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Kido J, Sugawara K, Sawada T, Matsumoto S, Nakamura K. Pathogenic variants of ornithine transcarbamylase deficiency: Nation-wide study in Japan and literature review. Front Genet 2022; 13:952467. [PMID: 36303552 PMCID: PMC9593096 DOI: 10.3389/fgene.2022.952467] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Accepted: 08/25/2022] [Indexed: 11/29/2022] Open
Abstract
Ornithine transcarbamylase deficiency (OTCD) is an X-linked disorder. Several male patients with OTCD suffer from severe hyperammonemic crisis in the neonatal period, whereas others develop late-onset manifestations, including hyperammonemic coma. Females with heterozygous pathogenic variants in the OTC gene may develop a variety of clinical manifestations, ranging from asymptomatic conditions to severe hyperammonemic attacks, owing to skewed lyonization. We reported the variants of CPS1, ASS, ASL and OTC detected in the patients with urea cycle disorders through a nation-wide survey in Japan. In this study, we updated the variant data of OTC in Japanese patients and acquired information regarding genetic variants of OTC from patients with OTCD through an extensive literature review. The 523 variants included 386 substitution (330 missense, 53 nonsense, and 3 silent), eight deletion, two duplication, one deletion-insertion, 55 frame shift, two extension, and 69 no category (1 regulatory and 68 splice site error) mutations. We observed a genotype-phenotype relation between the onset time (neonatal onset or late onset), the severity, and genetic mutation in male OTCD patients because the level of deactivation of OTC significantly depends on the pathogenic OTC variants. In conclusion, genetic information about OTC may help to predict long-term outcomes and determine specific treatment strategies, such as liver transplantation, in patients with OTCD.
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Affiliation(s)
- Jun Kido
- Department of Pediatrics, Kumamoto University Hospital, Kumamoto, Japan
- Department of Pediatrics, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Keishin Sugawara
- Department of Pediatrics, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Takaaki Sawada
- Department of Pediatrics, Kumamoto University Hospital, Kumamoto, Japan
- Department of Pediatrics, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Shirou Matsumoto
- Department of Pediatrics, Kumamoto University Hospital, Kumamoto, Japan
- Department of Pediatrics, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Kimitoshi Nakamura
- Department of Pediatrics, Kumamoto University Hospital, Kumamoto, Japan
- Department of Pediatrics, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
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Couchet M, Breuillard C, Corne C, Rendu J, Morio B, Schlattner U, Moinard C. Ornithine Transcarbamylase - From Structure to Metabolism: An Update. Front Physiol 2021; 12:748249. [PMID: 34658931 PMCID: PMC8517447 DOI: 10.3389/fphys.2021.748249] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Accepted: 09/07/2021] [Indexed: 12/30/2022] Open
Abstract
Ornithine transcarbamylase (OTC; EC 2.1.3.3) is a ubiquitous enzyme found in almost all organisms, including vertebrates, microorganisms, and plants. Anabolic, mostly trimeric OTCs catalyze the production of L-citrulline from L-ornithine which is a part of the urea cycle. In eukaryotes, such OTC localizes to the mitochondrial matrix, partially bound to the mitochondrial inner membrane and part of channeling multi-enzyme assemblies. In mammals, mainly two organs express OTC: the liver, where it is an integral part of the urea cycle, and the intestine, where it synthesizes citrulline for export and plays a major role in amino acid homeostasis, particularly of L-glutamine and L-arginine. Here, we give an overview on OTC genes and proteins, their tissue distribution, regulation, and physiological function, emphasizing the importance of OTC and urea cycle enzymes for metabolic regulation in human health and disease. Finally, we summarize the current knowledge of OTC deficiency, a rare X-linked human genetic disorder, and its emerging role in various chronic pathologies.
