1
|
Burgis NE, VanWormer K, Robbins D, Smith J. An ITPA Enzyme with Improved Substrate Selectivity. Protein J 2024; 43:62-71. [PMID: 38066288 PMCID: PMC10901923 DOI: 10.1007/s10930-023-10162-0] [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] [Accepted: 10/03/2023] [Indexed: 02/29/2024]
Abstract
Recent clinical data have identified infant patients with lethal ITPA deficiencies. ITPA is known to modulate ITP concentrations in cells and has a critical function in neural development which is not understood. Polymorphism of the ITPA gene affects outcomes for both ribavirin and thiopurine based therapies and nearly one third of the human population is thought to harbor ITPA polymorphism. In a previous site-directed mutagenesis alanine screen of the ITPA substrate selectivity pocket, we identified the ITPA mutant, E22A, as a gain-of function mutant with enhanced ITP hydrolysis activity. Here we report a rational enzyme engineering experiment to investigate the biochemical properties of position 22 ITPA mutants and find that the E22D ITPA has two- and four-fold improved substrate selectivity for ITP over the canonical purine triphosphates ATP and GTP, respectively, while maintaining biological activity. The novel E22D ITPA should be considered as a platform for further development of ITPA therapies.
Collapse
Affiliation(s)
- Nicholas E Burgis
- Department of Chemistry, Biochemistry & Physics, Eastern Washington University, Cheney, WA, 99004, USA.
| | - Kandise VanWormer
- Department of Chemistry, Biochemistry & Physics, Eastern Washington University, Cheney, WA, 99004, USA
| | - Devin Robbins
- Department of Chemistry, Biochemistry & Physics, Eastern Washington University, Cheney, WA, 99004, USA
| | - Jonathan Smith
- Department of Chemistry, Biochemistry & Physics, Eastern Washington University, Cheney, WA, 99004, USA
| |
Collapse
|
2
|
Nassogne MC, Marie S, Dewulf JP. Neurological presentations of inborn errors of purine and pyrimidine metabolism. Eur J Paediatr Neurol 2024; 48:69-77. [PMID: 38056117 DOI: 10.1016/j.ejpn.2023.11.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 11/25/2023] [Accepted: 11/30/2023] [Indexed: 12/08/2023]
Abstract
Purines and pyrimidines are essential components as they are the building blocks of vital molecules, such as nucleic acids, coenzymes, signalling molecules, as well as energy transfer molecules. Purine and pyrimidine metabolism defects are characterised by abnormal concentrations of purines, pyrimidines and/or their metabolites in cells or body fluids. This phenomenon is due to a decreased or an increased activity of enzymes involved in this metabolism and has been reported in humans for over 60 years. This review provides an overview of neurological presentations of inborn errors of purine and pyrimidine metabolism. These conditions can lead to psychomotor retardation, epilepsy, hypotonia, or microcephaly; sensory involvement, such as deafness and visual disturbances; multiple malformations, as well as muscular symptoms. Clinical signs are often nonspecific and thus overlooked, but some diseases are treatable and early diagnosis may improve the child's future. Although these metabolic hereditary diseases are rare, they are most probably under-diagnosed. When confronted with suggestive clinical or laboratory signs, clinicians should prescribe genetic testing in association with a biochemical screening including thorough purine and pyrimidine metabolites analysis and/or specific enzyme evaluation. This is most likely going to increase the number of confirmed patients.
Collapse
Affiliation(s)
- Marie-Cécile Nassogne
- Service de Neurologie Pédiatrique, Cliniques Universitaires Saint-Luc, UCLouvain, B-1200, Brussels, Belgium; Institut des Maladies Rares, Cliniques Universitaires Saint-Luc, UCLouvain, B-1200, Brussels, Belgium.
| | - Sandrine Marie
- Laboratoire des Maladies Métaboliques Héréditaires/Biochimie Génétique et Centre de Dépistage Néonatal, Cliniques Universitaires Saint-Luc, UCLouvain, B-1200, Brussels, Belgium.
| | - Joseph P Dewulf
- Institut des Maladies Rares, Cliniques Universitaires Saint-Luc, UCLouvain, B-1200, Brussels, Belgium; Laboratoire des Maladies Métaboliques Héréditaires/Biochimie Génétique et Centre de Dépistage Néonatal, Cliniques Universitaires Saint-Luc, UCLouvain, B-1200, Brussels, Belgium.
