HFE Gene Research Articles

ACMG SF v3.0 list for reporting of secondary findings in clinical exome and genome sequencing: a policy statement of the American College of Medical Genetics and Genomics (ACMG)

ACMG SF v3.0 list for reporting of secondary findings in clinical exome and genome sequencing: a policy statement of the American College of Medical Genetics and Genomics (ACMG)

HFE Genotype, Ferritin Levels and Transferrin Saturation in Patients with Suspected Hereditary Hemochromatosis.

HFE hemochromatosis is characterized by increased iron absorption and iron overload due to variants of the iron-regulating HFE gene. Overt disease is mainly associated with homozygosity for the C282Y variant, although the H63D variant in compound heterozygosity with C282Y (C282Y/H63D) contributes to disease manifestation. In this observational study, we describe the association between biochemical findings, age, gender and HFE genotype in patients referred from general practice to a tertiary care referral center for diagnostic workup based on suspected hemochromatosis due to persistent hyperferritinemia and HFE variants. C282Y and H63D homozygosity were, respectively, the most and least prevalent genotypes and we found a considerable variation in transferrin saturation and ferritin levels independent of HFE genotype, which may indeed represent a diagnostic challenge in general practice. While our results confirm C282Y homozygosity as the major cause of iron accumulation, non-C282Y homozygotes also displayed mild to moderate hyperferritinemia with median ferritin levels at 500–700 µg/L, well above the reference cut-off. Such findings have traditionally been ignored in the clinic, and initiation of iron depletion has largely been restricted to C282Y homozygotes. Nevertheless, superfluous iron can aggravate pathogenesis in combination with other diseases and risk factors, such as inflammation, cancer and hepatopathy, and this possibility should not be neglected by clinicians.

Contributions of HFE polymorphisms to brain and blood iron load, and their links to cognitive and motor function in healthy adults.

BackgroundBrain iron overload is linked to brain deterioration, and cognitive and motor impairment in neurodegenerative disorders and normal aging. Mutations in the HFE gene are associated with iron dyshomeostasis and are risk factors for peripheral iron overload. However, links to brain iron load and cognition are less consistent and data are scarce.Aims and methodsUsing quantitative susceptibility mapping with magnetic resonance imaging, we investigated whether C282Y and H63D contributed to aging‐related increases in brain iron load and lower cognitive and motor performance in 208 healthy individuals aged 20‐79 years. We also assessed the modulatory effects of HFE mutations on associations between performance and brain iron load, as well as peripheral iron metabolism.ResultsIndependent of age, carriers of either C282Y and/or H63D (HFE‐pos group, n = 66) showed a higher load of iron in putamen than non‐carriers (HFE‐neg group, n = 142), as well as higher transferrin saturation and lower transferrin and transferrin receptors in blood. In the HFE‐neg group, higher putaminal iron was associated with lower working memory. In the HFE‐pos group, higher putaminal iron was instead linked to higher executive function, and lower plasma transferrin was related to higher episodic memory. Iron‐performance associations were modest albeit reliable.ConclusionOur findings suggest that HFE status is characterized by higher regional brain iron load across adulthood, and support the presence of a modulatory effect of HFE status on the relationships between iron load and cognition. Future studies in healthy individuals are needed to confirm the reported patterns.

Identification of Variants Associated With Rare Hematological Disorder Erythrocytosis Using Targeted Next-Generation Sequencing Analysis.

