A D(V)-like phenotype is obliterated by A226P in the partial D DBS.
BACKGROUND
In D category V types, the RHD exon 5 or parts thereof are replaced by the corresponding RHCE DNA segments. In D category V types I and II, the amino acid at position 226 is alanine, which is typical of the prevalent RHD allele and is observed in all RHCE alleles encoding the antigen e. A proline at position 226 in RHCE encodes the antigen E.


METHODS
A blood sample of ccDEe phenotype was referred as suspected D category VI. The RHD nucleotide sequence and the D epitope pattern were determined.


RESULTS
A new partial D, DBS, encoded by an RHD-RHcE(5)-RHD hybrid allele, was found. Although it differed from D(Va) type II by an A226P substitution only, it lacked epitopes epD4, epD12, epD17, epD18, and epD22 that were present in D(Va). The 5' breakpoint region was located between the deletion in RHD intron 4 and the first polymorphic nucleotide of DBS exon 5.


CONCLUSIONS
The phenotypes of RHD alleles with gene conversions limited to exon 5 depended critically on the amino acid at position 226. If alanine was present at this position, gene conversions involving E233Q led to a D(Va)-like phenotype. If proline was present, many additional epitopes were lost, and the phenotype became reminiscent of DFR. The 5' breakpoint region is shared by 10 alleles and may represent the most active "hot spot" for gene conversions known in RH.
Wagner
F F
FF
Department of Transfusion Medicine, the Ulm University Clinic, Germay.
Ernst
M
M
Sonneborn
H H
HH
Flegel
W A
WA
D000328:Adult; D000483:Alleles; D019943:Amino Acid Substitution; D001483:Base Sequence; D000939:Epitopes / Q000235:genetics / Q000276:immunology; D005091:Exons; D005260:Female; D005785:Gene Conversion; D006023:Glycoproteins / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D010641:Phenotype; D011247:Pregnancy; D012204:Rh-Hr Blood-Group System / Q000235:genetics*; D017422:Sequence Analysis, DNA
D000939:Epitopes; D006023:Glycoproteins; C066468:RHCE protein, human; D012204:Rh-Hr Blood-Group System; C026410:Rho(D) antigen