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Affiliation(s)
- Morgane Couchet
- Université Grenoble Alpes, Inserm U1055, Laboratory of Fundamental and Applied Bioenergetics, Grenoble, France
| | - Charlotte Breuillard
- Université Grenoble Alpes, Inserm U1055, Laboratory of Fundamental and Applied Bioenergetics, Grenoble, France
| | | | - John Rendu
- Centre Hospitalier Université Grenoble Alpes, Grenoble, France
| | - Béatrice Morio
- CarMeN Laboratory, INSERM U1060, INRAE U1397, Lyon, France
| | - Uwe Schlattner
- Université Grenoble Alpes, Inserm U1055, Laboratory of Fundamental and Applied Bioenergetics, Grenoble, France.,Institut Universitaire de France, Paris, France
| | - Christophe Moinard
- Université Grenoble Alpes, Inserm U1055, Laboratory of Fundamental and Applied Bioenergetics, Grenoble, France
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3
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Lopes‐Marques M, Pacheco AR, Peixoto MJ, Cardoso AR, Serrano C, Amorim A, Prata MJ, Cooper DN, Azevedo L. Common polymorphic OTC variants can act as genetic modifiers of enzymatic activity. Hum Mutat 2021; 42:978-989. [PMID: 34015158 PMCID: PMC8362079 DOI: 10.1002/humu.24221] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2020] [Revised: 05/05/2021] [Accepted: 05/18/2021] [Indexed: 12/24/2022]
Abstract
Understanding the role of common polymorphisms in modulating the clinical phenotype when they co‐occur with a disease‐causing lesion is of critical importance in medical genetics. We explored the impact of apparently neutral common polymorphisms, using the gene encoding the urea cycle enzyme, ornithine transcarbamylase (OTC), as a model system. Distinct combinations of genetic backgrounds embracing two missense polymorphisms were created in cis with the pathogenic p.Arg40His replacement. In vitro enzymatic assays revealed that the polymorphic variants were able to modulate OTC activity both in the presence or absence of the pathogenic lesion. First, we found that the combination of the minor alleles of polymorphisms p.Lys46Arg and p.Gln270Arg significantly enhanced enzymatic activity in the wild‐type protein. Second, enzymatic assays revealed that the minor allele of the p.Gln270Arg polymorphism was capable of ameliorating OTC activity when combined in cis with the pathogenic p.Arg40His replacement. Structural analysis predicted that the minor allele of the p.Gln270Arg polymorphism would serve to stabilize the OTC wild‐type protein, thereby corroborating the results of the experimental assays. Our findings demonstrate the potential importance of cis‐interactions between common polymorphic variants and pathogenic missense mutations and illustrate how standing genetic variation can modulate protein function.
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Affiliation(s)
- Mónica Lopes‐Marques
- i3S‐Instituto de Investigação e Inovação em Saúde, Population Genetics and Evolution GroupUniversidade do PortoPortoPortugal
- IPATIMUP‐Institute of Molecular Pathology and Immunology, Population Genetics and Evolution GroupUniversity of PortoPortoPortugal
- Faculty of Sciences, Department of BiologyUniversity of PortoPortoPortugal
| | - Ana Rita Pacheco
- i3S‐Instituto de Investigação e Inovação em Saúde, Population Genetics and Evolution GroupUniversidade do PortoPortoPortugal
- IPATIMUP‐Institute of Molecular Pathology and Immunology, Population Genetics and Evolution GroupUniversity of PortoPortoPortugal
| | - Maria João Peixoto
- ICVS‐ Life and Health Sciences Research Institute, School of MedicineUniversity of MinhoBragaPortugal
- ICVS/3B's‐PT Government Associate LaboratoryBragaGuimarãesPortugal
| | - Ana Rita Cardoso
- i3S‐Instituto de Investigação e Inovação em Saúde, Population Genetics and Evolution GroupUniversidade do PortoPortoPortugal
- IPATIMUP‐Institute of Molecular Pathology and Immunology, Population Genetics and Evolution GroupUniversity of PortoPortoPortugal
- Faculty of Sciences, Department of BiologyUniversity of PortoPortoPortugal
| | - Catarina Serrano
- i3S‐Instituto de Investigação e Inovação em Saúde, Population Genetics and Evolution GroupUniversidade do PortoPortoPortugal
