A historical overview of advances in molecular genetic/genomic studies of the ABO blood group system

Novel missense mutation c.797T>C (p.Met266Thr) gives rise to the rare B(A) phenotype in a Chinese family

BACKGROUND AND OBJECTIVES

B(A) phenotype is usually formed by nucleotide mutations in the ABO*B.01 allele, with their products exhibiting glycosyltransferases (GTs) A and B overlapping functionality. We herein report a B(A) allele found in a Chinese family.

MATERIALS AND METHODS

The entire ABO genes of the probands, including flanking regulatory regions, were sequenced through PacBio third-generation long-read single-molecule real-time sequencing. 3D molecular models of the wild-type and mutant GTB were generated using the DynaMut web server. The effect of the mutation on the enzyme function was predicted by PROVEAN and PolyPhen2. The predictions of stability changes were performed using DynaMut and SNPeffect.

RESULTS

Based on serological and sequencing features, we concluded the two probands as possible cases of the B(A) phenotype. Crystallization analysis showed that Thr266 substitution does not disrupt the hydrogen bonds. However, some changes in interatomic contacts, such as loss of ionic interactions and hydrophobic contacts, and addition of weak hydrogen bonds, may have affected protein stability to some extent. This mutation was predicted to have a benign effect on enzyme function and slightly reduce protein stability.

CONCLUSION

The probands had the same novel B(A) allele with a c.797T>C (p.Met266Thr) mutation on the ABO*B.01 backbone.

Serological and molecular analysis of the B(A) subtype in China-A systematic review

OBJECTIVE

To study the serological and molecular biological characteristics of the B(A) subtype and its geographical distribution in China through case discussion and systematic review.

METHODS

A case of the B(A)02 subtype previously found in our laboratory was retrospectively analysed. The distribution characteristics and specific serological and genotypic characteristics of the B(A) subtype in China were systematically evaluated by searching four major Chinese databases.

RESULTS

In a previous case of an abnormal blood group, both the proband and her father were found to be genotype B(A)02/O02, while the mother was normal type B. After a systematic search, irrelevant studies were screened out, and 88 studies were included for analysis. The results showed that the B(A)04 subtype was significantly more frequently reported in the north than in the south, while the B(A)02 subtype was predominant in the southwest. The A antigen of the B(A)02 subtype reacts with monoclonal anti-A reagents in a wide range, while the A antigen of the B(A)04 subtype has a weak agglutination intensity of less than or equal to 2+.

CONCLUSION

The results showed that the B(A) subtype has specific characteristics in the Chinese population, and this study further enriched the serological and molecular biological characteristics of the B(A) subtype.