An erythrocytosis is present when the red blood cell mass is increased, demonstrated as elevated hemoglobin and hematocrit in the laboratory evaluation. Congenital predispositions for erythrocytosis are rare, with germline variants in several genes involved in oxygen sensing (VHL, EGLN1, and EPAS1), signaling for hematopoietic cell maturation (EPOR and EPO), and oxygen transfer (HBB, HBA1, HBA2, and BPGM) that were already associated with the eight congenital types (ECYT1–8). Screening for variants in known congenital erythrocytosis genes with classical sequencing approach gives a correct diagnosis for only up to one-third of the patients. The genetic background of erythrocytosis is more heterogeneous, and additional genes involved in erythropoiesis and iron metabolism could have a putative effect on the development of erythrocytosis. This study aimed to detect variants in patients with yet unexplained erythrocytosis using the next-generation sequencing (NGS) approach, targeting genes associated with erythrocytosis and increased iron uptake and implementing the diagnostics of congenital erythrocytosis in Slovenia. Selected 25 patients with high hemoglobin, high hematocrit, and no acquired causes were screened for variants in the 39 candidate genes. We identified one pathogenic variant in EPAS1 gene and three novel variants with yet unknown significance in genes EPAS1, JAK2, and SH2B3. Interestingly, a high proportion of patients were heterozygous carriers for two variants in HFE gene, otherwise pathogenic for the condition of iron overload. The association between the HFE variants and the development of erythrocytosis is not clearly understood. With a targeted NGS approach, we determined an actual genetic cause for the erythrocytosis in one patient and contributed to better management of the disease for the patient and his family. The effect of variants of unknown significance on the enhanced production of red blood cells needs to be further explored with functional analysis. This study is of great significance for the improvement of diagnosis of Slovenian patients with unexplained erythrocytosis and future research on the etiology of this rare hematological disorder.

Chronic hepatitis B in children carried out of the hemochromatosis gene HFE

Purpose: to establish the frequency and clinical significance of mutant variations of the HFE gene polymorphism in chronic hepatitis B (CHB) in children with iron overload syndrome (IOS).Materials and methods: 60 children with chronic hepatitis B with iron overload syndrome (IOS) were examined. When distributing children into groups, we took into account the criteria we developed for assessing the degree of life expectancy in children with CHB: CST>0.5 – mild degree of life expectancy (43,3% of children), CST˃0.5 – mild degree of life expectancy (43,3% of children), CST˂0,5 – moderate severity of life expectancy (31,7% of children) and CST˂0,2 – severe degree of SPL (25,0%). Virological verification of HBV was performed by ELISA and PCR. Using PCR Real Time and molecular genetic analysis, HFE gene C282Y, H63D, S65C mutations were detected from amplified DNA using the PRONTO Hemochromatosis reagent kit (Israel). The transferrin saturation coefficient (CST) was calculated using the formula CST = sTfR / log10.Ft. Results:Results: The study of the hemochromatosis gene HFE showed that the overwhelming majority (84,0%) of children with CHB with IOS were carriers of heterozygous, phenotypically different, mutant types. And only 16,0% of sick children were homozites of the wild (normal) HFE gene. Analysis of the phenotypic polymorphism of the hemochromatosis gene HFE revealed the presence of three point heterozygous mutations: H63D, S65C and combined variations in H63D / S65C, the latter of which is associated with severe forms of CHB and severe IOS.Conclusion. Children with CHB with IOS are characterized by a high incidence of heterozygous mutations in the HFE gene, the phenotypic manifestations of which were S65C, H63D, H63D / S65C. The comparability of the heterozygous combined mutation H63D / S65C with severe forms of CHB and a severe degree of IOS gives grounds to consider this phenotype of the HFE gene as a factor in the progression of the disease.

MRI-Based Iron Phenotyping and Patient Selection for Next-Generation Sequencing of Non-Homeostatic Iron Regulator Hemochromatosis Genes.