| |
Collapse
|
3
|
Zeka N, Zeka E, Zhubi E, Hoxha I. Case report: Diagnosis of a patient with Sifrim-Hitz-Weiss syndrome, development and epileptic encephalopathy-14, and medium chain acyl-CoA dehydrogenase deficiency. Front Pediatr 2023; 11:1230056. [PMID: 37732012 PMCID: PMC10507246 DOI: 10.3389/fped.2023.1230056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/27/2023] [Accepted: 07/25/2023] [Indexed: 09/22/2023] Open
Abstract
Background It is generally recognized that genetic metabolic disorders can result in neurological symptoms such as seizures, developmental delay, and intellectual disability. Heterogeneous clinical presentations make the diagnosis challenging. Case presentation In this case report, we present a unique and complex genetic disorder observed in a female patient who exhibited three pathogenic gene variants in the KCNT1, ACADM, and CHD4 genes. The convergence of these variants resulted in a multifaceted clinical presentation characterized by severe seizures of combined focal and generalized onset, metabolic dysfunction, and neurodevelopmental abnormalities. The identification and functional characterization of these gene variants shed light on the intricate interplay between these genes and the patient's phenotype. EEG revealed an epileptiform abnormality which presented in the inter-ictal period from the left frontal-central area and in the ictal period from the left mid-temporal area. The brain MRI revealed volume loss in the posterior periventricular area and parietal parenchyma, myelin destruction with no sign of hypoxic involvement, and left dominant enlargement of the lateral ventricles secondary to loss of central parenchyma. The patient was diagnosed through exome sequencing with Sifrim-Hitz-Weiss syndrome, development and epileptic encephalopathy-14, and medium-chain acyl-CoA dehydrogenase deficiency. An antiseizure medication regimen with valproic acid, levetiracetam, phenobarbital, and clonazepam was initiated. However, this led to only partial control of the seizures. Conclusion Clinical follow-up of the patient will further define the clinical spectrum of KCNT1, ACADM, and CHD4 gene variants. It will also determine the long-term efficacy of the treatment of seizures and the development of precision medicine for epilepsy syndromes due to gain-of-function variants. Special emphasis should be put on the role and importance of large-scale genomic testing in understanding and diagnosing complex phenotypes and atypical epileptic syndromes.
Collapse
Affiliation(s)
- Naim Zeka
- Pediatric Clinic, University Clinical Center of Kosovo, Prishtina, Kosovo
- Faculty of Medicine, University of Prishtina, Prishtina, Kosovo
| | - Eris Zeka
- Faculty of Medicine, University of Prishtina, Prishtina, Kosovo
| | - Esra Zhubi
- Evidence Synthesis Group, Prishtina, Kosovo
- Janos Szentagothai Doctoral School of Neurosciences, Semmelweis University, Budapest, Hungary
| | - Ilir Hoxha
- Evidence Synthesis Group, Prishtina, Kosovo
- The Dartmouth Institute for Health Policy and Clinical Practice, Geisel School of Medicine at Dartmouth, Lebanon, NH, United States
- Research Unit, Heimerer College, Prishtina, Kosovo
| |
Collapse
|
4
|
Omichi N, Kishita Y, Nakama M, Sasai H, Terazawa A, Kobayashi E, Fushimi T, Sugiyama Y, Ichimoto K, Nitta KR, Yatsuka Y, Ohtake A, Murayama K, Okazaki Y. Novel ITPA variants identified by whole genome sequencing and RNA sequencing. J Hum Genet 2023; 68:649-652. [PMID: 37246162 DOI: 10.1038/s10038-023-01156-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2023] [Revised: 04/20/2023] [Accepted: 04/21/2023] [Indexed: 05/30/2023]
Abstract
Approximately 80% of rare diseases have a genetic cause, and an accurate genetic diagnosis is necessary for disease management, prognosis prediction, and genetic counseling. Whole-exome sequencing (WES) is a cost-effective approach for exploring the genetic cause, but several cases often remain undiagnosed. We combined whole genome sequencing (WGS) and RNA sequencing (RNA-seq) to identify the pathogenic variants in an unsolved case using WES. RNA-seq revealed aberrant exon 4 and exon 6 splicing of ITPA. WGS showed a previously unreported splicing donor variant, c.263+1G>A, and a novel heterozygous deletion, including exon 6. Detailed examination of the breakpoint indicated the deletion caused by recombination between Alu elements in different introns. The proband was found to have developmental and epileptic encephalopathies caused by variants in the ITPA gene. The combination of WGS and RNA-seq may be effective in diagnosing conditions in proband who could not be diagnosed using WES.
