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Iron overload due to mutations in ferroportin
Ivana De Domenico1, Diane McVey Ward, Giovanni Musci
1Dipartimento di Scienze Microbiologiche Genetiche e Molecolari, Università di Messina, Messina, Italy.
Haematologica
|January 26, 2006
Summary
Mutations in ferroportin cause iron overload disease with varied symptoms. How these mutations affect iron export and hepcidin response explains the different patient outcomes and dominant inheritance patterns.
Area of Science:
- Genetics
- Cell Biology
- Biochemistry
Background:
- Ferroportin mutations cause iron overload disease with dominant inheritance and variable clinical phenotypes.
- Patient phenotypes range from early Kupffer cell iron loading with low transferrin saturation to hepatocyte iron loading with high transferrin saturation.
Purpose of the Study:
- To investigate the mechanisms underlying ferroportin mutations and their impact on iron export and disease presentation.
- To explain the dominant inheritance pattern observed in ferroportin-linked iron overload disorders.
Main Methods:
- Expression of ferroportin mutant proteins in cultured cells.
- Analysis of protein localization to the cell surface.
- Assessment of iron export capacity.
- Evaluation of response to the antimicrobial peptide hepcidin.
Main Results:
- Mutant ferroportin proteins were classified into two groups: those failing to localize to the cell surface and unable to export iron, and those localizing but unresponsive to hepcidin.
- Mutations causing cell surface mislocalization result in typical ferroportin disease with low transferrin saturation and Kupffer cell iron loading.
- Mutations conferring hepcidin resistance lead to high transferrin saturation and hepatocyte iron loading, mimicking hereditary hemochromatosis.
Conclusions:
- The distinct cellular behaviors of mutant ferroportin proteins explain the variable clinical phenotypes and iron loading patterns in patients.
- In vitro data suggest ferroportin functions as a multimer, explaining how mutant proteins can influence wild-type protein function and leading to dominant inheritance.