Background and AimsHigh serum ferritin is frequent among patients with chronic liver disease and commonly associated with hepatic iron overload. Genetic causes of high liver iron include homozygosity for the p.Cys282Tyr variant in homeostatic iron regulator (HFE) and rare variants in non‐HFE genes. The aims of the present study were to describe the landscape and frequency of mutations in hemochromatosis genes and determine whether patient selection by noninvasive hepatic iron quantification using MRI improves the diagnostic yield of next‐generation sequencing (NGS) in patients with hyperferritinemia.Approach and ResultsA cohort of 410 unselected liver clinic patients with high serum ferritin (defined as ≥200 μg/L for women and ≥300 μg/L for men) was investigated by HFE genotyping and abdominal MRI R2*. Forty‐one (10%) patients were homozygous for the p.Cys282Tyr variant in HFE. Of the remaining 369 patients, 256 (69%) had high transferrin saturation (TSAT; ≥45%) and 199 (53%) had confirmed hepatic iron overload (liver R2* ≥70 s−1). NGS of hemochromatosis genes was carried out in 180 patients with hepatic iron overload, and likely pathogenic variants were identified in 68 of 180 (38%) patients, mainly in HFE (79%), ceruloplasmin (25%), and transferrin receptor 2 (19%). Low spleen iron (R2* <50 s−1), but not TSAT, was significantly associated with the presence of mutations. In 167 patients (93%), no monogenic cause of hepatic iron overload could be identified.ConclusionsIn patients without homozygosity for p.Cys282Tyr, coincident pathogenic variants in HFE and non‐HFE genes could explain hyperferritinemia with hepatic iron overload in a subset of patients. Unlike HFE hemochromatosis, this type of polygenic hepatic iron overload presents with variable TSAT. High ferritin in blood is an indicator of the iron storage disease, hemochromatosis. A simple genetic test establishes this diagnosis in the majority of patients affected. MRI of the abdomen can guide further genetic testing.

Hemochromatoses

In the field of chronic iron overload diseases, hemochromatoses are genetic diseases where iron overload is caused by hepcidin deficiency and, much more rarely, by hepcidin resistance. These disorders are related to mutations of HFE or non-HFE genes that are involved in the control of hepcidin expression or bioactivity, which tunes systemic iron homeostasis.1

Deletion of BMP6 Worsens the Phenotype of Hemojuvelin-Deficient Mice and Attenuates Hepcidin Levels Reached after LPS Stimulation

Liver sinusoidal endothelial cells (LSEC) produce bone morphogenetic protein BMP6 which acts on the hepatocyte co-receptor hemojuvelin (HJV) to regulate hepcidin production. Both are required to ensure optimal maintenance of iron homeostasis. In the mouse, deletion of either Bmp6 or Hjv leads to a similar phenotype characterized by hepcidin insufficiency, severe iron loading and extrahepatic iron accumulation in males, which is consistent with the current views that HJV is a coreceptor for BMP6.Whether BMP6 and HJV may also signal to hepcidin independently of each other is still a topic of discussion. To provide evidence that BMP6 and HJV can separately stimulate hepcidin, we intercrossed Hjv and Bmp6 knockout mice and looked whether deletion of both Bmp6 and Hjv in mice of the F2 progeny was aggravating the phenotype of single knockout animals. Whether BMP6 and HJV are both required for the upregulation of hepcidin by inflammatory stimuli is another unresolved issue. We took the opportunity of having genetically comparable single and double knockout animals to challenge them with LPS and examine the impact of Bmp6 and/or Hjv deletion on Smad signaling and hepcidin expression after stimulation.Interestingly, deletion of Bmp6 more dramatically repressed the already reduced hepcidin expression of Hjv-/- mice, regardless of sex. These observations were confirmed at the protein level and Western-blot analyses showed that deletion of Bmp6 further altered Smad1/5/8 signaling in the liver of Hjv-/-mice. Whereas Bmp6-/- or Hjv-/- males have iron depositsin acinar cells of the exocrine pancreas and in the heart, females do not accumulate iron in these extrahepatic tissues, which reflects the fact that, in the absence of testosterone, their hepcidin is less strongly repressed than in males. Nevertheless, the concomitant loss of Bmp6 suppresses this hepcidin advantage over males. As a consequence, and in contrast to single Bmp6-/- or Hjv-/- females, double knockout females have massive iron loading in all extrahepatic tissues examined.Notably, while LPS significantly induces hepcidin mRNA and protein not only in wild-type males and females, but also in single and double knockout animals, the level reached after stimulation depends on basal expression of hepcidin. It is highest in wild-type mice, intermediate in Bmp6-/- and in Hjv-/- mice, and lowest in double knockout animals. This is compatible with the proposed synergy between IL6/STAT3 and BMP/SMAD signaling in regulating hepcidin during inflammation. Smad5 signaling was previously shown to be activated by activin B as a consequence of LPS stimulation but to have no impact on hepcidin induction. Here, although activation of Smad5 by LPS was similar in wild-type and in Bmp6-/- mice, the level of hepcidin reached after stimulation was much lower in Bmp6-/- mice. In contrast, Hjv-/- mice present with reduced Smad5 activation compared with Bmp6-/- mice but have similar induction of hepcidin. These data definitely confirm the lack of relationship between activation of Smad1/5/8 signaling by inflammatory stimuli and elevation of hepcidin expression.In conclusion, analysis of this Bmp6-/- x Hjv-/- intercross clearly shows that deletion of both Bmp6 and Hjv further represses hepcidin and aggravates the phenotype of single knockout animals. This indicates that, when one actor of the major hepcidin signaling pathway is lacking, alternative pathways, although less efficient to activate Smad1/5/8, succeed in maintaining hepcidin to a level avoiding extrahepatic iron accumulation in females. The suppression of these alternative pathways, as here in Bmp6/Hjv double knockout animals, leads to a greater repression of hepcidin in mice of both genders and a substantial exacerbation of the extrahepatic iron overload phenotype in females. Our data also show that induction of hepcidin by LPS in vivo is linked to BMP/Smad signaling before but not after stimulation. Notably, the less severely affected Bmp6-/- or Hjv-/- females produce, when challenged with LPS, more hepcidin than unchallenged wild-type mice. Thus, in females, treatments targeting BMP type I receptors will be more effective against anemia of inflammation than treatments that would target only hemojuvelin, as the latter would not prevent BMP6 to signal to hepcidin independently of HJV. DisclosuresNo relevant conflicts of interest to declare.

