title: Molecular genetic analysis for the B subgroup revealing two novel alleles in the ABO gene.
abstract: BACKGROUND
  B(x) is a very rare ABO blood group phenotype and the molecular mechanism underlying it still remains largely unknown. This study reports two novel B(x) alleles in two Chinese individuals.
  
  
  METHODS
  Serologic investigations including serum transferase activity assay were performed with standard methods. DNA sequences of all seven exons and exon-intron boundaries of ABO gene were analyzed using genomic DNA by polymerase chain reaction and direct DNA sequencing or sequencing after gene cloning.
  
  
  RESULTS
  B(x) phenotypes were diagnosed in these two individuals. DNA analysis revealed that the ABO gene of the two B(x) individuals was heterozygous of O01/B alleles. Two novel heterozygous mutations 905A>G and 541T>C were identified, respectively, which resulted in the amino acid changes D302G and W181R in the B glycosyltransferases. The mutations were not found in 120 randomly selected samples.
  
  
  CONCLUSIONS
  Amino acid substitutions resulted from novel mutations 905A>G and 541T>C on ABO gene change highly conserved regions of the enzyme and may reduce the activity of the glycosyltransferases, leading to the B(x) phenotype.
authors.affiliation: Blood Group Reference Laboratory, Shanghai Institute of Blood Transfusion, Shanghai Blood Center, Shanghai, China.
authors.forename: Xiao-Hong
authors.initials: XH
authors.lastname: Cai
authors.forename: Sha
authors.initials: S
authors.lastname: Jin
authors.forename: Xi
authors.initials: X
authors.lastname: Liu
authors.forename: Wei
authors.initials: W
authors.lastname: Shen
authors.forename: Qiong
authors.initials: Q
authors.lastname: Lu
authors.forename: Jian-Lian
authors.initials: JL
authors.lastname: Wang
authors.forename: Liang-Feng
authors.initials: LF
authors.lastname: Fan
authors.forename: Ji-Li
authors.initials: JL
authors.lastname: Sun
authors.forename: Da-Zhuang
authors.initials: DZ
authors.lastname: Liu
authors.forename: Dong
authors.initials: D
authors.lastname: Xiang
mesh_terms: D000017:ABO Blood-Group System / Q000235:genetics*; D000483:Alleles; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D002681:China; D017124:Conserved Sequence; D005260:Female; D005700:Galactosyltransferases / Q000737:chemistry / Q000235:genetics*; D006801:Humans; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D010641:Phenotype; D017354:Point Mutation; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
chemical_list: D000017:ABO Blood-Group System; D005700:Galactosyltransferases; C023155:blood-group-substance alpha-D-galactosyltransferase