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Dongerdiye R, Kamat P, Jain P, Warang P, Devendra R, Wasekar N, Sharma R, Mhaskar K, Madkaikar MR, Manglani MV, Kedar PS. Red cell adenylate kinase deficiency in India: identification of two novel missense mutations (c.71A>G and c.413G>A). J Clin Pathol 2019; 72:393-398. [PMID: 30918013 DOI: 10.1136/jclinpath-2019-205718] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Revised: 02/21/2019] [Accepted: 02/25/2019] [Indexed: 02/03/2023]
Abstract
Adenylate kinase (AK) deficiency is a rare erythroenzymopathy associated with hereditary nonspherocytic haemolytic anaemia along with mental/psychomotor retardation in few cases. Diagnosis of AK deficiency depends on the decreased level of enzyme activity in red cell and identification of a mutation in the AK1 gene. Until, only eight mutations causing AK deficiency have been reported in the literature. We are reporting two novel missense mutation (c.71A > G and c.413G > A) detected in the AK1 gene by next-generation sequencing (NGS) in a 6-year-old male child from India. Red cell AK enzyme activity was found to be 30% normal. We have screened a total of 32 family members of the patient and showed reduced red cell enzyme activity and confirm mutations by Sanger's sequencing. On the basis of Sanger sequencing, we suggest that the proband has inherited a mutation in AK1 gene exon 4 c.71A > G (p.Gln24Arg) from paternal family and exon 6 c.413G > A (p.Arg138His) from maternal family. Bioinformatics tools, such as SIFT, Polymorphism Phenotyping v.2, Mutation Taster, MutPred, also confirmed the deleterious effect of both the mutations. Molecular modelling suggests that the structural changes induced by p.Gln24Arg and p.Arg138His are pathogenic variants having a direct impact on the structural arrangement of the region close to the active site of the enzyme. In conclusion, NGS will be the best solution for diagnosis of very rare disorders leading to better management of the disease. This is the first report of the red cell AK deficiency from the Indian population.
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Affiliation(s)
- Rashmi Dongerdiye
- Department of Haematogenetics, National Institute of Immunohaematology, Mumbai, India
| | - Pranoti Kamat
- MCGM Comprehensive Thalassemia Care Pediatric Hematology-Oncology and Bone Marrow Transplantation Centre, Mumbai, India
| | - Punit Jain
- MCGM Comprehensive Thalassemia Care Pediatric Hematology-Oncology and Bone Marrow Transplantation Centre, Mumbai, India
| | - Prashant Warang
- Department of Haematogenetics, National Institute of Immunohaematology, Mumbai, India
| | - Rati Devendra
- Department of Haematogenetics, National Institute of Immunohaematology, Mumbai, India
| | - Nilesh Wasekar
- MCGM Comprehensive Thalassemia Care Pediatric Hematology-Oncology and Bone Marrow Transplantation Centre, Mumbai, India
| | - Ratna Sharma
- MCGM Comprehensive Thalassemia Care Pediatric Hematology-Oncology and Bone Marrow Transplantation Centre, Mumbai, India
| | - Ketaki Mhaskar
- MCGM Comprehensive Thalassemia Care Pediatric Hematology-Oncology and Bone Marrow Transplantation Centre, Mumbai, India
| | | | - Mamta V Manglani
- MCGM Comprehensive Thalassemia Care Pediatric Hematology-Oncology and Bone Marrow Transplantation Centre, Mumbai, India
| | - Prabhakar S Kedar
- Department of Haematogenetics, National Institute of Immunohaematology, Mumbai, India
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Zhang H, Yin M, Huang L, Wang J, Gong L, Liu J, Sun B. Evaluation of the Cellular and Animal Models for the Study of Antioxidant Activity: A Review. J Food Sci 2017; 82:278-288. [PMID: 28117894 DOI: 10.1111/1750-3841.13605] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Revised: 11/21/2016] [Accepted: 12/05/2016] [Indexed: 02/06/2023]
Abstract
The mechanisms of antioxidant activities of phytochemicals are highly complex, so various methods to study them have been developed. However, the diverse available methods show inconsistent results. Different stressors, cell models, and animal models have been used to evaluate the antioxidant properties of phytochemicals. However, the literature still lacks a summary of the effects of different stressors, cell models, and animal models on the evaluation of antioxidant activities. Therefore, the mechanisms of action of different oxidative stimuli and the characteristics of the available cell models and animal models are summarized in this review.
