Expression of hepcidin and other iron-related genes in type 3 hemochromatosis due to a novel mutation in transferrin receptor-2

Abstract

Citation: Pelucchi S, Mariani R, Trombini P, Coletti S, Pozzi M, Paolini V, Barisani D, Piperno A. Expression of hepcidin and other iron-related genes in type 3 hemochromatosis due to a novel mutation in transferrin receptor-2. Haematologica 2009; 94:276-279. doi: 10.3324/haematol.13576 ©2009 Ferrata Storti Foundation. This is an open-access paper. ABSTRACT Expression of hepcidin and other iron-related genes in type 3 hemochromatosis due to a novel mutation in transferrin receptor-2 © F e r r a t a S t o r t i F o u n d a t i o nTfR2 mutation and expression study haematologica | 2009; 94(2) | 277 | Liver biopsy was processed for histology and mRNA analysis. Assessment of hepatic fibrosis and iron overload, mRNA extraction and cDNA synthesis were performed as previously described in detail.11 cDNA was stored at -80°C until its use. cDNA was amplified by PCR (Online Supplementary Table S1), directly sequenced and compared with reference sequence (GenBank Accession N°NM_003227.2).mRNA expression levels of BMP2, BMP4, CP, DMT1, HAMP, HFE, HJV, SLC40A1, TFR1, TFR2 (the commercial probe was designed in exon boundary 3-4, Part Number Hs00162690_m1) and HPRT1, chosen as housekeeping gene, were evaluated by quantitative Real-Time PCR (qRT-PCR) as previously described.11 The proband's results were compared to those observed in 10 patients HFE-HH (C282Y homozygotes) and 8 controls with nonalcoholic-fatty-liver (NAFLD) without hepatic iron overload, absent fibrosis and inflammation. Full clinical data of HFE-HH patients and NAFLD subjects are reported in Barisani et al. 11Urinary hepcidin was measured by SELDI-TOF-MS according to Bozzini et al. 12 A challenge test by 65 mg oral iron as ferrous sulfate (iron, 65 mg, CVS Pharmacy) was conducted to assess hepatic response to iron, as previously reported. 13Written informed consent for genetic study, liver biopsy and iron challenge were obtained according to the Institution's guidelines. The study protocol conforms to the ethical guidelines of the 1975 Declaration of Helsinki as reflected in a priori approval by the Ethical Committee of San Gerardo Hospital. Results and Discussion Case descriptionA 47 year-old woman came to our attention in January 2007. In 1998, serum ferritin and transferrin saturation were 2207 µg/L and 88% respectively. HFE (C282Y and H63D), TFR2 (E60X, M172K, Y250X, AVAQ594-597 del) and Ferroportin1 (N144H, V162 del) mutations were absent. Hepatitis B and C viral infections, hematologic and inflammatory diseases were excluded. No further analysis and treatment were performed. At our evaluation, serum ferritin was 2674 µg/L, transferrin saturation 88%, hemoglobin 14.6 g/dL and mean corpuscular volume 89 fl. Both parents originated from the same village in Southern Italy but there was neither family history of consanguinity or hemocromatosis; her 2 offspring and 2 siblings have normal serum iron indices. She had regular menstrual blood losses, no history of alcohol intake, blood transfusions or parenteral iron administration. Metabolic syndrome, char...

Hepcidin response to acute iron intake and chronic iron loading in dysmetabolic iron overload syndrome

“…Thus, we suggest that the lack of response to acute iron test in DIOS patients with ‘higher’ hepcidin might be caused by the inhibitory action of hepcidin on intestinal iron absorption. This is different to that observed in haemochromatosis patients in whom the lack of response to iron ingestion is because of a defect of iron sensing at hepatocyte level (8, 24). We have no clear demonstration of our hypothesis in DIOS because we measured TS at 24 h after oral iron, which is unlikely to reflect the absorption of the test dose.…”

A time course of hepcidin response to iron challenge in patients with HFE and TFR2 hemochromatosis

“…A previously described third patient with TFR2 hemochromatosis whose urinary hepcidin was measured 24 h after an iron challenge also showed a lack of hepcidin response. 9 We propose that TFR2 may be involved in iron-sensing and may mediate the increase in hepcidin in response to the acute iron stimulus. However, detailed testing of this hypothesis would require lowering the transferrin saturation which, in our experience, is difficult even with weekly phlebotomy.…”

“…2 Hepcidin is undetectable or present at an extremely low level in the severe, juvenile form of hemochromatosis due to mutations of hepcidin 3 or hemojuvelin, 4 and is decreased/inadequate in HFE C282Y homozygotes [5][6][7] and in the few studied patients with TFR2-hemochromatosis. 8,9 Hepcidin levels inappropriately low for the severity of iron loading have also been found in animal models of the different types of hemochromatosis. [10][11][12][13] The molecular mechanism of iron sensing that maintains systemic iron homeostasis in mammals is unclear, but both HFE and transferrin receptor 2 (TFR2) have been implicated in this function due to their interaction and the ability of TFR2 to bind diferric transferrin.…”

Next-generation sequencing of hereditary hemochromatosis-related genes: Novel likely pathogenic variants found in the Portuguese population

“…Our patient presents this novel variant in homozygosity, TFR2: c.[967-1GN C)]; [967-1GN C)], which supports his HH type 3 phenotype. As far as we know, there are only four splicing mutations in TFR2 gene classified as pathogenic and are associated with HH type 3: c.1606-8AN G, c.1538-2AN G, c.2137-1GNA, and c.614+4AN G [26][27][28]30,31].…”