1
|
Häberle J, Siri B, Dionisi-Vici C. Quo vadis ureagenesis disorders? A journey from 90 years ago into the future. J Inherit Metab Dis 2024. [PMID: 38837457 DOI: 10.1002/jimd.12763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Revised: 04/30/2024] [Accepted: 05/14/2024] [Indexed: 06/07/2024]
Abstract
The pathway of ammonia disposal in the mammalian organism has been described in 1932 as a metabolic cycle present in the liver in different compartments. In 1958, the first human disorder affecting this pathway was described as a genetic condition leading to cognitive impairment and constant abnormalities of amino acid metabolism. Since then, defects in all enzymes and transporters of the urea cycle have been described, referring to them as primary urea cycle disorders causing primary hyperammonemia. In addition, there is a still increasing list of conditions that impact on the function of the urea cycle by various mechanisms, hereby leading to secondary hyperammonemia. Despite great advances in understanding the molecular background and the biochemical specificities of both primary and secondary hyperammonemias, there remain many open questions: we do not fully understand the pathophysiology in many of the conditions; we do not always understand the highly variable clinical course of affected patients; we clearly appreciate the need for novel and improved diagnostic and therapeutic approaches. This study does look back to the beginning of the urea cycle (hi)story, briefly describes the journey through past decades, hereby illustrating advancements and knowledge gaps, and gives examples for the extremely broad perspective imminent to some of the defects of ureagenesis and allied conditions.
Collapse
Affiliation(s)
- Johannes Häberle
- Division of Metabolism and Children's Research Center, University Children's Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Barbara Siri
- Division of Metabolic Diseases and Hepatology, Bambino Gesù Children's Hospital IRCCS, Rome, Italy
| | - Carlo Dionisi-Vici
- Division of Metabolic Diseases and Hepatology, Bambino Gesù Children's Hospital IRCCS, Rome, Italy
| |
Collapse
|
2
|
Gougeard N, Sancho-Vaello E, Fernández-Murga ML, Martínez-Sinisterra B, Loukili-Hassani B, Häberle J, Marco-Marín C, Rubio V. Use of pure recombinant human enzymes to assess the disease-causing potential of missense mutations in urea cycle disorders, applied to N-acetylglutamate synthase deficiency. J Inherit Metab Dis 2024. [PMID: 38740568 DOI: 10.1002/jimd.12747] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Revised: 04/21/2024] [Accepted: 04/23/2024] [Indexed: 05/16/2024]
Abstract
N-acetylglutamate synthase (NAGS) makes acetylglutamate, the essential activator of the first, regulatory enzyme of the urea cycle, carbamoyl phosphate synthetase 1 (CPS1). NAGS deficiency (NAGSD) and CPS1 deficiency (CPS1D) present identical phenotypes. However, they must be distinguished, because NAGSD is cured by substitutive therapy with the N-acetyl-L-glutamate analogue N-carbamyl-L-glutamate, while curative therapy of CPS1D requires liver transplantation. Since their differentiation is done genetically, it is important to ascertain the disease-causing potential of CPS1 and NAGS genetic variants. With this goal, we previously carried out site-directed mutagenesis studies with pure recombinant human CPS1. We could not do the same with human NAGS (HuNAGS) because of enzyme instability, leading to our prior utilization of a bacterial NAGS as an imperfect surrogate of HuNAGS. We now use genuine HuNAGS, stabilized as a chimera of its conserved domain (cHuNAGS) with the maltose binding protein (MBP), and produced in Escherichia coli. MBP-cHuNAGS linker cleavage allowed assessment of the enzymatic properties and thermal stability of cHuNAGS, either wild-type or hosting each one of 23 nonsynonymous single-base changes found in NAGSD patients. For all but one change, disease causation was accounted by the enzymatic alterations identified, including, depending on the variant, loss of arginine activation, increased Km Glutamate, active site inactivation, decreased thermal stability, and protein misfolding. Our present approach outperforms experimental in vitro use of bacterial NAGS or in silico utilization of prediction servers (including AlphaMissense), illustrating with HuNAGS the value for UCDs of using recombinant enzymes for assessing disease-causation and molecular pathogenesis, and for therapeutic guidance.
Collapse
Affiliation(s)
- Nadine Gougeard
- Instituto de Biomedicina de Valencia, IBV-CSIC, Valencia, Spain
- Group 739, Centro de Investigación Biomédica en Red de Enfermedades Raras, (CIBERER-ISCIII) at the IBV-CSIC, Valencia, Spain
| | | | | | | | | | - Johannes Häberle
- University Children's Hospital Zurich and Children's Research Centre, Zurich, Switzerland
| | - Clara Marco-Marín
- Instituto de Biomedicina de Valencia, IBV-CSIC, Valencia, Spain
- Group 739, Centro de Investigación Biomédica en Red de Enfermedades Raras, (CIBERER-ISCIII) at the IBV-CSIC, Valencia, Spain
| | - Vicente Rubio
- Instituto de Biomedicina de Valencia, IBV-CSIC, Valencia, Spain
- Group 739, Centro de Investigación Biomédica en Red de Enfermedades Raras, (CIBERER-ISCIII) at the IBV-CSIC, Valencia, Spain
| |
Collapse
|
3
|
Singh RH, Bourdages MH, Kurtz A, MacLoed E, Norman C, Ratko S, van Calcar SC, Kenneson A. The efficacy of Carbamylglutamate impacts the nutritional management of patients with N-Acetylglutamate synthase deficiency. Orphanet J Rare Dis 2024; 19:168. [PMID: 38637895 PMCID: PMC11027358 DOI: 10.1186/s13023-024-03167-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Accepted: 03/30/2024] [Indexed: 04/20/2024] Open
Abstract
BACKGROUND The autosomal recessive disorder N-acetylglutamate synthase (NAGS) deficiency is the rarest defect of the urea cycle, with an incidence of less than one in 2,000,000 live births. Hyperammonemic crises can be avoided in individuals with NAGS deficiency by the administration of carbamylglutamate (also known as carglumic acid), which activates carbamoyl phosphatase synthetase 1 (CPS1). The aim of this case series was to introduce additional cases of NAGS deficiency to the literature as well as to assess the role of nutrition management in conjunction with carbamylglutamate therapy across new and existing cases. METHODS We conducted retrospective chart reviews of seven cases of NAGS deficiency in the US and Canada, focusing on presentation, diagnosis, medication management, nutrition management, and outcomes. RESULTS Five new and two previously published cases were included. Presenting symptoms were consistent with previous reports. Diagnostic confirmation via molecular testing varied in protocol across cases, with consecutive single gene tests leading to long delays in diagnosis in some cases. All patients responded well to carbamylglutamate therapy, as indicated by normalization of plasma ammonia and citrulline, as well as urine orotic acid in patients with abnormal levels at baseline. Although protein restriction was not prescribed in any cases after carbamylglutamate initiation, two patients continued to self-restrict protein intake. One patient experienced two episodes of hyperammonemia that resulted in poor long-term outcomes. Both episodes occurred after a disruption in access to carbamylglutamate, once due to insurance prior authorization requirements and language barriers and once due to seizure activity limiting the family's ability to administer carbamylglutamate. CONCLUSIONS Follow-up of patients with NAGS deficiency should include plans for illness and for disruption of carbamylglutamate access, including nutrition management strategies such as protein restriction. Carbamylglutamate can help patients with NAGS deficiency to liberalize their diets, but the maximum safe level of protein intake to prevent hyperammonemia is not yet known. Patients using this medication should still monitor their diet closely and be prepared for any disruptions in medication access, which might require immediate dietary adjustments or medical intervention to prevent hyperammonemia.
