Novel polymorphisms in exons 6 and 7 of A/B alleles detected by polymerase chain reaction-single strand conformation polymorphism

Background and Objectives The ABO blood group system is the most important blood group system in transfusion medicine. In addition to the major A, B and O alleles, many rare alleles have been defined. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and analysis by PCR sequence specific primers (SSP) are commonly conducted for genotyping but have the limitation of being unable to detect unknown substitution(s) in amplified DNA fragments, whereas PCR-single strand conformation polymorphism (SSCP) can be used for both. Materials and Methods Three-hundred unrelated blood donors of the AB phenotype were enrolled. Four pairs of primers were designed to constitute two sets of multiplex PCRs: this amplifies four fragments spanning the entire exon 6 and its immediate flanking regions, nucleotides 432-1065, as well as the 3' untranslated region of exon 7 of the ABO gene. The SSCP electrophoresis was carried out on a 12.5% polyacrylamide gel in a GenePhor electrophoresis unit. For those with unexpected banding patterns, SSCP analyses were performed in duplicate and samples were cloned and sequenced for exons 6 and 7. Results Seven samples were noted to have six variant alleles, of which five have not been previously reported in the literature. Of these five novel variants, four were derived from the B allele, while the other derived from the A allele. Conclusions By using PCR-SSCP, five novel A/B alleles were found.