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Nakata M, Yokota N, Tabata K, Morikawa T, Shibata H, Kenzaka T. Hereditary Congenital Methemoglobinemia Diagnosed at the Age of 79 Years: A Case Report. MEDICINA (KAUNAS, LITHUANIA) 2023; 59:medicina59030615. [PMID: 36984616 PMCID: PMC10058039 DOI: 10.3390/medicina59030615] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Revised: 03/14/2023] [Accepted: 03/17/2023] [Indexed: 03/30/2023]
Abstract
Background: Cardiopulmonary disorders are the most common cause of central cyanosis, and methemoglobinemia is often overlooked in the differential diagnosis of patients with central cyanosis. In most cases, methemoglobinemia is acquired and hereditary congenital methemoglobinemia is rare. Only a few case reports of congenital methemoglobinemia can be found in PubMed. To date, only four cases of congenital methemoglobinemia diagnosed after the age of 50 years have been reported. Case Presentation: A 79-year-old Japanese woman presented at our hospital with the chief complaints of dyspnea and cyanosis. She exhibited cyanosis of the lips and extremities, and her SpO2 was 80%, with oxygen administration at 5 L/min. Blood gas analysis revealed a PaO2 of 325.4 mmHg and methemoglobin level of 36.9%. The SpO2 and PaO2 values were dissociated, and methemoglobin levels were markedly elevated. Genetic analysis revealed a nonsynonymous variant in the gene encoding nicotinamide adenine dinucleotide cytochrome (NADH) B5 reductase 3 (CYB5R3), and the patient was diagnosed with congenital methemoglobinemia. Conclusions: It is important to consider methemoglobinemia in the differential diagnosis of patients with central cyanosis. At 79 years of age, our patient represents the oldest patient with this diagnosis. This report indicates that it is crucial to consider the possibility of methemoglobinemia regardless of the patient's age.
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Affiliation(s)
- Marohito Nakata
- Department of Cardiology, Urasoe General Hospital, Urasoe 901-2132, Japan
| | - Naoko Yokota
- Department of Cardiology, Urasoe General Hospital, Urasoe 901-2132, Japan
| | - Kazuhiko Tabata
- Department of Internal Medicine, Naha City Hospital, Naha 902-8511, Japan
| | - Takuya Morikawa
- Division of Genomics, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8582, Japan
| | - Hiroki Shibata
- Division of Genomics, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8582, Japan
| | - Tsuneaki Kenzaka
- Division of Community Medicine and Career Development, Kobe University Graduate School of Medicine, Kobe 652-0032, Japan
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2
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Otsuka-Yamasaki Y, Inanami O, Shino H, Sato R, Yamasaki M. Characterization of a novel nicotinamide adenine dinucleotide-cytochrome b5 reductase mutation associated with canine hereditary methemoglobinemia. J Vet Med Sci 2020; 83:315-321. [PMID: 33342963 PMCID: PMC7972884 DOI: 10.1292/jvms.20-0390] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Hereditary methemoglobinemia associated with nicotinamide adenine dinucleotide-cytochrome b5 reductase (b5R) deficiency is a rare autosomal recessive disorder in animals. Recently, nonsynonymous b5R gene (CYB5R3) variants have been reported to be associated with canine and feline hereditary methemoglobinemia. However, the underlying molecular mechanisms of canine and feline methemoglobinemia caused by these nonsynonymous variants have not yet been reported. Previously, we reported a Pomeranian dog family with hereditary methemoglobinemia, carrying CYB5R3 mutation of an A>C transition at codon 194 in exon 7, replacing an isoleucine residue with leucine (p.Ile194Leu). In this study, we investigated the enzymatic and structural properties of the soluble form of wild-type and Ile194Leu canine b5Rs to characterize the effects of this missense mutation. Our results showed that the kinetic properties of the mutant enzyme were not affected by this amino acid substitution. The secondary structure of the wild-type and Ile194Leu b5Rs detected by circular dichroism showed a similar pattern. However, the mutant enzyme exhibited decreased heat stability and increased susceptibility to trypsin hydrolysis. Moreover, the thermostability and unfolding measurements indicated that the mutant enzyme was more sensitive to temperature-dependent denaturation than the wild-type b5R. We concluded from these results that unstable mutant enzyme properties with normal enzymatic activity would be associated with hereditary methemoglobinemia in the Pomeranian dog family.