Collapse
Affiliation(s)
- Rani H Singh
- Emory University School of Medicine, 101 Woodruff Circle, 7th Floor Suite 7130, 30322, Atlanta, GA, USA.
| | | | | | - Erin MacLoed
- Children's National Medical Center, Washington, DC, USA
| | | | | | | | - Aileen Kenneson
- Emory University School of Medicine, 101 Woodruff Circle, 7th Floor Suite 7130, 30322, Atlanta, GA, USA
| |
Collapse
|
4
|
Abou Haidar L, Pachnis P, Gotway GK, Ni M, DeBerardinis RJ, McNutt MC. Partial N-acetyl glutamate synthase deficiency presenting as postpartum hyperammonemia: Diagnosis and subsequent pregnancy management. JIMD Rep 2023; 64:403-409. [PMID: 37927481 PMCID: PMC10623101 DOI: 10.1002/jmd2.12388] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Revised: 07/28/2023] [Accepted: 08/01/2023] [Indexed: 11/07/2023] Open
Abstract
N-acetyl glutamate synthase (NAGS) deficiency (OMIM #: 237310) is a rare urea cycle disorder that usually presents early in life with hyperammonemia. NAGS catalyzes the synthesis of N-acetyl glutamate (NAG) which functions as an activator of the carbamoyl phosphate synthetase-1 mediated conversion of ammonia to carbamoyl phosphate. The absence of NAG results in a proximal urea cycle disorder which can result in severe neurologic sequelae secondary to hyperammonemia and even death. Unlike the other urea cycle disorders, a specific pharmacological treatment for NAGS deficiency exists in the form of carglumic acid, an analog of NAG. Here we present a 29-year-old previously healthy female who presented with hyperammonemia and obtundation just after the birth of her first child. Exome sequencing revealed two novel variants in the NAGS gene, and plasma metabolomics revealed extremely low levels of NAG. Carglumic acid treatment led to prompt resolution of her biochemical abnormalities and symptoms. She tolerated two subsequent pregnancies, 2 years and 6 years after her initial presentation, while taking carglumic acid, and breastfed her third child, all without complications in the mother or children. This case report emphasizes the importance of considering urea cycle disorders in previously-healthy adults presenting with neurological symptoms during periods of metabolic stress, including the postpartum period. It also highlights the efficacious and safe use of carglumic acid during pregnancy and while breastfeeding.
Collapse
Affiliation(s)
- Lea Abou Haidar
- Children's Medical Center Research InstituteThe University of Texas Southwestern Medical CenterDallasTexasUSA
- Howard Hughes Medical InstituteThe University of Texas Southwestern Medical CenterDallasTexasUSA
| | - Panayotis Pachnis
- Children's Medical Center Research InstituteThe University of Texas Southwestern Medical CenterDallasTexasUSA
- Department of PediatricsThe University of Texas Southwestern Medical CenterDallasTexasUSA
| | - Garrett K. Gotway
- Department of PediatricsThe University of Texas Southwestern Medical CenterDallasTexasUSA
- Eugene McDermott Center for Human Growth and DevelopmentThe University of Texas Southwestern Medical CenterDallasTexasUSA
- Department of Internal MedicineThe University of Texas Southwestern Medical CenterDallasTexasUSA
| | - Min Ni
- Children's Medical Center Research InstituteThe University of Texas Southwestern Medical CenterDallasTexasUSA
- Department of PediatricsThe University of Texas Southwestern Medical CenterDallasTexasUSA
| | - Ralph J. DeBerardinis
- Children's Medical Center Research InstituteThe University of Texas Southwestern Medical CenterDallasTexasUSA
- Howard Hughes Medical InstituteThe University of Texas Southwestern Medical CenterDallasTexasUSA
- Department of PediatricsThe University of Texas Southwestern Medical CenterDallasTexasUSA
- Eugene McDermott Center for Human Growth and DevelopmentThe University of Texas Southwestern Medical CenterDallasTexasUSA
| | - Markey C. McNutt
- Department of PediatricsThe University of Texas Southwestern Medical CenterDallasTexasUSA
- Eugene McDermott Center for Human Growth and DevelopmentThe University of Texas Southwestern Medical CenterDallasTexasUSA
- Department of Internal MedicineThe University of Texas Southwestern Medical CenterDallasTexasUSA
| |
Collapse
|
5
|
Caldovic L, Ahn JJ, Andricovic J, Balick VM, Brayer M, Chansky PA, Dawson T, Edwards AC, Felsen SE, Ismat K, Jagannathan SV, Mann BT, Medina JA, Morizono T, Morizono M, Salameh S, Vashist N, Williams EC, Zhou Z, Morizono H. Datamining approaches for examining the low prevalence of N-acetylglutamate synthase deficiency and understanding transcriptional regulation of urea cycle genes. J Inherit Metab Dis 2023. [PMID: 37847851 DOI: 10.1002/jimd.12687] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Revised: 10/09/2023] [Accepted: 10/10/2023] [Indexed: 10/19/2023]
Abstract
Ammonia, which is toxic to the brain, is converted into non-toxic urea, through a pathway of six enzymatically catalyzed steps known as the urea cycle. In this pathway, N-acetylglutamate synthase (NAGS, EC 2.3.1.1) catalyzes the formation of N-acetylglutamate (NAG) from glutamate and acetyl coenzyme A. NAGS deficiency (NAGSD) is the rarest of the urea cycle disorders, yet is unique in that ureagenesis can be restored with the drug N-carbamylglutamate (NCG). We investigated whether the rarity of NAGSD could be due to low sequence variation in the NAGS genomic region, high NAGS tolerance for amino acid replacements, and alternative sources of NAG and NCG in the body. We also evaluated whether the small genomic footprint of the NAGS catalytic domain might play a role. The small number of patients diagnosed with NAGSD could result from the absence of specific disease biomarkers and/or short NAGS catalytic domain. We screened for sequence variants in NAGS regulatory regions in patients suspected of having NAGSD and found a novel NAGS regulatory element in the first intron of the NAGS gene. We applied the same datamining approach to identify regulatory elements in the remaining urea cycle genes. In addition to the known promoters and enhancers of each gene, we identified several novel regulatory elements in their upstream regions and first introns. The identification of cis-regulatory elements of urea cycle genes and their associated transcription factors holds promise for uncovering shared mechanisms governing urea cycle gene expression and potentially leading to new treatments for urea cycle disorders.