Collapse
Affiliation(s)
- Nanako Omichi
- Department of Life Science, Faculty of Science and Engineering, Kindai University, Osaka, Japan
| | - Yoshihito Kishita
- Department of Life Science, Faculty of Science and Engineering, Kindai University, Osaka, Japan
- Diagnostics and Therapeutic of Intractable Diseases, Intractable Disease Research Center, Graduate School of Medicine, Juntendo University, Tokyo, Japan
| | - Mina Nakama
- Department of Life Science, Faculty of Science and Engineering, Kindai University, Osaka, Japan
- Clinical Genetics Center, Gifu University Hospital, Gifu, Japan
- Department of Pediatrics, Graduate School of Medicine, Gifu University, Gifu, Japan
| | - Hideo Sasai
- Clinical Genetics Center, Gifu University Hospital, Gifu, Japan
- Department of Pediatrics, Graduate School of Medicine, Gifu University, Gifu, Japan
- Department of Applied Genomics, Kazusa DNA Research Institute, Chiba, Japan
| | - Atsushi Terazawa
- Department of Pediatric Cardiology, Gifu Prefectural General Medical Center, Gifu, Japan
| | - Emiko Kobayashi
- Department of Pediatrics, Gifu Prefectural General Medical Center, Gifu, Japan
| | - Takuya Fushimi
- Department of Metabolism, Chiba Children's Hospital, Chiba, Japan
| | - Yohei Sugiyama
- Department of Metabolism, Chiba Children's Hospital, Chiba, Japan
| | - Keiko Ichimoto
- Department of Metabolism, Chiba Children's Hospital, Chiba, Japan
| | - Kazuhiro R Nitta
- Diagnostics and Therapeutic of Intractable Diseases, Intractable Disease Research Center, Graduate School of Medicine, Juntendo University, Tokyo, Japan
| | - Yukiko Yatsuka
- Diagnostics and Therapeutic of Intractable Diseases, Intractable Disease Research Center, Graduate School of Medicine, Juntendo University, Tokyo, Japan
| | - Akira Ohtake
- Department of Pediatrics and Clinical Genomics, Saitama Medical University, Moroyama, Saitama, Japan
- Center for Intractable Diseases, Saitama Medical University Hospital, Moroyama, Saitama, Japan
| | - Kei Murayama
- Diagnostics and Therapeutic of Intractable Diseases, Intractable Disease Research Center, Graduate School of Medicine, Juntendo University, Tokyo, Japan
- Department of Metabolism, Chiba Children's Hospital, Chiba, Japan
- Center for Medical Genetics, Chiba Children's Hospital, Chiba, Japan
| | - Yasushi Okazaki
- Diagnostics and Therapeutic of Intractable Diseases, Intractable Disease Research Center, Graduate School of Medicine, Juntendo University, Tokyo, Japan.
- Laboratory for Comprehensive Genomic Analysis, RIKEN Center for Integrative Medical Sciences, Kanagawa, Japan.
