1
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Ambrose A, McCabe M, Hung C, Sosova I, Seres P, Mercimek-Andrews S. Outcome of creatine supplementation therapy in phosphoglucomutase-1 deficiency associated congenital disorders of glycosylation: Novel insights. Mol Genet Metab Rep 2025; 43:101212. [PMID: 40242152 PMCID: PMC12002938 DOI: 10.1016/j.ymgmr.2025.101212] [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: 02/10/2025] [Revised: 03/24/2025] [Accepted: 03/25/2025] [Indexed: 04/18/2025] Open
Abstract
Background Biallelic pathogenic variants in PGM1 result in phosphoglucomutase 1 (PGM1) deficiency that is one of the congenital disorders of glycosylation (CDG) (PGM1-CDG). Phenotypic spectrum includes congenital malformations, and muscular, cardiac, hepatic, endocrine and hematologic phenotypes. Current treatment consists of D-galactose therapy that results in clinical and biochemical improvements. To improve fatigue, and exercise intolerance, we started creatine supplementation therapy. Material and methods We reviewed electronic patient chart. We applied Nijmegen Pediatric CDG Rating Scale (NPCRS) and The Functional Assessment of Chronic Illness Therapy Fatigue scale (FACIT-F). We measured creatine metabolism biomarkers. Results This is a 29-year-old female with PGM1-CDG, confirmed diagnosis by clinical exome sequencing. She has been treated with D-galactose therapy which did not improve her fatigue and exercise intolerance. She was started on creatine supplementation therapy at the age of 27 years which led to decreased daytime sleeping, increased exercise capacity and improvements in her NPCRS, and FACIT-F. Her plasma guanidinoacetate was low. She had elevated urine galactitol on D-galactose therapy. Discussion PGM1-CDG associated myopathy is likely due to combination of several factors including abnormal muscle carbohydrate metabolism, abnormal N-glycosylation of proteins involved in the muscle functions and creatine transport and altered muscle energy homeostasis. It was previously shown that creatine supplementation therapy improves myopathy in patients with mitochondrial cytopathies. We think that the use of creatine supplementation therapy coincided with improvements in fatigue and exercise intolerance subjectively and objectively in our patient.
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Affiliation(s)
- Anastasia Ambrose
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Morganne McCabe
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Clara Hung
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Iveta Sosova
- Alberta Newborn Screening and Biochemical Genetics Laboratory, University of Alberta Hospital, Alberta Precision Laboratories, Edmonton, Alberta, Canada
- Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, Alberta, Canada
| | - Peter Seres
- Department of Radiology and Diagnostic Imaging, Faculty of Medicine and Dentistry University of Alberta Edmonton Alberta, Canada
| | - Saadet Mercimek-Andrews
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
- Women and Children's Health Research Institute, University of Alberta, Edmonton, Alberta, Canada
- Alberta Health Services, Edmonton Zone, Alberta, Canada
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2
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Pertici I, D'Angelo D, Vecellio Reane D, Reconditi M, Morotti I, Putignano E, Napoli D, Rastelli G, Gherardi G, De Mario A, Rizzuto R, Boncompagni S, Baroncelli L, Linari M, Caremani M, Raffaello A. Creatine transporter (SLC6A8) knockout mice exhibit reduced muscle performance, disrupted mitochondrial Ca 2+ homeostasis, and severe muscle atrophy. Cell Death Dis 2025; 16:99. [PMID: 39952955 PMCID: PMC11828924 DOI: 10.1038/s41419-025-07381-x] [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: 08/14/2024] [Revised: 12/17/2024] [Accepted: 01/22/2025] [Indexed: 02/17/2025]
Abstract
Creatine (Cr) is essential for cellular energy homeostasis, particularly in muscle and brain tissues. Creatine Transporter Deficiency (CTD), an X-linked disorder caused by mutations in the SLC6A8 gene, disrupts Cr transport, leading to intellectual disability, speech delay, autism, epilepsy, and various non-neurological symptoms. In addition to neurological alterations, Creatine Transporter knockout (CrT-/y) mice exhibit severe muscle atrophy and functional impairments. This study provides the first characterization of the skeletal muscle phenotype in CrT-/y mice, revealing profound ultrastructural abnormalities accompanied by reduced fiber cross-sectional area and muscle performance. Notably, mitochondria are involved, as evidenced by disrupted cristae, increased mitochondrial size, impaired Ca2+ uptake, reduced membrane potential and ATP production. Mechanistically, the expression of atrophy-specific E3 ubiquitin ligases and suppression of the IGF1-Akt/PKB pathway, regulated by mitochondrial Ca2+ levels, further support the atrophic phenotype. These findings highlight the profound impact of Cr deficiency on skeletal muscle, emphasizing the need for targeted therapeutic strategies to address both the neurological and peripheral manifestations of CTD. Understanding the underlying mechanisms, particularly mitochondrial dysfunction, could lead to novel interventions for this disorder.
