V.N. Subramaniam

First phenotypic description of transferrin receptor 2 knockout mouse, and the role of hepcidin

Background: Transferrin receptor 2 (TfR2) is a key molecule involved in the regulation of iron homeostasis. Mutations in humans cause type 3 haemochromatosis and a targeted mutation in mice leads to iron overload with a similar phenotype. We have previously described the generation of a complete TfR2-knockout (KO) mouse. Aims: The aims of this study were to determine the phenotype and analyse expression of iron related molecules in the liver, duodenum, and spleen of homozygous TfR2-KO, heterozygous, and wild-type mice. Methods: Serum and tissue iron levels were determined in 10 week old male mice. Expression of iron related mRNA transcripts were analysed in the liver, duodenum, and spleen using real time polymerase chain reaction. Expression of iron related proteins in the liver were analysed by immunoblotting and immunohistochemistry. Results: Homozygous TfR2-KO mice had no TfR2 protein expression and developed significant iron overload typical of TfR2 associated haemochromatosis. In the liver of TfR2-KO mice there was no upregulation of hepcidin mRNA or prohepcidin protein in response to iron loading. Conclusions: Our results suggest that TfR2 is required for iron regulated expression of hepcidin and is involved in a pathway related to Hfe and hemojuvelin.

A novel mutation in ferroportin1 is associated with haemochromatosis in a Solomon Islands patient

Background: A severe form of iron overload with the clinicopathological features of haemochromatosis inherited in an autosomal dominant manner has been described in the Solomon Islands. The genetic basis of the disorder has not been identified. The disorder has similarities to type 4 haemochromatosis, which is caused by mutations in ferroportin1. Aims: The aims of this study were to identify the genetic basis of iron overload in a patient from the Solomon Islands. Patient and methods: Genomic DNA was isolated from peripheral blood leucocytes of a Solomon Islands man with severe iron overload. The entire coding region and splice sites of the ferroportin1 gene was sequenced. Results and conclusions: A novel missense mutation (431A>C; N144T) was identified in exon 5 of the ferroportin1 gene. A novel restriction endonuclease based assay which identifies both the N144T and N144H mutations was developed which will simplify the diagnosis and screening of patients for iron overload in the Solomon Islands and other populations. This is the first identified mutation associated with haemochromatosis in the Solomon Islands population.

Identification of ferroportin disease in the Indian subcontinent

Haemochromatosis is a common inherited disorder of iron metabolism, characterised by excessive iron absorption and deposition in tissues. The majority of cases are associated with mutations in the HFE gene and inherited in an autosomal recessive manner.1 Autosomal dominant forms of haemochromatosis have been reported, mainly associated with mutations in the ferroportin 1 gene.2 This syndrome, termed type 4 haemochromatosis or more recently ferroportin disease,3 is usually characterised by an early increase in serum ferritin with normal transferrin saturation. Iron accumulation is most prominent in Kupffer cells and other macrophages, in addition to hepatocytes. Some patients do not tolerate venesection therapy well and can develop anaemia. Hereditary iron overload disorders appear to be uncommon in Asia. Secondary iron overload due to beta thalassaemia is relatively common in the Indian subcontinent. However, primary iron overload disorders …

Ferroportin disease due to the A77D mutation in Australia

Ferroportin disease or type 4 haemochromatosis is an autosomal dominant iron overload disorder caused by mutations in the iron exporter ferroportin.1,2 Numerous mutations in ferroportin ( SLC40A1 ) have been identified (see review by Pietrangelo3). The A77D mutation of ferroportin has thus far only been reported in Italy.2 We report the first A77D mutation of ferroportin which resulted in hepatic iron overload in an Australian family. The study was approved by and performed in accordance with the ethical standards of the Queensland Institute of Medical Research Human Research Ethics Committee and the Helsinki Declaration of 1975, as revised in 1983. Informed and written consent was obtained from the patient and family members. The subject, a 45 year old Caucasian male, presented with complaints of lethargy and malaise. He had no risk factors for viral hepatitis, consumed minimal alcohol (20 g/week), and was married with two …

Molecular and cellular characterization of transferrin receptor 2

Iron is an essential component of many biological processes. However, an excess of iron in the body is also toxic; thus, the levels of this element are tightly regulated. Our knowledge of the mechanism by which iron levels are maintained has been bolstered by the dramatic increase in the discovery of novel molecules implicated in iron homeostasis. The transferrin receptor-transferrin pathway is the main mechanism by which cells take up iron. The recently identified homolog of transferrin receptor, its characterization and its role in iron metabolism is the subject of this review.

Exome sequencing in HFE C282Y homozygous men with extreme phenotypes identifies a GNPAT variant associated with severe iron overload

To identify polymorphisms associated with variability of iron overload severity in HFE‐associated hemochromatosis, we performed exome sequencing of DNA from 35 male HFE C282Y homozygotes with either markedly increased iron stores (n = 22; cases) or with normal or mildly increased iron stores (n = 13; controls). The 35 participants, residents of the United States, Canada, and Australia, reported no or light alcohol consumption. Sequencing data included 82,068 single‐nucleotide variants, and 10,337 genes were tested for a difference between cases and controls. A variant in the GNPAT gene showed the most significant association with severe iron overload (P = 3 × 10−6; P = 0.033 by the likelihood ratio test after correction for multiple comparisons). Sixteen of twenty‐two participants with severe iron overload had glyceronephosphate O‐acyltransferase (GNPAT) polymorphism p.D519G (rs11558492; 15 heterozygotes, one homozygote). No control participant had this polymorphism. To examine functional consequences of GNPAT deficiency, we performed small interfering RNA–based knockdown of GNPAT in the human liver‐derived cell line, HepG2/C3A. This knockdown resulted in a >17‐fold decrease in expression of the messenger RNA encoding the iron‐regulatory hormone, hepcidin. Conclusion: GNPAT p.D519G is associated with a high‐iron phenotype in HFE C282Y homozygotes and may participate in hepcidin regulation. (Hepatology 2015;62:429–439

