RHD Gene Polymorphisms among RhD-Negative Chinese in Taiwan

Abstract

Background and Objective: The rare occurrence of anti-D-associated hemolytic disease of the newborn among Chinese is attributable in part to the existence of the weak D phenotype D_el among apparently RhD-negative individuals. While exciting advances in the molecular genetics of the Rh blood group have been noted in recent years, the genomic structure of the D_el phenotype has seldom been studied in the literature. We try to explore the genomic structure of the RhD gene among apparently Rh-negative Chinese in Taiwan in this study. Methods: Genomic DNA from 230 samples of apparently RhD-negative Chinese was studied using four polymerase chain reaction (PCR)-based RhD typing methods. These PCR methods amplified RHD and RHCE genes at exons 4, 5, 7 and 10. All nucleotides responsible for exofacial amino acid differences between RhD and RhCeEe peptides, including amino acids 169, 170, 172, 223, 226, 233, 238, 350, 353, and 354, were contained in these amplified DNA segments. Southern blot analysis using RHD cDNA fragments as probes was performed. Results: According to the serological study, 155 samples (67.4%) were genuinely RhD-negative and 75 samples (32.6%) were of the D_el phenotype. Successful amplifications for RHD sequences were possible in all 75 D_el samples using four PCR methods. Apparently, all D_el individuals carried an intact RHD gene. While 145 individuals of 155 genuinely Rh-negative (63.0% of apparently RhD-negative individuals) had total deletion of their RHD genes, 10 individuals (4.3% of apparently RhD-negative individuals) were shown to have a preserved 3′ noncoding region of the RHD exon 10 and a gross deletion of RHD exons 4–10. Conclusions: Three classes of RhD-negative polymorphisms among Chinese in Taiwan were observed. These included D_el with grossly intact RHD and weak RhD expression, genuinely RhD-negative with partial preservation of the RHD gene, and genuinely RhD-negative with total deletion of the RHD gene. A molecular study is warranted to clarify the mechanism responsible for the weak RHD gene expression in D_el individuals.

RHD positive haplotypes in D negative Europeans

“…4). We cannot exclude the possibility that some of the seven remaining alleles have been observed previously [18,19,20,21,22,24,25,26]. Because of the limited published data for those observations, we found more than one "compatible" allele in our study for each previous observation.…”

“…Apart from a probably lower absolute frequency, we detected in Europeans many parallels to oriental populations: Both populations shared the diverse nature of RHD haplotypes of the first group (probable RHD/CE hybrids) [18,19,20], the preferential occurrence of RHD positive antigen D negative alleles in Cde haplotypes [18], and the comparatively frequent observation of D el phenotypes [19]. In contrast, RHDψ and Cde s are predominant in African populations [14].…”

“…Two RHD positive antigen D negative alleles are frequent in Africans: RHDψ carries a 37 bp insertion at the intron 3/exon 4 boundary and also harbors a stop codon [14]; Cde s is a RHD-CE-D hybrid gene [15,16,17]. In Asians, a major allele may be associated with a G314V missense mutation [18], and several other alleles may represent RHD-CE-D hybrid alleles [18,19,20]. …”

Prospective Evaluation of a Transfusion Policy of RhD-Positive Red Blood Cells into DEL Patients in China

“…Molecular studies have shown that a heterogeneous array of variant RHD alleles can result in the DEL phenotype [10,18,19,20,21,22,23]. DEL derives from several mechanisms, including splice-site mutation, missense mutation, RHD-CE-D hybrid, frame shift mutation, and a long deletion of the RHD gene [14,24,25,26,27,28].…”

Rh and RHAG Blood Group Systems

“…Between 10 and 33% of Japanese, Chinese, and Korean red cell samples shown to be D − by conventional serological techniques were found to be DEL [116,134,135,258] . Between 10 and 33% of Japanese, Chinese, and Korean red cell samples shown to be D − by conventional serological techniques were found to be DEL [116,134,135,258] .…”