Collapse
Affiliation(s)
- Ljubica Caldovic
- Center for Genetic Medicine Research, Children's National Research Institute, Children's National Hospital, Washington, DC, USA
- Department of Genomics and Precision Medicine, School of Medicine and Health Sciences, The George Washington University, Washington, DC, USA
| | - Julie J Ahn
- Department of Anatomy and Cell Biology, The George Washington University School of Medicine and Health Sciences, Washington, DC, USA
| | - Jacklyn Andricovic
- Department of Anatomy and Cell Biology, The George Washington University School of Medicine and Health Sciences, Washington, DC, USA
| | - Veronica M Balick
- Department of Biochemistry and Molecular Medicine, The George Washington University School of Medicine and Health Sciences, Washington, DC, USA
| | - Mallory Brayer
- Department of Biological Sciences, The George Washington University, Washington, DC, USA
| | - Pamela A Chansky
- The Institute for Biomedical Science, School of Medicine and Health Sciences, George Washington University, Washington, DC, USA
| | - Tyson Dawson
- The Institute for Biomedical Science, School of Medicine and Health Sciences, George Washington University, Washington, DC, USA
- AMPEL BioSolutions LLC, Charlottesville, Virginia, USA
| | - Alex C Edwards
- The Institute for Biomedical Science, School of Medicine and Health Sciences, George Washington University, Washington, DC, USA
- Center for Neuroscience Research, Children's National Research Institute, Children's National Hospital, Washington, DC, USA
| | - Sara E Felsen
- The Institute for Biomedical Science, School of Medicine and Health Sciences, George Washington University, Washington, DC, USA
- Center for Neuroscience Research, Children's National Research Institute, Children's National Hospital, Washington, DC, USA
| | - Karim Ismat
- Center for Genetic Medicine Research, Children's National Research Institute, Children's National Hospital, Washington, DC, USA
- Department of Genomics and Precision Medicine, School of Medicine and Health Sciences, The George Washington University, Washington, DC, USA
| | - Sveta V Jagannathan
- The Institute for Biomedical Science, School of Medicine and Health Sciences, George Washington University, Washington, DC, USA
| | - Brendan T Mann
- Department of Microbiology, Immunology, and Tropical Medicine, School of Medicine and Health Sciences, George Washington University, Washington, DC, USA
| | - Jacob A Medina
- The Institute for Biomedical Science, School of Medicine and Health Sciences, George Washington University, Washington, DC, USA
| | - Toshio Morizono
- College of Science and Engineering, University of Minnesota, Minneapolis, Minnesota, USA
| | - Michio Morizono
- College of Science and Engineering, University of Minnesota, Minneapolis, Minnesota, USA
| | - Shatha Salameh
- Department of Pharmacology & Physiology, School of Medicine and Health Sciences, George Washington University, Washington, DC, USA
- Sheikh Zayed Institute for Pediatric Surgical Innovation, Children's National Hospital, Washington, DC, USA
| | - Neerja Vashist
- Center for Genetic Medicine Research, Children's National Research Institute, Children's National Hospital, Washington, DC, USA
- Department of Genomics and Precision Medicine, School of Medicine and Health Sciences, The George Washington University, Washington, DC, USA
| | - Emily C Williams
- Department of Anatomy and Cell Biology, The George Washington University School of Medicine and Health Sciences, Washington, DC, USA
- The George Washington University Cancer Center, School of Medicine and Health Sciences, George Washington University, Washington, DC, USA
| | - Zhe Zhou
- Department of Civil and Environmental Engineering, The George Washington University, Washington, DC, USA
| | - Hiroki Morizono
- Center for Genetic Medicine Research, Children's National Research Institute, Children's National Hospital, Washington, DC, USA
- Department of Genomics and Precision Medicine, School of Medicine and Health Sciences, The George Washington University, Washington, DC, USA
| |
Collapse
|
6
|
Bai R, He AL, Guo J, Li Z, Yu X, Zeng J, Mi Y, Wang L, Zhang J, Yang D. Novel pathogenic variant (c.2947C > T) of the carbamoyl phosphate synthetase 1 gene in neonatal-onset deficiency. Front Neurosci 2022; 16:1025572. [PMID: 36340787 PMCID: PMC9634248 DOI: 10.3389/fnins.2022.1025572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Accepted: 10/06/2022] [Indexed: 11/13/2022] Open
Abstract
Background Carbamoyl phosphate synthetase 1 deficiency (CPS1D) is a rare autosomal recessive urea cycle disorder characterized by hyperammonaemia. The biochemical measurement of the intermediate metabolites is helpful for CPS1D diagnosis; it however cannot distinguish CPS1D from N-acetylglutamate synthetase deficiency. Therefore, next-generation sequencing (NGS) is often essential for the accurate diagnosis of CPS1D. Methods NGS was performed to identify candidate gene variants of CPS1D in a Asian neonatal patient presented with poor feeding, reduced activity, tachypnea, lethargy, and convulsions. The potential pathogenicity of the identified variants was predicted by various types of bioinformatical analyses, including evolution conservation, domain and 3D structure simulations. Results Compound heterozygosity of CPS1D were identified. One was in exon 24 with a novel heterozygous missense variant c.2947C > T (p.P983S), and another was previously reported in exon 20 with c.2548C > T (p.R850C). Both variants were predicted to be deleterious. Conservation analysis and structural modeling showed that the two substituted amino acids were highly evolutionarily conserved, resulting in potential decreases of the binding pocket stability and the partial loss of enzyme activity. Conclusion In this study, two pathogenic missense variants were identified with NGS, expanding the variants pectrum of the CPS1 gene. The variants and related structural knowledge of CPS enzyme demonstrate the applicability for the accurate diagnosis of CPS1D.
Collapse
Affiliation(s)
- Ruimiao Bai
- Department of Neonatology, Northwest Women’s and Children’s Hospital, Xi’an, Shaanxi, China
| | - ALing He
- Department of Neonatology, Northwest Women’s and Children’s Hospital, Xi’an, Shaanxi, China
| | - Jinzhen Guo
- Department of Neonatology, Northwest Women’s and Children’s Hospital, Xi’an, Shaanxi, China
| | - Zhankui Li
- Department of Neonatology, Northwest Women’s and Children’s Hospital, Xi’an, Shaanxi, China
| | - Xiping Yu
- Department of Neonatology, Northwest Women’s and Children’s Hospital, Xi’an, Shaanxi, China
| | - JunAn Zeng
- Department of Neonatology, Northwest Women’s and Children’s Hospital, Xi’an, Shaanxi, China
| | - Yang Mi
- Department of Obstetrics, Northwest Women’s and Children’s Hospital, Xi’an, Shaanxi, China
| | - Lin Wang
- Genetics Center, Northwest Women’s and Children’s Hospital, Xi’an, Shaanxi, China
| | - Jingjing Zhang
- Medical Imaging Center, Northwest Women’s and Children’s Hospital, Xi’an, Shaanxi, China
| | - Dong Yang
- Department of Neonatology, Northwest Women’s and Children’s Hospital, Xi’an, Shaanxi, China
| |
Collapse
|
7
|
Häberle J, Moore MB, Haskins N, Rüfenacht V, Rokicki D, Rubio-Gozalbo E, Tuchman M, Longo N, Yandell M, Andrews A, AhMew N, Caldovic L. Noncoding sequence variants define a novel regulatory element in the first intron of the N-acetylglutamate synthase gene. Hum Mutat 2021; 42:1624-1636. [PMID: 34510628 DOI: 10.1002/humu.24281] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Revised: 08/19/2021] [Accepted: 09/08/2021] [Indexed: 11/10/2022]
Abstract
N-acetylglutamate synthase deficiency is an autosomal recessive urea cycle disorder caused either by decreased expression of the NAGS gene or defective NAGS enzyme resulting in decreased production of N-acetylglutamate (NAG), an allosteric activator of carbamylphosphate synthetase 1 (CPS1). NAGSD is the only urea cycle disorder that can be effectively treated with a single drug, N-carbamylglutamate (NCG), a stable NAG analog, which activates CPS1 to restore ureagenesis. We describe three patients with NAGSD due to four novel noncoding sequence variants in the NAGS regulatory regions. All three patients had hyperammonemia that resolved upon treatment with NCG. Sequence variants NM_153006.2:c.427-222G>A and NM_153006.2:c.427-218A>C reside in the 547 bp-long first intron of NAGS and define a novel NAGS regulatory element that binds retinoic X receptor α. Sequence variants NC_000017.10:g.42078967A>T (NM_153006.2:c.-3065A>T) and NC_000017.10:g.42078934C>T (NM_153006.2:c.-3098C>T) reside in the NAGS enhancer, within known HNF1 and predicted glucocorticoid receptor binding sites, respectively. Reporter gene assays in HepG2 and HuH-7 cells demonstrated that all four substitutions could result in reduced expression of NAGS. These findings show that analyzing noncoding regions of NAGS and other urea cycle genes can reveal molecular causes of disease and identify novel regulators of ureagenesis.
