Blood, 15 January 2003, Vol. 101, No. 2, pp. 752-757
RED CELLS
Scianna antigens including Rd are expressed by ERMAP
Franz F. Wagner,
Joyce Poole, and
Willy A. Flegel
From the Department of Transfusion Medicine, University
of Ulm, DRK (German Red Cross)-Blood Donation Service
Baden-Württemberg-Hessen, Institute Ulm, Germany;
and International Blood Group Reference Laboratory, Bristol,
United Kingdom.
The Scianna blood group encompasses the high-frequency
antigens Sc1 and Sc3 and the low-frequency antigen Sc2. Another
low-frequency antigen Rd (Radin) was suggested to belong to the Scianna
blood group. The molecular basis of the Scianna blood group was
unknown. The erythrocyte membrane-associated protein (ERMAP) shared the genomic location, protein product size, and localization to the red
blood cell (RBC) membrane surface with Scianna. The
ERMAP gene was sequenced in probands with known
Scianna and Radin phenotypes. In a Sc:-1,-2 proband, only an
ERMAP allele with a 2-bp deletion in exon 3 causing a
frameshift could be detected. A Sc:-1,2 proband was homozygous for the
ERMAP(Gly57Arg) allele. An Rd+
proband was heterozygous for the ERMAP(Pro60Ala) allele.
Polymerase chain reaction with sequence-specific priming (PCR-SSP)
systems was developed to detect the Sc2 and Rd alleles of the
ERMAP gene. The 2 alleles occurred with about 1% and less
than 1% frequency in the population, which was compatible with the
frequency of the Sc2 and Rd antigens known in whites. Two
Sc2+ and one Rd+ samples that were found by
genotyping were confirmed by serology. The antigens of the Scianna
blood group include Rd and are expressed by the human ERMAP protein.
Sc2 is caused by an ERMAP(Gly57Arg) allele and Rd by
an ERMAP(Pro60Ala) allele. Scianna is the last of
the previously characterized protein-based blood group systems whose
molecular basis was discerned. Hence, the phenotype prediction by
genotyping became possible for all human blood group systems encoded by proteins.