- IPATIMUP‐Institute of Molecular Pathology and Immunology, Population Genetics and Evolution GroupUniversity of PortoPortoPortugal
- Faculty of Sciences, Department of BiologyUniversity of PortoPortoPortugal
| | - António Amorim
- i3S‐Instituto de Investigação e Inovação em Saúde, Population Genetics and Evolution GroupUniversidade do PortoPortoPortugal
- IPATIMUP‐Institute of Molecular Pathology and Immunology, Population Genetics and Evolution GroupUniversity of PortoPortoPortugal
- Faculty of Sciences, Department of BiologyUniversity of PortoPortoPortugal
| | - Maria João Prata
- i3S‐Instituto de Investigação e Inovação em Saúde, Population Genetics and Evolution GroupUniversidade do PortoPortoPortugal
- IPATIMUP‐Institute of Molecular Pathology and Immunology, Population Genetics and Evolution GroupUniversity of PortoPortoPortugal
- Faculty of Sciences, Department of BiologyUniversity of PortoPortoPortugal
| | - David N. Cooper
- Institute of Medical Genetics; School of MedicineCardiff UniversityCardiffUK
| | - Luísa Azevedo
- i3S‐Instituto de Investigação e Inovação em Saúde, Population Genetics and Evolution GroupUniversidade do PortoPortoPortugal
- IPATIMUP‐Institute of Molecular Pathology and Immunology, Population Genetics and Evolution GroupUniversity of PortoPortoPortugal
- Faculty of Sciences, Department of BiologyUniversity of PortoPortoPortugal
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4
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Cavicchi C, Chilleri C, Fioravanti A, Ferri L, Ripandelli F, Costa C, Calabresi P, Prontera P, Pochiero F, Pasquini E, Funghini S, la Marca G, Donati MA, Morrone A. Late-Onset N-Acetylglutamate Synthase Deficiency: Report of a Paradigmatic Adult Case Presenting with Headaches and Review of the Literature. Int J Mol Sci 2018; 19:ijms19020345. [PMID: 29364180 PMCID: PMC5855567 DOI: 10.3390/ijms19020345] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Revised: 01/17/2018] [Accepted: 01/18/2018] [Indexed: 12/30/2022] Open
Abstract
N-acetylglutamate synthase deficiency (NAGSD) is an extremely rare urea cycle disorder (UCD) with few adult cases so far described. Diagnosis of late-onset presentations is difficult and delayed treatment may increase the risk of severe hyperammonemia. We describe a 52-year-old woman with recurrent headaches who experienced an acute onset of NAGSD. As very few papers focus on headaches in UCDs, we also report a literature review of types and pathophysiologic mechanisms of UCD-related headaches. In our case, headaches had been present since puberty (3–4 days a week) and were often accompanied by nausea, vomiting, or behavioural changes. Despite three previous episodes of altered consciousness, ammonia was measured for the first time at 52 years and levels were increased. Identification of the new homozygous c.344C>T (p.Ala115Val) NAGS variant allowed the definite diagnosis of NAGSD. Bioinformatic analysis suggested that an order/disorder alteration of the mutated form could affect the arginine-binding site, resulting in poor enzyme activation and late-onset presentation. After optimized treatment for NAGSD, ammonia and amino acid levels were constantly normal and prevented other headache bouts. The manuscript underlies that headache may be the presenting symptom of UCDs and provides clues for the rapid diagnosis and treatment of late-onset NAGSD.
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Affiliation(s)
- Catia Cavicchi
- Molecular and Cell Biology Laboratory of Neurometabolic Diseases, Neuroscience Department, Meyer Children's Hospital, 50139 Florence, Italy.
| | - Chiara Chilleri
- Molecular and Cell Biology Laboratory of Neurometabolic Diseases, Neuroscience Department, Meyer Children's Hospital, 50139 Florence, Italy.
| | - Antonella Fioravanti
- Structural Biology Researcher Center, VIB, Vrije Universiteit Brussel, 1050 Brussels, Belgium.
| | - Lorenzo Ferri
- Molecular and Cell Biology Laboratory of Neurometabolic Diseases, Neuroscience Department, Meyer Children's Hospital, 50139 Florence, Italy.
