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Normally, HFE facilitates the binding of transferrin, which is iron's carrier protein in the blood. Transferrin levels are typically elevated at times of iron depletion (low ferritin stimulates the release of transferrin from the liver). When transferrin is high, HFE works to increase the intestinal release of iron into the blood.
Majority of the cases of hemochromatosis are caused by mutations in the HFE (Homeostatic Iron Regulator) gene. [17] Type 3 HH is characterized by compound heterozygote mutations in both transferrin receptor 2 (TFR2) and HFE, i.e. a single mutation in each gene. HFE is located on chromosome 6 and TFR2 is located on chromosome 7.
This mutation is associated with diverse health issues, however H63D syndrome is the only known specific expression of a homozygous HFE-H63D mutation to date. The homozygous HFE-H63D mutation is the cause of classic and treatable hemochromatosis in only 6.7% of its carriers. [25] H63D syndrome is independently a distinct entity, and the ...
At least 42 mutations involving HFE introns and exons have been discovered, most of them in persons with hemochromatosis or their family members. [25] Most of these mutations are rare. Many of the mutations cause or probably cause hemochromatosis phenotypes, often in compound heterozygosity with HFE C282Y.
Type 4 hemochromatosis is caused by mutations of the SLC40A1 gene, located on the long arm of chromosome 2, specifically at 2q32.2. The SLC40A1 gene encodes ferroportin, a protein responsible for exporting iron from cells in the intestine, liver, spleen, and kidney, as well as from reticuloendothelial macrophages and the placenta.
An additional aggravating mutation affecting variegate porphyria can be found at 6p21.3 on the HFE gene. [ 7 ] A 2006 clinical, biochemical and mutational study of eight Swiss variegate porphyria patients and their families found four novel PPOX gene mutations believed to be unique to the Swiss population.
This protein mediates cellular uptake of transferrin-bound iron and mutations in this gene have been associated with hereditary hemochromatosis type III. Alternatively spliced variants which encode different protein isoforms have been described; however, not all variants have been fully characterized.
Hepcidin is a protein that in humans is encoded by the HAMP gene. Hepcidin is a key regulator of the entry of iron into the circulation in mammals. [6]During conditions in which the hepcidin level is abnormally high, such as inflammation, serum iron falls due to iron trapping within macrophages and liver cells and decreased gut iron absorption.