title: A novel GYPB-A-B hybrid gene responsible for Ss and MN typing discrepancies.
abstract: BACKGROUND
  Transfusion support of S-s- patients is very challenging but can now be alleviated by genotyping mutations in the GYPB gene to predict their U- or U+(var) phenotype. However, the phenotype predicted by genotyping does not always correspond to the observed phenotype of red blood cells (RBCs), which requires further investigation to avoid such a typing discrepancy in the future. In this study, we elucidated the case of an S-s- female patient of African origin who was predicted to be S+s- by our genotyping platform.
  
  
  METHODS
  Long-range polymerase chain reaction (PCR) amplification and extended Sanger sequencing were required.
  
  
  RESULTS
  The Ss typing discrepancy in the proband resulted from a converted GYPB allele that encodes neither S nor s due to the replacement of Exon B4 of GYPB by the homologous Exon A4 of GYPA. In this novel GYPB-A-B hybrid gene, the GYPA segment actually starts just downstream of Exon B2, causing a MN typing discrepancy too. While the proband's RBCs were M+N-, the genotyping predicted the M+N+ phenotype.
  
  
  CONCLUSIONS
  The reported GYPB-A-B hybrid gene constitutes a limitation for the accurate prediction of the MN and Ss phenotypes by current genotyping methods. A PCR assay was therefore developed to detect its presence.
authors.affiliation: Département Centre National de Référence pour les Groupes Sanguins (CNRGS), Institut National de la Transfusion Sanguine (INTS), Paris, France.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Willemetz
authors.affiliation: Département Centre National de Référence pour les Groupes Sanguins (CNRGS), Institut National de la Transfusion Sanguine (INTS), Paris, France.
authors.forename: Joelle
authors.initials: J
authors.lastname: Nataf
authors.affiliation: Département Centre National de Référence pour les Groupes Sanguins (CNRGS), Institut National de la Transfusion Sanguine (INTS), Paris, France.
authors.forename: Thierry
authors.initials: T
authors.lastname: Peyrard
authors.affiliation: Département Centre National de Référence pour les Groupes Sanguins (CNRGS), Institut National de la Transfusion Sanguine (INTS), Paris, France.
authors.forename: Lionel
authors.initials: L
authors.lastname: Arnaud
mesh_terms: D000483:Alleles; D001789:Blood Group Antigens / Q000235:genetics*; D005091:Exons / Q000235:genetics; D005260:Female; D005838:Genotype; D006021:Glycophorins / Q000235:genetics*; D006801:Humans; D008951:MNSs Blood-Group System / Q000235:genetics*; D010641:Phenotype; D016133:Polymerase Chain Reaction; D011247:Pregnancy
chemical_list: D001789:Blood Group Antigens; D006021:Glycophorins; D008951:MNSs Blood-Group System