Biomedical subjects

Sonia Levi

Publications and source records attributed to Sonia Levi.

23 records · Page 2Linked to original sources

PubMed2002

A novel deletion of the L-ferritin iron-responsive element responsible for severe hereditary hyperferritinaemia-cataract syndrome.

In the last few years, mutations that cause disease through increased efficiency of mRNA translation have been discovered. Hereditary hyperferritinaemia-cataract syndrome (HHCS) arises from various point mutations or deletions within the iron-responsive element (IRE) in the 5'-UTR of the L-ferritin mRNA. Each unique mutation confers a characteristic degree of hyperferritinaemia and severity of cataract in affected individuals. We report a novel six-nucleotide deletion identified in an Italian family presenting with elevated serum ferritin and early onset bilateral cataract. This deletion involves a sequence with a TCT repetition and may have occurred through a mechanism of slippage mispairing. Because of the above repetition, the observed mutation can be interpreted as deletion 22-27, 23-28, 24-29 or 25-30. Structural modelling predicted an IRE stem modification that is expected to markedly reduce the binding to iron-regulatory proteins. A double-gradient denaturing gradient gel electrophoresis (DG-DGGE) method easily detected the above deletion.

Adult↗

PubMed2002

Genetic hyperferritinaemia and reticuloendothelial iron overload associated with a three base pair deletion in the coding region of the ferroportin gene (SLC11A3).

Iron overload may predominantly involve parenchymal or reticuloendothelial cells, the prototype of parenchymal iron overload being HFE-related genetic haemochromatosis. We studied a family with autosomal dominant hyperferritinaemia in whom the proband showed selective iron accumulation in the Kupffer cells on liver biopsy. Analysis of L and H ferritin genes excluded mutations responsible for hereditary hyperferritinaemia/cataract syndrome or similar translational disorders. Sequence analysis of the ferroportin gene (SLC11A3) in four individuals with hyperferritinaemia singled out a three base pair deletion in a region that contains four TTG repeats. This mutation removes a TTG unit from 780 to 791, and predicts the loss of one of three sequential valine residues 160-162. Denaturing high performance liquid chromatography can be used for its detection. SLC11A3 polymorphism analysis indicates that this probably represents a recurrent mutation due to slippage mispairing. Affected individuals may show marginally low serum iron and transferrin saturation, and young women may have marginally low haemoglobin concentration levels. Serum ferritin levels are directly related to age, but are 10-20 times higher than normal. Heterozygosity for the ferroportin Val 162 deletion represents the prototype of selective reticuloendothelial iron overload, and should be taken into account in the differential diagnosis of hereditary or congenital hyperferritinaemias.

Adult↗

PubMedDate not supplied

Mitochondrial ferritin: a new player in iron metabolism.

Mitochondrial ferritin (MtF) is a novel H-type ferritin encoded by an intronless gene on chromosome 5q23.1. The protein is synthesized as a precursor of about 30 kDa that is targeted to mitochondria by a leader sequence of 60 amino acids. This leader is proteolytically removed inside the mitochondria and the resulting 22 kDa subunit forms typical ferritin shells. These shells have ferroxidase activity and are therefore likely to sequester potentially harmful free iron. However, this may be a limited function since MtF has a very restricted tissue expression. High amounts are found in testis but only very low levels are found in iron storage organs. The levels of MtF appear to correlate more with mitochondrial abundance than with iron metabolism. MtF does not seem to be an obligatory intermediate in transfer of free iron to heme and other iron compounds in mitochondria. However, its level increases dramatically in sideroblastic anemia when heme synthesis is disrupted. This increased synthesis does not appear to involve the classical translational control since MtF mRNA lacks an apparent iron response element. In transfected HeLa cells added iron is incorporated as quickly into MtF as into cytosolic ferritin. In addition, increased levels of MtF cause a redistribution of iron from cytosol to mitochondria and this effect is enhanced by iron chelation. Thus high levels of MtF result in an iron deficient phenotype in cytosol with decreased expression of ferritin and increased expression of transferrin receptor. This avidity for iron may explain why MtF levels are maintained at low levels in most normal cells. The regulation of MtF expression and possible therapeutic applications of MtF in neurological disorders involving increased iron deposition are topics for future research.

Amino Acid Sequence↗

PubMedDate not supplied

C29G in the iron-responsive element of L-ferritin: a new mutation associated with hyperferritinemia-cataract.

Hyperferritinemia-cataract syndrome (HHCS) is a dominant disorder characterized by high serum ferritin and early onset of bilateral cataract. The disorder is caused by mutations in the iron-responsive element (IRE) of l-ferritin, which disrupt the postranscriptional control of l-ferritin synthesis. Here, we report a new (C>G) mutation which affects base 29 in the loop (c.-169C>G), previously unrecognized as essential for the stem loop stability. The mutation was identified in two members of an Italian family. Computer modeling and electrophoretic mobility shift assay (EMSA) confirm a decreased affinity of the C29G IRE for IRPs control proteins.

Adult↗

PubMedDate not supplied

Recombinant human hepcidin expressed in Escherichia coli isolates as an iron containing protein.

Hepcidin is a small peptide that acts as a regulator of systemic iron homeostasis. To study some of its functional properties, a synthetic cDNA for the minimal, 20-amino-acid, form of human hepcidin was cloned into different constructs for expression in Escherichia coli. The fusion ferritin-hepcidin produced molecules retaining most of ferritin structural and functional properties, including ferroxidase and iron incorporation activities. However, it showed spectroscopic properties compatible with the presence of iron-sulfur complexes on the hepcidin moiety, which was buried into protein cavity. Similar complexes were reconstituted by in vitro incubation of the iron-free protein with iron and sulfide salts. Two other unrelated fusion products were constructed, which, when expressed in E. coli, formed insoluble aggregates retaining a large proportion of total bacterial iron. Analysis of the solubilized preparations showed them to contain iron-sulfur complexes. We concluded that the cysteine-rich hepcidin acts as an iron-sequestering molecule during expression in E. coli. This may have implications for the biological functions of this key protein of iron metabolism.

Antimicrobial Cationic Peptides↗