| |
Collapse
|
5
|
Schroader JH, Handley MT, Reddy K. Inosine triphosphate pyrophosphatase: A guardian of the cellular nucleotide pool and potential mediator of RNA function. WILEY INTERDISCIPLINARY REVIEWS. RNA 2023; 14:e1790. [PMID: 37092460 DOI: 10.1002/wrna.1790] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 02/10/2023] [Accepted: 03/20/2023] [Indexed: 04/25/2023]
Abstract
Inosine triphosphate pyrophosphatase (ITPase), encoded by the ITPA gene in humans, is an important enzyme that preserves the integrity of cellular nucleotide pools by hydrolyzing the noncanonical purine nucleotides (deoxy)inosine and (deoxy)xanthosine triphosphate into monophosphates and pyrophosphate. Variants in the ITPA gene can cause partial or complete ITPase deficiency. Partial ITPase deficiency is benign but clinically relevant as it is linked to altered drug responses. Complete ITPase deficiency causes a severe multisystem disorder characterized by seizures and encephalopathy that is frequently associated with fatal infantile dilated cardiomyopathy. In the absence of ITPase activity, its substrate noncanonical nucleotides have the potential to accumulate and become aberrantly incorporated into DNA and RNA. Hence, the pathophysiology of ITPase deficiency could arise from metabolic imbalance, altered DNA or RNA regulation, or from a combination of these factors. Here, we review the known functions of ITPase and highlight recent work aimed at determining the molecular basis for ITPA-associated pathogenesis which provides evidence for RNA dysfunction. This article is categorized under: RNA in Disease and Development > RNA in Disease RNA in Disease and Development > RNA in Development.
Collapse
Affiliation(s)
- Jacob H Schroader
- The RNA Institute, University at Albany, State University of New York, Albany, New York, USA
- Department of Biological Sciences, University at Albany, State University of New York, Albany, New York, USA
| | - Mark T Handley
- Faculty of Biological Sciences, University of Leeds, Leeds, UK
| | - Kaalak Reddy
- The RNA Institute, University at Albany, State University of New York, Albany, New York, USA
- Department of Biological Sciences, University at Albany, State University of New York, Albany, New York, USA
| |
Collapse
|
6
|
Burgis NE, April C, VanWormer K. Arginine-178 is an essential residue for ITPA function. Arch Biochem Biophys 2023; 744:109700. [PMID: 37506994 PMCID: PMC10530447 DOI: 10.1016/j.abb.2023.109700] [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: 06/20/2023] [Revised: 07/18/2023] [Accepted: 07/22/2023] [Indexed: 07/30/2023]
Abstract
The inosine triphosphate pyrophosphatase (ITPA) enzyme plays a critical cellular role by removing noncanonical nucleoside triphosphates from nucleotide pools. One of the first pathological ITPA mutants identified is R178C (rs746930990), which causes a fatal infantile encephalopathy, termed developmental and epileptic encephalopathy 35 (DEE 35). The accumulation of noncanonical nucleotides such as inosine triphosphate (ITP), is suspected to affect RNA and/or interfere with normal nucleotide function, leading to development of DEE 35. Molecular dynamics simulations have shown that the very rare R178C mutation does not significantly perturb the overall structure of the protein, but results in a high level of structural flexibility and disrupts active-site hydrogen bond networks, while preliminary biochemical data indicate that ITP hydrolyzing activity is significantly reduced for the R178C mutant. Here we report Michaelis-Menten enzyme kinetics data for the R178C ITPA mutant and three other position 178 ITPA mutants. These data confirm that position 178 is essential for ITPA activity and even conservative mutation at this site (R178K) results in significantly reduced enzyme activity. Our data support that disruption of the active-site hydrogen bond network is a major cause of diminished ITP hydrolyzing activity for the R178C mutation. These results suggest an avenue for developing therapies to address DEE 35.
Collapse
Affiliation(s)
- Nicholas E Burgis
- Department of Chemistry, Biochemistry & Physics, Eastern Washington University, Cheney, WA, 99004, USA.
