EVIDENCE OF GENETIC DIVERSITY UNDERLYING RH-D-, WEAK-D (D-U), AND PARTIAL-D PHENOTYPES AS DETERMINED BY MULTIPLEX POLYMERASE CHAIN-REACTIONANALYSIS OF THE RHD GENE
Nd. Avent et al., EVIDENCE OF GENETIC DIVERSITY UNDERLYING RH-D-, WEAK-D (D-U), AND PARTIAL-D PHENOTYPES AS DETERMINED BY MULTIPLEX POLYMERASE CHAIN-REACTIONANALYSIS OF THE RHD GENE, Blood, 89(7), 1997, pp. 2568-2577
The human blood group Ph antigens are expressed by proteins encoded by
a pair of highly homologous genes located at chromosome 1p34-36. One
of the genes (RHCE) encodes ph CcEe antigens, while the other (RHD) th
e 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 RH
CE and RHD genes and have defined the site of an RHD-specific deletion
located in this intron. Using a multiplex RHD typing assay, which com
bines a reverse polymerase chain reaction (PCR) primer, which straddle
s this RHH-specific sequence, and a pair of primers located in exon 10
of the RHD gene, we have analyzed 357 different genomic DNA samples d
erived from individuals expressing D+, D-, weak D, and partial D pheno
types. Of these, we have noted a significant discordance with our mult
iplex 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 fu
ll-length RHD transcripts, which have a point mutation at nucleotide 1
21 (C --> T), which generates an in-frame stop codon (Gln41Stop). Thus
, we describe a different molecular basis for generating the D- phenot
ype to the complete RHD gene deletion described previously, We also sh
ow that there are discordances with serotype and the multiplex assay i
n weak D and partial D phenotypes, indicating that the underlying mole
cular basis can be heterogeneous. Existing ph D PCR assays assume the
complete absence of the RHD gene in D- phenotypes. We describe a diffe
rent molecular basis for generating the D- phenotype to the complete R
HD gene deletion described previously. (C) 1997 by The American Societ
y of Hematology.