Blood, Vol. 95 No. 1 (January 1), 2000:
pp. 12-18
PLENARY PAPER
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
Belinda K. Singleton,
Carole A. Green,
Neil D. Avent,
Peter G. Martin,
Elizabeth Smart,
Abigail Daka,
Edwin G. Narter-Olaga,
Linda M. Hawthorne, and
Geoff Daniels
From the Bristol Institute for Transfusion Sciences, Bristol,
England; the International Blood Group Reference Laboratory, Bristol,
England; the Natal Blood Transfusion Service, Pinetown, South Africa;
the Blood Transfusion Service, Harare, Zimbabwe; the National Blood
Transfusion Service, Accra, Ghana; and the Louisiana State University
Medical Center, Shreveport, LA.
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 of
RHD. 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 
) in Rh
D-negative Africans. RHD 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. RHD contains another stop codon in exon 6. The frequency of
RHD in black South Africans is approximately 0.0714. Of 82 D-negative black Africans, 66% had
RHD, 15% had the RHD-CE-D hybrid gene associated
with the VS+ V- phenotype, and only 18% completely lacked
RHD. RHD 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 RHD, 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 RHD. (Blood. 2000; 95:12-18)