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Affiliation(s)
- Yayoi Otsuka-Yamasaki
- Cooperative of Department of Veterinary Medicine, Faculty of Agriculture, Iwate University, Morioka, Iwate 020-8550, Japan
| | - Osamu Inanami
- Department of Veterinary Medicine, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Hokkaido 060-0818, Japan
| | - Haruka Shino
- Cooperative of Department of Veterinary Medicine, Faculty of Agriculture, Iwate University, Morioka, Iwate 020-8550, Japan
| | - Reeko Sato
- Cooperative of Department of Veterinary Medicine, Faculty of Agriculture, Iwate University, Morioka, Iwate 020-8550, Japan
| | - Masahiro Yamasaki
- Cooperative of Department of Veterinary Medicine, Faculty of Agriculture, Iwate University, Morioka, Iwate 020-8550, Japan
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3
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Gupta V, Kulkarni A, Warang P, Devendra R, Chiddarwar A, Kedar P. Mutation update: Variants of the CYB5R3 gene in recessive congenital methemoglobinemia. Hum Mutat 2020; 41:737-748. [PMID: 31898843 DOI: 10.1002/humu.23973] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 12/05/2019] [Accepted: 12/26/2019] [Indexed: 11/07/2022]
Abstract
NADH-cytochrome b5 reductase 3 deficiency is an important genetic cause of recessive congenital methemoglobinemia (RCM) and occurs worldwide in autosomal recessive inheritance. In this Mutation Update, we provide a comprehensive review of all the pathogenic mutations and their molecular pathology in RCM along with the molecular basis of RCM in 21 new patients from the Indian population, including four novel variants: c.103A>C (p.Thr35Pro), c.190C>G (p.Leu64Val), c.310G>T (p.Gly104Cys), and c.352C>T (p.His118Tyr). In this update, over 78 different variants have been described for RCM globally. Molecular modeling of all the variants reported in CYB5R3 justifies association with the varying severity of the disease. The majority of the mutations associated with the severe form with a neurological disorder (RCM Type 2) were associated with the FAD-binding domain of the protein while the rest were located in another domain of the protein (RCM Type 1).
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Affiliation(s)
- Vinod Gupta
- Department of Haematogenetics, ICMR-National Institute of Immunohaematology, King Edward Memorial Hospital Campus, Mumbai, India
| | - Anuja Kulkarni
- Department of Haematogenetics, ICMR-National Institute of Immunohaematology, King Edward Memorial Hospital Campus, Mumbai, India
| | - Prashant Warang
- Department of Haematogenetics, ICMR-National Institute of Immunohaematology, King Edward Memorial Hospital Campus, Mumbai, India
| | - Rati Devendra
- Department of Haematogenetics, ICMR-National Institute of Immunohaematology, King Edward Memorial Hospital Campus, Mumbai, India
| | - Ashish Chiddarwar
- Department of Haematogenetics, ICMR-National Institute of Immunohaematology, King Edward Memorial Hospital Campus, Mumbai, India
| | - Prabhakar Kedar
- Department of Haematogenetics, ICMR-National Institute of Immunohaematology, King Edward Memorial Hospital Campus, Mumbai, India
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4
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Shino H, Otsuka-Yamasaki Y, Sato T, Ooi K, Inanami O, Sato R, Yamasaki M. Familial Congenital Methemoglobinemia in Pomeranian Dogs Caused by a Missense Variant in the NADH-Cytochrome B5 Reductase Gene. J Vet Intern Med 2018; 32:165-171. [PMID: 29356095 PMCID: PMC5787195 DOI: 10.1111/jvim.15031] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Revised: 10/02/2017] [Accepted: 11/29/2017] [Indexed: 01/07/2023] Open
Abstract
Background In veterinary medicine, congenital methemoglobinemia associated with nicotinamide adenine dinucleotide (NADH)‐cytochrome b5 reductase (b5R) deficiency is rare. It has been reported in several breeds of dogs, but little information is available about its etiology. Objectives To analyze the NADH‐cytochrome b5 reductase gene, CYB5R3, in a Pomeranian dog family with methemoglobinemia suspected to be caused by congenital b5R deficiency. Animals Three Pomeranian dogs from a family with methemoglobinemia were analyzed. Five healthy beagles and 5 nonrelated Pomeranian dogs without methemoglobinemia were used as controls. Methods Methemoglobin concentration, b5R activity, and reduced glutathione (GSH) concentration were measured, and a turbidity index was used to evaluate Heinz body formation. The CYB5R3 genes of the affected dog and healthy dogs were analyzed by direct sequencing. Results Methemoglobin concentrations in erythrocytes of the affected dogs were remarkably higher than those of the control dogs. The b5R activity of the affected dogs was notably lower than that of the control dogs. DNA sequencing indicated that this Pomeranian family carried a CYB5R3 gene missense variant (ATC→CTC at codon 194) that resulted in the replacement of isoleucine (Ile) by leucine (Leu). Conclusions and Clinical Importance This dog family had familial congenital methemoglobinemia caused by b5R deficiency, which resulted from a nonsynonymous variant in the CYB5R3 gene. This variation (c.580A>C) led to an amino acid substitution (p.Ile194Leu), and Ile194 was located in the proximal region of the NADH‐binding motif. Our data suggested that this variant in the canine CYB5R3 gene would affect function of the b5R in erythrocytes.
