Understanding alpha-globin gene regulation: Aiming to improve the management of thalassemia.

Over the past 50 years, many advances in our understanding of the general principles controlling gene expression during hematopoiesis have come from studying the synthesis of hemoglobin. Discovering how the alpha- and beta-globin genes are normally regulated and documenting the effects of inherited mutations that cause thalassemia have played a major role in establishing our current understanding of how genes are switched on or off in hematopoietic cells. Previously, nearly all mutations causing thalassemia have been found in or around the globin loci, but rare inherited and acquired trans-acting mutations are being found more often. Such mutations have demonstrated new mechanisms underlying human genetic disease. Furthermore, they are revealing new pathways in the regulation of globin gene expression that, in turn, may open up new avenues for improving the management of patients with common types of thalassemia.

Diagnosis of juvenile hemochromatosis in an 11-year-old child combining genetic analysis and non-invasive liver iron quantitation.

UNLABELLED: Juvenile or type2 hemochromatosis is a rare autosomal recessive disorder which leads to severe iron overload early in life. As in the classic adult form of the disease iron toxicity causes liver cirrhosis, cardiomyopathy, and endocrine complications, but the onset of the disease is anticipated in the second to third decades of life. Experience of this disease in children is limited. Molecular diagnosis is unfeasible because the type2 hemochromatosis gene is still unknown, although it is known that the disease locus maps to chromosome 1q. Combining linkage analysis with markers encompassing chromosome 1 locus and a non-invasive method for liver iron quantitation we diagnosed juvenile hemochromatosis in a presymptomatic stage in an 11-year-old Italian child. A regular phlebotomy protocol reduced iron overload preventing all the disease complications. CONCLUSION: Juvenile hemochromatosis patients have severe iron overload within the first years of life, strengthening the greater iron absorption that occurs in this as compared to other types of hemochromatosis. Early detection is essential, because treatment in presymptomatic stages prevents organ damage.

New mutations inactivating transferrin receptor 2 in hemochromatosis type 3.

Hereditary hemochromatosis usually results from C282Y homozygosity in the HFE gene on chromosome 6p. Recently, a new type of hemochromatosis (HFE3) has been characterized in 2 unrelated Italian families with a disorder linked to 7q. Patients with HFE3 have transferrin receptor 2 (TFR2) inactivated by a homozygous nonsense mutation (Y250X). Here the identification of 2 new TFR2 mutations is reported. In a large inbred family from Campania, a frameshift mutation (84-88 insC) in exon 2 that causes a premature stop codon (E60X) is identified. In a single patient with nonfamilial hemochromatosis, a T-->A transversion (T515A), which causes a Methionine-->Lysine substitution at position 172 of the protein (M172K), has been characterized. TFR2 gene gives origin to 2 alternatively spliced transcripts-the alpha-transcript, which may encode a transmembrane protein, and the beta-transcript, a shorter, possibly intracellular variant. Based on their positions, the effects of the identified mutations on the 2 TFR2 forms are expected to differ. Y250X inactivates both transcripts, whereas E60X inactivates only the alpha-form. M172K has a complex effect: it causes a missense in the alpha-form, but it may also prevent the beta-form production because it affects its putative initiation codon. Analysis of the clinical phenotype of 13 HFE3 homozygotes characterized at the molecular level has shown a variable severity, from nonexpressing patients to severe clinical complications. The identification of new mutations of TFR2 confirms that this gene is associated with iron overload and offers a tool for molecular diagnosis in patients without HFE mutations.

A pilot C282Y hemochromatosis screening in Italian newborns by TaqMan technology.

Hereditary hemochromatosis (HH) is a disorder of iron metabolism that leads to iron overload in middle age and can be caused by homozygosity for the C282Y mutation in the HFE gene. Preliminary studies have estimated the frequency of this mutation at 0.5-1% in Italy, but this has not been verified on a large sample. We analyzed 1,331 Italian newborns for the C282Y mutation in the HFE gene using dried blood spots (DBS) from the Neonatal Screening Center in Turin, Italy. The mutation was assessed using a semi-automatable 5'-nuclease assay (TaqMan technology). We detected 55 heterozygotes and no homozygotes in our sampling, resulting in an overall frequency of 2.1% +/- 0.6 for the C282Y allele. Differences in allele frequency were observed, and ranged from 2.7% +/- 1.3 in samples from Northern Italy, to 1.7% +/- 0.9 in samples from Central-Southern Italy. The low frequency of the at-risk genotype for iron overload suggests that genetic screening for HFE in Italy would not be cost effective. The present study, in addition to defining C282Y frequency, documents detection of the major HFE mutation on routine DBS samples from neonatal screening programs using a semi-automatable, rapid, reliable, and relatively inexpensive approach.

Juvenile hemochromatosis associated with B-thalassemia treated by phlebotomy and recombinant human erythropoietin.

Juvenile hemochromatosis is a rare genetic disorder that causes iron overload. Clinical complications, which include liver cirrhosis, heart failure, hypogonadotropic hypogonadism and diabetes, appear earlier and are more severe than in HFE-related hemochromatosis. This disorder, therefore, requires an aggressive therapeutic approach to achieve iron depletion. We report here the case of a young Italian female with juvenile hemochromatosis who was unable to tolerate frequent phlebotomy because of coexistent ss-thalassemia trait. The patient was successfully iron-depleted by combining phlebotomy with recombinant human erythropoietin.

The gene TFR2 is mutated in a new type of haemochromatosis mapping to 7q22.

Haemochromatosis is a common recessive disorder characterized by progressive iron overload, which may lead to severe clinical complications. Most patients are homozygous for the C282Y mutation in HFE on 6p (refs 1-5). A locus for juvenile haemochromatosis (HFE2) maps to 1q (ref. 7). Here we report a new locus (HFE3) on 7q22 and show that a homozygous nonsense mutation in the gene encoding transferrin receptor-2 (TFR2) is found in people with haemochromatosis that maps to HFE3.