BACKGROUND/AIMS: To determine the molecular basis of a mild hemochromatosis phenotype in a man of Scottish-Irish descent. METHODS: We sequenced genomic DNA to detect mutations of HFE, SLC40A1, TFR2, HAMP, and HFE2. RNA isolated from blood mononuclear cells was used to make cDNA. RT-PCR was performed to amplify ferroportin from cDNA, and amplified products were visualized by electrophoresis and sequenced. RESULTS: The proband was heterozygous for the novel mutation c.1402G-->A (predicted G468S) in exon 7 of the ferroportin gene (SLC40A1). Located in the last nucleotide before the splice junction, this mutation results in aberrant splicing to a cryptic upstream splice site located at nt 990 within the same exon. This causes truncation of ferroportin after glycine 330 and the addition of 4 irrelevant amino acids before terminating. The truncated ferroportin protein, missing its C-terminal 241 amino acids, would lack all structural motifs beyond transmembrane region 7. The patient was also heterozygous for the common HFE H63D polymorphism, but did not have coding region mutations in TFR2, HAMP, or HFE2. CONCLUSIONS: We conclude that this patient represents a unique example of hemochromatosis due to a single base-pair mutation of SLC40A1 that results in aberrant splicing and truncation of ferroportin.
BACKGROUND/AIMS: To determine the molecular basis of a mild hemochromatosis phenotype in a man of Scottish-Irish descent. METHODS: We sequenced genomic DNA to detect mutations of HFE, SLC40A1, TFR2, HAMP, and HFE2. RNA isolated from blood mononuclear cells was used to make cDNA. RT-PCR was performed to amplify ferroportin from cDNA, and amplified products were visualized by electrophoresis and sequenced. RESULTS: The proband was heterozygous for the novel mutation c.1402G-->A (predicted G468S) in exon 7 of the ferroportin gene (SLC40A1). Located in the last nucleotide before the splice junction, this mutation results in aberrant splicing to a cryptic upstream splice site located at nt 990 within the same exon. This causes truncation of ferroportin after glycine 330 and the addition of 4 irrelevant amino acids before terminating. The truncated ferroportin protein, missing its C-terminal 241 amino acids, would lack all structural motifs beyond transmembrane region 7. The patient was also heterozygous for the common HFE H63D polymorphism, but did not have coding region mutations in TFR2, HAMP, or HFE2. CONCLUSIONS: We conclude that this patient represents a unique example of hemochromatosis due to a single base-pair mutation of SLC40A1 that results in aberrant splicing and truncation of ferroportin.
Authors: Roman Mayr; Andreas R Janecke; Melanie Schranz; William J H Griffiths; Wolfgang Vogel; Antonello Pietrangelo; Heinz Zoller Journal: J Hepatol Date: 2010-07-17 Impact factor: 25.083