A rapid method of haplotyping HFE mutations and linkage disequilibrium in a Caucasoid population
- Transplantation Immunology, Nuffield Department of Surgery, Churchill Hospital, Headington, Oxford OX3 7LJ, UK
- Dr Mullighan.
- Accepted 31 October 1997
Background—HFE mutations are associated with hereditary haemochromatosis. However, a simple method capable of demonstrating the cis/transarrangement of alleles is lacking, and linkage disequilibrium betweenHFE alleles and classic HLA loci is unknown. These are important issues as the pathogenic role of the mutations is not known.
Aims—To develop a simple method of genotypingHFE mutations suitable for clinical use in addition to large disease studies.
Patients—A total of 330 Caucasoid cadaveric organ donor controls were examined. Ten individuals previouslyHLA-H genotyped by polymerase chain reaction using restriction fragment length polymorphism (PCR-RFLP) were also examined to validate the method.
Methods—A simple polymerase chain reaction using sequence specific primers (PCR-SSP) capable of haplotyping the mutations was developed. HFE allele and haplotype frequencies and linkage disequilibrium with eight HLA class I and II loci were examined in the control population.
Results—27% and 19.7% of patients were positive for the 63D and 282Y alleles, respectively. No chromosome carried both 63D and 282Y. Linkage disequilibrium between 282Y and HLA-A*03 was confirmed, but was not straightforward: some A*03-associated alleles (DRB1*15, DQB1*06), but not all (B*07, Cw*0702), were associated with 282Y.
Conclusions—Linkage disequilibrium data suggest that an HLA-B*07 containing haplotype contains an element affording protection from haemochromatosis and may suggest the timing of the founder 282Y mutation.
* There is confusion regarding this nomenclature. The term “HLA-H” was first used by Feder et al, 1 but was previously used to denote a distinct HLA class I-like pseudogene unrelated to haemochromatosis.2 It has thus been recommended that the name of the gene under discussion revert to “HFE”, the name assigned by the Genome Database Nomenclature Committee to the haemochromatosis locus.3 † The currently accepted nomenclature for the codon 63 His(Asp (‘H63D’) and 282 Cys(Tyr (‘C282Y’) mutations results in confusion when haplotypes are described. Thus in this paper, alleles are referred to by the codon number followed by the amino acid variant (63H, 63D, 282C and 282Y); haplotypes are denoted by each codon number followed by the amino acid allele, e.g. a haplotype of His at codon 63 andTyr at codon 282 is denoted as ‘63H-282Y’.