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Affiliation(s)
- H Shino
- Department of Veterinary Medicine, Faculty of Agriculture, Iwate University, Morioka, Iwate, Japan
| | - Y Otsuka-Yamasaki
- Department of Veterinary Medicine, Faculty of Agriculture, Iwate University, Morioka, Iwate, Japan
| | - T Sato
- Estie Animal Hospital, Kooriyama, Fukushima, Japan
| | - K Ooi
- Ooi Animal Hospital, Kooriyama, Fukushima, Japan
| | - O Inanami
- Department of Veterinary Medicine, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Hokkaido, Japan
| | - R Sato
- Department of Veterinary Medicine, Faculty of Agriculture, Iwate University, Morioka, Iwate, Japan
| | - M Yamasaki
- Department of Veterinary Medicine, Faculty of Agriculture, Iwate University, Morioka, Iwate, Japan
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5
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Mannino EA, Pluim T, Wessler J, Cho MT, Juusola J, Schrier Vergano SA. Congenital methemoglobinemia type II in a 5-year-old boy. Clin Case Rep 2018; 6:170-178. [PMID: 29375859 PMCID: PMC5771927 DOI: 10.1002/ccr3.1310] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Revised: 10/24/2017] [Accepted: 11/13/2017] [Indexed: 11/26/2022] Open
Abstract
Congenital Methemoglobinemia is a rare neurologic condition which can mimic other diseases such as epilepsy syndromes and leukodystrophies. The responsible gene, CYB5R3, is not typically included on commonly order neurologic and epilepsy panels. We recommend that laboratories include this gene on these tests which often precede larger-scale genetic studies.
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Affiliation(s)
| | - Thomas Pluim
- Division of Pediatric Critical Care MedicineNaval Medical Center PortsmouthPortsmouthVirginia
| | - Jacob Wessler
- Division of Pediatric Hematology/OncologyNaval Medical Center PortsmouthPortsmouthVirginia
| | | | | | - Samantha A. Schrier Vergano
- Division of Medical Genetics and MetabolismChildren's Hospital of The King's DaughtersNorfolkVirginia
- Department of PediatricsEastern Virginia Medical SchoolNorfolkVirginia
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6
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Elahian F, Sepehrizadeh Z, Moghimi B, Mirzaei SA. Human cytochrome b5 reductase: structure, function, and potential applications. Crit Rev Biotechnol 2012; 34:134-43. [PMID: 23113554 DOI: 10.3109/07388551.2012.732031] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Cytochrome b5 reductase is a flavoprotein that is produced as two different isoforms that have different localizations. The amphipathic microsomal isoform, found in all cell types with the exception of erythrocytes, consists of one hydrophobic membrane-anchoring domain and a larger hydrophilic flavin catalytic domain. The soluble cytochrome b5 reductase isoform, found in human erythrocytes, is a truncated protein that is encoded by an alternative transcript and consists of the larger domain only. Cytochrome b5 reductase is involved in the transfer of reducing equivalents from the physiological electron donor, NADH, via an FAD domain to the small molecules of cytochrome b5. This protein has received much attention from researchers due to its involvement in many oxidation and reduction reactions, such as the reduction of methemoglobin to hemoglobin. Autosomal cytochrome b5 reductase gene deficiency manifests with the accumulation of oxidized Fe+3 and recessive congenital methemoglobinemia in humans. In this article, we provide a comprehensive overview of the structure and function of cytochrome b5 reductase from different eukaryotic sources and its potential use in the food industry, biosensor, and diagnostic areas.