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Affiliation(s)
- Huijuan Zhang
- Innovation Center for Food Nutrition and Human Health, Beijing Technology & Business Univ. (BTBU), Beijing, 100048, China
| | - Meng Yin
- Innovation Center for Food Nutrition and Human Health, Beijing Technology & Business Univ. (BTBU), Beijing, 100048, China
| | - Lianyan Huang
- Innovation Center for Food Nutrition and Human Health, Beijing Technology & Business Univ. (BTBU), Beijing, 100048, China
| | - Jing Wang
- Innovation Center for Food Nutrition and Human Health, Beijing Technology & Business Univ. (BTBU), Beijing, 100048, China.,Beijing Engineering and Technology Research Center of Food Additives, Beijing, 100048, China.,Key Laboratory of Space Nutrition and Food Engineering, Beijing, 100094, China
| | - Lingxiao Gong
- Innovation Center for Food Nutrition and Human Health, Beijing Technology & Business Univ. (BTBU), Beijing, 100048, China
| | - Jie Liu
- Innovation Center for Food Nutrition and Human Health, Beijing Technology & Business Univ. (BTBU), Beijing, 100048, China
| | - Baoguo Sun
- Innovation Center for Food Nutrition and Human Health, Beijing Technology & Business Univ. (BTBU), Beijing, 100048, China
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3
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Fermo E, Bianchi P, Chiarelli LR, Maggi M, Mandarà GML, Vercellati C, Marcello AP, Barcellini W, Cortelezzi A, Valentini G, Zanella A. A new variant of phosphoglycerate kinase deficiency (p.I371K) with multiple tissue involvement: molecular and functional characterization. Mol Genet Metab 2012; 106:455-61. [PMID: 22705348 DOI: 10.1016/j.ymgme.2012.05.015] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Revised: 05/22/2012] [Accepted: 05/22/2012] [Indexed: 12/20/2022]
Abstract
Phosphoglycerate kinase (PGK) is a key glycolytic enzyme that catalyzes the reversible phosphotransfer reaction from 1,3-bisphosphoglycerate to MgADP, to form 3-phosphoglycerate and MgATP. Two isozymes encoded by distinct genes are present in humans: PGK-1, located on Xq-13.3, encodes a ubiquitous protein of 417 amino acids, whereas PGK-2 is testis-specific. PGK1 deficiency is characterized by mild to severe hemolytic anemia, neurological dysfunctions and myopathy; patients rarely exhibit all three clinical features. Nearly 40 cases have been reported, 27 of them characterized at DNA or protein level, and 20 different mutations were described. Here we report the first Italian case of PGK deficiency characterized at a molecular and biochemical level. The patient presented during infancy with hemolytic anemia, increased CPK values, and respiratory distress; the study of red blood cell enzymes showed a drastic reduction in PGK activity. In adulthood he displayed mild hemolytic anemia, mental retardation and severe myopathy. PGK-1 gene sequencing revealed the new missense mutation c.1112T>A (p.Ile371Lys). The mutation was not found among 100 normal alleles, and even if located in the third to the last nucleotide of exon 9, it did not alter mRNA splicing. The p.Ile371Lys mutation falls in a conserved region of the enzyme, near the nucleotide binding site. The mutant enzyme shows reduced catalytic rates toward both substrates (apparent k(cat) values, 12-fold lower than wild-type) and a decreased affinity toward MgATP (apparent K(m), 6-fold higher than wild-type). Moreover, it lost half of activity after nearly 9-min incubation at 45°C, a temperature that did not affect the wild-type enzyme (t(1/2)>1 h). The possible compensatory expression of PGK2 isoenzyme was investigated in the proband and in the heterozygote healthy sisters, and found to be absent. Therefore, the highly perturbed catalytic properties of the new variant p.Ile371Lys, combined with protein instability, account for the PGK deficiency found in the patient and correlate with the clinical expression of the disease.