| | | | - Cinzia Costa
- Neurology Unit, Santa Maria della Misericordia Hospital, 06123 Perugia, Italy.
| | - Paolo Calabresi
- Neurology Unit, Santa Maria della Misericordia Hospital, 06123 Perugia, Italy.
| | - Paolo Prontera
- Medical Genetics Unit, Santa Maria della Misericordia Hospital, 06123 Perugia, Italy.
| | - Francesca Pochiero
- Metabolic and Muscular Unit, Neuroscience Department, Meyer Children's Hospital, 50139 Florence, Italy.
| | - Elisabetta Pasquini
- Metabolic and Muscular Unit, Neuroscience Department, Meyer Children's Hospital, 50139 Florence, Italy.
| | - Silvia Funghini
- Newborn Screening, Biochemistry and Pharmacology Laboratory, Neuroscience Department, Meyer Children's Hospital, 50139 Florence, Italy.
| | - Giancarlo la Marca
- Newborn Screening, Biochemistry and Pharmacology Laboratory, Neuroscience Department, Meyer Children's Hospital, 50139 Florence, Italy.
- Department of Experimental and Clinical Biomedical Sciences, University of Florence, 50139 Florence, Italy.
| | - Maria Alice Donati
- Metabolic and Muscular Unit, Neuroscience Department, Meyer Children's Hospital, 50139 Florence, Italy.
| | - Amelia Morrone
- Molecular and Cell Biology Laboratory of Neurometabolic Diseases, Neuroscience Department, Meyer Children's Hospital, 50139 Florence, Italy.
- Department of Neurosciences, Psychology, Drug Research and Child Health (NEUROFARBA), University of Florence, 50139 Florence, Italy.
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5
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Jang YJ, LaBella AL, Feeney TP, Braverman N, Tuchman M, Morizono H, Ah Mew N, Caldovic L. Disease-causing mutations in the promoter and enhancer of the ornithine transcarbamylase gene. Hum Mutat 2018; 39:527-536. [PMID: 29282796 DOI: 10.1002/humu.23394] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Revised: 12/19/2017] [Accepted: 12/21/2017] [Indexed: 12/17/2022]
Abstract
The ornithine transcarbamylase (OTC) gene is on the X chromosome and its product catalyzes the formation of citrulline from ornithine and carbamylphosphate in the urea cycle. About 10%-15% of patients, clinically diagnosed with OTC deficiency (OTCD), lack identifiable mutations in the coding region or splice junctions of the OTC gene on routine molecular testing. We collected DNA from such patients via retrospective review and by prospective enrollment. In nine of 38 subjects (24%), we identified a sequence variant in the OTC regulatory regions. Eight subjects had unique sequence variants in the OTC promoter and one subject had a novel sequence variant in the OTC enhancer. All sequence variants affect positions that are highly conserved in mammalian OTC genes. Functional studies revealed reduced reporter gene expression with all sequence variants. Two sequence variants caused decreased binding of the HNF4 transcription factor to its mutated binding site. Bioinformatic analyses combined with functional assays can be used to identify and authenticate pathogenic sequence variants in regulatory regions of the OTC gene, in other urea cycle disorders or other inborn errors of metabolism.