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Affiliation(s)
- Fatemeh Elahian
- Department of Pharmaceutical Biotechnology, School of Pharmacy, Zanjan University of Medical Sciences , Iran and
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7
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Fermo E, Bianchi P, Vercellati C, Marcello AP, Garatti M, Marangoni O, Barcellini W, Zanella A. Recessive hereditary methemoglobinemia: two novel mutations in the NADH-cytochrome b5 reductase gene. Blood Cells Mol Dis 2008; 41:50-5. [PMID: 18343696 DOI: 10.1016/j.bcmd.2008.02.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2008] [Revised: 02/06/2008] [Accepted: 02/06/2008] [Indexed: 10/22/2022]
Abstract
We report the clinical and molecular characteristics of 6 new patients with recessive hereditary methemoglobinemia due to cytochrome b5 reductase deficiency. One patient was affected by Type-II disease with cyanosis and severe progressive neurological dysfunction, whereas the others displayed the benign Type-I phenotype. Methemoglobin levels ranged from 12.1% to 26.2% and cytochrome b5 reductase activity from 0 to 10% of normal. Eight different mutations were detected among the twelve mutated alleles identified, one splicing mutation, two stop codon, and five missense. Two mutations c. 82 C>T(Gln27STOP) and c. 136 C>T(Arg45Trp) are new. Prenatal diagnosis was performed in the family with Type-II disease.
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Affiliation(s)
- Elisa Fermo
- U.O. Ematologia 2, Fondazione IRCCS Ospedale Maggiore, Mangiagalli e Regina Elena, Via F. Sforza, 35, 20122 Milano, Italy
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8
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Percy MJ, Lappin TR. Recessive congenital methaemoglobinaemia: cytochrome b(5) reductase deficiency. Br J Haematol 2008; 141:298-308. [PMID: 18318771 DOI: 10.1111/j.1365-2141.2008.07017.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Some 60 years ago, Quentin Gibson reported the first hereditary disorder involving an enzyme when he deduced that familial methaemoglobinaemia was caused by an enzymatic lesion associated with the glycolysis pathway in red blood cells. This disorder, now known as recessive congenital methaemoglobinaemia (RCM), is caused by NADH-cytochrome b5 reductase (cb(5)r) deficiency. Two distinct clinical forms, types I and II, have been recognized, both characterized by cyanosis from birth. In type II, the cyanosis is accompanied by neurological impairment and reduced life expectancy. Cytochrome b(5) reductase is composed of one FAD and one NADH binding domain linked by a hinge region. It is encoded by the CYB5R3 (previously known as DIA1) gene and more than 40 mutations have been described, some of which are common to both types of RCM. Mutations associated with type II tend to cause incorrect splicing, disruption of the active site or truncation of the protein. At present the description of the sequence variants of cb(5)r in the literature is confusing, due to the use of two conventions which differ by one codon position. Herein we propose a new system for nomenclature of cb(5)r based on recommendations of the Human Genome Variation Society. The development of a heterologous expression system has allowed the impact of naturally occurring variants of cb(5)r to be assessed and has provided insight into the function of cb(5)r.
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9
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Kinoshita A, Nakayama Y, Kitayama T, Tomita M. Simulation study of methemoglobin reduction in erythrocytes. Differential contributions of two pathways to tolerance to oxidative stress. FEBS J 2007; 274:1449-58. [PMID: 17489100 DOI: 10.1111/j.1742-4658.2007.05685.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Methemoglobin (metHb), an oxidized form of hemoglobin, is unable to bind and carry oxygen. Erythrocytes are continuously subjected to oxidative stress and nitrite exposure, which results in the spontaneous formation of metHb. To avoid the accumulation of metHb, reductive pathways mediated by cytochrome b5 or flavin, coupled with NADH-dependent or NADPH-dependent metHb reductases, respectively, keep the level of metHb in erythrocytes at less than 1% of the total hemoglobin under normal conditions. In this work, a mathematical model has been developed to quantitatively assess the relative contributions of the two major metHb-reducing pathways, taking into consideration the supply of NADH and NADPH from central energy metabolism. The results of the simulation experiments suggest that these pathways have different roles in the reduction of metHb; one has a high response rate to hemoglobin oxidation with a limited reducing flux, and the other has a low response rate with a high capacity flux. On the basis of the results of our model, under normal oxidative conditions, the NADPH-dependent system, the physiological role of which to date has been unclear, is predicted to be responsible for most of the reduction of metHb. In contrast, the cytochrome b5-NADH pathway becomes dominant under conditions of excess metHb accumulation, only after the capacity of the flavin-NADPH pathway has reached its limit. We discuss the potential implications of a system designed with two metHb-reducing pathways in human erythrocytes.
