A new mutation in the hepcidin promoter impairs its BMP response and contributes to a severe phenotype in HFE related hemochromatosis

Abstract

BPM-RE. In conclusion, our results suggest that a mutation in the BMP-RE of hepcidin promoter may impact on human iron metabolism.Key words: hepcidin, BMP, hemochromatosis, iron, gene expression. hemochromatosis. Haematologica 2009; 94:720-724. doi: 10.3324/haematol.2008 This is an open-access paper. Citation: Island M-L, Jouanolle A-M, Mosser A, Deugnier Y, David V, Brissot P, and Loréal O. A new mutation in the hepcidin promoter impairs its BMP response and contributes to a severe phenotype in HFE related ABSTRACTA new mutation in the hepcidin promoter impairs its BMP response and contributes to a severe phenotype in HFE related hemochromatosis © F e r r a t a S t o r t i F o u n d a t i o n Design and Methods Patient and genetic studiesIn 1994, the diagnosis of genetic hemochromatosis was established in a 37-year old man with massive hepatic iron overload (450 µmoL of iron/g dry liver weight, n<36) involving mainly hepatocytes and associated to liver fibrosis stage 2-3 in Metavir classification. 18 Iron depletive treatment based on weekly 400 mL phlebotomies was initiated. In 1997, the patient was demonstrated to be homozygous for the p.Cys282Tyr mutation. In 2004 (47 years), 468 venesections had been performed, corresponding to the removal of 85g of iron. However, the patient was always exhibiting abnormal iron parameters with 40 µmol/L for serum iron, 100% for transferrin saturation, and 2,066 µg/L for serum ferritin. In addition, hepatic iron concentration remained very high (close to 300 µmol/g dry liver weight) at MRI. Serum hepcidin level quantified by Elisa 19 was low (24 ng/L; 29<N< 254 for men) despite major iron overload with a decoupling between serum hepcidin and ferritin values compared to the correlation between both parameters reported by Ganz et al. 19 Clinical iron burden consisted of asthenia, icthyosis, melanodermia, gonalgia, osteoporosis, and hypogonadism. There were no heart symptoms and serum glucose was normal. Prothrombin time was normal (90%). Serum transaminases and GGT activities were slightly increased (1.5-2N). Complete sequencing of the coding sequence of the HFE, HJV, TFR2, FPN and HAMP (including its promoter) genes was performed, as part of the diagnostic procedure, after having obtained a written informed consent from the patient. Unfortunately, the realization of a family study did not prove possible.Sequencing of these genes was performed in one hundred subjects recruited from a health appraisal center with normal iron metabolism as judged on serum iron parameters and hemoglobin levels. These subjects had given their informed written consent for the study of iron metabolism genes after approval of the protocol by the local ethical committee (98/35-197). Cell cultureHuman hepatoma HepG2 cells were grown in Minimum Essential Medium α (invitrogen) supplemented with 10% fetal bovine serum (invitrogen), 100 UI/mL penicillin, 100 mg/mL streptomycin and 2 mM L-glutamine. Plasmid constructionsThe -1024 bp from the translation start site of the human hepcidin promoter were ampl...

HAMP promoter mutation nc.-153C>T in non p.C282Y homozygous patients with iron overload

“…It is clinically characterized by hemophagocytic lymphohistiocytosis (HLH), which usually develops in response to an Epstein-Barr virus (EBV) infection, dysgammaglobulinemia and malignant lymphoma. Most cases of XLP are caused by mutation in the SLAM-associated protein (SAP) or SH2D1A [1][2][3] . The X-linked inhibitor of apoptosis (XIAP) is also reported to cause XLP, 4 and at least 9 families with XIAP deficiency have been reported in Europe and the United States.…”

“…To clarify the differences in the clinical picture of SAP deficiency and XIAP deficiency, a greater number of patients with XLP should be surveyed. Meina Zhao, 1 Hirokazu Kanegane, 1 Kazutaka Ouchi, 2 Toshihiko Imamura, 2 Sylvain Latour, 3 Toshio Miyawaki…”

Genetic variation in hepcidin expression and its implications for phenotypic differences in iron metabolism

“…15 In support of the contribution of regulatory SNPs in hepcidin expression variation and iron metabolism, Island et al found a C>T polymorphism (underlined) in one of two bone morphogenetic protein response elements, BMP-RE, (GGCGCC→GGTGCC) in the promoter that impaired transcription of the gene, its IL-6-responsiveness and binding by Smads. 16 Similarly, Marco et al found association between a -582A>G polymorphism in the hepcidin promoter and iron overload in thalassemia major. 17 Porto et al previously reported a SNP (a G to A substitution) in the 5'UTR of the human hepcidin gene which correlated with severe hemochromatosis.…”

HAMP promoter mutation nc.-153C>T in 785 HEIRS Study participants

“…We conclude that routine testing to detect HAMP nc.-153C>T is not indicated in populationbased hemochromatosis and IO screening programs in North America. James C. Barton, 1,2 Catherine Leiendecker-Foster, 3 Honggui Li, 3 Susie DelRio-LaFreniere, 3 Ronald T. Acton, 4 and John H. Eckfeldt, 3 …”

“…Island and colleagues recently described a 37-year old French man with HFE p.C282Y homozygosity, severe iron overload (IO), and heterozygosity for the novel hepcidin (HAMP) promoter mutation nc.-153C>T. 1 In vitro nc.-153C>T decreased transcriptional activity of the promoter altered its interleukin-6 (IL-6) responsiveness and prevented binding of SMAD1/5/8/4 protein complex to the bone morphogenetic protein-responsive element (BMP-RE) of HAMP. Thus, nc.-153C>T could decrease hepcidin levels and contribute to IO.…”