[Indentification and Sequence Analysis of A Individual with B305 Blood Group Gene Subtypes of ABO Variant]

To investigate and identify the molecular and biological characteristics of B305 blood group gene subtypes of a ABO variant.

The individual was confirmed by standard serological techniques. The genotyping and sequencing were performed by using polymerase chain reaction-sequence specific primer (PCR-SSP), direct sequencing and gene cloning for Exon 6 and exon 7 of ABO locus respectively.

B antigen was detected on red blood cells of the proband and there was anti-A antibody in the serum. The PCR-SSP result showed BO1 phenotype. DNA sequencing showed 261delG, 297A/G, 425T/C, 526C/G, 657C/T, 703A/G, 796C/A, 803G/C and 930G/A heterozygote in exon 6 to exon 7. After cloning and sequencing, 2 alleles B305 and O01 were obtained. The sequence of B305 allele had one nucleotide mutation (T to C) at position 425 compared with that of B101 allele, resulting in an amino acid substitution (M142T).

T>C at nt425 of α-1,3 galactosyltransferase gene can result in B305 blood group gene subtypes, which reduce the expression of B antigen.