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Affiliation(s)
- Ayako Kinoshita
- Institute for Advanced Biosciences, Keio University, Fujisawa, Kanagawa 252-8520, Japan
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10
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Chan B, Ui LQ, Ming TP, Lai CK, Chan BY, Poon WT, Chan A, Bong CC. Methemoglobinemia after ingestion of Chinese herbal medicine in a 9-day-old infant. Clin Toxicol (Phila) 2007; 45:281-3. [PMID: 17453881 DOI: 10.1080/15563650601118028] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Traditional Chinese Medicine has long been popular among Chinese people, but it is always difficult for physicians to ascertain the nature and use of different ingredients involved. We report case of a 9-day-old infant who ingested home-made herbal medicine and developed cyanosis with methemoglobinemia. He responded to a single dose of methylene blue therapy. The suspected causative agent identified in the herbal medicine was sulfamethazine. This is the first reported case of methemoglobinemia related to the use of Chinese herbal medicine in the newborn period.
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Affiliation(s)
- Bosco Chan
- Department of Paediatrics and Adolescent Medicine, Princess Margaret Hospital, Hong Kong SAR, People's Republic of China.
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11
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Wu Y, Tu X, Lian Y, Chen F, Lan F, Zhu Z. Characterization of a Cys329Gly mutation causing hereditary factor VII deficiency. Acta Haematol 2006; 116:96-100. [PMID: 16914903 DOI: 10.1159/000093638] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2005] [Accepted: 10/03/2005] [Indexed: 11/19/2022]
Abstract
We have previously reported a homozygous Cys329Gly mutation in a Chinese patient with factor VII (FVII) deficiency. Others have found a heterozygous Cys329Gly mutation in the F7 gene from patients of three different pedigrees. However, none of the reports included the expression and characterization of the mutant FVII in vitro. To investigate the effect of Cys329Gly on FVII function, we carried out transient transfections of baby hamster kidney cells (BHK-21) with a mutant FVII construct and compared the results to those obtained using a wild-type FVII construct and vector control. The results demonstrate that the level of FVII:Ag secreted into the medium by transfected BHK-21 cells with mutant construct was not affected, but the coagulation activity of the mutant FVII was undetectable. We conclude that Cys329 is critical to FVII coagulation, and the replacement of cysteine 329 by glycine leads to the loss of coagulation activity in the patients, possibly the molecular basis for FVII deficiency in the patients.
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Affiliation(s)
- Yushui Wu
- Medical Laboratory Center, Fuzhou General Hospital, Fuzhou, China.
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12
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Gokalp S, Unuvar E, Oguz F, Kilic A, Sidal M. A case with quadriparetic cerebral palsy and cyanosis: congenital methemoglobinemia. Pediatr Neurol 2005; 33:131-3. [PMID: 16087059 DOI: 10.1016/j.pediatrneurol.2005.02.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2004] [Revised: 10/26/2004] [Accepted: 02/05/2005] [Indexed: 11/21/2022]
Abstract
The recessive form of congenital methemoglobinemia, caused by a defect of nicotinamide adenine dinucleotide-cytb5 reductase enzyme (cytb5r), is a rare disorder clinically presenting with cyanosis. Two different forms of recessive congenital methemoglobinemia have been described: In type I, cyanosis is the only major symptom and enzyme deficiency is restricted to erythrocytes. In type II, observed in 10-15% of all patients, enzyme deficiency occurs in the entire body and cyanosis is associated with severe, progressive neurologic impairment. This report presents a 10-year-old female with recessive congenital methemoglobinemia type II. She was admitted with quadriparetic cerebral palsy, mental retardation, convulsions, swallowing difficulty, and cyanosis. Etiology of cyanosis was not clarified exactly but was readily but erroneously attributed to uncontrolled, repetitive convulsions and aspiration of excessive oral secretions. Her methemoglobin level was measured as 51%, and a diagnosis of congenital methemoglobinemia was established. Oral ascorbic acid 500 mg/day was initiated. She responded well to therapy. Interestingly, neurologic deficits improved after ascorbic acid treatment. In conclusion, cyanosis and repetitive convulsions associated with neurologic deficits may be explained by congenital methemoglobinemia, a potentially treatable condition.
