Hereditary hemochromatosis (HH) is an autosomal recessive disorder characterized by excessive iron absorption resulting in pathologically increased body iron stores. It is typically associated with common HFE gene mutation (p.Cys282Tyr and p.His63Asp). However, in Southern European populations up to one third of HH patients do not carry the risk genotypes. This study aimed to explore the use of next-generation sequencing (NGS) technology to analyse a panel of iron metabolism-related genes (HFE, TFR2, HJV, HAMP, SLC40A1, and FTL) in 87 non-classic HH Portuguese patients. A total of 1241 genetic alterations were detected corresponding to 53 different variants, 13 of which were not described in the available public databases. Among them, five were predicted to be potentially pathogenic: three novel mutations in TFR2 [two missense (p.Leu750Pro and p.Ala777Val) and one intronic splicing mutation (c.967-1G NC)], one missense mutation in HFE (p.Tyr230Cys), and one mutation in the 5′-UTR of HAMP gene (c. -25GN A). The results reported here illustrate the usefulness of NGS for targeted iron metabolism-related gene panels, as a likely cost-effective approach for molecular genetics diagnosis of non-classic HH patients. Simultaneously, it has contributed to the knowledge of the pathophysiology of those rare iron metabolism-related disorders.
Measurement of the concentration of iron in the skin, if correlated with total body iron stores, may enable better informed decisions on when to initiate, change or stop therapy in hereditary heamochromatosis. Naïve haemochromatosis patients with iron overload and with C282Y and/or H63D HFE mutations were evaluated at the following time-points: disease diagnosis, end of the therapy programme, and 6 months after the end of therapy. The distribution and concentration of iron in the skin were assessed by quantitative nuclear microscopy methods, in parallel with serum and plasma iron concentration. Iron content in the liver was determined by nuclear magnetic resonance. Iron accumulated in the epidermis; its concentration increased from outer to inner layers, being maximal in the basal layer (7.33 ± 0.98 µmol/g). At all 3 time-points, most of the iron was associated with the extracellular space. During the phlebotomy programme the iron content of the skin and the liver decreased by a factor of 2. These data suggest that measurements of iron concentration in the epidermis, which is a readily accessible tissue, reflect iron overload in the liver.
Hereditary haemochromatosis (HH) is an autosomal recessive disorder characterized by excessive intestinal iron absorption resulting in increased pathological body iron stores. It is typically associated with homozygosity for the c.845G>A (p.C282Y) mutation in the HFE gene. However, other HFE alterations have been reported in affected individuals but their association with the disease is unclear. This study analysed the functional consequences of two HFE mutations, c.829G>A (p.E277K) and c.884T>C (p.V295A). Firstly, it was shown that c.829G>A affects the HFE splicing by diminishing the full length HFE and ivs4_66bp inclusion transcript levels, while increasing the amount of exon 4 skipping transcript. Immunofluorescent techniques showed that the HFE_E277K protein had a diffuse distribution (similar to HFE_C282Y) while HFE_V295A presented at the cell surface and perinuclear compartments (resembling HFE_wt). Immunoprecipitation assays revealed a decreased association of HFE_E277K and HFE_V295A with both β2-microglobulin (B2M; 38 ± 7% and 66 ± 8%, respectively) and transferrin receptor (TFRC, also termed TFR1) (58 ± 2% and 49 ± 16%, respectively). Herein, we prove that both mutations partially abrogate HFE association with B2M and TFRC, crucial for its correct processing and cell surface presentation. Although E277K has a more deleterious effect than V295A, we propose that both mutations may play a role in the development of hereditary haemochromatosis.
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