The JR blood group system: identification of alleles that alter expression.

Background: The ABCG2 gene encodes antigens of the JR blood group system. Red blood cells (RBCs) from individuals homozygous for ABCG2 null alleles are nonreactive with polyclonal and monoclonal anti-Jr(a) . However, some RBCs have been defined as Jr(a+(W) /-) or Jr(a-), particularly when tested with polyclonal anti-Jr(a) . In an effort to resolve these apparent serologic ambiguities, the current study was undertaken.
Study Design and Methods: Hemagglutination of RBCs from two individuals known to express a single copy of functional ABCG2 were compared to RBCs from eight unrelated, previously characterized, Jr(a+(W) /-) donors. Standard polymerase chain reaction-based methods were used to characterize ABCG2 alleles.
Results: Two monoclonal anti-Jr(a) clones agglutinated RBCs from the eight Jr(a+(W) /-) study subjects. Two of these subjects were homozygous for a missense ABCG2 change (c.1858A; Asp620Asn). Two were heterozygous for two missense changes; one was c.1858G>A and c.421C>A (Asp620Asn; Gln141Lys), and the other was c.1714A>C and c.421C>A (Ser572Arg; Gln141Lys). The remaining four subjects were heterozygous for c.421C>A (Gln141Lys), and for one of four null alleles.
Conclusions: We have identified three ABCG2 alleles that are newly associated with weakened Jr(a) expression. One of these is novel, the missense allele c.1714A>C (Ser572Arg) and two that have been previously described c.421C>A (rs2231142; Gln141Lys) and c.1858G>A (rs34783571; Asp620Asn). In addition, we found a novel, presumed null allele, c.1017_1019delCTC (Ser340del).
(© 2013 American Association of Blood Banks.)