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Affiliation(s)
- Selman Gokalp
- Department of Pediatrics, Istanbul Medical Faculty, Istanbul, Turkey
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13
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Leroux A, Leturcq F, Deburgrave N, Szajnert MF. Prenatal diagnosis of recessive congenital methaemoglobinaemia type II: novel mutation in the NADH-cytochrome b5 reductase gene leading to stop codon read-through. Eur J Haematol 2005; 74:389-95. [PMID: 15813912 DOI: 10.1111/j.1600-0609.2004.00388.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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.
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Affiliation(s)
- Alena Leroux
- Institut Cochin, Département Génétique, Développement et Pathologie Moléculaire, Unité 567 INSERM, Université René Descartes, Paris, France.
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14
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Abstract
Methaemoglobinaemia arises from the production of non-functional haemoglobin containing oxidised Fe(3+) which results in reduced oxygen supply to the tissues and manifests as cyanosis in the patient. It can develop by three distinct mechanisms: genetic mutation resulting in the presence of abnormal haemoglobin, a deficiency of methaemoglobin reductase enzyme and toxin-induced oxidation of haemoglobin. The normal haemoglobin fold forms a pocket to bind the haem and stabilise its complex with molecular oxygen, simultaneously preventing spontaneous oxidation of the Fe(2+) ion chelated by the haem pyrroles and the globin histidines. In the abnormal, M forms of haemoglobin (Hb Ms) amino acid substitution in or near the haem pocket creates a propensity to form methaemoglobin instead of oxyhaemoglobin in the presence of molecular oxygen. Normally, haemoglobin continually oxidises but significant accumulation of methaemoglobin is prevented by the action of a group of methaemoglobin reductase enzymes. In the autosomal recessive form of methaemoglobinaemia there is a deficiency of one of these reductase enzymes thereby allowing accumulation of oxidised Fe(3+) in methaemoglobin. Oxidising drugs and other toxic chemicals may greatly enhance the normal spontaneous rate of methaemoglobin production and if levels exceed 70% of total haemoglobin, vascular collapse occurs resulting in coma and death. Under these conditions, if the source of toxicity can be eliminated methaemoglobin levels will return to normal. Disorders of oxidised haemoglobin are relatively easily diagnosed and in most cases, except for the presence of congenitally defective haemoglobin M, can be treated successfully.
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Affiliation(s)
- Melanie J Percy
- Department of Haematology, Belfast City Hospital, Tower Block, Lisburn Road, Belfast BT9 7AB, N. Ireland, UK
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15
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Davis CA, Crowley LJ, Barber MJ. Cytochrome b5 reductase: the roles of the recessive congenital methemoglobinemia mutants P144L, L148P, and R159*. Arch Biochem Biophys 2004; 431:233-44. [PMID: 15488472 DOI: 10.1016/j.abb.2004.08.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2004] [Revised: 08/06/2004] [Indexed: 10/26/2022]
Abstract
Recessive congenital methemoglobinemia (RCM, OMIM 250800) arises from defects in either the erythrocytic or microsomal forms of the flavoprotein, cytochrome b5 reductase (cb5r) and was the first disease to be directly associated with a specific enzyme deficiency. Of the 33 verified mutations in cb5r that give rise to either the type I (erythrocytic) or type II (generalized) forms of RCM, three of the mutations, corresponding to P144L, L148P, and R159*, are located in a segment of the primary sequence composed of residues G143 to V171 which serves as a "hinge" or "linker" region between the FAD- and NADH-binding lobes of the protein. With the exception of R159*, which produces a truncated non-functional cb5r resulting in type II RCM, the type I methemoglobinemias resulting from the P144L or L148P mutations have been proposed to be due to decreased enzyme stability. Utilizing a recombinant form of the rat cb5r enzyme, we have generated the P144L, L148P, and P144L/L148P mutants, purified the resulting proteins to homogeneity and characterized their spectroscopic, kinetic, and thermodynamic properties. The three mutant proteins retained full complements of FAD with the P144L and L148P variants being spectroscopically indistinguishable from wild-type cb5r. In contrast, kinetic analyses revealed that the P144L, L148P, and P144L/L148P variants retained only 28, 31, and 8% of wild-type NADH:cytochrome b5 reductase activity, respectively, together with significant alterations in affinity for both NADH and NAD+. In addition, FAD oxidation-reduction potentials were 32, 19, and 65 mV more positive for the mutants than the corresponding FAD/FADH2 couple in native cb5r (E0'=-272 mV). Thermal and proteolytic stability measurements indicated that all three mutants were less stable than the wild-type protein while differential spectroscopy indicated altered pyridine nucleotide binding in all three variants. These results demonstrate that the "hinge" region is important in maintaining the correct orientation of the flavin- and pyridine nucleotide-binding lobes within the protein for efficient electron transfer and that the P144L and L148P mutations disrupt the normal registration of the FAD- and NADH-binding lobes resulting in altered affinities for both the physiological reducing substrate, NADH and its product, NAD+.
