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Mol Genet Genomic Med. 2015 May;3(3):221-32. doi: 10.1002/mgg3.136. Epub 2015 Mar 6.

Functional consequences of transferrin receptor-2 mutations causing hereditary hemochromatosis type 3.

Author information

1
Cancer and Iron Group and Advanced Genetic Diagnostic Unit of Rare Iron Disorders (UDGAEMH), Institut of Predictive and Personalized Medicine of Cancer (IMPPC) Barcelona, Spain.
2
Cancer and Iron Group and Advanced Genetic Diagnostic Unit of Rare Iron Disorders (UDGAEMH), Institut of Predictive and Personalized Medicine of Cancer (IMPPC) Barcelona, Spain ; Diagnostics in Iron Metabolism Service (D·IRON) and Iron Metabolism: Regulation and Diseases group, Josep Carreras Leukemia Research Institute (IJC) Barcelona, Spain.
3
Vall d'Hebron Research Institute (VHIR) Barcelona, Spain.
4
Vall d'Hebron Research Institute (VHIR) Barcelona, Spain ; Institució Catalana de Recerca i Estudis Avançats (ICREA) Barcelona, Catalonia, Spain.
5
Service of Hepatology, Clinic Hospital of Barcelona Barcelona, Spain.
6
Service of Haematology, Hospital Materno-Infantil de Badajoz Badajoz, Spain.
7
Department of Surgical & Medical Therapeutics, University of Extremadura Badajoz, Spain.
8
Service of Haematology and Hemotherapy, Clinic Hospital of Barcelona Barcelona, Spain.

Abstract

Hereditary hemochromatosis (HH) type 3 is an autosomal recessive disorder of iron metabolism characterized by excessive iron deposition in the liver and caused by mutations in the transferrin receptor 2 (TFR2) gene. Here, we describe three new HH type 3 Spanish families with four TFR2 mutations (p.Gly792Arg, c.1606-8A>G, Gln306*, and Gln672*). The missense variation p.Gly792Arg was found in homozygosity in two adult patients of the same family, and in compound heterozygosity in an adult proband that also carries a novel intronic change (c.1606-8A>G). Two new nonsense TFR2 mutations (Gln306* and Gln672*) were detected in a pediatric case. We examine the functional consequences of two TFR2 variants (p.Gly792Arg and c.1606-8A>G) using molecular and computational methods. Cellular protein localization studies using immunofluorescence demonstrated that the plasma membrane localization of p.Gly792Arg TFR2 is impaired. Splicing studies in vitro and in vivo reveal that the c.1606-8A>G mutation leads to the creation of a new acceptor splice site and an aberrant TFR2 mRNA. The reported mutations caused HH type 3 by protein truncation, altering TFR2 membrane localization or by mRNA splicing defect, producing a nonfunctional TFR2 protein and a defective signaling transduction for hepcidin regulation. TFR2 genotyping should be considered in adult but also in pediatric cases with early-onset of iron overload.

KEYWORDS:

Hereditary hemochromatosis type 3; TFR2 gene; iron overload; missense; nonsense; p.Gly792Arg; splicing mutation

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