[Discovery and sequence analysis of a novel allele of A subtype]

To identify the genotypes of two probands with ambiguous blood serological typing and explore their serological feature and molecular basis.

Serology assays including absorption-elution test were carried out. With genomic DNA extracted from peripheral blood samples, exons 6 and 7 of the ABO gene were subjected to cloning and haplotype sequencing analyses.

Red blood cells from the probands showed no agglutination with monoclonal anti-A and anti-B, whilst their serum showed weak agglutination with A1 cells and moderate agglutination with B cells. Absorption-elution test failed in detecting A antigen on such cells. Direct cloning sequencing analysis indicated that they were heterozygous for an ABO*O01.01 allele and a novel A allele. The novel A allele contained c.467C>T (p.Pro156Leu) and insertion of a nucleotide C at position 963_964 in exon 7 (c.963_964insC) compared with ABO*A1.01.

Through serological and sequencing analysis, the two samples were identified as A subgroup due to novel A alleles.