DMT1 Mutations Research Articles

DMT1-Mutant Erythrocytes Have Shortened Life Span, Accelerated Glycolysis and Increased Oxidative Stress

Divalent metal transporter 1 (DMT1, also known as NRAMP2 and SLC11A2) is a transmembrane protein important for intestinal iron (Fe2+) absorption and erythroid iron utilization. Homozygous or compound heterozygous mutations in DMT1 are associated with moderate to severe hypochromic microcytic anemia in human patients and a mouse model - mk/mk mice. We have previously reported that DMT1 deficiency leads to an impaired erythroid differentiation hallmarked by accumulation of immature forms of erythroblast which also showed increased rate of apoptosis. For human samples we observed suppression of colony-forming capacity of erythroid progenitors that can be corrected by the addition of iron saturated chelate Fe-SIH. Later we proved this result also for mk/mk progenitors and showed reduced number of mk/mk CFU-E (164±25 vs. 283±50) and BFU-E (9±4 vs. 22±5) colonies in comparison to the colonies of wild-type (wt) mice and improvement of the colony growth with Fe-SIH.In our following studies we focused on mature erythrocytes, the last stage of erythroid differentiation that has not been analyzed yet. We first determined the in vivo half-life of red blood cells (RBC). Isolated RBCs from mk/mk mice and wt controls were in vitro labeled with CFSE fluorescent dye and injected into the wt mice. The intensity of RBCs fluorescence was measured on the 1st, 7th, 10th, 14th, 19th, 26th and 30th day following the injection. We observed an accelerated clearance of CFSE-labeled mk/mk RBCs from circulating blood when compared to wt RBCs, which indicates increased destruction of DMT1-mutant erythrocytes in vivo. It is known, that mature RBCs retain the ability to undergo stress-induced death (eryptosis), characterized by their shrinkage, membrane blebbing and phosphatidylserine surface exposure. This process may be triggered by iron deficiency. To determine the involvement of eryptosis in mk/mk RBCs clearance, RBCs were exposed to different stress conditions in vitro. A significantly increased number of Annexin V-positive RBCs was detected for mk/mk RBCs when compared to wt RBCs after 5 and 7 hour exposure to hyperosmotic shock (400mM sucrose) and glucose depletion, respectively. These results indicate shortened life span of DMT1-mutant erythrocytes and their reduced ability to cope with stress.To unravel the possible underlying mechanisms we focus on two processes important for RBC survival; anti-oxidative defense and anaerobic glycolysis. We observed 1.5 to 2-fold higher activity of glutathione peroxidase, catalase and methemoglobin reductase and elevated levels of methemoglobin in mk/mk RBCs in comparison to wt RBCs, indicating increased oxidative stress in mk/mk RBCs. Increased activity of hexokinase (2.5 times) and pyruvatkinase (2.4 times) together with reduced ratio of ATP/ADP in mk/mk mice compared with wt mice (from 2.89±0.56 μmol/L to 1.71±0.49 μmol/L) shows enhanced demand for glycolytically derived ATP to maintain the stability of RBC membrane in mk/mk mice.Our analyzes suggest that DMT1 deficiency negatively affects metabolism and life span of mature erythrocytes; two other aspects of defective erythropoiesis contributing to the pathophysiology of the disease. Grant supportCzech Grant Agency, grant No. P305/11/1745; Ministry of Health Czech Republic Grant No. NT11208 and Internal Grant of Palacky University Olomouc (LF_2013_010). Disclosures:No relevant conflicts of interest to declare.

Mutation Of The Divalent Metal Transporter (Dmt1) Gene Results In Inefficient Induction Of The Erythroid Transcriptional Program Due To Latter Onset Of GATA-1 and Epor Expression