The protective effects of corn-oil diet against alcohol and iron-induced hepatotoxicity in a mouse model of hemochromatosis

This journal suppl. contain abstracts of the 62nd Annual Meeting of the American Association for the Study of Liver Diseases: The Liver Meeting 2011This journal suppl. contain abstracts of the 62nd Annual Meeting of the American Association for the Study of Liver Diseases: The Liver Meeting 2011Nutzungsbedingungen Die ETH-Bibliothek ist Anbieterin der digitalisierten Zeitschriften. Sie besitzt keine Urheberrechte an den Inhalten der Zeitschriften. Die Rechte liegen in der Regel bei den Herausgebern. Die auf der Plattform e-periodica veröffentlichten Dokumente stehen für nicht-kommerzielle Zwecke in Lehre und Forschung sowie für die private Nutzung frei zur Verfügung. Einzelne Dateien oder Ausdrucke aus diesem Angebot können zusammen mit diesen Nutzungsbedingungen und den korrekten Herkunftsbezeichnungen weitergegeben werden. Das Veröffentlichen von Bildern in Printund Online-Publikationen ist nur mit vorheriger Genehmigung der Rechteinhaber erlaubt. Die systematische Speicherung von Teilen des elektronischen Angebots auf anderen Servern bedarf ebenfalls des schriftlichen Einverständnisses der Rechteinhaber.

Failure of hepcidin upregulation in HFE-associated haemochromatosis implicates the liver in the regulation of body iron homeostasis

Extrahepatic Portal Vein Thrombosis (EHPVT) is often seen in malignancy. Our aim was to study the clinical profile of non-malignant acute and chronic EHPVT. Method Retrospective study of the clinical presentation, assessment and management of 16 (8M,8F) pts with EHPVT. Clinical presentations were either acute PVT or the chronic sequelae of unrecognised PVT. Results 8 pts presented with acute EHPVT (median age at presentation 47 yr & follow up 4 yr) and 8 with chronic EHPVT (median age 35 yr & follow up 10 yr). In the acute pts, all had abdominal pain. The initial LFT’s were abnormal in 6 of 8 pts but later returned to normal. US was diagnostic in 2 out of 6 pts only. CT was performed in all pts and was diagnostic on initial report in 5, however, PVT was misinterpreted in the remaining 3 who were diagnosed at laparotomy. Aetiology of PVT was from an underlying thrombophilic disorder in 2 of 8 cases, post splenectomy 2 cases and no cause found in 4. Five pts received initial heparin and long term warfarin. Overall 5 of 8 pts developed superior mesenteric vein thrombosis, 1 required bowel resection. Six pts who had follow up CT at mean 17 mo had PV cavernous transformation. Similarly, varices were evident at endoscopy in 5 of 6 pts by 24 mo. For these, 3 pts received prophylactic banding and all pts were trialed on propranolol. No acute presenter has bled during follow up. In the chronic group, 3 presented initially with variceal bleeding, 1 with chronic pain and the other 4 were diagnosed during investigation for thrombocytopenia and/or splenomegaly. Only 2 pts had initial LFT elevation while 4 had thrombocytopenia and 2 leucopenia. US was reported abnormal in only 4 of 7 examinations but CT was diagnostic in all pts with evidence of portal hypertension. 7 of 8 pts had varices at initial endoscopy. During the study period, 5 pts bled requiring sclerotherapy or banding and 2 of these subsequently required emergency shunt surgery, but the shunts thrombosed within 24 mo. The 2 other non-bleeding variceal pts received prophylactic band ligation and 5 of 7 variceal pts received propranolol. An underlying thrombophilic disorder was present in 5 of 8 chronic presenters, subsequently only 1 has received warfarin. No patient has died in either group. Conclusions The clinical presentation and course of pts with EHPVT varies between the acute and chronic groups. Acute pts usually present with pain and elevated LFTs. CT is the most accurate diagnostic modality but may be misinterpreted. Chronic pts present with manifestations of chronic PHT. Bleeding in EHPVT can usually be controlled with endoscopy, but surgery has a role in endoscopic failures. 119

Blunted hepcidin response to inflammation in the absence of Hfe and Tfr2

Matrix metalloproteinases and their inhibitors are altered in a time-course model of irinotecaninduced mucositis N AL-DASOOQI, R GIBSON, J BOWEN, R LOGAN, A STRINGER, D KEEFE Department of Medicine, University of Adelaide, Department of Medical Oncology, Royal Adelaide Hospital, School of Medical Sciences, University of Adelaide, Division of Surgical Pathology, SA Pathology, Oral Pathology, School of Dentistry, Faculty of Health Sciences, University of Adelaide, Cancer Council South Australia, Eastwood, Australia

G80S-linked ferroportin disease: classical ferroportin disease in an Australian family of Asian descent and reclassification of the mutant as iron transport defective

Matrix metalloproteinases and their inhibitors are altered in a time-course model of irinotecaninduced mucositis N AL-DASOOQI, R GIBSON, J BOWEN, R LOGAN, A STRINGER, D KEEFE Department of Medicine, University of Adelaide, Department of Medical Oncology, Royal Adelaide Hospital, School of Medical Sciences, University of Adelaide, Division of Surgical Pathology, SA Pathology, Oral Pathology, School of Dentistry, Faculty of Health Sciences, University of Adelaide, Cancer Council South Australia, Eastwood, Australia