Novel alleles at the JK blood group locus explain the absence of the erythrocyte urea transporter in European families.
The Kidd (JK) blood group system is of importance in transfusion medicine. The Jk(null) phenotype is associated with absence of the urea transporter in erythrocytes and moderately reduced ability to concentrate urine. We and others recently reported different molecular alterations in the silenced Jkb-like alleles of Polynesians and Finns, populations with higher Jk(null) frequencies. Here we report novel molecular bases of this phenotype in Caucasians. Blood samples from a Swiss and an English family were investigated by serological methods, urea haemolysis test and JK genotyping. Genomic DNA and JK mRNA were sequenced. Genotyping showed homozygosity for Jka-like alleles. The Swiss Jk(null) alleles deviated from wild-type Jka sequence by a nonsense mutation in exon 7 causing an immediate stop codon (Tyr194stop). The English Jk(null) alleles revealed a genomic 1.6 kilobase pair deletion including exons 4 and 5, the former of which includes the translation start codon. Multiple mRNA splicing variants were detected in reticulocytes but exons 3-5 were absent in all transcripts analysed. Screening for these alleles was negative in random donors. Two novel molecular alterations at the JK locus were defined and a multiplex polymerase chain reaction method for detection of the five known silent Jk alleles was developed to complement JK genotyping in clinical transfusion medicine.
Irshaid
Nidal M
NM
Department of Transfusion Medicine, Institute of Laboratory Medicine, Lund University, Lund, Sweden.
Eicher
Nicole I
NI
Hustinx
Hein
H
Poole
Joyce
J
Olsson
Martin L
ML
D000483:Alleles; D002352:Carrier Proteins / Q000378:metabolism*; D018389:Codon, Nonsense; D004739:England; D004912:Erythrocytes / Q000378:metabolism*; D017353:Gene Deletion; D006801:Humans; D007597:Jordan; D007667:Kidd Blood-Group System / Q000235:genetics*; D007671:Kidney Concentrating Ability / Q000235:genetics*; D008562:Membrane Glycoproteins / Q000378:metabolism*; D026901:Membrane Transport Proteins; D010641:Phenotype; D016133:Polymerase Chain Reaction / Q000379:methods; D012333:RNA, Messenger / Q000032:analysis; D017422:Sequence Analysis, DNA; D013557:Switzerland; D000096982:Urea Transporters
D002352:Carrier Proteins; D018389:Codon, Nonsense; D007667:Kidd Blood-Group System; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D012333:RNA, Messenger; D000096982:Urea Transporters