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Affiliation(s)
- Elisa Fermo
- UO Ematologia e Centro Trapianti di Midollo, Fondazione IRCCS Cà Granda Ospedale Maggiore Policlinico, Milano, Italy
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Shimo H, Nishino T, Tomita M. Predicting the Kinetic Properties Associated with Redox Imbalance after Oxidative Crisis in G6PD-Deficient Erythrocytes: A Simulation Study. Adv Hematol 2011; 2011:398945. [PMID: 21977034 PMCID: PMC3184397 DOI: 10.1155/2011/398945] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2011] [Revised: 06/15/2011] [Accepted: 06/15/2011] [Indexed: 12/05/2022] Open
Abstract
It is well known that G6PD-deficient individuals are highly susceptible to oxidative stress. However, the differences in the degree of metabolic alterations among patients during an oxidative crisis have not been extensively studied. In this study, we applied mathematical modeling to assess the metabolic changes in erythrocytes of various G6PD-deficient patients during hydrogen peroxide- (H(2)O(2)-) induced perturbation and predict the kinetic properties that elicit redox imbalance after exposure to an oxidative agent. Simulation results showed a discrepancy in the ability to restore regular metabolite levels and redox homeostasis among patients. Two trends were observed in the response of redox status (GSH/GSSG) to oxidative stress, a mild decrease associated with slow recovery and a drastic decline associated with rapid recovery. The former was concluded to apply to patients with severe clinical symptoms. Low V(max) and high K(mG6P) of G6PD were shown to be kinetic properties that enhance consequent redox imbalance.
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Affiliation(s)
- Hanae Shimo
- Institute for Advanced Biosciences, Keio University, 403-1, Daihoji, Tsuruoka, Yamagata 997-0017, Japan
- Department of Environment and Information Studies, Keio University, Endo 5322, Fujisawa, Kanagawa 252-8520, Japan
| | - Taiko Nishino
- Institute for Advanced Biosciences, Keio University, 403-1, Daihoji, Tsuruoka, Yamagata 997-0017, Japan
- Systems Biology Program, Graduate School of Media and Governance, Keio University, Endo 5322, Fujisawa, Kanagawa 252-8520, Japan
| | - Masaru Tomita
- Institute for Advanced Biosciences, Keio University, 403-1, Daihoji, Tsuruoka, Yamagata 997-0017, Japan
- Department of Environment and Information Studies, Keio University, Endo 5322, Fujisawa, Kanagawa 252-8520, Japan
- Systems Biology Program, Graduate School of Media and Governance, Keio University, Endo 5322, Fujisawa, Kanagawa 252-8520, Japan
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Enzymatic and metabolic characterization of the phosphoglycerate kinase deficiency associated with chronic hemolytic anemia caused by the PGK-Barcelona mutation. Blood Cells Mol Dis 2011; 46:206-11. [PMID: 21269848 DOI: 10.1016/j.bcmd.2010.12.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2010] [Revised: 11/24/2010] [Accepted: 12/14/2010] [Indexed: 11/22/2022]
Abstract
Recently, we reported a new mutation of phosphoglycerate kinase (PGK), called PGK-Barcelona, which causes chronic hemolytic anemia associated with progressive neurological impairment. We found a 140T→A substitution that produces an Ile46Asn change located at the N-domain of the enzyme and we suggested that the decrease of the PGK activity is probably related to a loss of enzyme stability. In this paper, by analyzing whole hemolysates and cloned enzymes, we show that both enzymes possess similar kinetic properties (although some differences are observed in the Km values) and the same electrophoretic mobility. However, PGK-Barcelona has higher thermal instability. Therefore, we confirm that the decrease of the red blood cell (RBC) PGK activity caused by the PGK-Barcelona mutation is more closely related to a loss of enzyme stability than to a decrease of enzyme catalytic function. Furthermore, we have measured the levels of glycolytic metabolites and adenine nucleotides in the RBC from controls and from the patient. The increase of 2,3-bisphosphoglycerate and the decrease of ATP RBC levels are the only detected metabolic changes that could cause hemolytic anemia.