IntroductionDivalent metal transporter 1 (DMT1; SLC11A2) encodes trans-membrane protein variants that execute either non-heme iron absorption through apical duodenal membrane of enterocytes or transferrin-bound iron uptake through endosomal membrane of erythroid (and other) cells. Since 2005 several DMT1 mutations affecting accurate protein folding and localization were identified in patients with defective iron uptake leading to microcytic anemia, abnormal growth of erythroid progenitors in vitro, and iron overload in the liver. We have previously demonstrated that defective growth of DMT-1-mutatnt BFU-Es in vitro and anemia associated with ineffective erythropoiesis in vivo can be improved with high-dose erythropoietin (EPO) supplementation (Horvathova et al., 2012). Data from Dmt1-mutant mk/mk mice (Gunshin et al., 2005) suggested that the anemic phenotype is a result of ineffective erythropoiesis within bone marrow and spleen. HypothesisDMT1-mutant erythropoiesis inhibits EPO receptor (EPOR) signaling whose end-point target as well as upstream activator is the key transcription factor GATA-1. This results in defective erythroid development characterized by impaired survival capacity of erythroid progenitors, increased apoptosis of erythroblasts, and dysregulation of erythroid gene expression leading to ineffective erythropoiesis. MaterialsBone marrow cells of murine mk/mk mice were sorted using flow cytometry to obtain differentiating erythroid fractions based on antigens Cd71 and Ter119 (Sokolovsky et al., 2001) which were then subjected to gene expression analysis. ResultsFirstly, four consecutive fractions (proerythroblasts and early basophilic erythroblasts - stage I, late basophilic erythroblasts – stage II, chromathophillic and orthochromathophillic erythroblasts – stage III, and late chromathophillic erythroblasts and reticulocytes – stage IV) were isolated from mk/mk mice and control littermates. Flow cytometry showed enrichment in stages I and II and depletion in stage IV in the mk/mk bone marrow when compared to wild type controls, consistent with our previous data. In the spleen the major cellular enrichment was seen in stage III accompanied by cell depletion in stage IV. Gene expression of GATA-1 was markedly decreased at the onset (in stages I and II) of erythropoiesis while it was increased in terminal stage IV. The expression pattern of the GATA-1 target gene Epor was similar to that of GATA-1 expression, while expression of b-maj globin was significantly reduced indicating developmental delay of the erythroid Dmt1-mutant compartment (compared to wild type). Whereas GATA-1 and Epor expression is low in early erythropoiesis, a compensatory increase in their expression at later stages is not capable to efficiently upregulate b-maj globin. These data together with flow cytometry analysis identify a developmental blockade of erythropoiesis between stages II(III) and IV. To better understand whether Dmt1 levels regulate GATA-1 and Epor expression we used murine erythroleukemia (MEL) cells containing conditional (estrogen-regulated) transgene encoding GATA-1 fused with estrogen receptor ligand-binding domain (GER). MEL cells are cytologically characterized as proerythroblasts and early basophilic erythroblasts, stage I. Firstly, we established that GATA-1 upregulates Epor expression and directly binds to the Epor gene using RT-PCR, Immunoblotting, and chromatin immunoprecipitation (ChIP) in activated GER cells. Using ChIP-sequencing analysis of GATA-1 (and a panel of histone modifications) the GATA-1 enrichment was clearly identified at three distinct Epor regions in murine erythroblasts and differentiating MEL cells. Next, we downregulated Dmt1 using siRNA and observed that GATA-1-mediated upregulation of Epor in activated GER cells became inhibited. In addition, the knockdown of Dmt1 also inhibited steady state levels of GATA-1 in MEL cells by 25%. ConclusionsIneffective erythropoiesis in Dmt1-mutant mice is blocked at stages II (III) and display deregulation of the Epor signaling cascade involving GATA-1 and its targets. Our data thus interconnect iron uptake and the Epor/GATA-1 pathways and suggest their roles during erythroid pathogenesis upon DMT1 mutations. Grants: P305/11/1745, P301/12/P380, P305/12/1033, UNCE 204021, PRVOUK-P24/LF1/3, SVV-2012-264507, GAUK 251135 82210 Disclosures:No relevant conflicts of interest to declare.