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Affiliation(s)
- C Ainsley Davis
- Department of Biochemistry and Molecular Biology, College of Medicine, University of South Florida, Tampa, FL 33612, USA
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Davis CA, Barber MJ. Cytochrome b5 oxidoreductase: expression and characterization of the original familial ideopathic methemoglobinemia mutations E255- and G291D. Arch Biochem Biophys 2004; 425:123-32. [PMID: 15111120 DOI: 10.1016/j.abb.2003.12.041] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2003] [Revised: 12/08/2003] [Indexed: 10/26/2022]
Abstract
NADH:cytochrome b5 oxidoreductase catalyzes the transfer of reducing equivalents from the physiological electron donor, NADH, to two molecules of cytochrome b5. Utilizing a heterologous expression system for the soluble, catalytic domain of the rat microsomal enzyme, we have produced two mutants, corresponding to E255- and G291D. These mutants correspond to the two specific mutations that were identified over a half century later following diagnosis of the original cases of type I recessive congenital methemoglobinemia (RCM). We have purified both the E255- and G291D variants to homogeneity to determine the molecular basis for type I RCM in these individuals. Both the E255- and G291D variants retained a full complement of FAD and exhibited absorption and CD spectroscopic properties comparable to those of the wild-type protein. Oxidation-reduction potentiometric titrations yielded standard midpoint potentials (E0') for the FAD/FADH2 couple of -271 and -273 mV for the E255- and G291D variants, respectively, which were comparable to the value of -268 mV obtained for the wild-type protein and confirmed that the redox potential of the flavin was unaffected by either mutation. Thermal and proteolytic stability studies revealed that while the G291D variant exhibited stability comparable to that of wild-type, the E255- variant was markedly less stable, indicative of an altered conformation. Initial-rate kinetic studies revealed that both mutants had decreased catalytic activity (kcat), with the E255- and G291D variants retaining approximately 38 and 58% of wild-type activity, respectively. However, the affinity for NADH (KmNADH) was decreased approximately 100-fold for E255- compared to only approximately 1.3-fold for G291D, results supported by the spectroscopic binding constant (Ks) obtained for G291D. These results indicate that the properties of both the E255- and G291D cytochrome b5 oxidoreductase mutants are similar to those of other variants that have been identified as resulting in the type I form of RCM.
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Affiliation(s)
- C Ainsley Davis
- Department of Biochemistry and Molecular Biology, College of Medicine, University of South Florida, Tampa, Florida 33612, USA
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Grabowska D, Plochocka D, Jablonska-Skwiecinska E, Chelstowska A, Lewandowska I, Staniszewska K, Majewska Z, Witos I, Burzynska B. Compound heterozygosity of two missense mutations in the NADH-cytochrome b5 reductase gene of a Polish patient with type I recessive congenital methaemoglobinaemia. Eur J Haematol 2003; 70:404-9. [PMID: 12756024 DOI: 10.1034/j.1600-0609.2003.00070.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
A case of type I methaemoglobinaemia observed in a Polish subject with compound heterozygosity for two mutations in the reduced nicotinamide adenine dinucleotide (NADH) cytochrome b5 reductase (b5R) gene is described. One is a novel mutation 647T-->C which leads to substitution of isoleucine by threonine at position 215 (I215T). This maternal mutation was found in several family members. A previously known mutation, 757G-->A, leads to the replacement of valine by methionine at position 252 (V252M). The latter mutation was found also in the father and one of the two brothers. The effects of these mutations were analysed on a model of the human b5R protein obtained by homology modelling. Although both amino acid substitutions are located in the NADH-binding domain, the whole protein structure, especially the region between the flavin adenine dinucleotide and NADH-binding domains, is disturbed. The structural changes in the I215T mutant are less prominent than those in the V252M mutant. We presume that the 647T-->C mutation is a type I mutation, however, it has not been observed in the homozygous state.
