Carriers of the Complex Allele HFE c.[187C>G;340+4T>C] Have Increased Risk of Iron Overload in São Miguel Island Population (Azores, Portugal)

• Published in: PloS one Vol. 10; no. 10; p. e0140228
• Main Authors: Branco, Claudia C, Gomes, Cidália T, De Fez, Laura, Bulhões, Sara, Brilhante, Maria José, Pereirinha, Tânia, Cabral, Rita, Rego, Ana Catarina, Fraga, Cristina, Miguel, António G, Brasil, Gracinda, Macedo, Paula, Mota-Vieira, Luisa
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 26.10.2015; Public Library of Science (PLoS)
• Subjects: Adolescent; Adult; Aged; Alleles; Alternative splicing; Amino acids; Association analysis; Azores - epidemiology; Carriers; Case-Control Studies; Configurations; Consanguinity; Deoxyribonucleic acid; DNA; Ethics; Exons; Female; Gene banks; Genetic Predisposition to Disease - genetics; Genetic testing; Genetics; Haplotypes; Hemochromatosis; Hemochromatosis Protein; Heredity; Heterozygote; Histocompatibility Antigens Class I - genetics; HLA-A Antigens - genetics; HLA-B Antigens - genetics; Homozygote; Hospitals; Humans; Internal medicine; Iron; Iron Overload - genetics; Male; Marriage; Membrane Proteins - genetics; Middle Aged; Mutation; Mutation - genetics; Pathology; Patients; Population; Population studies; Proteins; Risk; Risk Factors; Transferrin; Transferrins; Young Adult; Azores; Portugal
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0140228

Iron overload is associated with acquired and genetic conditions, the most common being hereditary hemochromatosis (HH) type-I, caused by HFE mutations. Here, we conducted a hospital-based case-control study of 41 patients from the São Miguel Island (Azores, Portugal), six belonging to a family with HH type-I pseudodominant inheritance, and 35 unrelated individuals fulfilling the biochemical criteria of iron overload compatible with HH type-I. For this purpose, we analyzed the most common HFE mutations- c.845G>A [p.Cys282Tyr], c.187C>G [p.His63Asp], and c.193A>T [p.Ser65Cys]. Results revealed that the family's HH pseudodominant pattern is due to consanguineous marriage of HFE-c.845G>A carriers, and to marriage with a genetically unrelated spouse that is a -c.187G carrier. Regarding unrelated patients, six were homozygous for c.845A, and three were c.845A/c.187G compound heterozygous. We then performed sequencing of HFE exons 2, 4, 5 and their intron-flanking regions. No other mutations were observed, but we identified the -c.340+4C [IVS2+4C] splice variant in 26 (74.3%) patients. Functionally, the c.340+4C may generate alternative splicing by HFE exon 2 skipping and consequently, a protein missing the α1-domain essential for HFE/ transferrin receptor-1 interactions. Finally, we investigated HFE mutations configuration with iron overload by determining haplotypes and genotypic profiles. Results evidenced that carriers of HFE-c.187G allele also carry -c.340+4C, suggesting in-cis configuration. This data is corroborated by the association analysis where carriers of the complex allele HFE-c.[187C>G;340+4T>C] have an increased iron overload risk (RR = 2.08, 95% CI = 1.40-2.94, p<0.001). Therefore, homozygous for this complex allele are at risk of having iron overload because they will produce two altered proteins--the p.63Asp [c.187G], and the protein lacking 88 amino acids encoded by exon 2. In summary, we provide evidence that the complex allele HFE-c.[187C>G;340+4T>C] has a role, as genetic predisposition factor, on iron overload in the São Miguel population. Independent replication studies in other populations are needed to confirm this association.