Genetic/Metabolic Effect of Iron Metabolism and Rare Anemias

Advances in iron metabolism have allowed a novel classification of iron disorders and to identify previously unknown diseases. These disorders include genetic iron overload (hemochromatosis) and inherited iron-related anemias, in some cases accompanied by iron overload. Rare inherited anemias may affect the hepcidin pathway, iron absorption, transport, utilization and recycling. Among the genetic iron-related anemias the most common form is likely the iron-refractory iron-deficiency anemia (IRIDA), due to mutations of the hepcidin inhibitor TMPRSS6 encoding the serine protease matriptase-2. IRIDA is characterized by hepcidin up-regulation, decrease iron absorption and macrophage recycling and by microcytic- hypochromic anemia, unresponsive to oral iron. High serum hepcidin levels may suggest the diagnosis, which requires demonstrating the causal TMPRSS6 mutations by gene sequencing. Other rare microcytic hypochromic anemias associated with defects of iron transport-uptake are the rare hypotransferrinemia, and DMT1 and STEAP3 mutations. The degree of anemia is variable and accompanied by secondary iron overload even in the absence of blood transfusions. This is due to the iron-deficient or expanded erythropoiesis that inhibits hepcidin transcription, increases iron absorption, through the erythroid regulator, as in untransfused beta-thalassemia. Sideroblastic anemias are due to decreased mitochondrial iron utilization for heme or sulfur cluster synthesis. Their diagnosis requires demonstrating ringed sideroblasts by Perl’s staining of the bone marrow smears. The commonest X-linked form is due to deltaamino- levulinic-synthase-2-acid (ALAS2) mutations. The recessive, more severe form, affects SLC25A38, which encodes a potential mitochondrial importer of glycine, an amino acid essential for ALA synthesis and thus results in heme deficiency. Two disorders affect iron/sulfur cluster biogenesis: deficiency of the ATP-binding cassette B7 (ABCB7) causes X-linked sideroblastic anemia/ataxia, likely impairing the activity of ferrochelatase, which is an iron/sulfur-cluster- dependent enzyme. A recessive form affects GLRX5, a protein involved in the iron/sulfur cluster biogenesis. Aceruloplasminemia is a rare recessive syndrome characterized by anemia, diabetes, retinal degeneration, ataxia and other neurological symptoms, low serum iron but high serum ferritin, due to decreased iron recycling from macrophages and other cells. The study of these rare conditions has greatly contributed to our understanding of iron transport, utilization and recycling. Their distinction is clinically essential in order to plan the best treatment.

A novel N491S mutation in the human SLC11A2 gene impairs protein trafficking and in association with the G212V mutation leads to microcytic anemia and liver iron overload

Background DMT1 is a transmembrane iron transporter involved in iron duodenal absorption and cellular iron uptake. Mutations in the human SLC11A2 gene coding DMT1 lead to microcytic anemia and hepatic iron overload, with unexpectedly low levels of plasma ferritin in the presence of iron stores. Design and methods We report a patient with a similar phenotype due to two mutations in the SLC11A2 gene, the known p.Gly212Val (G212V) mutation and a novel one, p.Asn491Ser (N491S). To assess the expression of DMT1 in human liver, we studied the expression of the four DMT1 mRNA isoforms by real-time quantitative PCR in control human liver samples. We also studied the effect of G212V and N491S DMT1 mutations on RNA splicing in blood leukocytes and cellular trafficking of dsRed2-tagged-DMT1 protein in the human hepatic cell line HuH7. Results Our results showed that i) only the isoforms 1B-IRE and 1B-nonIRE were significantly expressed in human liver; ii) the G212V mutation did not seem to affect mRNA splicing and the N491S mutation induced a splicing alteration leading to a truncated protein, which seemed quantitatively of low relevance; and iii) the N491S mutation, in contrast to the G212V mutation, led to abnormal protein trafficking. Conclusions Our data confirm the major role of DMT1 in the maintenance of iron homeostasis in humans and demonstrate that the N491S mutation, through its deleterious effect on protein trafficking, contributes together with the G212V mutation to the development of anemia and hepatic iron overload.

Iron Homeostasis and Nutritional Iron Deficiency1–3

Nonheme food ferritin (FTN) iron minerals, nonheme iron complexes, and heme iron contribute to the balance between food iron absorption and body iron homeostasis. Iron absorption depends on membrane transporter proteins DMT1, PCP/HCP1, ferroportin (FPN), TRF2, and matriptase 2. Mutations in DMT1 and matriptase-2 cause iron deficiency; mutations in FPN, HFE, and TRF2 cause iron excess. Intracellular iron homeostasis depends on coordinated regulation of iron trafficking and storage proteins encoded in iron responsive element (IRE)-mRNA. The noncoding IRE-mRNA structures bind protein repressors, IRP1 or 2, during iron deficiency. Integration of the IRE-RNA in translation regulators (near the cap) or turnover elements (after the coding region) increases iron uptake (DMT1/TRF1) or decreases iron storage/efflux (FTN/FPN) when IRP binds. An antioxidant response element in FTN DNA binds Bach1, a heme-sensitive transcription factor that coordinates expression among antioxidant response proteins like FTN, thioredoxin reductase, and quinone reductase. FTN, an antioxidant because Fe 2+and O 2 (reactive oxygen species generators) are consumed to make iron mineral, is also a nutritional iron concentrate that is an efficiently absorbed, nonheme source of iron from whole legumes. FTN protein cages contain thousands of mineralized iron atoms and enter cells by receptor-mediated endocytosis, an absorption mechanism distinct from transport of nonheme iron salts (ferrous sulfate), iron chelators (ferric-EDTA), or heme. Recognition of 2 nutritional nonheme iron sources, small and large (FTN), will aid the solution of iron deficiency, a major public health problem, and the development of new policies on iron nutrition.