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Affiliation(s)
- Dorota Grabowska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
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Percy MJ, Gillespie MJS, Savage G, Hughes AE, McMullin MF, Lappin TRJ. Familial idiopathic methemoglobinemia revisited: original cases reveal 2 novel mutations in NADH-cytochrome b5 reductase. Blood 2002; 100:3447-9. [PMID: 12393396 DOI: 10.1182/blood-2002-05-1405] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In 1943, the first description of familial idiopathic methemoglobinemia in the United Kingdom was reported in 2 members of one family. Five years later, Quentin Gibson (then of Queen's University, Belfast, Ireland) correctly identified the pathway involved in the reduction of methemoglobin in the family, thereby describing the first hereditary trait involving a specific enzyme deficiency. Recessive congenital methemoglobinemia (RCM) is caused by a deficiency of reduced nicotinamide adenine dinucleotide (NADH)-cytochrome b5 reductase. One of the original propositi with the type 1 disorder has now been traced. He was found to be a compound heterozygote harboring 2 previously undescribed mutations in exon 9, a point mutation Gly873Ala predicting a Gly291Asp substitution, and a 3-bp in-frame deletion of codon 255 (GAG), predicting loss of glutamic acid. A brother and a surviving sister are heterozygous; each bears one of the mutations. Thirty-three different mutations have now been recorded for RCM. The original authors' optimism that RCM would provide material for future genetic studies has been amply justified.
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Affiliation(s)
- Melanie J Percy
- Department of Haematology, Belfast City Hospital, Northern Ireland.
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Abstract
Molecular diagnostics is changing the face of clinical laboratories and laboratory medicine. The case of China is no exception. In the present paper, a brief description on this promising discipline is given first, followed by an overview of the development of molecular diagnostics in China. Work done in the author's own laboratory is introduced in the third part and a short discussion on the challenges ahead is provided last.
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Affiliation(s)
- F Lan
- Research Laboratory, Center for Laboratory Medicine, Fuzhou General Hospital, Fuzhou, Fujian Province, China.
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Dekker J, Eppink MH, van Zwieten R, de Rijk T, Remacha AF, Law LK, Li AM, Cheung KL, van Berkel WJ, Roos D. Seven new mutations in the nicotinamide adenine dinucleotide reduced-cytochrome b(5) reductase gene leading to methemoglobinemia type I. Blood 2001; 97:1106-14. [PMID: 11159544 DOI: 10.1182/blood.v97.4.1106] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cytochrome b(5) reductase (b5R) deficiency manifests itself in 2 distinct ways. In methemoglobinemia type I, the patients only suffer from cyanosis, whereas in type II, the patients suffer in addition from severe mental retardation and neurologic impairment. Biochemical data indicate that this may be due to a difference in mutations, causing enzyme instability in type I and complete enzyme deficiency or enzyme inactivation in type II. We have investigated 7 families with methemoglobulinemia type I and found 7 novel mutations in the b5R gene. Six of these mutations predicted amino acid substitutions at sites not involved in reduced nicotinamide adenine dinucleotide (NADH) or flavin adenine dinucleotide (FAD) binding, as deduced from a 3-dimensional model of human b5R. This model was constructed from comparison with the known 3-dimensional structure of pig b5R. The seventh mutation was a splice site mutation leading to skipping of exon 5 in messenger RNA, present in heterozygous form in a patient together with a missense mutation on the other allele. Eight other amino acid substitutions, previously described to cause methemoglobinemia type I, were also situated in nonessential regions of the enzyme. In contrast, 2 other substitutions, known to cause the type II form of the disease, were found to directly affect the consensus FAD-binding site or indirectly influence NADH binding. Thus, these data support the idea that enzyme inactivation is a cause of the type II disease, whereas enzyme instability may lead to the type I form.
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Affiliation(s)
- J Dekker
- Central Laboratory of the Netherlands Blood Transfusion Service (CLB), and Laboratory for Experimental and Clinical Immunology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
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