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Affiliation(s)
- Yoon J Jang
- Center for Genetic Medicine Research, Children's National Health System, Washington, District of Columbia
| | - Abigail L LaBella
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee
| | - Timothy P Feeney
- Harvard T.H. Chan School of Public Health, Harvard University, Cambridge, Massachusetts
| | - Nancy Braverman
- McGill University Health Centre, McGill University, Montreal, Quebec, Canada
| | - Mendel Tuchman
- Center for Genetic Medicine Research, Children's National Health System, Washington, District of Columbia
| | - Hiroki Morizono
- Center for Genetic Medicine Research, Children's National Health System, Washington, District of Columbia
| | - Nicholas Ah Mew
- Center for Translational Sciences, Children's National Health System, Washington, District of Columbia
| | - Ljubica Caldovic
- Center for Genetic Medicine Research, Children's National Health System, Washington, District of Columbia
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6
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Li Y, Lai-Han Leung E, Pan H, Yao X, Huang Q, Wu M, Xu T, Wang Y, Cai J, Li R, Liu W, Liu L. Identification of potential genetic causal variants for rheumatoid arthritis by whole-exome sequencing. Oncotarget 2017; 8:111119-111129. [PMID: 29340042 PMCID: PMC5762310 DOI: 10.18632/oncotarget.22630] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2017] [Accepted: 09/23/2017] [Indexed: 12/31/2022] Open
Abstract
Rheumatoid arthritis (RA) is a highly prevalent chronic autoimmune disease. However, genetic and environmental factors involved in RA pathogenesis are still remained largely unknown. To identify the genetic causal variants underlying pathogenesis and disease progression of RA patients, we undertook the first comprehensive whole-exome sequencing (WES) study in a total of 124 subjects including 58 RA cases and 66 healthy controls in Han Chinese population. We identified 378 novel genes that were enriched with deleterious variants in RA patients using a gene burden test. The further functional effects of associated genetic genes were classified and assessed, including 21 newly identified genes that were involved in the extracellular matrix (ECM)-receptor interaction, protein digestion and absorption, focal adhesion and glycerophospholipid metabolism pathways relevant to RA pathogenesis. Moreover, six pathogenic variants were investigated and structural analysis predicted their potentially functional alteration by homology modeling. Importantly, five novel and rare homozygous variants (NCR3LG1, RAP1GAP, CHCHD5, HIPK2 and DIAPH2) were identified, which may exhibit more functional impact on RA pathogenesis. Notably, 7 genes involved in the olfactory transduction pathway were enriched and associated with RA disease progression. Therefore, we performed an efficient and powerful technique WES in Chinese RA patients and identified novel, rare and common disease causing genes that alter innate immunity pathways and contribute to the risk of RA. Findings in this study may provide potential diagnostic tools and therapeutic strategies for RA patients.
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Affiliation(s)
- Ying Li
- State Key Laboratory of Quality Research in Chinese Medicine/Macau Institute for Applied Research in Medicine and Health, Macau University of Science and Technology, Macau, China
| | - Elaine Lai-Han Leung
- State Key Laboratory of Quality Research in Chinese Medicine/Macau Institute for Applied Research in Medicine and Health, Macau University of Science and Technology, Macau, China
| | - Hudan Pan
- State Key Laboratory of Quality Research in Chinese Medicine/Macau Institute for Applied Research in Medicine and Health, Macau University of Science and Technology, Macau, China
| | - Xiaojun Yao
- State Key Laboratory of Quality Research in Chinese Medicine/Macau Institute for Applied Research in Medicine and Health, Macau University of Science and Technology, Macau, China
| | - Qingchun Huang
- Guangdong Provincial Hospital of Traditional Chinese Medicine, Guangzhou, China
| | - Min Wu
- The Third Affiliated Hospital of Soochow University, Changzhou, China
| | - Ting Xu
- The Third Affiliated Hospital of Soochow University, Changzhou, China
| | - Yuwei Wang
- State Key Laboratory of Quality Research in Chinese Medicine/Macau Institute for Applied Research in Medicine and Health, Macau University of Science and Technology, Macau, China
| | - Jun Cai
- State Key Laboratory of Quality Research in Chinese Medicine/Macau Institute for Applied Research in Medicine and Health, Macau University of Science and Technology, Macau, China
| | - Runze Li
- State Key Laboratory of Quality Research in Chinese Medicine/Macau Institute for Applied Research in Medicine and Health, Macau University of Science and Technology, Macau, China