Collapse
Affiliation(s)
- Johannes Häberle
- Division of Metabolism and Children's Research Center, University Children's Hospital, Zurich, Switzerland
| | - Marvin B Moore
- Department of Human Genetics, University of Utah Health Science Center, Salt Lake City, Utah, USA
| | - Nantaporn Haskins
- Center for Genetic Medicine Research, Children's National Hospital, Washington, District of Columbia, USA
| | - Véronique Rüfenacht
- Division of Metabolism and Children's Research Center, University Children's Hospital, Zurich, Switzerland
| | - Dariusz Rokicki
- Department of Pediatrics, Nutrition and Metabolic Diseases, The Children's Memorial Health Institute, Warsaw, Poland
| | - Estela Rubio-Gozalbo
- Department of Pediatrics and Clinical Genetics, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Mendel Tuchman
- Center for Genetic Medicine Research, Children's National Hospital, Washington, District of Columbia, USA
| | - Nicola Longo
- Division of Medical Genetics, Department of Pediatrics, University of Utah Health Science Center, Salt Lake City, Utah, USA
| | - Mark Yandell
- Eccles Institute of Human Genetics, University of Utah Health Science Center, Salt Lake City, Utah, USA.,8USTAR Center for Genetic Discovery, University of Utah Health Science Center, Salt Lake City, Utah, USA
| | - Ashley Andrews
- Division of Medical Genetics, Pediatrics, University of Utah Health Science Center, Salt Lake City, Utah, USA
| | - Nicholas AhMew
- Center for Genetic Medicine Research, Children's National Hospital, Washington, District of Columbia, USA
| | - Ljubica Caldovic
- Center for Genetic Medicine Research, Children's National Hospital, Washington, District of Columbia, USA.,Department of Genomics and Precision Medicine, School of Medical and Health Sciences, The George Washington University, Washington, District of Columbia, USA
| |
Collapse
|
8
|
Gene delivery corrects N-acetylglutamate synthase deficiency and enables insights in the physiological impact of L-arginine activation of N-acetylglutamate synthase. Sci Rep 2021; 11:3580. [PMID: 33574402 PMCID: PMC7878489 DOI: 10.1038/s41598-021-82994-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Accepted: 01/20/2021] [Indexed: 11/19/2022] Open
Abstract
The urea cycle protects the central nervous system from ammonia toxicity by converting ammonia to urea. N-acetylglutamate synthase (NAGS) catalyzes formation of N-acetylglutamate, an essential allosteric activator of carbamylphosphate synthetase 1. Enzymatic activity of mammalian NAGS doubles in the presence of L-arginine, but the physiological significance of NAGS activation by L-arginine has been unknown. The NAGS knockout (Nags−/−) mouse is an animal model of inducible hyperammonemia, which develops hyperammonemia without N-carbamylglutamate and L-citrulline supplementation (NCG + Cit). We used adeno associated virus (AAV) based gene transfer to correct NAGS deficiency in the Nags−/− mice, established the dose of the vector needed to rescue Nags−/− mice from hyperammonemia and measured expression levels of Nags mRNA and NAGS protein in the livers of rescued animals. This methodology was used to investigate the effect of L-arginine on ureagenesis in vivo by treating Nags−/− mice with AAV vectors encoding either wild-type or E354A mutant mouse NAGS (mNAGS), which is not activated by L-arginine. The Nags−/− mice expressing E354A mNAGS were viable but had elevated plasma ammonia concentration despite similar levels of the E354A and wild-type mNAGS proteins. The corresponding mutation in human NAGS (NP_694551.1:p.E360D) that abolishes binding and activation by L-arginine was identified in a patient with NAGS deficiency. Our results show that NAGS deficiency can be rescued by gene therapy, and suggest that L-arginine binding to the NAGS enzyme is essential for normal ureagenesis.
Collapse
|
9
|
Bernal AC, Tubio MC, Crespo C, Eiroa HD. Clinical and Genetic Characterization and Biochemical Correlation at Presentation in 48 Patients Diagnosed with Urea Cycle Disorders at the Hospital Juan P Garrahan, Argentina. JOURNAL OF INBORN ERRORS OF METABOLISM AND SCREENING 2021. [DOI: 10.1590/2326-4594-jiems-2020-0026] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/03/2023] Open
|
10
|
Makris G, Lauber M, Rüfenacht V, Gemperle C, Diez-Fernandez C, Caldovic L, Froese DS, Häberle J. Clinical and structural insights into potential dominant negative triggers of proximal urea cycle disorders. Biochimie 2020; 183:89-99. [PMID: 33309754 DOI: 10.1016/j.biochi.2020.12.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 12/04/2020] [Accepted: 12/08/2020] [Indexed: 12/31/2022]
Abstract
Despite biochemical and genetic testing being the golden standards for identification of proximal urea cycle disorders (UCDs), genotype-phenotype correlations are often unclear. Co-occurring partial defects affecting more than one gene have not been demonstrated so far in proximal UCDs. Here, we analyzed the mutational spectrum of 557 suspected proximal UCD individuals. We probed oligomerizing forms of NAGS, CPS1 and OTC, and evaluated the surface exposure of residues mutated in heterozygously affected individuals. BN-PAGE and gel-filtration chromatography were employed to discover protein-protein interactions within recombinant enzymes. From a total of 281 confirmed patients, only 15 were identified as "heterozygous-only" candidates (i.e. single defective allele). Within these cases, the only missense variants to potentially qualify as dominant negative triggers were CPS1 p.Gly401Arg and NAGS p.Thr181Ala and p.Tyr512Cys, as assessed by residue oligomerization capacity and surface exposure. However, all three candidates seem to participate in critical intramolecular functions, thus, unlikely to facilitate protein-protein interactions. This interpretation is further supported by BN-PAGE and gel-filtration analyses revealing no multiprotein proximal urea cycle complex formation. Collectively, genetic analysis, structural considerations and in vitro experiments point against a prominent role of dominant negative effects in human proximal UCDs.
Collapse
Affiliation(s)
- Georgios Makris
- Division of Metabolism and Children's Research Center, University Children's Hospital Zurich, Zurich, Switzerland
| | - Matthias Lauber
- Division of Metabolism and Children's Research Center, University Children's Hospital Zurich, Zurich, Switzerland
| | - Véronique Rüfenacht
- Division of Metabolism and Children's Research Center, University Children's Hospital Zurich, Zurich, Switzerland
| | - Corinne Gemperle
- Division of Metabolism and Children's Research Center, University Children's Hospital Zurich, Zurich, Switzerland
| | - Carmen Diez-Fernandez
- Division of Metabolism and Children's Research Center, University Children's Hospital Zurich, Zurich, Switzerland; Nextech Invest, Bahnhofstrasse 18, 8001, Zurich, Switzerland
| | - Ljubica Caldovic
- Center for Genetic Medicine Research, Children's National Hospital, Washington, DC, USA
| | - D Sean Froese
- Division of Metabolism and Children's Research Center, University Children's Hospital Zurich, Zurich, Switzerland
| | - Johannes Häberle
- Division of Metabolism and Children's Research Center, University Children's Hospital Zurich, Zurich, Switzerland.
