The novel c.634+4A>G splicing variant in RHCE results in weak C and e antigen expression in a pregnant woman originated from Japan.

BACKGROUND: In the RH blood group genes, molecular variants that alter antigen expression with potential clinical relevance are frequently identified and reported in the literature. STUDY DESIGN AND METHODS: A pregnant woman in her first pregnancy, who originates from Japan, was typed by routine serological testing. The RHCE gene was investigated to identify single nucleotide variants (SNVs) and/or structural variants by a commercial platform, Sanger sequencing, and quantitative multiplex PCR of short fluorescent fragments. The haplotypes were determined by sequencing PCR fragments generated from genomic DNA and subcloned into a plasmid vector. Effect on splicing was predicted by bioinformatics tools, including SpliceAI and the splicing module of Alamut. In parallel, functional analysis was carried out by a minigene splicing assay. RESULTS: A patient with no transfusion history was typed RH:1,2w,3,4,5w. An unreported single variant was identified in RHCE intron 4 at the heterozygous state: c.634+4A>G. Minigene splicing assay showed that this SNV decreases significantly the relative abundance of the full-length transcript, in accordance with the predictions made by the Alamut tools, but not SpliceAI, suggesting expression of a normal RhCE protein. CONCLUSION: Overall, the novel RHCE*02(c.634+4A>G) allele alters quantitatively, but not qualitatively, the expression of C and e in the RH blood group system, indicating that the patient is not at risk for alloimmunization and may safely receive C+e+ red blood cell units. This report illustrates the relevance of functional assays for the interpretation of rare variants and, specifically, how it may help guide transfusion management in patients.

Variant screening of the RHD gene in a large cohort of subjects with D phenotype ambiguity: report of 17 novel rare alleles.

BACKGROUND: A considerable number of RHD alleles responsible for weak and partial D phenotypes have been identified over the past decade. Two particular concerns, namely, 1) that red blood cells of these phenotypes may cause anti-D immunization when transfused to D- recipients and 2) that serologic determination of these phenotypes is often doubtful, make genetic analysis of the RHD gene highly desirable. STUDY DESIGN AND METHODS: Blood samples that displayed D phenotype ambiguity (as determined by serologic analyses) were collected from several sites of the Etablissement Français du Sang and subjected to RHD variant screening by means of a previously established denaturing high-performance liquid chromatography method followed by direct sequencing. RESULTS: Systematic screening of the RHD coding sequences as well as the exon-intron boundaries identified DNA variants in 755 of the 806 samples analyzed. In particular, this resulted in the identification of 10 novel single-nucleotide substitutions and seven novel complex alleles. CONCLUSION: This study further increased the already large repertoire of RHD allelic variants. Whereas most of the newly found variants are putative weak or partial D alleles, most of the complex alleles are readily understandable in the present phylogenetic model of RHD.

Identification of 12 novel RHD alleles in western France by denaturing high-performance liquid chromatography analysis.

BACKGROUND: Unlike the standard RHD+ or RHD- alleles, serologic determination of weak or partial D alleles is often not clear-cut. Most importantly, rare weak D alleles, not typed by serology, are prone to alloimmunization when transfused with D+ blood. Although more than 100 RHD variants have currently been reported, many more rare alleles probably remain to be identified. STUDY DESIGN AND METHODS: To identify novel unusual RHD alleles, genomic DNA samples were collected from 333 blood donors or recipients in western France. All displayed ambiguity for D phenotype as determined by routinely used serologic reagents and analyzed by means of denaturing high-performance liquid chromatography (DHPLC) analysis in parallel with direct sequencing. RESULTS: For the first time it has been established that a reliable DHPLC-based approach potentiates the rapid screening of the entire RHD gene-coding sequence. In so doing, a total of 12 novel RHD alleles were identified. Except for the null allele that is in trans with a Weak D type 4 allele, the predicted effects of the other new alleles on gene expression correlated well with the discrepant routine D phenotype results. In particular, the carrier of the p.Leu214Phe missense mutation developed alloanti-D antibodies after transfusion of D+ blood. CONCLUSION: The identification of 12 novel RHD alleles represents a significant addition to the known repertoire of unusual RHD variants and, at the same time, serves to deepen our understanding of the molecular basis of weak and partial D. The accurate molecular typing of RHD alleles would allow to reduce the alloimmunization risk.