New mutations on platelet GPIIb in Sub-Saharan Mrican populations revealed by genotyping discrepancies

Abstract

BACKGROUND: Previous studies of platelet al/ele frequencies in Sub-Saharan African population~nabled us to identity discrepancies in HPA-3 typing, suggesting the presence of new mutations and of a greater polymorphism than 50 far described in other populations. OBJECTIVES: To analyze these discrepancies and to 0sess the factors leading to potential alloimmunization .. 1 these populations. f'ATERIALS AND METHODS: Samples: Matemal samples from a Beninese woman following in utero death and panels of blood donors from Benin, Cameroon, Congo, and Pygmies from Central Africa. Techniques: Genotyping was performed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), PCR-sequence specifie primers (PCR-SSP) and sequencing techniques. RESULTS: Three new mutations were found on GPllb gene: exon 26 a) 2614C>A situated belween HPA-3 and HPA-9w, b) 2645C>T downstream of HPA-3, c) intron 26 IVS26+89G>A. These mutations may lead to discrepant DNA typing results, due either to a localization in the complementary sequence r8cognized bl the primer or to the appearance of a new enzyme restriction site. Furthermore, a bilaterallinkage « deletion (.19 bp) intron 21 and the HPA-3b allele (exon 26) f""\> fO!Jnd in Caucasian, Asian, and Oceanian populaHions is not found in African populations, suggesting that f ts appearance was prior to HPA-3. CONCLUSION: Three new mutations have been identified, two of them potentially irnmunogenic through their position. Furthermore, the polymorphism found on intron 26, localized in'the complementary sequence of the PCR primer, may lead to a false typing assignation. It is therefore important to diversify techniques, both genomic (PCR-RFLP and PCR-SSP), and proteomic monoclonal antibody-specitic immobilization of platelets antigen (MAIPA) to ensure accurate HPA antigenic system typing.