Prenatal diagnosis of recessive congenital methaemoglobinaemia type II: novel mutation in the NADH-cytochrome b5 reductase gene leading to stop codon read-through.

A case of type II recessive congenital methaemoglobinaemia (RCM) observed in a Lebanese subject with a novel mutation in NADH-cytochrome b5 reductase gene is described. A homozygous mutation CAC to AA identified at Thr 295 with an out-of-frame 1-bp deletion leads to a frameshift with translational read-through of the natural stop codon. The molecular mechanism is demonstrated by an in vitro translation study. The model of mutated cytochrome b5 reductase protein possessing 46 additional amino acids was obtained by homology modelling. The mutation causes an alteration of hydrophobicity in the carboxyl-terminal portion, resulting in the conformation being drastically disturbed by the presence of 46 supplementary amino acids. The identical mutation was found in the heterozygous state in the patient's parents and sister. Identification of this new mutation enabled us to perform the molecular prenatal diagnosis of type II RCM at the DNA level.

Functional differences between hepcidin 1 and 2 in transgenic mice.

Hepcidin is a 25-amino acid peptide involved in iron homeostasis in mice and humans. It is produced in the liver from a larger precursor, and it is detectable in blood and urine. In contrast to the human genome, which contains only one copy of the gene, the mouse genome contains 2 highly similar hepcidin genes, hepc1 and hepc2, which are, however, considerably divergent at the level of the corresponding mature 25-amino acid peptide. This striking observation led us to ask whether hepc1 and hepc2 performed the same biologic activity with regard to iron metabolism in the mouse. We recently described the severe iron-deficient anemia phenotype in transgenic mice overexpressing hepc1 in the liver. Here we report that, in contrast to the hepc1-transgenic mice, none of the 7 founder hepc2-transgenic animals suffered from anemia. They all developed normally with hematologic parameters similar to the nontransgenic littermates. Hepc2 transgenic mRNA level was found to be very high for all lines compared with the level of hepc1 transgene mRNA necessary to produce severe anemia. These data provide evidence that hepc2 does not act on iron metabolism like hepc1 and give clues for the identification of amino acids important for the iron-regulatory action of the mature 25-amino acid peptide.

The enlarging clinical, genetic, and population spectrum of tumor necrosis factor receptor-associated periodic syndrome.

OBJECTIVE: To characterize the frequency, clinical signs, and genotypic features of tumor necrosis factor receptor-associated periodic syndrome (TRAPS) in a series of 394 patients of various ethnic origins who have recurrent inflammatory syndromes. METHODS: Sequencing of the coding region of the TNFRSF1A gene was performed in 128 patients in whom there was a high suspicion of TRAPS, and denatured high-performance liquid chromatography was used to systematically screen for TNFRSF1A in 266 patients with recurrent inflammatory syndrome and no or only 1 Mediterranean fever gene (MEFV) mutation. RESULTS: TNFRSF1A mutations were found in 28 (7.1%) of 394 unrelated patients. Nine (32%) of the 28 patients had a family history of recurrent inflammatory syndromes. In 13 patients, the length of the attack of inflammation was fewer than 5 days. Three of the mutations (Y20H, L67P, and C96Y) were novel. Two mutations, R92Q and (mainly) P46L, found in 12 and 10 patients, respectively, had lower penetrance compared with other mutations. TNFRSF1A mutations were found in patients of various ethnic origins, including those at risk for familial Mediterranean fever (FMF): Armenians, Sephardic Jews, and especially Arabs from Maghreb. Only 3 (10.7%) of the 28 patients had amyloidosis. CONCLUSION: TRAPS is an underdiagnosed cause of recurrent inflammatory syndrome. Its presence in the population of persons of Mediterranean ancestry and the short duration of the attacks of inflammation can lead to a fallacious diagnosis of FMF. Because an accurate diagnosis in patients with recurrent inflammatory syndromes is crucial for proper clinical management and treatment, genetic screening for TNFRSF1A is warranted.