| | - Wei Liu
- The First Teaching Hospital of Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Liang Liu
- State Key Laboratory of Quality Research in Chinese Medicine/Macau Institute for Applied Research in Medicine and Health, Macau University of Science and Technology, Macau, China
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7
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Storkanova G, Vlaskova H, Chuzhanova N, Zeman J, Stranecky V, Majer F, Peskova K, Luksan O, Jirsa M, Hrebicek M, Dvorakova L. Ornithine carbamoyltransferase deficiency: molecular characterization of 29 families. Clin Genet 2013; 84:552-9. [DOI: 10.1111/cge.12085] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Revised: 12/21/2012] [Accepted: 12/21/2012] [Indexed: 11/30/2022]
Affiliation(s)
- G Storkanova
- Institute of Inherited Metabolic Disorders, First Faculty of Medicine; Charles University in Prague, and General University Hospital in Prague; Czech Republic
| | - H Vlaskova
- Institute of Inherited Metabolic Disorders, First Faculty of Medicine; Charles University in Prague, and General University Hospital in Prague; Czech Republic
| | - N Chuzhanova
- School of Science and Technology; Nottingham Trent University; Nottingham NG11 8NS UK
| | - J Zeman
- Department of Paediatrics and Adolescent Medicine; First Faculty of Medicine, Charles University in Prague, and General University Hospital in Prague; Czech Republic
| | - V Stranecky
- Institute of Inherited Metabolic Disorders, First Faculty of Medicine; Charles University in Prague, and General University Hospital in Prague; Czech Republic
| | - F Majer
- Institute of Inherited Metabolic Disorders, First Faculty of Medicine; Charles University in Prague, and General University Hospital in Prague; Czech Republic
| | - K Peskova
- Institute of Inherited Metabolic Disorders, First Faculty of Medicine; Charles University in Prague, and General University Hospital in Prague; Czech Republic
| | - O Luksan
- Laboratory of Experimental Hepatology; Institute for Clinical and Experimental Medicine (IKEM); Prague Czech Republic
| | - M Jirsa
- Laboratory of Experimental Hepatology; Institute for Clinical and Experimental Medicine (IKEM); Prague Czech Republic
| | - M Hrebicek
- Institute of Inherited Metabolic Disorders, First Faculty of Medicine; Charles University in Prague, and General University Hospital in Prague; Czech Republic
| | - L Dvorakova
- Institute of Inherited Metabolic Disorders, First Faculty of Medicine; Charles University in Prague, and General University Hospital in Prague; Czech Republic
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8
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Heibel SK, Lopez GY, Panglao M, Sodha S, Mariño-Ramírez L, Tuchman M, Caldovic L. Transcriptional regulation of N-acetylglutamate synthase. PLoS One 2012; 7:e29527. [PMID: 22383952 PMCID: PMC3287996 DOI: 10.1371/journal.pone.0029527] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2011] [Accepted: 11/30/2011] [Indexed: 01/13/2023] Open
Abstract
The urea cycle converts toxic ammonia to urea within the liver of mammals. At least 6 enzymes are required for ureagenesis, which correlates with dietary protein intake. The transcription of urea cycle genes is, at least in part, regulated by glucocorticoid and glucagon hormone signaling pathways. N-acetylglutamate synthase (NAGS) produces a unique cofactor, N-acetylglutamate (NAG), that is essential for the catalytic function of the first and rate-limiting enzyme of ureagenesis, carbamyl phosphate synthetase 1 (CPS1). However, despite the important role of NAGS in ammonia removal, little is known about the mechanisms of its regulation. We identified two regions of high conservation upstream of the translation start of the NAGS gene. Reporter assays confirmed that these regions represent promoter and enhancer and that the enhancer is tissue specific. Within the promoter, we identified multiple transcription start sites that differed between liver and small intestine. Several transcription factor binding motifs were conserved within the promoter and enhancer regions while a TATA-box motif was absent. DNA-protein pull-down assays and chromatin immunoprecipitation confirmed binding of Sp1 and CREB, but not C/EBP in the promoter and HNF-1 and NF-Y, but not SMAD3 or AP-2 in the enhancer. The functional importance of these motifs was demonstrated by decreased transcription of reporter constructs following mutagenesis of each motif. The presented data strongly suggest that Sp1, CREB, HNF-1, and NF-Y, that are known to be responsive to hormones and diet, regulate NAGS transcription. This provides molecular mechanism of regulation of ureagenesis in response to hormonal and dietary changes.
