The presence of an RHD pseudogene containing a 37 base pair duplication and a nonsense mutation in Africans with the Rh D-negative blood group phenotype

Abstract

Antigens of the Rh blood group system are encoded by 2 homologous genes, RHD and RHCE, that produce 2 red cell membrane proteins. The D-negative phenotype is considered to result, almost invariably, from homozygosity for a complete deletion ofRHD. The basis of all PCR tests for predicting fetal D phenotype from DNA obtained from amniocytes or maternal plasma is detection of the presence of RHD. These tests are used in order to ascertain the risk of hemolytic disease of the newborn. We have identified an RHD pseudogene (RHD ψ) in Rh D-negative Africans. RHDψ contains a 37 base pair (bp) insert in exon 4, which may introduce a stop codon at position 210. The insert is a sequence duplication across the boundary of intron 3 and exon 4.RHDψ contains another stop codon in exon 6. The frequency ofRHDψ in black South Africans is approximately 0.0714. Of 82 D-negative black Africans, 66% hadRHDψ, 15% had the RHD-CE-D hybrid gene associated with the VS+ V– phenotype, and only 18% completely lackedRHD. RHDψ is present in about 24% of D-negative African Americans and 17% of D-negative South Africans of mixed race. No RHD transcript could be detected in D-negative individuals with RHDψ, probably as a result of nonsense-mediated mRNA decay. Existing PCR-based methods for predicting D phenotype from DNA are not suitable for testing Africans or any population containing a substantial proportion of people with African ethnicity. Consequently, we have developed a new test that detects the 37 bp insert in exon 4 of RHDψ. (Blood. 2000; 95:12-18)

Molecular basis for D− Japanese: identification of novel DEL and D− alleles

“… This allele has been reported to be common in Africans , while no information concerning the family and ancestors of the donor (sample no. 3305) could be available. …”

A comprehensive survey of both RHD and RHCE allele frequencies in sub‐Saharan Africa

“…The high incidence of some aberrant RHD or RHCE alleles in African black persons has been deduced from clinical experience and screening for certain variant RH alleles . However, a survey of both genes has never been performed in sub‐Saharan populations.…”

A convenient qualitative and quantitative method to investigate RHD‐RHCE hybrid genes

“…Because the test developed by Haer‐Wigman and colleagues was not designed to identify this 4‐bp insertion, the two RHD Ψ alleles could not be discriminated by their approach but may coexist in their cohort. Considering their findings and ours, we hypothesize that there may exist only one RHD Ψ allele that is characterized, in addition to the well‐known nucleotide changes (http://www.uni-ulm.de/~fwagner/RH/RB2/RHDRHDpsi.htm), by the c.1074‐214_1074‐213insACAG insertion in Intron 7 and a RHCE‐D (9) ‐CE hybrid gene in cis. To validate this assumption, additional molecular studies both at the genomic DNA and at the messenger RNA levels including several dozens of RHD Ψ DNA samples will be required.…”

“…To exhaustively complete the process of validating a routine genotyping strategy by testing the main alleles that are likely to be found, six compound heterozygous samples carrying one D − allele, such as RHD Ψ (n = 4) and (C)ce s (Type 1 or 2; n = 2), were subjected to the analyses (http://onlinelibrary.wiley.com/doi/10.1111/trf.12179/suppinfo, available as supporting information in the online version of this paper). An interesting feature is that Exon 8 marker derived from either the RHD or the RHCE gene (http://onlinelibrary.wiley.com/doi/10.1111/trf.12179/suppinfo), which illustrates gene conversion of this exon between the two genes in several alleles that remain to be precisely defined by haplotype studies.…”