Deletion of arginine codon 229 in the Rhce gene alters e and f but not c antigen expression.
BACKGROUND
Rh CcEe antigens occur as ce, Ce, cE, or CE alleles in the RBC membrane. Their epitope structures and the location of their cis interacting products remain to be defined.


METHODS
A rare blood sample from a white male whose parents are first cousins was identified. Hemagglutination was performed using standard methods. RH structure and genotype was assessed by Southern blots. Rh transcripts were obtained by gene-specific RT-PCR and sequenced. The mutation was verified by genomic PCR assays.


RESULTS
The donor's RBCs typed D+C-c+E-e-f(Rh6)- with a normal c dose, suggesting the Dc- phenotype. Further tests revealed a weak and qualitatively altered e expression. Southern blots indicated a genotype of Dce/dce without other gross changes. RT-PCR detected a triplet deletion (Delta685AGA687) in the Rhce gene that specifies codon 229 for arginine (Arg229). Sequencing of the region around the mutated exon 5 confirmed the donor to be homozygous for the AGA deletion.


CONCLUSIONS
Arg229 is invariant on external loop 4 and close to the Ala226Pro change specific for e/E polymorphism. The qualitative and quantitative alteration of e antigen defines Arg229 as a crucial component for e/E epitope presentation. Given a normal dose of c antigen, the disruption of f (Rh6) by Arg229 deletion suggests that external loop 4 is a major structural element contributing to the expression of RHCE cis interacting antigenic products.
Biochemistry and Molecular Genetics Laboratory and the Immunohematology Laboratory, New York Blood Center, 310 East 67th Street, New York, NY 10021, USA.
Y X
YX
Chen
J
J
Peng
M
M
Novaretti
M E
ME
Reid
C-H
CH
Huang
D000595:Amino Acid Sequence; D001120:Arginine / Q000235:genetics; D001483:Base Sequence; D001798:Blood Proteins / Q000235:genetics*; D000939:Epitopes / Q000235:genetics; D005192:Family Health; D005838:Genotype; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D010641:Phenotype; D017354:Point Mutation; D011110:Polymorphism, Genetic; D012333:RNA, Messenger; D015183:Restriction Mapping; D012204:Rh-Hr Blood-Group System / Q000235:genetics*
D001798:Blood Proteins; D000939:Epitopes; D008565:Membrane Proteins; C066468:RHCE protein, human; D012333:RNA, Messenger; D012204:Rh-Hr Blood-Group System; D001120:Arginine