title: [Molecular mechanism of an individual with weaken B phenotype in ABO blood group].
abstract: OBJECTIVE
  To elucidate the serological characteristics and molecular mechanism of a blood donor with weaken B antigen.
  
  
  METHODS
  The ABO blood group antigens on red blood cells were identified by monoclonal antibodies, the ABO antibodies in serum were detected by standard A, B, O cells and the activity of the B glycosyltransferase was analyzed. The full-length sequence and 5'-untranslated region (5'-UTR) sequence of ABO gene were amplified by polymerase chain reaction (PCR) respectively and direct sequencing. The alternative splicing isoforms of ABO cDNA were obtained by reverse transcription-PCR(RT-PCR) and analyzed with cloning and sequencing techniques. The level of methylation of the CpG island in ABO gene promoter was analyzed by bisulfite sequencing method.
  
  
  RESULTS
  The serological characteristic of the donor showed that the B antigen was decreased obviously without anti-B antibodies in serum and the B glycosyltransferase activity was decreased as well. The genotype of the donor was B101/O01 without any other mutations in the full-length coding sequences and splice receptor sites. The nucleotide characteristics of the 5'-UTR was consistent with B101/O01 and no any abnormity was identified in the promoter, enhancer and the negative regulatory sequence regions. The integrative cDNA transcript of ABO gene was obtained and no new splicing isoform was found. Compared with the normal B phenotype, a number of methylated CpG sites were found near the promoter of ABO gene in this sample.
  
  
  CONCLUSIONS
  The methylation in the CpG island of ABO gene promoter region may cause weak expression of the B antigen.
authors.affiliation: Key Laboratory of Blood Safety Research, Ministry of Health, Institute of Transfusion Medicine, Blood Center of Zhejiang Province, Hangzhou, Zhejiang 310006, P. R. China.
authors.forename: Yan-ling
authors.initials: YL
authors.lastname: Ying
authors.forename: Su-dan
authors.initials: SD
authors.lastname: Tao
authors.forename: Yan-min
authors.initials: YM
authors.lastname: He
authors.forename: Xian-guo
authors.initials: XG
authors.lastname: Xu
authors.forename: Fa-ming
authors.initials: FM
authors.lastname: Zhu
authors.forename: Hang-jun
authors.initials: HJ
authors.lastname: Lv
authors.forename: Li-xing
authors.initials: LX
authors.lastname: Yan
mesh_terms: D000017:ABO Blood-Group System / Q000235:genetics* / Q000276:immunology; D000483:Alleles; D000911:Antibodies, Monoclonal / Q000276:immunology; D001782:Blood Donors; D018899:CpG Islands / Q000235:genetics; D004912:Erythrocytes / Q000276:immunology; D005786:Gene Expression Regulation / Q000276:immunology; D006801:Humans; D010641:Phenotype; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D000017:ABO Blood-Group System; D000911:Antibodies, Monoclonal