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Optimal fluxes, reaction replaceability, and response to enzymopathies in the human red blood cell. J Biomed Biotechnol 2010; 2010. [PMID: 20706609 PMCID: PMC2914339 DOI: 10.1155/2010/415148] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2009] [Accepted: 05/14/2010] [Indexed: 11/18/2022] Open
Abstract
Characterizing the capabilities, key dependencies, and response to perturbations of genome-scale metabolic networks is a basic problem with important applications. A key question concerns the identification of the potentially
most harmful reaction knockouts. The integration of combinatorial methods with sampling techniques to explore the space of viable flux states may provide crucial insights on this issue. We assess the replaceability of every metabolic conversion in the human red blood cell by enumerating the alternative paths from substrate to product, obtaining a complete map of
he potential damage of single enzymopathies. Sampling the space of optimal steady state fluxes in the healthy and in the mutated cell reveals both correlations and complementarity between topologic and dynamical aspects.
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Affiliation(s)
- Fuad El Rassi
- Department of Internal Medicine, American University of Beirut Medical Center, Beirut, Lebanon
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Cimen MYB. Free radical metabolism in human erythrocytes. Clin Chim Acta 2008; 390:1-11. [PMID: 18243141 DOI: 10.1016/j.cca.2007.12.025] [Citation(s) in RCA: 307] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2007] [Revised: 12/13/2007] [Accepted: 12/21/2007] [Indexed: 02/07/2023]
Abstract
As the red cell emerges from the bone marrow, it loses its nucleus, ribosomes, and mitochondria and therefore all capacity for protein synthesis. However, because of the high O(2) tension in arterial blood and heme Fe content, reactive oxygen species (ROS) are continuously produced within red cells. Erythrocytes transport large amount of oxygen over their lifespan resulting in oxidative stress. Various factors can lead to the generation of oxidizing radicals such as O(2)(-), H(2)O(2), HO in erythrocytes. Evidence indicates that many physiological and pathological conditions such as aging, inflammation, eryptosis develop through ROS action. As such, red cells have potent antioxidant protection consisting of enzymatic and nonenzymatic pathways that modify highly ROS into substantially less reactive intermediates. The object of this review is to shed light on the role of ROS both at physiological and pathological levels and the structural requirements of antioxidants for appreciable radical-scavenging activity. Obviously, much is still to be discovered before we clearly understand mechanisms of free radical systems in erythrocytes. Ongoing trends in the field are recognition of undetermined oxidant/antioxidant interactions and elucidation of important signaling networks in radical metabolism.
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Affiliation(s)
- M Y Burak Cimen
- Mersin University, Medical Faculty, Department of Biochemistry, 33079 Mersin/Turkey.
