New mutations inactivating transferrin receptor 2 in hemochromatosis type 3

Antonella Roetto, Angela Totaro, Alberto Piperno, Antonio Piga, Filomena Longo, Giovanni Garozzo, Angelita Calì, Marco De Gobbi, Paolo Gasparini, Clara Camaschella

Research output: Contribution to journalArticle

Abstract

Hereditary hemochromatosis usually results from C282Y homozygosity in the HFE gene on chromosome 6p. Recently, a new type of hemochromatosis (HFE3) has been characterized in 2 unrelated Italian families with a disorder linked to 7q. Patients with HFE3 have transferrin receptor 2 (TFR2) inactivated by a homozygous nonsense mutation (Y250X). Here the identification of 2 new TFR2 mutations is reported. In a large inbred family from Campania, a frameshift mutation (84-88 insC) in exon 2 that causes a premature stop codon (E60X) is identified. In a single patient with nonfamilial hemochromatosis, a T→A transversion (T515A), which causes a Methionine→Lysine substitution at position 172 of the protein (M172K), has been characterized. TFR2 gene gives origin to 2 alternatively spliced transcripts-the α-transcript, which may encode a transmembrane protein, and the β-transcript, a shorter, possibly intracellular variant. Based on their positions, the effects of the identified mutations on the 2 TFR2 forms are expected to differ. Y250X inactivates both transcripts, whereas E60X inactivates only the α-form. M172K has a complex effect: it causes a missense in the α-form, but it may also prevent the β-form production because it affects its putative initiation codon. Analysis of the clinical phenotype of 13 HFE3 homozygotes characterized at the molecular level has shown a variable severity, from nonexpressing patients to severe clinical complications. The identification of new mutations of TFR2 confirms that this gene is associated with iron overload and offers a tool for molecular diagnosis in patients without HFE mutations.

Original languageEnglish
Pages (from-to)2555-2560
Number of pages6
JournalBlood
Volume97
Issue number9
DOIs
Publication statusPublished - May 1 2001

ASJC Scopus subject areas

  • Hematology

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    Roetto, A., Totaro, A., Piperno, A., Piga, A., Longo, F., Garozzo, G., Calì, A., De Gobbi, M., Gasparini, P., & Camaschella, C. (2001). New mutations inactivating transferrin receptor 2 in hemochromatosis type 3. Blood, 97(9), 2555-2560. https://doi.org/10.1182/blood.V97.9.2555