Haplotype analysis of the H63D, IVS2+4t/c, and C282Y polymorphisms of the HFE gene reveals rare events of intragenic recombination.

OBJECTIVE

Two missense mutations of the HFE gene, one (C282Y) being a major gene for hereditary hemochromatosis and the other (H63D) playing a minor role in this disease, are carried by different haplotypes. Among other sequence variants of HFE, IVS2+4t/c polymorphism has been reported as a possible splicing mutation or risk modifier. Our aims were to identify sequence variants possibly associated with iron overload in our population, to study the intragenic haplotypes of the HFE gene, and to evaluate the role of IVS2+4t/c in hyperferritinemia.

METHODS

We screened by direct sequencing the coding sequence and intron-exon boundaries of HFE in 265 patients with hyperferritinemia and 185 subjects from the general population.

RESULTS

Linkage disequilibrium between the three pairs of polymorphic sites was complete between H63D and C282Y, whereas all four gametic types were present for both the H63D-IVS2+4t/c and the IVS2+4t/c-C282Y site pairs. The data supported a model in which the IVS2+4t/c polymorphism was ancestral, the D(63) mutation occurred on the t chromosome, and the Y(282) mutation occurred on the c chromosome; after the population spread of both mutations, intragenic recombination occurred on both sides of the t/c polymorphism, generating the rare haplotypes D(63)-c(IVS2+4)-C(282) and H(63)-t(IVS2+4)-Y(282).

CONCLUSIONS

The IVS2+4c/t is a neutral polymorphism with regard to risk of iron overload. The presence of recombinant haplotypes on both its sides suggests a considerable evolutionary age of the two main risk alleles.