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Durmuş Tekir S, Cakir T, Ulgen KO. Analysis of enzymopathies in the human red blood cells by constraint-based stoichiometric modeling approaches. Comput Biol Chem 2006; 30:327-38. [PMID: 16987707 DOI: 10.1016/j.compbiolchem.2006.07.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2005] [Revised: 04/10/2006] [Accepted: 07/03/2006] [Indexed: 11/18/2022]
Abstract
The human red blood cell (RBC) metabolism is investigated by calculating steady state fluxes using constraint-based stoichiometric modeling approaches. For the normal RBC metabolism, flux balance analysis (FBA) is performed via optimization of various alternative objective functions, and the maximization of production of ATP and NADPH is found to be the primary objective of the RBC metabolism. FBA and two novel approaches, minimization of metabolic adjustment (MOMA) and regulatory on-off minimization (ROOM), which can describe the behavior of the metabolic networks in case of enzymopathies, are applied to observe the relative changes in the flux distribution of the deficient network. The deficiencies in several enzymes in RBC metabolism are investigated and the flux distributions are compared with the non-deficient FBA distribution to elucidate the metabolic changes in response to enzymopathies. It is found that the metabolism is mostly affected by the glucose-6-phosphate dehydrogenase (G6PDH) and phosphoglycerate kinase (PGK) enzymopathies, whereas the effects of the deficiency in DPGM on the metabolism are negligible. These stoichiometric modeling results are found to be in accordance with the experimental findings in the literature related to metabolic behavior of the human red blood cells, showing that human RBC metabolism can be modeled stoichiometrically.
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Affiliation(s)
- Saliha Durmuş Tekir
- Department of Chemical Engineering, Boğaziçi University, 34342 Bebek-Istanbul, Turkey
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Chiarelli LR, Bianchi P, Fermo E, Galizzi A, Iadarola P, Mattevi A, Zanella A, Valentini G. Functional analysis of pyrimidine 5′-nucleotidase mutants causing nonspherocytic hemolytic anemia. Blood 2005; 105:3340-5. [PMID: 15604219 DOI: 10.1182/blood-2004-10-3895] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AbstractInherited pyrimidine 5′-nucleotidase type I (P5′N-1) deficiency is the third most common erythrocyte enzymopathy that causes hemolysis. Fourteen different mutations have been identified to date. We have investigated the molecular bases of the disease by studying the biochemical properties of the recombinant wild-type human enzyme and 4 variant proteins (D87V, L131P, N179S, and G230R) bearing missense mutations found in patients affected by nonspherocytic hemolytic anemia. P5′N-1 is a relatively stable protein and has essentially identical catalytic efficiency toward cytidine monophosphate (CMP) and uridine monophosphate (UMP). All investigated mutant proteins display impaired catalytic properties and/or reduced thermostability, providing a rationale for the pathological effects of the mutations. Despite the substantial changes in the kinetic and thermostability parameters, the enzyme activity detected in the red blood cells of patients homozygous for mutations L131P and G230R exhibits moderate alterations. This suggests that P5′N-1 deficiency is compensated, possibly by other nucleotidases or alternative pathways in nucleotide metabolism. Therefore, nucleotidase activity may not be considered a prognostic indicator in patients affected by the enzymopathy. (Blood. 2005;105:3340-3345)
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Merritt J, Butz JA, Ogunnaike BA, Edwards JS. Parallel analysis of mutant human glucose 6-phosphate dehydrogenase in yeast using PCR colonies. Biotechnol Bioeng 2005; 92:519-31. [PMID: 16193512 DOI: 10.1002/bit.20726] [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] [Indexed: 12/25/2022]
Abstract
We demonstrate a highly parallel strategy to analyze the impact of single nucleotide mutations on protein function. Using our method, it is possible to screen a population and quickly identify a subset of functionally interesting mutants. Our method utilizes a combination of yeast functional complementation, growth competition of mutant pools, and polymerase colonies. A defined mutant human glucose-6-phosphate-dehydrogenase library was constructed which contains all possible single nucleotide missense mutations in the eight-residue glucose-6-phosphate binding peptide of the enzyme. Mutant human enzymes were expressed in a zwf1 (gene encoding yeast homologue) deletion strain of Saccharomyces cerevisiae. Growth rates of the 54 mutant strains arising from this library were measured in parallel in conditions selective for active hG6PD. Several residues were identified which tolerated no mutations (Asp200, His201 and Lys205) and two (Ile199 and Leu203) tolerated several substitutions. Arg198, Tyr202, and Gly204 tolerated only 1-2 specific substitutions. Generalizing from the positions of tolerated and non-tolerated amino acid substitutions, hypotheses were generated about the functional role of specific residues, which could, potentially, be tested using higher resolution/lower throughput methods.