| |
Collapse
|
11
|
Kenneson A, Singh RH. Presentation and management of N-acetylglutamate synthase deficiency: a review of the literature. Orphanet J Rare Dis 2020; 15:279. [PMID: 33036647 PMCID: PMC7545900 DOI: 10.1186/s13023-020-01560-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Accepted: 09/24/2020] [Indexed: 12/19/2022] Open
Abstract
Background N-Acetylglutamate synthase (NAGS) deficiency is an extremely rare autosomal recessive metabolic disorder affecting the urea cycle, leading to episodes of hyperammonemia which can cause significant morbidity and mortality. Since its recognition in 1981, NAGS deficiency has been treated with carbamylglutamate with or without other measures (nutritional, ammonia scavengers, dialytic, etc.). We conducted a systematic literature review of NAGS deficiency to summarize current knowledge around presentation and management. Methods Case reports and case series were identified using the Medline database, as well as references from other articles and a general internet search. Clinical data related to presentation and management were abstracted by two reviewers. Results In total, 98 cases of NAGS deficiency from 79 families, in 48 articles or abstracts were identified. Of these, 1 was diagnosed prenatally, 57 were neonatal cases, 34 were post-neonatal, and 6 did not specify age at presentation or were asymptomatic at diagnosis. Twenty-one cases had relevant family history. We summarize triggers of hyperammonemic episodes, diagnosis, clinical signs and symptoms, and management strategies. DNA testing is the preferred method of diagnosis, although therapeutic trials to assess response of ammonia levels to carbamylglutamate may also be helpful. Management usually consists of treatment with carbamylglutamate, although the reported maintenance dose varied across case reports. Protein restriction was sometimes used in conjunction with carbamylglutamate. Supplementation with citrulline, arginine, and sodium benzoate also were reported. Conclusions Presentation of NAGS deficiency varies by age and symptoms. In addition, both diagnosis and management have evolved over time and vary across clinics. Prompt recognition and appropriate treatment of NAGS deficiency with carbamylglutamate may improve outcomes of affected individuals. Further research is needed to assess the roles of protein restriction and supplements in the treatment of NAGS deficiency, especially during times of illness or lack of access to carbamylglutamate.
Collapse
Affiliation(s)
- Aileen Kenneson
- Department of Human Genetics, Emory University, Atlanta, GA, USA.
| | - Rani H Singh
- Department of Human Genetics, Emory University, Atlanta, GA, USA. .,Department of Pediatrics, Emory University, Atlanta, GA, USA.
| |
Collapse
|
12
|
Rumping L, Vringer E, Houwen RHJ, van Hasselt PM, Jans JJM, Verhoeven‐Duif NM. Inborn errors of enzymes in glutamate metabolism. J Inherit Metab Dis 2020; 43:200-215. [PMID: 31603991 PMCID: PMC7078983 DOI: 10.1002/jimd.12180] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Revised: 10/01/2019] [Accepted: 10/04/2019] [Indexed: 12/29/2022]
Abstract
Glutamate is involved in a variety of metabolic pathways. We reviewed the literature on genetic defects of enzymes that directly metabolise glutamate, leading to inborn errors of glutamate metabolism. Seventeen genetic defects of glutamate metabolising enzymes have been reported, of which three were only recently identified. These 17 defects affect the inter-conversion of glutamine and glutamate, amino acid metabolism, ammonia detoxification, and glutathione metabolism. We provide an overview of the clinical and biochemical phenotypes of these rare defects in an effort to ease their recognition. By categorising these by biochemical pathway, we aim to create insight into the contributing role of deviant glutamate and glutamine levels to the pathophysiology. For those disorders involving the inter-conversion of glutamine and glutamate, these deviant levels are postulated to play a pivotal pathophysiologic role. For the other IEM however-with the exception of urea cycle defects-abnormal glutamate and glutamine concentrations were rarely reported. To create insight into the clinical consequences of disturbed glutamate metabolism-rather than individual glutamate and glutamine levels-the prevalence of phenotypic abnormalities within the 17 IEM was compared to their prevalence within all Mendelian disorders and subsequently all disorders with metabolic abnormalities notated in the Human Phenotype Ontology (HPO) database. For this, a hierarchical database of all phenotypic abnormalities of the 17 defects in glutamate metabolism based on HPO was created. A neurologic phenotypic spectrum of developmental delay, ataxia, seizures, and hypotonia are common in the inborn errors of enzymes in glutamate metabolism. Additionally, ophthalmologic and skin abnormalities are often present, suggesting that disturbed glutamate homeostasis affects tissues of ectodermal origin: brain, eye, and skin. Reporting glutamate and glutamine concentrations in patients with inborn errors of glutamate metabolism would provide additional insight into the pathophysiology.
Collapse
Affiliation(s)
- Lynne Rumping
- Department of GeneticsUniversity Medical Center Utrecht, Utrecht UniversityUtrechtthe Netherlands
- Center for Molecular MedicineUniversity Medical Center Utrecht, Utrecht UniversityUtrechtthe Netherlands
- Department of PediatricsUniversity Medical Center Utrecht, Utrecht UniversityUtrechtthe Netherlands
| | - Esmee Vringer
- Department of GeneticsUniversity Medical Center Utrecht, Utrecht UniversityUtrechtthe Netherlands
| | - Roderick H. J. Houwen
- Department of PediatricsUniversity Medical Center Utrecht, Utrecht UniversityUtrechtthe Netherlands
| | - Peter M. van Hasselt
- Department of PediatricsUniversity Medical Center Utrecht, Utrecht UniversityUtrechtthe Netherlands
| | - Judith J. M. Jans
- Department of GeneticsUniversity Medical Center Utrecht, Utrecht UniversityUtrechtthe Netherlands
- Center for Molecular MedicineUniversity Medical Center Utrecht, Utrecht UniversityUtrechtthe Netherlands
| | - Nanda M. Verhoeven‐Duif
- Department of GeneticsUniversity Medical Center Utrecht, Utrecht UniversityUtrechtthe Netherlands
- Center for Molecular MedicineUniversity Medical Center Utrecht, Utrecht UniversityUtrechtthe Netherlands
| |
Collapse
|
13
|
Peoc'h K, Damaj L, Pelletier R, Lefèvre C, Dubourg C, Denis MC, Bendavid C, Odent S, Moreau C. Early care of N-acetyl glutamate synthase (NAGS) deficiency in three infants from an inbred family. Mol Genet Metab Rep 2020; 22:100558. [PMID: 32021803 PMCID: PMC6994713 DOI: 10.1016/j.ymgmr.2019.100558] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Revised: 12/20/2019] [Accepted: 12/21/2019] [Indexed: 12/30/2022] Open
Abstract
N-acetyl glutamate synthase (NAGS) deficiency is the rarest urea cycle defect presenting as neonatal onset life-threatening hyperammonemia. We report here a family history of severe NAGS deficiency: after the index-case with severe hyperammonemia, one patient benefited from antenatal diagnosis, and from primary care at birth, another one was diagnosed at 2-days and immediately treated with carbaglumic-acid. Finally, we report excellent tolerance to long-term carbaglumic-acid treatment, with no side effects, and healthy neurological and psychomotor development.
