SLC40A1 c.1402G-->a results in aberrant splicing, ferroportin truncation after glycine 330, and an autosomal dominant hemochromatosis phenotype.
OBJECTIVE
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.
Lee
Pauline L
PL
Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, Calif, USA.
Gelbart
Terri
T
West
Carol
C
Barton
James C
JC
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D027682:Cation Transport Proteins / Q000737:chemistry / Q000172:deficiency / Q000235:genetics*; D017124:Conserved Sequence; D004252:DNA Mutational Analysis; D005091:Exons / Q000235:genetics; D005799:Genes, Dominant; D006432:Hemochromatosis / Q000235:genetics* / Q000628:therapy; D000071020:Hemochromatosis Protein; D006579:Heterozygote; D015395:Histocompatibility Antigens Class I / Q000235:genetics; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000235:genetics; D008875:Middle Aged; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D010375:Pedigree; D010641:Phenotype; D018962:Phlebotomy; D017354:Point Mutation; D012326:RNA Splicing; D000098742:Ferroportin
D027682:Cation Transport Proteins; C103673:HFE protein, human; D000071020:Hemochromatosis Protein; D015395:Histocompatibility Antigens Class I; D008565:Membrane Proteins; D000098742:Ferroportin