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Affiliation(s)
- Joshua Merritt
- Department of Chemical Engineering, University of Delaware, Newark, Delaware 19716, USA
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12
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Cakir T, Tacer CS, Ulgen KO. Metabolic pathway analysis of enzyme-deficient human red blood cells. Biosystems 2004; 78:49-67. [PMID: 15555758 DOI: 10.1016/j.biosystems.2004.06.004] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2004] [Revised: 06/10/2004] [Accepted: 06/12/2004] [Indexed: 10/26/2022]
Abstract
Five enzymopathies (G6PDH, TPI, PGI, DPGM and PGK deficiencies) in the human red blood cells are investigated using a stoichiometric modeling approach, i.e., metabolic pathway analysis. Elementary flux modes (EFMs) corresponding to each enzyme deficiency case are analyzed in terms of functional capabilities. When available, experimental findings reported in literature related to metabolic behavior of the human red blood cells are compared with the results of EFM analysis. Control-effective flux (CEF) calculation, a novel approach which allows quantification and interpretation of determined EFMs, is performed for further analysis of enzymopathies. Glutathione reductase reaction is found to be the most effective reaction in terms of its CEF value in all enzymopathies in parallel with its known essential role for red blood cells. Efficiency profiles of the enzymatic reactions upon the degree of enzyme deficiency are obtained by the help of the CEF approach, as a basis for future experimental studies. CEF analysis, which is found to be promising in the analysis of erythrocyte enzymopathies, has the potential to be used in modeling efforts of human metabolism.
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Affiliation(s)
- Tunahan Cakir
- (a)Department of Chemical Engineering, Boğaziçi University, 34342 Bebek-Istanbul, Turkey
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13
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Clarke JL, Vulliamy TJ, Roper D, Mesbah-Namin SA, Wild BJ, Walker JI, Will AM, Bolton-Maggs PH, Mason PJ, Layton DM. Combined glucose-6-phosphate dehydrogenase and glucosephosphate isomerase deficiency can alter clinical outcome. Blood Cells Mol Dis 2003; 30:258-63. [PMID: 12737943 DOI: 10.1016/s1079-9796(03)00027-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Glucosephosphate isomerase (GPI) deficiency in humans is an autosomal recessive disorder, which results in nonspherocytic hemolytic anemia of variable clinical expression. A 4-year-old female with severe congenital hemolytic anemia had low red cell GPI activity of 15.5 IU/g Hb (50% of normal mean) indicating GPI deficiency. Subsequent DNA sequence analysis revealed a novel homozygous 921C to G mutation in the GPI gene sequence, predicting a Phe307 to Leu replacement. Strikingly, the red cell GPI activity in this patient was higher than that found in a second patient expressing the same GPI variant, with a more severe clinical phenotype. We propose that the hemolysis in the first patient may be modified by an accompanying deficiency of glucose-6-phosphate dehydrogenase (G6PD). The proband's red cell G6PD activity was reduced at 4.5 IU/g Hb (50% of normal mean) and molecular studies revealed heterozygosity for the G6PD Viangchan mutation and a skewed pattern of X-chromosome inactivation, producing almost exclusive expression of the mutated allele. The G6PD Viangchan variant is characterised by severe enzyme deficiency, but not chronic hemolysis. This study suggests that the metabolic consequences of a combined deficiency of GPI and G6PD might be responsible for a different clinical outcome than predicted for either defect in isolation.
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Affiliation(s)
- Julia L Clarke
- Department of Haematology, Faculty of Medicine, Imperial College of Science Technology and Medicine, Hammersmith Hospital, London, UK
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