Weak D phenotypes caused by intronic mutations in the RHD gene: four novel weak D alleles identified in the Chinese population

Abstract

Although more than 80 weak D types have been reported, many rare alleles probably remain unidentified. However, direct evidence that associates intronic mutations in the RHD gene with weak D types is lacking. Blood samples were obtained from Shanghai Blood Center. D- samples typed in routine laboratories were tested using a monoclonal immunoglobulin M reagent, an indirect antiglobulin test, and a commercial panel of monoclonal anti-D (Diagast D-Screen). RHD nucleotide sequencing that included adjacent flanking intron regions was performed. The RHD zygosity was determined. Bioinformatics analysis was performed. Four different RHD alleles were identified among six blood samples, namely, RHD IVS3+3G>C, RHD IVS6-14del3, RHD IVS4+5G>A, and RHD IVS4+5G>T. The serologic tests were consistent with weak D phenotypes. The bioinformatics results indirectly suggest that these sequence changes affect splicing. This study is the first to describe weak D types caused by intronic variations near the splice sites in the RHD gene, which is supported by the genotyping results combined with serologic profiles and bioinformatics analysis. The identification of the four novel RHD alleles represents a new significant addition to the molecular bases that underlie weak D, which would deepen our understanding of the mechanism of the low expression of the RhD antigen. These nucleotide changes are predicted to have regulatory effects on RHD splicing.