Not all DMT1 mutations lead to iron overload

DMT1 is a membrane-bound divalent metal transporter, which co-transports protons and (Fe 2+) from an acidic microenvironment (endosome, duodenal lumen) to the cell cytosol. Results from animal models and from patients have shown that DMT1 is required for intestinal iron absorption and iron acquisition by erythrocytes. Only three human patients with DMT1 mutations have been described so far. They presented with hypochromic microcytic anemia and heavy liver iron overload, even at a very young age. Here, we report the fourth human case, a 7-year old boy with a new homozygous DMT1 mutation, microcytic anemia but no liver iron overload. The mutation introduces a Glycine to Arginine (p.G75R) amino acid substitution. Glycine75 is a highly conserved amino acid present in the first transmembrane domain of the protein and we hypothesize that this mutation fully impairs ferrous iron uptake from the diet and prevents the onset of liver iron overload.

Molecular impact of divalent metal‐ion transporter (DMT1) mutations (V114del and G212V) found in a compound heterozygote with microcytic anemia and hepatic iron overload

DMT1 is a H+‐coupled divalent metal‐ion transporter critical for intestinal iron (Fe) absorption and erythroid Fe utilization. Beaumont et al (Blood 107, 4168 [2006]) described a patient compound heterozygous for two new DMT1 mutations (V114 deletion and G212V) associated with hypochromic‐microcytic anemia and hepatic Fe overload. The proband's sibling and parents each possess one mutated allele but were asymptomatic. We expressed mutant and wildtype (wt) DMT1 in Xenopus oocytes and used voltage‐clamp and radiotracer assays to examine the molecular impact of these novel mutations. The V114 deletion abolished 55Fe2+ transport activity whereas 55Fe2+ transport mediated by G212V‐DMT1 did not differ from wtDMT1. G212V had no effect on the pH dependence of 55Fe2+ transport, presteady‐state kinetics, or the affinity for Fe2+ (K0.5 = 1.7 ± 1.1 μM c.f. 1.3 ± 0.5 μM in wtDMT1). To our surprise, however, G212V‐DMT1 mediated much smaller Fe2+‐evoked currents than did wtDMT1. From simultaneous measurement of currents and 55Fe2+ fluxes, we arrived at a wildtype H+/Fe2+ ratio of 17 ± 1 which greatly exceeds that expected for strict stoichiometric transport, i.e. most of the wtDMT1‐mediated current arises from H+ slippage. Such slippage is normally thought of in terms of the energetic penalty to the cell; however, indications that H+ slippage, but not Fe2+ transport, is disrupted in the G212V mutant associated with disease raise the possibility that H+ slippage serve a physiological role.

Natural History of Recessive Inheritance of DMT1 Mutations

DMT1 deficiency causes microcytic hypochromic anemia due to decreased erythroid iron utilization. Anemia is present from birth. Transferrin saturation is high and serum ferritin is mildly elevated, despite liver iron overload. DMT1 deficiency must be considered in the differential diagnosis of microcytic hypochromic anemia observed in the newborn period.

Two new human DMT1 gene mutations in a patient with microcytic anemia, low ferritinemia, and liver iron overload

DMT1 mediates the pH-dependent uptake of Fe(2+) from the diet in duodenal enterocytes and in most other cells. It transfers iron from the endosomes to the cytosol following the uptake of the transferrin-transferrin receptor complex. DMT1 mutations are responsible for severe hypochromic microcytic anemia in rodents and in 2 human patients described recently. We report a compound heterozygote for 2 new DMT1 mutations, associated with microcytic anemia from birth and progressive liver iron overload. The first mutation is a GTG deletion in exon 5, leading to the V114 in-frame deletion in transmembrane domain 2, and the second is a G --> T substitution in exon 8 leading to the G212V replacement in transmembrane domain 5. Together with the 2 previously reported cases, this patient defines a new syndrome of congenital microcytic hypochromic anemia, poorly responsive to oral iron treatment, with liver iron overload associated paradoxically with normal to moderately elevated serum ferritin levels.