Collapse
Affiliation(s)
- Katell Peoc'h
- APHP, HUPNVS, UF de Biochimie Clinique, Hôpital Beaujon, F-91118 Clichy, France.,Université de Paris, U1149 INSERM, F-75018 Paris, France
| | - Léna Damaj
- Service de Pédiatrie, Hôpital Sud, CHU Rennes Boulevard de Bulgarie, 35000 Rennes, France
| | - Romain Pelletier
- Laboratoire de Biochimie-Toxicologie, Hôpital Pontchaillou CHU Rennes, 2 rue Henri Le Guilloux, 35000 Rennes, France
| | - Charles Lefèvre
- Laboratoire de Biochimie-Toxicologie, Hôpital Pontchaillou CHU Rennes, 2 rue Henri Le Guilloux, 35000 Rennes, France
| | - Christèle Dubourg
- Laboratoire de Génétique moléculaire et Génomique Hôpital Pontchaillou CHU Rennes, 2 rue Henri Le Guilloux, 35000 Rennes, France.,UMR6290 IGDR, Univ Rennes, France
| | | | - Claude Bendavid
- Laboratoire de Biochimie-Toxicologie, Hôpital Pontchaillou CHU Rennes, 2 rue Henri Le Guilloux, 35000 Rennes, France.,Univ Rennes, INSERM, INRA, Institut NuMeCan, CHU, Rennes, France
| | - Sylvie Odent
- UMR6290 IGDR, Univ Rennes, France.,Service de Génétique clinique, Hôpital Sud, CHU Rennes Boulevard de Bulgarie, UMR6290 IGDR, Univ Rennes, 35000 Rennes, France
| | - Caroline Moreau
- Laboratoire de Biochimie-Toxicologie, Hôpital Pontchaillou CHU Rennes, 2 rue Henri Le Guilloux, 35000 Rennes, France.,Univ Rennes, INSERM, INRA, Institut NuMeCan, CHU, Rennes, France
| |
Collapse
|
14
|
Waisbren SE, Stefanatos AK, Kok TMY, Ozturk‐Hismi B. Neuropsychological attributes of urea cycle disorders: A systematic review of the literature. J Inherit Metab Dis 2019; 42:1176-1191. [PMID: 31268178 PMCID: PMC7250134 DOI: 10.1002/jimd.12146] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Revised: 06/25/2019] [Accepted: 07/01/2019] [Indexed: 12/30/2022]
Abstract
Urea cycle disorders (UCDs) are rare inherited metabolic conditions that impair the effectiveness of the urea cycle responsible for removing excess ammonia from the body. The estimated incidence of UCDs is 1:35 000 births, or approximately 113 new patients with UCD per year. This review summarizes neuropsychological outcomes among patients with the eight UCDs in reports published since 1980. Rates of intellectual disabilities published before (and including) 2000 and after 2000 were pooled and compared for each UCD. Since diagnoses for UCDs tended to occur earlier and better treatments became more readily available after the turn of the century, this assessment will characterize the extent that current management strategies have improved neuropsychological outcomes. The pooled sample included data on cognitive abilities of 1649 individuals reported in 58 citations. A total of 556 patients (34%) functioned in the range of intellectual disabilities. The decline in the proportion of intellectual disabilities in six disorders, ranged from 7% to 41%. Results from various studies differed and the cohorts varied with respect to age at symptom onset, age at diagnosis and treatment initiation, current age, severity of the metabolic deficiency, management strategies, and ethnic origins. The proportion of cases with intellectual disabilities ranged from 9% to 65% after 2000 in the seven UCDs associated with cognitive deficits. Positive outcomes from some studies suggest that it is possible to prevent or reverse the adverse impact of UCDs on neuropsychological functioning. It is time to "raise the bar" in terms of expectations for treatment effectiveness.
Collapse
Affiliation(s)
- Susan E. Waisbren
- Division of Genetics and Genomics, Department of Pediatrics, Boston Children's HospitalBostonMassachusetts
- Department of Medicine, Harvard Medical SchoolBostonMassachusetts
| | - Arianna K. Stefanatos
- Department of Child & Adolescent Psychiatry and Behavioral Sciences, Children's Hospital of PhiladelphiaPhiladelphiaPennsylvania
| | | | - Burcu Ozturk‐Hismi
- Division of Genetics and Genomics, Department of Pediatrics, Boston Children's HospitalBostonMassachusetts
- Tepecik Education and Research HospitalIzmirTurkey
| |
Collapse
|
15
|
Häberle J, Burlina A, Chakrapani A, Dixon M, Karall D, Lindner M, Mandel H, Martinelli D, Pintos-Morell G, Santer R, Skouma A, Servais A, Tal G, Rubio V, Huemer M, Dionisi-Vici C. Suggested guidelines for the diagnosis and management of urea cycle disorders: First revision. J Inherit Metab Dis 2019; 42:1192-1230. [PMID: 30982989 DOI: 10.1002/jimd.12100] [Citation(s) in RCA: 249] [Impact Index Per Article: 49.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 04/04/2019] [Accepted: 04/08/2019] [Indexed: 02/06/2023]
Abstract
In 2012, we published guidelines summarizing and evaluating late 2011 evidence for diagnosis and therapy of urea cycle disorders (UCDs). With 1:35 000 estimated incidence, UCDs cause hyperammonemia of neonatal (~50%) or late onset that can lead to intellectual disability or death, even while effective therapies do exist. In the 7 years that have elapsed since the first guideline was published, abundant novel information has accumulated, experience on newborn screening for some UCDs has widened, a novel hyperammonemia-causing genetic disorder has been reported, glycerol phenylbutyrate has been introduced as a treatment, and novel promising therapeutic avenues (including gene therapy) have been opened. Several factors including the impact of the first edition of these guidelines (frequently read and quoted) may have increased awareness among health professionals and patient families. However, under-recognition and delayed diagnosis of UCDs still appear widespread. It was therefore necessary to revise the original guidelines to ensure an up-to-date frame of reference for professionals and patients as well as for awareness campaigns. This was accomplished by keeping the original spirit of providing a trans-European consensus based on robust evidence (scored with GRADE methodology), involving professionals on UCDs from nine countries in preparing this consensus. We believe this revised guideline, which has been reviewed by several societies that are involved in the management of UCDs, will have a positive impact on the outcomes of patients by establishing common standards, and spreading and harmonizing good practices. It may also promote the identification of knowledge voids to be filled by future research.