| | - Caitlin April
- Department of Chemistry, Biochemistry & Physics, Eastern Washington University, Cheney, WA, 99004, USA
| | - Kandise VanWormer
- Department of Chemistry, Biochemistry & Physics, Eastern Washington University, Cheney, WA, 99004, USA
| |
Collapse
|
7
|
AlBakheet A, AlQudairy H, Alkhalifah J, Almoaily S, Kaya N, Rahbeeni Z. Detailed genetic and clinical analysis of a novel de novo variant in HPRT1: Case report of a female patient from Saudi Arabia with Lesch-Nyhan syndrome. Front Genet 2023; 13:1044936. [PMID: 36778911 PMCID: PMC9908584 DOI: 10.3389/fgene.2022.1044936] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Accepted: 11/16/2022] [Indexed: 01/27/2023] Open
Abstract
Background: Hypoxanthine-guanine phosphoribosyltransferase (HPRT1) deficiency is an inborn error of purine metabolism responsible for Lesch-Nyhan syndrome (LNS). The disease is inherited in an X-linked recessive manner and predominantly affects male individuals. Female individuals can carry a mutation as heterozygotes, but typically, they are asymptomatic because of the random inactivation of the affected allele. Nevertheless, although rare, heterozygote female individuals may manifest LNS with full characteristics. Herein, we describe a female patient from Saudi Arabia with LNS. Results: The patient (a 4-year-old girl) presented with typical characteristics of the disease, which include global developmental delay, self-mutilation, hyperuricemia, hypotonia, speech delay, spasticity, and seizures. Her general biochemical laboratory results were normal except for high levels of uric acid. The abdominal MRI\MRS, mostly unremarkable, showed bilateral echogenic foci within the renal collecting system. Genetic testing (whole-exome sequencing, iterative variant filtering, segregation analysis, and Sanger sequencing) pointed a novel de novo frameshift variant in HPRT1. X-inactivation assay using HpaII showed the presence of a 100% skewed X chromosome carrying the affected allele. RT-PCR of the cDNA indicated complete loss of the expression of the normal allele. Conclusion: Our study presents a female patient who has a severe case of LNSand found to be the 15th female patient with the disease in the world. The study emphasizethe need for a streamlined protocol that will help an early and accurate diagnosis of female LNS patients to avoid unnecessary interventions that lead to costly patient care.
Collapse
Affiliation(s)
- Albandary AlBakheet
- Department of Translational Genomics, Center for Genomic Medicine, King Faisal Specialist Hospital and Research Centre (KFSHRC), Riyadh, Saudi Arabia
| | - Hanan AlQudairy
- Department of Translational Genomics, Center for Genomic Medicine, King Faisal Specialist Hospital and Research Centre (KFSHRC), Riyadh, Saudi Arabia
| | - Joud Alkhalifah
- College of Medicine, King Saud University, Riyadh, Saudi Arabia
| | | | - Namik Kaya
- Department of Translational Genomics, Center for Genomic Medicine, King Faisal Specialist Hospital and Research Centre (KFSHRC), Riyadh, Saudi Arabia,*Correspondence: Namik Kaya, ; Zuhair Rahbeeni,
| | - Zuhair Rahbeeni
- Department of Medical Genetics, Center for Genomic Medicine, KFSHRC, Riyadh, Saudi Arabia,*Correspondence: Namik Kaya, ; Zuhair Rahbeeni,
| |
Collapse
|
8
|
Zamzami MA. Inosine Triphosphate Pyrophosphatase (ITPase): Functions, Mutations, Polymorphisms and Its Impact on Cancer Therapies. Cells 2022; 11:384. [PMID: 35159194 PMCID: PMC8833965 DOI: 10.3390/cells11030384] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 01/18/2022] [Accepted: 01/19/2022] [Indexed: 11/16/2022] Open
Abstract
Inosine triphosphate pyrophosphatase (ITPase) is an enzyme encoded by the ITPA gene and functions to prevent the incorporation of noncanonical purine nucleotides into DNA and RNA. Specifically, the ITPase catalyzed the hydrolysis of (deoxy) nucleoside triphosphates ((d) NTPs) into the corresponding nucleoside monophosphate with the concomitant release of pyrophosphate. Recently, thiopurine drug metabolites such as azathioprine have been included in the lists of ITPase substrates. Interestingly, inosine or xanthosine triphosphate (ITP/XTP) and their deoxy analogs, deoxy inosine or xanthosine triphosphate (dITP/dXTP), are products of important biological reactions such as deamination that take place within the cellular compartments. However, the incorporation of ITP/XTP, dITP/dXTP, or the genetic deficiency or polymorphism of the ITPA gene have been implicated in many human diseases, including infantile epileptic encephalopathy, early onset of tuberculosis, and the responsiveness of patients to cancer therapy. This review provides an up-to-date report on the ITPase enzyme, including information regarding its discovery, analysis, and cellular localization, its implication in human diseases including cancer, and its therapeutic potential, amongst others.
Collapse
Affiliation(s)
- Mazin A. Zamzami
- Department of Biochemistry, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia;
- Centre of Artificial Intelligence in Precision Medicines, King Abdulaziz University, Jeddah 21589, Saudi Arabia
| |
Collapse
|