Microcytic anemia and hepatic iron overload in a child with compound heterozygous mutations in DMT1 (SCL11A2)

Divalent metal transporter 1 (DMT1) mediates apical iron uptake in duodenal enterocytes and iron transfer from the transferrin receptor endosomal cycle into the cytosol in erythroid cells. Both mk mice and Belgrade rats, which carry an identical DMT1 mutation, exhibit severe microcytic anemia at birth and defective intestinal iron use and erythroid iron use. We report the hematologic phenotype of a child, compound heterozygote for 2 DMT1 mutations, who was affected by severe anemia since birth and showed hepatic iron overload. The novel mutations were a 3-bp deletion in intron 4 (c.310-3_5del CTT) resulting in a splicing abnormality and a C>T transition at nucleotide 1246(p. R416C). A striking reduction of DMT1 protein in peripheral blood mononuclear cells was demonstrated by Western blot analysis. The proband required blood transfusions until erythropoietin treatment allowed transfusion independence when hemoglobin levels between 75 and 95 g/L (7.5 and 9.5 g/dL) were achieved. Hematologic data of this patient at birth and in the first years of life strengthen the essential role of DMT1 in erythropoiesis. The early onset of iron overload indicates that, as in animal models, DMT1 is dispensable for liver iron uptake, whereas its deficiency in the gut is likely bypassed by the up-regulation of other pathways of iron use.

Two New Human DMT1 Mutations in a Compound Heterozygous Patient with Microcytic Anemia and Low Iron Stores.

DMT1 is a divalent metal transporter with 12 transmembrane domains. It is expressed at the apical membrane of duodenal enterocytes, where it mediates pH-dependent uptake of Fe2+. In erythroid cells, it is found in the endosomal membrane where it transfers iron internalized through the transferrin-transferrin receptor pathway from the endosome to the cytosol. The same homozygous G>A substitution resulting in the G185A replacement is responsible for a severe hypochromic microcytic anemia in both the mk mouse and in the Belgrade rat. In humans, a homozygous G>C mutation has been described in a Czech patient, affecting the last nucleotide of exon 12. This mutation leads to the G399A replacement, without affecting the transport function of the protein. However, this mutation also induces a preferential in-frame skipping of exon 12, albeit not in all tissues. Accordingly, the patient has impaired iron acquisition in erythrocytes while duodenal iron absorption is increased leading to progressive iron overload.Here, we report a female patient born in 1996, with low birth weight and hypochromic microcytic anemia (Hb = 7.5 g/dl; MCV = 53 fL). She was transfused at day 0 and put on oral iron treatment. She was then lost to follow-up for five years. At the age of five, more extensive explorations showed a persistent microcytic anemia. The bone marrow displayed normal cellularity, 30% of nucleated cells were erythroid precursors with a moderate maturation defect, acidophilic forms being under-represented as compared to more immature forms. Soluble transferrin receptors were increased (8.3 mg/L; N = 0.83–1.76). Following oral iron therapy, serum ferritin levels remained low (15–25 μg/L; N = 14–197) despite an increase in transferrin saturation from 68 to 95 %. This high transferrin saturation resulted from the combination of reduced transferrin levels (1.64 g/L, N = 2.2–4.0) and increased serum iron levels (35 μmol/L; N = 11–24). On the other hand, hemoglobin raised from 7 to 9 g/dL only through increased number of RBC (5 to 5.7 T/L), since MCV and MCHC remained unchanged.We sequenced the entire transferrin receptor cDNA in this patient and found no mutation. We then sequenced the exons and the intron-exon boundaries of the DMT1 gene and found two heterozygous mutations. One mutation was a deletion of a GTG codon in exon 5, leading to the V114 in-frame deletion, in transmembrane domain 2. The other mutation is a G>T substitution in exon 8 leading to the G212V replacement in transmembrane domain 5. Both parents were asymptomatic, the father being heterozygous for the delV114 mutation and the mother heterozygous for the G212V mutation.This is the second patient described with a neonatal hypochromic microcytic anemia due to DMT1 mutations. Our data suggest that the two combined DMT1 mutations are responsible for the defect in iron utilization by erythroid cells, resulting in persistant microcytosis and impaired red cell maturation. The effect of the mutations on intestinal iron absorption is more difficult to evaluate since iron therapy allowed serum iron and transferrin saturation to increase but serum ferritin remained low and hemoglobin did not reach normal values.

