Identification of a Novel Mutation in B Allele in a Chinese Individual.

Background: There are 49 B alleles in the ISBT ABO blood group list. This study will describe a new missense mutation, c.784G>T, in exon 7 of the ABO in a Chinese individual.

Methods: A weak B was analyzed by serologic techniques. Exons 6 and 7 were sequenced directly through polymerase chain reaction-based typing (PCR-SBT). Subsequently, the heterozygous mutation sites in exon 7 were determined through cloning and sequencing. The mutated GTB proteins were expressed in HEK293F cells after being subcloned into a pCAG vector with a Strep-tag. The potential impact of the mutations on GTB stability was predicted using mCSM software, while UCSF Chimera X software was utilized for visualization of the mutation.

Results: The ABO blood typing of serologic characteristics showed weak B phenotype, and the heterozygous site ABO*B.01 (c.784G>T) in Exon 7 was identified by PCR-SBT analysis after TA cloning, which led to an alteration of Asp to Tyr at residue 262 in B glycosyltransferase. Like the ABO*BW.17 (D262Y), D262N also significantly de-creased ABO*B.01 expression and lead to GTB destabilizing.

Conclusions: The novel B allele with 784G>T caused an alteration of Asp to Tyr at residue 262 in B glycosyltransferase, affecting the expression of GTB protein and influencing GTB structural instability.