Idiopathic Hemochromatosis Presenting As a Sicca Syndrome. A Case Report and Review of the Literature

Hemochromatosis is one of the most common heritable genetic conditions in people of northern European extraction with a prevalence of 1 in 200. The disease has a variable penetration and about 1 in 10 people of this demographic carry a mutation in one of the genes regulating iron metabolism, the most common allele being the C282Y allele in the HFE gene. Despite the increased awareness of Hemochromatosis, the disease is commonly under diagnosed. Symptoms of hemochromatosis can be non-specific and are related to iron deposition within various body organs. Clinical findings seen in fully established disease include liver cirrhosis, cardiomyopathy, hypogonadism, diabetes mellitus and skin pigmentation (bronze diabetes). In early stages, the disease is either asymptomatic or could present with weakness, fatigue and joint pains. Other rare manifestations include night sweats, movement disorders, including chorea and parkinsonism, as well as non-specific GI symptoms.We present a case of a 35-year-old gentleman who was following in the outpatient clinic with the complaints of fatigue, dry eyes, dry mouth and throat for the past several years. He also reported hand tremors, occasional low back, knee and ankle pain without stiffness, since childhood. He had a medical history of Raynaud syndrome treated with Nifedipine. Physical examination was consistent with dry mucus membranes and dry mouth. Patient workup revealed positive ANA, borderline low level of C3 and C4, normal ESR, CRP, TSH and negative serologies for Sjogren's A and B antibodies. Patient's excessive dryness was clinically diagnosed as Sicca syndrome and was treated with artificial tears and hydroxychloroquine which helped with the dryness, however the fatigue persisted.Few years later, he developed worsening of his hand tremors and developed transient unsteadiness with no focal weakness or sensory symptoms. He also developed right upper quadrant pain with tenderness. U/s abdomen and Ct scan were unremarkable. Further work up revealed slight elevation of liver enzymes with normal bilirubin. He had no history of alcohol use and hepatitis serologies were negative. Iron studies were ordered, which showed marked elevation of ferritin and iron saturation was found to be 61%. Genetic analysis showed that he was a carrier of a hemochromatosis-associated alleles C282Y/H63D. A diagnosis of hemochromatosis was confirmed by liver biopsy which showed heavy iron deposition. Patient received treatment with maintenance phlebotomies and has remained well without evidence of disease progression.Our patient had a long standing constellation of nonspecific symptoms including hand tremors, arthralgia, sicca like symptoms, which were misdiagnosed as Sicca syndrome. On review of the literature, only a handful of cases have been reported describing the initial presentation of idiopathic hemochromatosis as Sicca syndrome. Our case emphasizes the importance of early recognition of rare presenting features of this disease. It also underlines whether there is an association between these two distinct diseases, which needs to be further explored. DisclosuresNo relevant conflicts of interest to declare.

