Two novel Jk(null) alleles derived from 222C>A in Exon 5 and 896G>A in Exon 9 of the JK gene.
BACKGROUND
Polynesian Jk(null) is well known for its mutation as Intron 5 g>a at the 3' splice acceptor site. After sequencing analysis, however, it was noticed that only three of eight samples with the Jknull phenotype carried typical homozygous Polynesian Jk(null) mutation. Five others were noted to be unreported heterozygous Polynesian Jk(null) mutation. An investigation was then conducted to characterize the underlying mechanism leading to this particular Jk(null) genotype.


METHODS
Genomic DNA covering 5'-untranslated region exons and intervening introns of the JK gene was amplified by polymerase chain reaction, and the fragments were directly sequenced. The sequencing results were compared with those published in literature and related biologic Web sites.


RESULTS
In all five samples with a heterozygous Polynesian Jk(null) mutation, additional mutations were identified. Two samples carried missense mutations: 222C>A (Asn74Lys) in Exon 5 and 499A>G (Met167Val) in Exon 7. Three others had missense mutation 896G>A (Gly299Glu) in Exon 9. These substituted amino acids were located either near or at transmembrane domains, respectively. In addition, two polymorphic nucleotides at positions -103 (a>g) and -119(c>a) from the 3' end of Intron 1 were also Polynesian mutation-related.


CONCLUSIONS
In contrast to the typical homozygous Polynesian Jk(null) mutation, two novel heterozygous Jk(null) alleles were noted to be associated with the Jknull phenotype. One carried missense mutation 222C>A in Exon 5, and the other had 896G>A missense mutation in Exon 9. These findings may have implications in designing a molecular screening assay for people with the Jknull phenotype.
Liu
Hsueng-Mei
HM
Department of Medicine, Taipei Veterans General Hospital, National Yang-Ming University, Taiwan.
Lin
Jeong-Shi
JS
Chen
Pei-Shan
PS
Lyou
Jau-Yi
JY
Chen
Ying-Ju
YJ
Tzeng
Cheng-Hwai
CH
D020121:5' Untranslated Regions; D000483:Alleles; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001483:Base Sequence; D004247:DNA / Q000097:blood / Q000235:genetics / Q000378:metabolism; D005091:Exons; D018698:Glutamic Acid / Q000378:metabolism; D006579:Heterozygote; D006801:Humans; D007438:Introns; D007667:Kidd Blood-Group System / Q000235:genetics*; D008239:Lysine / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D020125:Mutation, Missense; D016133:Polymerase Chain Reaction / Q000379:methods; D017422:Sequence Analysis, DNA; D014633:Valine / Q000378:metabolism
D020121:5' Untranslated Regions; D007667:Kidd Blood-Group System; D018698:Glutamic Acid; D004247:DNA; D014633:Valine; D008239:Lysine