Molecular characterization of the JK null phenotype in the Maori and Polynesian population in New Zealand; and using this information to design an informative assay for High Resolution Melting Analysis

Abstract

Background: The frequency of the Jk(a-b-) phenotype is very low in all populations except the Maori, Polynesians and the Finns. The New Zealand Maori and Polynesians have a high frequency of the JK null phenotype estimated as 0.27%. These two diverse ethnic groups provide the majority of the global supply of JK null blood for transfusion. Purpose: The aim of this study was to molecular characterize the JK null phenotype in the Maori and Polynesian population in New Zealand; from this information design a High Resolution Melting Analysis assay that will capture all the alleles that cause the JK null phenotype. The risk of misinterpretation of results due to the presence of null alleles, only identified by molecular typing has been highlighted in the literature. Methodology: Forty-four samples tested for this project were Jk(a-b-) by 2 M urea lysis and haemagglutination. These samples were tested by High Resolution Melting on the LightCycler® 480 .The samples, that had a high resolution melt curve, that did not follow the expected curve of the Polynesian IVS5-1 g>a mutation (JK*02N.01) were further analysed. Results: Thirty-six of the 44 samples identified themselves as Maori or Polynesian. Forty of the 44 samples tested were homozygous for the Polynesian JK*02N.01 allele. Two novel alleles; namely a compound heterozygous 190C>T, and a homozygous 118G>A were identified. This sample also had 499 A>G (JK*02N.12) allele which has not been previously associated with 118G>A. A compound heterozygous 896G>A (JK*02N.07) together with JK*02N.01 allele was identified and one sample had the 810G>A allele. Conclusion: The molecular characterization of the JK null phenotype in the Maori and Polynesian population in New Zealand was successfully performed. This population group has a high incidence of the intron 5, JK*02N.01 allele. High Resolution Melting Analysis using the LightCycler® 480 is a simple and fast screening method for the investigation of the rare variants.