Screening of Mutations Related to Hereditary Anemias Using NGS-Targeted Sequencing Panel

Hereditary forms of anemia arise due to defects in erythrocyte differentiation from bone marrow precursor cells, or shortened survival of erythrocytes. Both cases result in the deficiency of mature cells in the bloodstream. Defects in the erythrocyte membrane proteins (e.g. hereditary spherocytosis and elliptocytosis/ pyropoikilocytosis) are common, and they manifest in association with morphological changes in the red blood cells. Other causes of hemolytic anemias include hemoglobinopathies (e.g. sickle cell diseases, thalassemias, etc) and enzymopathies (e.g. Glucose 6 phosphate dehydrogenase deficiency and pyruvate kinase deficiency), caused by defects in metabolic enzymes. Hereditary anemia can also be caused by erythroid lineage disorders such as congenital dyserythropoietic anemias (CDA), characterized by distinct morphologic abnormalities of marrow erythroblasts. Diseases that result in hereditary anemias are difficult to diagnose, due to the large clinical and genetic heterogeneity. The use of conventional techniques for the systematic screening of all potentially implicated genes would be impractical, costly and time-consuming. To address this issue, we have customized a rapid comprehensive next-generation sequencing-based assay that evaluates 58 genes with published disease-causing mutations for future clinical application. Of these genes, 27 were related with RBC cytoskeletal disorders and enzymopathies, 8 were involved with CDAs and 23 genes were related with hemochromatosis, sideroblastic anemia and porphyria. Our panel covers the complete coding region, splice site junctions, and some promoter regions. Exon capture probes were designed with the aid of the Sure Design program (Agilent Technologies, Inc., CA, USA). Targeted gene capture and library construction for next-generation sequencing (NGS) were performed using Haloplex kit (Agilent Technologies, Santa Clara, USA). Enriched samples were then sequenced on an Illumina HiSeq 2500 sequencer with 150 base pair, paired-end reads. Overall, the quality scores obtained were high, with an average of 91% of the bases analyzed with >Q30. This means that the probability that a given base is wrong is less than 0.1%. Sequencing reads were aligned to the human genome reference sequence and analysis of coverage and variants was completed using Sure Call software (Agilent Technologies, Inc., CA, USA). The validation included the benchmark sample NA12878 (Coriell Institute, NJ, USA) in triplicate. All variants were detected using Haloplex amplification followed by NGS were compared to the results available in the coding region sequencing databases of the NA12878 sample. The panel showed a sensitivity of 98.7% and a specificity of 99.9%. We also tested our panel in 43 patients with hereditary anemia searching for causative variants. Possible pathogenic variants were identified in 37 patients (86%) and explained the etiology of the diseases in 69.8% of the cases. Variants in the β-spectrin (SPTB gene) were the most frequent cause of hereditary spherocytosis (HS) in our sample, identified in 13 out of the 26 patients with previous diagnosis of HS (50%). Variants in the ankyrin (ANK1) were the second most frequent cause of HS, identified in 6 cases. Variants in SPTA1, SLC4A1, PKLR, CDAN1, G6PD, HFE and KIF23 genes were also identified. Most of the identified variants were novel. To conclude, next-generation sequencing provides a cost-effective and relatively rapid approach to molecular characterization of a disease. The identification of pathogenic variants is essential for genetic counselling, pre-implantation genetic diagnosis and even for future gene therapy. The panel we developed proved to be robust, with very low false positive and negative results and successfully determined the molecular causes of hereditary anemia in most cases. DisclosuresNo relevant conflicts of interest to declare.

