title: A novel ABO O allele caused by a large deletion covering two exons of the ABO gene identified in a Caucasian family showing discrepant ABO blood typing results.
abstract: The presence of ABO subgroup alleles and unusual O alleles often is associated with discrepant serologic findings in ABO blood group typing. In the ABO gene of a Caucasian female and her daughters who had aberrant ABO phenotypes, a novel ABO O allele characterized by a large deletion that included two exons was identified.
  
  
  
  ABO phenotypes were determined by standard agglutination tests and adsorption-elution studies. Allele-specific sequencing analyses of the ABO gene as well as messenger RNA transcripts were carried out.
  
  
  
  All three samples showed the same discrepant ABO blood typing results lacking A and B antigens, indicating Blood Group O, whereas anti-A1 and anti-A2 isoagglutinins were not detectable in reverse typing. Analyses of the ABO gene revealed a novel allele characterized by a deletion of 2169 base pairs, including sequences of Intron 1, Exon 2, Intron 2, Exon 3, and Intron 3. Exon 1 was directly joined to Exon 4 in the ABO transcript.
  
  
  
  Because the novel allele was associated with a well-described O allele, the absence of A-antigens in the inherited ABO subtype phenotype may be due to the identified mutation affecting the transmembrane-spanning domain of the encoded protein and impairing the transferase activity.
authors.affiliation: Department of Blood Group Serology and Transfusion Medicine, Medical University of Graz, Graz, Austria.
authors.forename: Eva M
authors.initials: EM
authors.lastname: Matzhold
authors.affiliation: Department of Blood Group Serology and Transfusion Medicine, Medical University of Graz, Graz, Austria.
authors.forename: Camilla
authors.initials: C
authors.lastname: Drexler
authors.affiliation: Department of Blood Group Serology and Transfusion Medicine, Medical University of Graz, Graz, Austria.
authors.forename: Thomas
authors.initials: T
authors.lastname: Wagner
mesh_terms: D000017:ABO Blood-Group System / Q000235:genetics*; D000483:Alleles; D001788:Blood Grouping and Crossmatching / Q000379:methods*; D005091:Exons; D005190:Family; D005260:Female; D006801:Humans; D009154:Mutation; D010641:Phenotype; D017384:Sequence Deletion; D044465:White People
chemical_list: D000017:ABO Blood-Group System