title: Prenatal diagnosis of recessive congenital methaemoglobinaemia type II: novel mutation in the NADH-cytochrome b5 reductase gene leading to stop codon read-through.
abstract: 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.
authors.affiliation: Institut Cochin, Département Génétique, Développement et Pathologie Moléculaire, Unité 567 INSERM, Université René Descartes, Paris, France. leroux@cochin.inserm.fr
authors.forename: Alena
authors.initials: A
authors.lastname: Leroux
authors.forename: France
authors.initials: F
authors.lastname: Leturcq
authors.forename: Nathalie
authors.initials: N
authors.lastname: Deburgrave
authors.forename: Marie-France
authors.initials: MF
authors.lastname: Szajnert
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D018388:Codon, Terminator / Q000235:genetics*; D042966:Cytochrome-B(5) Reductase / Q000235:genetics*; D017931:DNA Primers; D016368:Frameshift Mutation; D006720:Homozygote; D006801:Humans; D008708:Methemoglobinemia / Q000175:diagnosis / Q000235:genetics*; D008969:Molecular Sequence Data; D011296:Prenatal Diagnosis; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D018388:Codon, Terminator; D017931:DNA Primers; D012333:RNA, Messenger; D042966:Cytochrome-B(5) Reductase