An unusual case of hemochromatosis due to a new compound heterozygosity in HFE (p.[Gly43Asp;His63Asp]+[Cys282Tyr]): structural implications with respect to binding with transferrin receptor 1

Most adults affected with HFE hereditary hemochromatosis (HH type 1, MIMmusical sharp 235200) are homozygous for the p.Cys282Tyr mutation in HFE (NC_000006.10, region 26195427 to 26205038). The aim of this study was to investigate the molecular basis of iron overload in a patient presenting with severe clinical HH with one c.845G>A (p.Cys282Tyr) allele only. Molecular and pedigree studies demonstrated the presence of the c.845G>A (p.Cys282Tyr) mutation in one allele whereas the other carried the c.187C>G (p.His63Asp) mutation plus a new c.128G>A (p.Gly43Asp) substitution in cis. A molecular modeling study of the p.[Gly43Asp;His63Asp] and p.His63Asp variants versus the wild type was carried out using molecular dynamics (MD) simulation in presence of implicit solvent. We found that the c.187C>G (p.His63Asp) mutation does not introduce any major change in the 1- domains of HFE whereas the c.128G>A (p.Gly43Asp) substitution is responsible for a modification of the dynamics and the structure of the Gln40-Ser45 loop, a critical region for HFE-TfR1 interaction thus impairing HFE-TfR1 normal contact. We conclude that the occurrence of complex alleles may be an alternative explanation for the variability of the phenotype in individuals who are compound heterozygous for c.[187C>G]+[845G>A] (p.[His63Asp]+[Cys282Tyr]).