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Affiliation(s)
- Sandra Kirsch Heibel
- Center for Genetic Medicine Research, Children's National Medical Center, Washington, D. C., United States of America
- Molecular and Cellular Biology Program, University of Maryland, College Park, Maryland, United States of America
| | - Giselle Yvette Lopez
- Department of Pathology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Maria Panglao
- The George Washington University School of Medicine and Health Sciences, Washington, D. C., United States of America
| | - Sonal Sodha
- Johns Hopkins School of Medicine in Baltimore, Maryland, United States of America
| | - Leonardo Mariño-Ramírez
- Computational Biology Branch, National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Mendel Tuchman
- Center for Genetic Medicine Research, Children's National Medical Center, Washington, D. C., United States of America
| | - Ljubica Caldovic
- Center for Genetic Medicine Research, Children's National Medical Center, Washington, D. C., United States of America
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9
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Lopes-Marques M, Pereira-Castro I, Amorim A, Azevedo L. Characterization of the human ornithine transcarbamylase 3' untranslated regulatory region. DNA Cell Biol 2011; 31:427-33. [PMID: 22054066 DOI: 10.1089/dna.2011.1391] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Mutations in the untranslated regulatory regions of genes may result in abnormal gene expression or transcriptional regulation. In this study, we characterize the ornithine transcarbamylase (OTC) mRNA isoforms of the X-linked OTC gene involved in the urea formation in the liver. Our data revealed that two major transcripts (OTC-t1 and OTC-t2) are more highly expressed than any of the other isoforms in all the tissues analyzed, though a longer transcript (OTC-t3) was also isolated and characterized from the brain sample. The OTC-t2 sequence fully matches the OTC mRNA reference sequence (NM_000531.5). All three isoforms use a canonical AAUAAA hexamer that is predicted to fold into a hairpin secondary structure which might be exposed to the cleavage and polyadenylation specificity factor. In addition, we observed that the OTC-t1 and OTC-t2 transcripts display heterogeneity at the cleavage sites in a tissue-dependent manner. Taken together, our data demonstrate that several mRNA isoforms are transcribed from the OTC gene, thereby indicating a wide degree of variability in post-transcriptional regulation.
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Affiliation(s)
- Monica Lopes-Marques
- Population Genetics Group, IPATIMUP-Institute of Molecular Pathology and Immunology of the University of Porto, Porto, Portugal
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10
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Heibel SK, Ah Mew N, Caldovic L, Daikhin Y, Yudkoff M, Tuchman M. N-carbamylglutamate enhancement of ureagenesis leads to discovery of a novel deleterious mutation in a newly defined enhancer of the NAGS gene and to effective therapy. Hum Mutat 2011; 32:1153-60. [PMID: 21681857 DOI: 10.1002/humu.21553] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2011] [Accepted: 06/01/2011] [Indexed: 11/09/2022]
Abstract
N-acetylglutamate synthase (NAGS) catalyzes the conversion of glutamate and acetyl-CoA to NAG, the essential allosteric activator of carbamyl phosphate synthetase I, the first urea cycle enzyme in mammals. A 17-year-old female with recurrent hyperammonemia attacks, the cause of which remained undiagnosed for 8 years in spite of multiple molecular and biochemical investigations, showed markedly enhanced ureagenesis (measured by isotope incorporation) in response to N-carbamylglutamate (NCG). This led to sequencing of the regulatory regions of the NAGS gene and identification of a deleterious single-base substitution in the upstream enhancer. The homozygous mutation (c.-3064C>A), affecting a highly conserved nucleotide within the hepatic nuclear factor 1 (HNF-1) binding site, was not found in single nucleotide polymorphism databases and in a screen of 1,086 alleles from a diverse population. Functional assays demonstrated that this mutation decreases transcription and binding of HNF-1 to the NAGS gene, while a consensus HNF-1 binding sequence enhances binding to HNF-1 and increases transcription. Oral daily NCG therapy restored ureagenesis in this patient, normalizing her biochemical markers, and allowing discontinuation of alternate pathway therapy and normalization of her diet with no recurrence of hyperammonemia. Inc.
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Affiliation(s)
- Sandra K Heibel
- Research Center for Genetic Medicine, Children's National Medical Center, The George Washington University, Washington, DC, USA
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