as the gene we identified wasn’t an obvious candidate and little is known about Mal protein in red cells. Proving our findings was challenging."
Nicole Thornton, Head of IBGRL Red Cell Reference at NHS Blood and Transplant, said: “Resolving the genetic basis for AnWj has been one of our most challenging projects. Now genotyping tests can be designed to identify genetically AnWj-negative patients and donors. Such tests can be added to the existing genotyping platforms.”
Professor Ash Toye, director of the NIHR Blood and Transplant Research Unit in red cell products at the University of Bristol, said: “It’s really exciting we were able to use our ability to manipulate gene expression in the developing blood cells to help confirm the identity of the AnWj blood group, which has been an outstanding puzzle for half a century. This development will help identify these rare donors and help patients in the future.”
Dr Tim Satchwell, who contributed to the study whilst a Research Fellow at the University of Bristol, said: “Mal is a very small protein with some interesting properties which made it difficult to identify and meant we needed to pursue multiple lines of investigation to accumulate the proof we needed to establish this blood group system.”
Source:
Tilley LA, Karamatic Crew V, Mankelow TJ, AlSubhi SA, Jones B, Borowski A, Yahalom V, Finkel L, Singleton BK, Walser PJ, Toye AM, Satchwell TJ, Thornton NM. (2024) “Deletions in the MAL gene result in loss of Mal protein, defining the rare inherited AnWj-negative blood group phenotype.” Blood, 16 August 2024, doi: 10.1182/blood.2024025099.
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