Carboxyl-Terminus Determinants of the Iron Transporter DMT1/SLC11A2 Isoform II (−IRE/1B) Mediate Internalization from the Plasma Membrane into Recycling Endosomes

Mutations in DMT1 (Nramp2 and Slc11a2) impair iron metabolism and cause microcytic anemia. DMT1 is expressed at the duodenal brush border where it controls uptake of dietary iron and is present at the plasma membrane and in recycling endosomes of most cells, where it is necessary for acquisition of transferrin-associated iron. The goal of this study was to identify signal(s) in the cytoplasmic segments of DMT1 responsible for its subcellular targeting and internalization from the plasma membrane into recycling endosomes. We introduced mutations in the amino terminus (DeltaNT), carboxyl terminus (DeltaCT), as well as in NPAY28-31, YSCF62-65, and YLLNT555-559 motifs of a DMT1 construct bearing an exofacial epitope tag, which allowed labeling of the transporter at the cell surface for kinetic studies. Mutants were stably expressed in LLC-PK1 kidney cells and were studied for transport activity, subcellular localization, cell-surface and recycling pool distribution, and internalization from the plasma membrane. Kinetic studies showed that carboxyl-terminus mutants (DeltaCT and DeltaYLLNT) had an increased fraction of the "recycling pool" that was expressed at the cell surface because of impaired internalization from the plasma membrane. Further cell-surface-labeling and immunofluorescence studies in intact cells showed that the DeltaYLLNT and DeltaCT mutants were targeted to the lysosomal compartment upon internalization. These results suggest that the major signal for internalization and recycling of DMT1 isoform II (-IRE/1B) resides in its carboxyl terminus and that removal of this signal leads to a default lysosomal targeting.

Mechanisms of Haem and Non-Haem Iron Absorption: Lessons from Inherited Disorders of Iron Metabolism

Our current state of knowledge of the mechanism and regulation of intestinal iron absorption has been critically dependent on the analysis of inherited disorders of iron homeostasis in both humans and other animal species. Mutations in DMT1 and Ireg1 have revealed that these molecules are major mediators of iron transport across the brush border and basolateral membranes of the enterocyte, respectively. Similarly, the iron oxidase hephaestin has been shown to play an important role in basolateral iron efflux. The analysis of a range of human iron loading disorders has provided very strong evidence that the products of the HFE, TfR2, hepcidin and hemojuvelin genes comprise integral components of the machinery that regulates iron absorption and iron traffic around the body. Engineered mouse strains have already proved very effective in helping to dissect pathways of iron homeostasis, and in the future they will continue to provide important insights into the absorption of both inorganic and haem iron by the gut.

A spontaneous, recurrent mutation in divalent metal transporter-1 exposes a calcium entry pathway.

Divalent metal transporter-1 (DMT1/DCT1/Nramp2) is the major Fe2+ transporter mediating cellular iron uptake in mammals. Phenotypic analyses of animals with spontaneous mutations in DMT1 indicate that it functions at two distinct sites, transporting dietary iron across the apical membrane of intestinal absorptive cells, and transporting endosomal iron released from transferrin into the cytoplasm of erythroid precursors. DMT1 also acts as a proton-dependent transporter for other heavy metal ions including Mn2+, Co2+, and Cu2, but not for Mg2+ or Ca2+. A unique mutation in DMT1, G185R, has occurred spontaneously on two occasions in microcytic (mk) mice and once in Belgrade (b) rats. This mutation severely impairs the iron transport capability of DMT1, leading to systemic iron deficiency and anemia. The repeated occurrence of the G185R mutation cannot readily be explained by hypermutability of the gene. Here we show that G185R mutant DMT1 exhibits a new, constitutive Ca2+ permeability, suggesting a gain of function that contributes to remutation and the mk and b phenotypes.

Of metals, mice, and men: what animal models can teach us about body iron loading.

Of metals, mice, and men: what animal models can teach us about body iron loading.