Mutation Analysis and Allele Frequencies of HFE Gene C282Y, H63D and S65D in Patients with Hyperferritinemia and Healthy Controls from a City in Northeastern Brazil

Hereditary hemochromatosis (HH) is a genetic disease caused by high iron absorption and deposition in several organs. This accumulation results in clinical disturbances such as cirrhosis, arthritis, cardiopathies, diabetes, sexual disorders and skin darkening. The C282Y mutation is well defined in hemochromatosis etiology. Two other mutations have been described, H63D and S65C, associated with a milder form of the disease. The aims of this study were to identify the H63D, S65C and C282Y genetic mutations in the hemochromatosis gene and assess the frequency of these mutations in the HFE protein gene in patients with hyperferritinemia which are sent to the DNA Center laboratory in Natal, Rio Grande do Norte state, in addition to evaluating the correlation between the H63D, C282Y and S65C mutations in hereditary hemochromatosis and serum ferritin. The biochemical dosages and molecular analyses are carried out using the enzymatic method and PCR with enzymatic restriction, respectively. Of the 300 patients investigated, 48.7% showed no mutation and 51.3% some type of mutation: 4.4 % exhibited C282Y heterozygous mutation; 2.7% C282Y homozygous mutation; 31.9% H63D heterozygous mutation; 8.1% H63D homozygous mutation; and 5.1%, heterozygous mutation in both genes. The S65C mutation was studied in 112 patients, 2.7% with heterozygous mutation (S65D/WT) and 1.8% with double heterozygosity (H63D/S65C). With regard to sex, we observed the highest number of cases with molecular changes in men compared to women in the two mutations evaluated. Since it is considered a public health problem and exhibits low toxicity with treatment, early genetic diagnosis of HH is recommended, especially in patients with elevated serum ferritin, thereby preventing severe clinical manifestations resulting from late diagnosis. Our findings show the importance of genetic studies in patients with suspected hereditary hemochromatosis due to the high incidence of this hereditary disease in our region. DisclosuresNo relevant conflicts of interest to declare.

Discovery of the main genes regulating iron metabolism is the result of the study of hemochromatosis

The review article is devoted to the history of the discovery of genes that regulate iron metabolism. The natural model that became the basis for the study of genes was hemochromatosis (HC). HC is a hereditary disease caused by excess iron in tissues. The first to be discovered was the HFE gene, whose physiological role is to prevent iron overload in cells by decreasing the binding of transferrin receptor-1 (TFR-1) to metal-saturated transferrin. This happened in 1996; the gene was mapped to chromosome 6p.23.3. In the European population, mutations in the HFE gene were detected in 80-100% of patients with HC. This variant of the disease is classified as type 1 He in OMIM. In 1999, the HJV gene on chromosome 1q21 was discovered, the product of which, hemouvelin, was later found to modulate the expression of hepcidin, and the SLC40A1 gene on chromosome 2q32, which encodes ferroportin, an iron transporter from enterocytes, macrophages, hepatocytes and placental cells into blood plasma. HC associated with mutations in these genes is represented by types 2A and 4 in the OMIM classification. In 2000, the HAMP gene on chromosome 19q13.1 was discovered, encoding the main iron regulatory hormone hepcidin, which blocks ferroportin, and the TFR-2 gene on chromosome 7q22. controlling the capture of iron by hepato-cytes and bone marrow cells, as well as the level of metal in the blood plasma. HC associated with mutations in these genes is represented by types 2B and 3 in the OMIM classification.

Whole-body R2∗ mapping to quantify tissue iron in iron storage organs: reference values and a genotype

