Jra (ISBT 901005) is a high-prevalence antigen unassigned to a blood group system. People lacking this antigen have been found in all populations studied but most commonly in Asians. Two recent reports established that ABCG2-null alleles encode the Jr(a–) phenotype and these studies provided the impetus to study other Jr(a−) individuals.Study Design and Methods
Blood samples were part of our rare donor-patient collection. DNA was isolated and analyzed by standard techniques.Results
In samples from 13 Jr(a–) study subjects, we found six alleles with nonsense nucleotide changes, three (c.784T, c.1591T, and c.337T) were novel. Twelve of the samples were homozygous for nonsense single-nucleotide polymorphisms (SNPs): eight were c.376T, two were c.706T, one was c.784T, and one was c.1591T. Each of these alleles predicts a truncated ABCG2 product, Gln126Stop, Arg236Stop, Gly262Stop, and Gln531Stop, respectively. One study subject was heterozygous for two nonsense SNPs: c.337C/T (Arg113Stop) and c.736C/T (Arg246Stop).Conclusions
Jra is the sole antigen in the newly established JR blood group system (ISBT 032001). The previous ISBT designation (901005) is now obsolete. Since ABCG2null alleles define the Jr(a–) phenotype, an explanation for why no antithetical low-prevalence antigen to Jra has been found, and also why anti-Jra made by people with any of these JRnull alleles are mutually compatible has been determined. Based on our findings DNA-based genotyping can be developed to replace the serologic methods that are currently used to identify Jr(a–) blood donors.