The low prevalence Rh antigen Be(a) (Rh36) is associated with RHCE*ce 662C>G in exon 5, which is predicted to encode Rhce 221Arg.
OBJECTIVE
The low prevalence antigen, Be(a), is produced by a complex that also produces weak c, e and f (ce). We report here the molecular basis associated with Be(a) antigen expression.


METHODS
Peripheral blood samples from four Be(a+) probands were tested. Haemagglutination, gDNA extraction, PCR-based assays, reticulocyte RNA isolation, Rh-cDNA analyses, and sequencing were performed by standard procedures.


RESULTS
RBCs from Probands 1 and 3 were D-C-E-c+e+, and from Probands 2 and 4 were D+C+E-c+(W)e+. In proband 1, cDNA sequencing of RHCE revealed heterozygosity of nucleotide (nt) 662C/G in exon 5 of RHCE*ce. No other nucleotide changes were observed. As the 662C>G nucleotide change ablates a MscI restriction enzyme cleavage site, PCR-RFLP analysis was performed and the RHCE*ce nt 662C/G heterozygosity was detected on gDNA from the four probands and two children from both Proband 3 and Proband 4.


CONCLUSIONS
The low prevalence Rh antigen, Be(a), is associated with a single nucleotide change in exon 5 of RHCE*ce; that of 662C>G and this change is predicted to alter proline at amino acid position 221 of Rhce to arginine. The fundamental differences in the properties of these two amino acids may impose a steric and/or charge-related effect on the protein, and thereby provide an explanation for the weakened expression of c, e and f (ce) antigens in the Be(a) phenotype.
Hue-Roye
K
K
New York Blood Center, 310 East 67th Street, New York, NY 10065, USA.
O'Shea
K
K
Gillett
R
R
Wadsworth
L D
LD
Hume
H
H
Barnes
J
J
Kinney
J
J
Hodgins
K
K
Fuchisawa
A
A
Lomas-Francis
C
C
Reid
M
M
D000328:Adult; D000483:Alleles; D019943:Amino Acid Substitution; D018076:DNA, Complementary / Q000235:genetics; D004899:Erythroblastosis, Fetal / Q000235:genetics*; D005091:Exons / Q000235:genetics*; D005260:Female; D005838:Genotype; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D020641:Polymorphism, Single Nucleotide; D011247:Pregnancy; D012204:Rh-Hr Blood-Group System / Q000235:genetics*; D017422:Sequence Analysis, DNA
D018076:DNA, Complementary; C066468:RHCE protein, human; D012204:Rh-Hr Blood-Group System