Collapse
Affiliation(s)
- Johannes Häberle
- University Children's Hospital Zurich and Children's Research Centre, Zurich, Switzerland
| | - Alberto Burlina
- Division of Inborn Metabolic Disease, Department of Pediatrics, University Hospital Padua, Padova, Italy
| | - Anupam Chakrapani
- Department of Metabolic Medicine, Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
| | - Marjorie Dixon
- Dietetics, Great Ormond Street Hospital for Children, NHS Trust, London, UK
| | - Daniela Karall
- Clinic for Pediatrics, Division of Inherited Metabolic Disorders, Medical University of Innsbruck, Innsbruck, Austria
| | - Martin Lindner
- University Children's Hospital, Frankfurt am Main, Germany
| | - Hanna Mandel
- Institute of Human Genetics and metabolic disorders, Western Galilee Medical Center, Nahariya, Israel
| | - Diego Martinelli
- Division of Metabolism, Bambino Gesù Children's Hospital, Rome, Italy
| | - Guillem Pintos-Morell
- Centre for Rare Diseases, University Hospital Vall d'Hebron, Barcelona, Spain
- CIBERER_GCV08, Research Institute IGTP, Barcelona, Spain
- Universitat Autònoma de Barcelona, Barcelona, Spain
| | - René Santer
- Department of Pediatrics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Anastasia Skouma
- Institute of Child Health, Agia Sofia Children's Hospital, Athens, Greece
| | - Aude Servais
- Service de Néphrologie et maladies métaboliques adulte Hôpital Necker 149, Paris, France
| | - Galit Tal
- The Ruth Rappaport Children's Hospital, Rambam Medical Center, Haifa, Israel
| | - Vicente Rubio
- Instituto de Biomedicina de Valencia (IBV-CSIC), Centro de Investigación Biomédica en Red para Enfermedades Raras (CIBERER), Valencia, Spain
| | - Martina Huemer
- University Children's Hospital Zurich and Children's Research Centre, Zurich, Switzerland
- Department of Paediatrics, Landeskrankenhaus Bregenz, Bregenz, Austria
| | | |
Collapse
|
16
|
N-Acetylglutamate Synthase Deficiency Due to a Recurrent Sequence Variant in the N-acetylglutamate Synthase Enhancer Region. Sci Rep 2018; 8:15436. [PMID: 30337552 PMCID: PMC6194121 DOI: 10.1038/s41598-018-33457-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Accepted: 09/26/2018] [Indexed: 12/31/2022] Open
Abstract
N-acetylglutamate synthase deficiency (NAGSD, MIM #237310) is an autosomal recessive disorder of the urea cycle that results from absent or decreased production of N-acetylglutamate (NAG) due to either decreased NAGS gene expression or defective NAGS enzyme. NAG is essential for the activity of carbamylphosphate synthetase 1 (CPS1), the first and rate-limiting enzyme of the urea cycle. NAGSD is the only urea cycle disorder that can be treated with a single drug, N-carbamylglutamate (NCG), which can activate CPS1 and completely restore ureagenesis in patients with NAGSD. We describe a novel sequence variant NM_153006.2:c.-3026C > T in the NAGS enhancer that was found in three patients from two families with NAGSD; two patients had hyperammonemia that resolved upon treatment with NCG, while the third patient increased dietary protein intake after initiation of NCG therapy. Two patients were homozygous for the variant while the third patient had the c.-3026C > T variant and a partial uniparental disomy that encompassed the NAGS gene on chromosome 17. The c.-3026C > T sequence variant affects a base pair that is highly conserved in vertebrates; the variant is predicted to be deleterious by several bioinformatics tools. Functional assays in cultured HepG2 cells demonstrated that the c.-3026C > T substitution could result in reduced expression of the NAGS gene. These findings underscore the importance of analyzing NAGS gene regulatory regions when looking for molecular causes of NAGSD.
Collapse
|
17
|
Hediger N, Landolt MA, Diez-Fernandez C, Huemer M, Häberle J. The impact of ammonia levels and dialysis on outcome in 202 patients with neonatal onset urea cycle disorders. J Inherit Metab Dis 2018. [PMID: 29520739 DOI: 10.1007/s10545-018-0157-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Neonatal onset hyperammonemia in patients with urea cycle disorders (UCDs) is still associated with high morbidity and mortality. Current protocols consistently recommend emergency medical and dietary management. In case of increasing or persistent hyperammonemia, with continuous or progressive neurological signs, dialysis is performed, mostly as ultima ratio. It is presently unknown whether the currently defined ammonia threshold (e.g., at 500 μmol/L) to start dialysis is useful to improve clinical outcome. A systematic review of clinical and biochemical data from published neonatal onset UCD patients was performed to identify factors determining clinical outcome and to investigate in which clinical and biochemical setting dialysis was most effective. A total of 202 patients (118 proximal and 84 distal UCDs) described in 90 case reports or case series were included according to predefined inclusion/exclusion criteria. Median age at onset was three days and mean ammonia that triggered start of dialysis was 1199 μmol/L. Seventy-one percent of all patients received any form of dialysis. Total mortality was 25% and only 20% of all patients had a "normal" outcome. In general, patients with higher ammonia levels were more likely to receive dialysis, but this had for most patients no influence on outcome. In conclusion, in severe neonatal onset hyperammonemia, the current practice of dialysis, which effectively clears ammonia, had no impact on outcome. It may be essential for improving outcome to initiate all available treatment options, including dialysis, as early as possible.
Collapse
Affiliation(s)
- Nina Hediger
- Division of Metabolism and Children's Research Center, University Children's Hospital Zurich, 8032, Zurich, Switzerland
| | - Markus A Landolt
- Department of Psychosomatics and Psychiatry, University Children's Hospital Zurich, 8032, Zurich, Switzerland
- Division of Child and Adolescent Health Psychology, Department of Psychology, University of Zurich, Zurich, Switzerland
| | - Carmen Diez-Fernandez
- Division of Metabolism and Children's Research Center, University Children's Hospital Zurich, 8032, Zurich, Switzerland
| | - Martina Huemer
- Division of Metabolism and Children's Research Center, University Children's Hospital Zurich, 8032, Zurich, Switzerland
- Department of Paediatrics, Landeskrankenhaus Bregenz, Bregenz, Austria
| | - Johannes Häberle
- Division of Metabolism and Children's Research Center, University Children's Hospital Zurich, 8032, Zurich, Switzerland.
| |
Collapse
|
18
|
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.
Collapse
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.
| |
Collapse
|
19
|
Chen X, Yuan L, Sun M, Liu Q, Wu Y. Two novel CPS1 mutations in a case of carbamoyl phosphate synthetase 1 deficiency causing hyperammonemia and leukodystrophy. J Clin Lab Anal 2018; 32:e22375. [PMID: 29314318 DOI: 10.1002/jcla.22375] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Accepted: 12/02/2017] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Carbamoyl phosphate synthetase 1 deficiency (CPS1D) is a rare autosomal recessive disorder of the urea cycle, mostly characterized by hyperammonemia and the concomitant leukodystrophy. The onset of CPS1D can be at any age, and the clinical manifestations are variable and atypical. Genetic tests are indispensable for accurate diagnosis of CPS1D on the basis of biochemical tests. METHODS Blood tandem mass spectrometric analysis and urea organic acidemia screening were performed on a Chinese neonatal patient with low activity, recurrent seizures, and hyperammonemia. Next-generation sequencing and Sanger sequencing were followed up for making a definite diagnosis. Bioinformatics tools were used for the conservation analysis and pathogenicity predictions of the identified mutations. RESULTS Increased lactate in urea and decreased citrulline in blood were detected in the patient. Two novel mutations (c.173G>T, p.G58V in exon 2 and c.796G>A, p.G266R in exon 8) in CPS1 identified in the neonatal patient were found through coseparation verification. Both of the two mutations were predicted to be deleterious, and the two relevant amino acids exerted highly evolutionarily conserved. The final diagnosis of the patient was compound heterozygous CPS1D. CONCLUSION This study described the specific clinical characteristics and the variations of physiological and biochemical indices in a Chinese neonatal patient with CPS1D, which facilitated the diagnosis and mechanism research of the disease. Two novel causative missense mutations were identified, which enriched the mutation spectrum of CPS1D in China and worldwide. Advice of prenatal diagnosis was given to the family for a new pregnancy.
