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).
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.
Molecular Genetics and Pathology Unit, Hospital of Divino Espirito Santo of Ponta Delgada, EPE, São Miguel Island, Azores, Portugal; Instituto Gulbenkian de Ciência, Oeiras, Portugal; BioISI - Biosystems & Integrative Sciences Institute, Faculty of Sciences, University of Lisboa, Lisboa, Portugal.
Claudia C
CC
Branco
Molecular Genetics and Pathology Unit, Hospital of Divino Espirito Santo of Ponta Delgada, EPE, São Miguel Island, Azores, Portugal.
Cidália T
CT
Gomes
Molecular Genetics and Pathology Unit, Hospital of Divino Espirito Santo of Ponta Delgada, EPE, São Miguel Island, Azores, Portugal.
Laura
L
De Fez
Molecular Genetics and Pathology Unit, Hospital of Divino Espirito Santo of Ponta Delgada, EPE, São Miguel Island, Azores, Portugal.
Sara
S
Bulhões
Molecular Genetics and Pathology Unit, Hospital of Divino Espirito Santo of Ponta Delgada, EPE, São Miguel Island, Azores, Portugal.
Maria José
MJ
Brilhante
Molecular Genetics and Pathology Unit, Hospital of Divino Espirito Santo of Ponta Delgada, EPE, São Miguel Island, Azores, Portugal.
Tânia
T
Pereirinha
Molecular Genetics and Pathology Unit, Hospital of Divino Espirito Santo of Ponta Delgada, EPE, São Miguel Island, Azores, Portugal.
Rita
R
Cabral
Gastroenterology Department, Hospital of Divino Espirito Santo of Ponta Delgada, EPE, São Miguel Island, Azores, Portugal.
Ana Catarina
AC
Rego
Hematology Department, Hospital of Divino Espirito Santo of Ponta Delgada, EPE, São Miguel Island, Azores, Portugal.
Cristina
C
Fraga
Pneumology Department, Hospital of Divino Espirito Santo of Ponta Delgada, EPE, São Miguel Island, Azores, Portugal.
António G
AG
Miguel
Internal Medicine Department, Hospital of Divino Espirito Santo of Ponta Delgada, EPE, São Miguel Island, Azores, Portugal.
Gracinda
G
Brasil
Internal Medicine Department, Hospital of Divino Espirito Santo of Ponta Delgada, EPE, São Miguel Island, Azores, Portugal.
Paula
P
Macedo
Molecular Genetics and Pathology Unit, Hospital of Divino Espirito Santo of Ponta Delgada, EPE, São Miguel Island, Azores, Portugal; Instituto Gulbenkian de Ciência, Oeiras, Portugal; BioISI - Biosystems & Integrative Sciences Institute, Faculty of Sciences, University of Lisboa, Lisboa, Portugal.
Luisa
L
Mota-Vieira
D000293:Adolescent; D000328:Adult; D000368:Aged; D000483:Alleles; D001394:Azores / Q000453:epidemiology; D016022:Case-Control Studies; D003241:Consanguinity; D005260:Female; D020022:Genetic Predisposition to Disease / Q000235:genetics; D015234:HLA-A Antigens / Q000235:genetics; D015235:HLA-B Antigens / Q000235:genetics; D000071020:Hemochromatosis Protein; D006579:Heterozygote; D015395:Histocompatibility Antigens Class I / Q000235:genetics*; D006720:Homozygote; D006801:Humans; D019190:Iron Overload / Q000235:genetics*; D008297:Male; D008565:Membrane Proteins / Q000235:genetics*; D008875:Middle Aged; D009154:Mutation / Q000235:genetics; D012307:Risk Factors; D055815:Young Adult
C103673:HFE protein, human; D015234:HLA-A Antigens; D015235:HLA-B Antigens; D000071020:Hemochromatosis Protein; D015395:Histocompatibility Antigens Class I; D008565:Membrane Proteins