To define reference values for the transverse relaxation rate (R2∗) in iron storage organs and to investigate the role of human haemochromatosis protein (HFE) genotype on iron storage. Whole-body magnetic resonance imaging (MRI) including a five-echo gradient-echo sequence was performed in 483 volunteers (269 men, mean age 59.3±12.2 years) without clinical evidence of an iron storage disease at 1.5 T. R2∗ values were assessed for liver, spleen, pancreas, heart, bones, and brain parenchyma. The HFE genotype was determined regarding the single nucleotide polymorphisms (SNPs) rs74315324, rs1799945, rs41303501, rs1800562, rs1800730. R2∗ values were compared among participants without and with at least one mutation. R2∗ reference values were defined using volunteers without any mutation. Three hundred and one participants had no mutations in any HFE SNP, 182 had at least one mutation. HFE gene mutations were distributed as (heterozygous/homozygous) rs1799945:132/9, rs1800562:33/1, and rs1800730:11/0. Mean R2∗ values±SD (per second) in the group without mutation were: liver: 33.4±12.7, spleen: 24.1±13.8, pancreas: 27.2±6.6, heart: 32.7±11.8, bone: 69.3±21.0, brain parenchyma: 13.9±1.2. No significant difference in R2∗ values were found between participants with and without the HFE gene mutation for any examined iron storage organ (pliver=0.09, pspleen=0.36, ppancreas=0.08, pheart=0.36, pbone=0.98, pbrain=0.74). Reference values of R2∗ in iron storage organs are feasible to support the diagnosis of iron storage diseases. Non-specific mutations in HFE SNPs appear not to affect the phenotype of tissue iron accumulation.

Hémochromatoses

AbstractHemochromatoses benefit from a great clarification of their nosology thanks to the consideration of the mechanism underlying the development of iron overload. Thus, the mechanistic common denominator is hepcidin deficiency which, by stimulating the cellular iron export activity of ferroportin in the duodenum and the spleen, leads to a cascade: hyper-sideremia, appearance of non-transferrin bound iron that first targets the liver, and exerts cellular toxicity damaging key organs and corresponding to the development of hemochromatosis, that is source of morbidity and mortality. In the Caucasian subject, hemochromatosis linked to the HFE gene is by far the most frequent. Non HFE-related hemochromatoses are rare but multi-ethnic and often severe. The contribution of biology is major for the understanding of the pathophysiology (role of hypo-hepcidinemia), for the diagnosis (coefficient of transferrin saturation, ferritinemia) including the etiological identification (genetic tests), and for the therapeutic follow-up (importance of ferritinemia and possibly in the future of hepcidinemia). The diagnosis of hemochromatosis has become totally non-invasive (based on clinical, biological and imaging techniques) and its therapy, which remains based on phlebotomies, should in the future call for innovative approaches aimed at restoring normal iron metabolism.

Impact of HFE-2 and HAMP Gene Variations on Iron Overload in Pediatric Patients with Non-Transfusion Dependent Thalassemia: A Pilot Study.

The online version contains supplementary material available at 10.1007/s12288-021-01442-9.

SLN124, a GalNac-siRNA targeting transmembrane serine protease 6, in combination with deferiprone therapy reduces ineffective erythropoiesis and hepatic iron-overload in a mouse model of β-thalassaemia.

SummaryBeta‐thalassaemia is an inherited blood disorder characterised by ineffective erythropoiesis and anaemia. Consequently, hepcidin expression is reduced resulting in increased iron absorption and primary iron overload. Hepcidin is under the negative control of transmembrane serine protease 6 (TMPRSS6) via cleavage of haemojuvelin (HJV), a co‐receptor for the bone morphogenetic protein (BMP)‐mothers against decapentaplegic homologue (SMAD) signalling pathway. Considering the central role of the TMPRSS6/HJV/hepcidin axis in iron homeostasis, the inhibition of TMPRSS6 expression represents a promising therapeutic strategy to increase hepcidin production and ameliorate anaemia and iron overload in β‐thalassaemia. In the present study, we investigated a small interfering RNA (siRNA) conjugate optimised for hepatic targeting of Tmprss6 (SLN124) in β‐thalassaemia mice (Hbbth3/+). Two subcutaneous injections of SLN124 (3 mg/kg) were sufficient to normalise hepcidin expression and reduce anaemia. We also observed a significant improvement in erythroid maturation, which was associated with a significant reduction in splenomegaly. Treatment with the iron chelator, deferiprone (DFP), did not impact any of the erythroid parameters. However, the combination of SLN124 with DFP was more effective in reducing hepatic iron overload than either treatment alone. Collectively, we show that the combination therapy can ameliorate several disease symptoms associated with chronic anaemia and iron overload, and therefore represents a promising pharmacological modality for the treatment of β‐thalassaemia and related disorders.