Collapse
Affiliation(s)
- Xihui Chen
- Department of Biochemistry and Molecular Biology, Fourth Military Medical University, Xi'an, China.,Center for DNA Typing, Fourth Military Medical University, Xi'an, China
| | - Lijuan Yuan
- Department of Biochemistry and Molecular Biology, Fourth Military Medical University, Xi'an, China.,Center for DNA Typing, Fourth Military Medical University, Xi'an, China.,Department of General Surgery, Tangdu Hospital, Fourth Military Medical Universiy, Xi'an, China
| | - Mao Sun
- Department of Biochemistry and Molecular Biology, Fourth Military Medical University, Xi'an, China.,Center for DNA Typing, Fourth Military Medical University, Xi'an, China
| | - Qingbo Liu
- Department of Biochemistry and Molecular Biology, Fourth Military Medical University, Xi'an, China.,Center for DNA Typing, Fourth Military Medical University, Xi'an, China
| | - Yuanming Wu
- Department of Biochemistry and Molecular Biology, Fourth Military Medical University, Xi'an, China.,Center for DNA Typing, Fourth Military Medical University, Xi'an, China
| |
Collapse
|
20
|
Tremiño L, Forcada-Nadal A, Contreras A, Rubio V. Studies on cyanobacterial protein PipY shed light on structure, potential functions, and vitamin B 6 -dependent epilepsy. FEBS Lett 2017; 591:3431-3442. [PMID: 28914444 DOI: 10.1002/1873-3468.12841] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2017] [Revised: 08/21/2017] [Accepted: 09/01/2017] [Indexed: 11/11/2022]
Abstract
The Synechococcus elongatus COG0325 gene pipY functionally interacts with the nitrogen regulatory gene pipX. As a first step toward a molecular understanding of such interactions, we characterized PipY. This 221-residue protein is monomeric and hosts pyridoxal phosphate (PLP), binding it with limited affinity and losing it upon incubation with D-cycloserine. PipY crystal structures with and without PLP reveal a single-domain monomer folded as the TIM barrel of type-III fold PLP enzymes, with PLP highly exposed, fitting a role for PipY in PLP homeostasis. The mobile PLP phosphate-anchoring C-terminal helix might act as a trigger for PLP exchange. Exploiting the universality of COG0325 functions, we used PipY in site-directed mutagenesis studies to shed light on disease causation by epilepsy-associated mutations in the human COG0325 gene PROSC.
Collapse
Affiliation(s)
- Lorena Tremiño
- Instituto de Biomedicina de Valencia (IBV-CSIC), CIBER de Enfermedades Raras (CIBERER-ISCIII), Valencia, Spain
| | - Alicia Forcada-Nadal
- Instituto de Biomedicina de Valencia (IBV-CSIC), CIBER de Enfermedades Raras (CIBERER-ISCIII), Valencia, Spain.,Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Spain
| | - Asunción Contreras
- Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Spain
| | - Vicente Rubio
- Instituto de Biomedicina de Valencia (IBV-CSIC), CIBER de Enfermedades Raras (CIBERER-ISCIII), Valencia, Spain
| |
Collapse
|
21
|
Abstract
A girl born at term was admitted to the neonatal intensive care unit because of mild respiratory distress after a complicated delivery. She recovered, but was readmitted at 58 h of life with mild respiratory distress and increased muscle tone. Neonatal abstinence syndrome because of maternal use of lithium, clomipramine, and quetiapine during pregnancy was suspected, but at 115 h of life she became unresponsive, and an immediate work-up for coma was initiated. An ammonia of 2,235 μmol/l was found, and treatment with sodium benzoate, sodium phenylacetate, arginine, glucose, and N-carbamylglutamate (NCG, Carbaglu®) was started. This treatment normalized plasma ammonia levels within 16 h.Biochemical results suggested a mitochondrial urea cycle defect, either of N-acetyl glutamate synthase (NAGS) or carbamoyl phosphate synthetase 1. DNA analysis later confirmed a diagnosis of NAGS deficiency. Under long-term treatment with NCG, the patient developed normally at last follow-up at 7 months of age.In conclusion, the standard neonatal situation of a neurologically compromised newborn turned out as a treatable rare inborn error of metabolism. In all neonates with somnolence and coma and hence the suspicion of a bacterial sepsis, plasma ammonia should be included in the work-up. NCG was immediately beneficial for the patient described and should be considered for the emergency treatment of neonatal hyperammonemia. Even a very high ammonia may allow for a normal neurological development in infancy (and possibly beyond).
Collapse
|
22
|
Finding Treatments for Genetic Metabolic Disease. CURRENT PEDIATRICS REPORTS 2016. [DOI: 10.1007/s40124-016-0113-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
23
|
Chapel-Crespo CC, Diaz GA, Oishi K. Efficacy of N-carbamoyl-L-glutamic acid for the treatment of inherited metabolic disorders. Expert Rev Endocrinol Metab 2016; 11:467-473. [PMID: 30034506 PMCID: PMC6054484 DOI: 10.1080/17446651.2016.1239526] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
INTRODUCTION N-carbamoyl-L-glutamic acid (NCG) is a synthetic analogue of N-acetyl glutamate (NAG) that works effectively as a cofactor for carbamoyl phosphate synthase 1 and enhances ureagenesis by activating the urea cycle. NCG (brand name, Carbaglu) was recently approved by the United States Food and Drug Administration (US FDA) for the management of NAGS deficiency and by the European Medicines Agency (EMA) for the treatment of NAGS deficiency as well as for the treatment of hyperammonenia in propionic, methylmalonic and isovaleric acidemias in Europe. AREAS COVERED The history, mechanism of action, and efficacy of this new drug are described. Moreover, clinical utility of NCG in a variety of inborn errors of metabolism with secondary NAGS deficiency is discussed. EXPERT COMMENTARY NCG has favorable pharmacological features including better bioavailability compared to NAG. The clinical use of NCG has proven to be so effective as to make dietary protein restriction unnecessary for patients with NAGS deficiency. It has been also demonstrated to be effective for hyperammonemia secondary to other types of inborn errors of metabolism. NCG may have additional therapeutic potential in conditions such as hepatic hyperammonemic encephalopathy secondary to chemotherapies or other liver pathology.
Collapse
Affiliation(s)
- Cristel C Chapel-Crespo
- Department of Genetics and Genomic Sciences, Department of Pediatrics, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - George A Diaz
- Department of Genetics and Genomic Sciences, Department of Pediatrics, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Kimihiko Oishi
- Department of Genetics and Genomic Sciences, Department of Pediatrics, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| |
Collapse
|
24
|
Al Kaabi EH, El-Hattab AW. N-acetylglutamate synthase deficiency: Novel mutation associated with neonatal presentation and literature review of molecular and phenotypic spectra. Mol Genet Metab Rep 2016; 8:94-8. [PMID: 27570737 PMCID: PMC4992009 DOI: 10.1016/j.ymgmr.2016.08.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2016] [Revised: 08/07/2016] [Accepted: 08/07/2016] [Indexed: 12/30/2022] Open
Abstract
The urea cycle is the main pathway for the disposal of excess nitrogen. Carbamoylphosphate synthetase 1 (CPS1), the first and rate-limiting enzyme of urea cycle, is activated by N-acetylglutamate (NAG), and thus N-acetylglutamate synthase (NAGS) is an essential part of the urea cycle. Although NAGS deficiency is the rarest urea cycle disorder, it is the only one that can be specifically and effectively treated by a drug, N-carbamylglutamate, a stable structural analogous of NAG that activates CPS1. Here we report an infant with NAGS deficiency who presented with neonatal hyperammonemia. She was found to have a novel homozygous splice-site mutation, c.1097-2A>T, in the NAGS gene. We describe the clinical course of this infant, who had rapid response to N-carbamylglutamate treatment. In addition, we reviewed the clinical and molecular spectra of previously reported individuals with NAGS deficiency, which presents in most cases with neonatal hyperammonemia, and in some cases the presentation is later, with a broad spectrum of ages and manifestations. With this broad later-onset phenotypic spectrum, maintaining a high index of suspicion is needed for the early diagnosis of this treatable disease.
Collapse
Affiliation(s)
- Eiman H Al Kaabi
- Pediatrics Department, Tawam Hospital, Al-Ain, United Arab Emirates
| | - Ayman W El-Hattab
- Division of Clinical Genetics and Metabolic Disorders, Pediatrics Department, Tawam Hospital, Al-Ain, United Arab Emirates
| |
Collapse
|