Evidence of genetic diversity underlying Rh D-, weak D (Du), and partial D phenotypes as determined by multiplex polymerase chain reaction analysis of the RHD gene.
The human blood group Rh antigens are expressed by proteins encoded by a pair of highly homologous genes located at chromosome 1p34-36. One of the genes (RHCE) encodes Rh CcEe antigens, while the other (RHD) the D antigen. Point mutations in the RHCE gene generate the C/c and E/e polymorphisms, while it has been shown that an RHD gene deletion can generate the D-negative phenotype. We have analyzed intron 4 of the RHCE and RHD genes and have defined the site of an RHD-specific deletion located in this intron. Using a multiplex RHD typing assay, which combines a reverse polymerase chain reaction (PCR) primer, which straddles this RHD-specific sequence, and a pair of primers located in exon 10 of the RHD gene, we have analyzed 357 different genomic DNA samples derived from individuals expressing D+, D-, weak D, and partial D phenotypes. Of these, we have noted a significant discordance with our multiplex PCR assay in the D- phenotypes dCcee and dccEe (which have been previously described) and weak D phenotypes. Our results suggest that in five serologically D- individuals we have identified an apparently intact RHD gene. Sequence analysis of transcripts obtained from one of these individuals (of phenotype dCCee) illustrates the presence of full-length RHD transcripts, which have a point mutation at nucleotide 121 (C --> T), which generates an in-frame stop codon (Gln41Stop). Thus, we describe a different molecular basis for generating the D- phenotype to the complete RHD gene deletion described previously. We also show that there are discordances with serotype and the multiplex assay in weak D and partial D phenotypes, indicating that the underlying molecular basis can be heterogeneous. Existing Rh D PCR assays assume the complete absence of the RHD gene in D- phenotypes. We describe a different molecular basis for generating the D- phenotype to the complete RHD gene deletion described previously.
Avent
N D
ND
International Blood Group Reference Laboratory, Southmead, Bristol, UK.
Martin
P G
PG
Armstrong-Fisher
S S
SS
Liu
W
W
Finning
K M
KM
Maddocks
D
D
Urbaniak
S J
SJ
D000595:Amino Acid Sequence; D001483:Base Sequence; D002872:Chromosome Deletion; D002878:Chromosomes, Human, Pair 1 / Q000235:genetics; D003001:Cloning, Molecular; D005796:Genes; D014644:Genetic Variation; D006801:Humans; D007438:Introns / Q000235:genetics; D008969:Molecular Sequence Data; D010641:Phenotype; D017354:Point Mutation; D016133:Polymerase Chain Reaction / Q000379:methods*; D012204:Rh-Hr Blood-Group System / Q000235:genetics*; D013728:Terminator Regions, Genetic
D012204:Rh-Hr Blood-Group System; C026410:Rho(D) antigen