Molecular genetic analysis for the B subgroup revealing two novel alleles in the ABO gene.
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.
Cai
Xiao-Hong
XH
Blood Group Reference Laboratory, Shanghai Institute of Blood Transfusion, Shanghai Blood Center, Shanghai, China.
Jin
Sha
S
Liu
Xi
X
Shen
Wei
W
Lu
Qiong
Q
Wang
Jian-Lian
JL
Fan
Liang-Feng
LF
Sun
Ji-Li
JL
Liu
Da-Zhuang
DZ
Xiang
Dong
D
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
D000017:ABO Blood-Group System; D005700:Galactosyltransferases; C023155:blood-group-substance alpha-D-galactosyltransferase