Low incidence of focal lesions in the thyroid glands of patients with hereditary haemochromatosis — a single-centre study from Poland

Hereditary hemochromatosis (HH) is a disease characterized by the excessive absorption of iron and its deposition in various organs. Late complications of this disease include cirrhosis, hepatocellular carcinoma and endocrine disorders. Data from literature on thyroid disorders in patients with HH are inconsistent and ambiguous and no research has been done to determine the relationship between excessive accumulation of iron and the thyroid volume. Therefore, the aim of this study was to characterize thyroid function and ultrasound image in patients with clinically overt hereditary hemochromatosis. We studied 40 patients who were diagnosed with hereditary hemochromatosis with one of the mutation of HFE gene and iron deposites in liver in specimen from liver biopsy (graded G2 to G4) or in MRI. To assess the thyroid function, the ultrasound examination of the thyroid gland was performed and serum TSH concentrations were measured. We showed in our study that patients with HH have diagnosed with nodular goiters statistically less frequent than in control group. We did not reveal any statistically significant differences in TSH concentrations between patients with HH and the general population. However patients with more severe iron deposits in liver showed lower TSH. Our results indicate that iron overload syndromes and iron deposition could have prevent from formation of focal lesions in thyroid gland. Excess iron may act as a "protective" factor against the formation of nodular lesions in the thyroid gland through the production of peripheral thyroid hormones, i.e. thyroxine (T4) and triiodothyronine (T3), and the reduction of TSH concentration.

Hepatocyte neogenin is required for hemojuvelin-mediated hepcidin expression and iron homeostasis in mice

AbstractNeogenin (NEO1) is a ubiquitously expressed multifunctional transmembrane protein. It interacts with hemojuvelin (HJV), a BMP coreceptor that plays a pivotal role in hepatic hepcidin expression. Earlier studies suggest that the function of HJV relies on its interaction with NEO1. However, the role of NEO1 in iron homeostasis remains controversial because of the lack of an appropriate animal model. Here, we generated a hepatocyte-specific Neo1 knockout (Neo1fl/fl;Alb-Cre+) mouse model that circumvented the developmental and lethality issues of the global Neo1 mutant. Results show that ablation of hepatocyte Neo1 decreased hepcidin expression and caused iron overload. This iron overload did not result from altered iron utilization by erythropoiesis. Replacement studies revealed that expression of the Neo1L1046E mutant that does not interact with Hjv, was unable to correct the decreased hepcidin expression and high serum iron in Neo1fl/fl;Alb-Cre+ mice. In Hjv−/− mice, expression of HjvA183R mutant that has reduced interaction with Neo1, also displayed a blunted induction of hepcidin expression. These observations indicate that Neo1-Hjv interaction is essential for hepcidin expression. Further analyses suggest that the Hjv binding triggered the cleavage of the Neo1 cytoplasmic domain by a protease, which resulted in accumulation of truncated Neo1 on the plasma membrane. Additional studies did not support that Neo1 functions by inhibiting Hjv shedding as previously proposed. Together, our data favor a model in which Neo1 interaction with Hjv leads to accumulation of cleaved Neo1 on the plasma membrane, where Neo1 acts as a scaffold to induce the Bmp signaling and hepcidin expression.

Pathology of Hepatic Iron Overload

Pathology of Hepatic Iron Overload

CME Laboratory 63/Answers: Diagnostics of Iron Metabolism

CME Laboratory 63/Answers: Diagnostics of Iron Metabolism Abstract. Abstract: Iron deficiency is common and affects the course of many chronic diseases. The diagnosis of absolute and manifest iron deficiency anemia can be easily made by measuring hemoglobin and serum ferritin levels. In inflammatory diseases, the diagnosis can be facilitated by additional laboratory parameters such as soluble transferrin receptor. In several chronic diseases like cardiac or renal failure, different and higher thresholds for serum ferritin apply depending on the disease and stage, sometimes with additional consideration of transferrin saturation. Transferrin saturation is also important for the diagnosis of hemochromatosis. In patients with transferrin saturation >45 %, diagnosis usually requires evidence of homozygosity for the C282Y mutation in the HFE gene.