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Affiliation(s)
- Irene Pertici
- PhysioLab (Department of Biology and Department of Experimental and Clinical Medicine), University of Florence, Florence, Italy
| | - Donato D'Angelo
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Denis Vecellio Reane
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum Munich, Munich, Germany
| | - Massimo Reconditi
- PhysioLab (Department of Biology and Department of Experimental and Clinical Medicine), University of Florence, Florence, Italy
| | - Ilaria Morotti
- PhysioLab (Department of Biology and Department of Experimental and Clinical Medicine), University of Florence, Florence, Italy
| | - Elena Putignano
- Institute of Neuroscience, National Research Council (CNR), Pisa, Italy
| | - Debora Napoli
- Institute of Neuroscience, National Research Council (CNR), Pisa, Italy
| | - Giorgia Rastelli
- Center for Advanced Studies and Technology, Department of Neuroscience, Imaging, and Clinical Sciences, University G. D'Annunzio of Chieti-Pescara, Chieti, Italy
| | - Gaia Gherardi
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Agnese De Mario
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Rosario Rizzuto
- Department of Biomedical Sciences, University of Padova, Padova, Italy
- National Center of Gene Therapy and RNA-based Drugs, Padova, Italy
| | - Simona Boncompagni
- Center for Advanced Studies and Technology, Department of Neuroscience, Imaging, and Clinical Sciences, University G. D'Annunzio of Chieti-Pescara, Chieti, Italy
| | - Laura Baroncelli
- Institute of Neuroscience, National Research Council (CNR), Pisa, Italy
- Department of Developmental Neuroscience, IRCCS Stella Maris Foundation, Pisa, Italy
| | - Marco Linari
- PhysioLab (Department of Biology and Department of Experimental and Clinical Medicine), University of Florence, Florence, Italy
| | - Marco Caremani
- PhysioLab (Department of Biology and Department of Experimental and Clinical Medicine), University of Florence, Florence, Italy.
| | - Anna Raffaello
- Department of Biomedical Sciences, University of Padova, Padova, Italy.
- Myology Center (CIR-Myo), University of Padua, Padua, Italy.
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3
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Ferrada E, Wiedmer T, Wang WA, Frommelt F, Steurer B, Klimek C, Lindinger S, Osthushenrich T, Garofoli A, Brocchetti S, Bradberry S, Huang J, MacNamara A, Scarabottolo L, Ecker GF, Malarstig A, Superti-Furga G. Experimental and Computational Analysis of Newly Identified Pathogenic Mutations in the Creatine Transporter SLC6A8. J Mol Biol 2024; 436:168383. [PMID: 38070861 DOI: 10.1016/j.jmb.2023.168383] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Revised: 11/26/2023] [Accepted: 12/01/2023] [Indexed: 12/24/2023]
Abstract
Creatine is an essential metabolite for the storage and rapid supply of energy in muscle and nerve cells. In humans, impaired metabolism, transport, and distribution of creatine throughout tissues can cause varying forms of mental disability, also known as creatine deficiency syndrome (CDS). So far, 80 mutations in the creatine transporter (SLC6A8) have been associated to CDS. To better understand the effect of human genetic variants on the physiology of SLC6A8 and their possible impact on CDS, we studied 30 missense variants including 15 variants of unknown significance, two of which are reported here for the first time. We expressed these variants in HEK293 cells and explored their subcellular localization and transport activity. We also applied computational methods to predict variant effect and estimate site-specific changes in thermodynamic stability. To explore variants that might have a differential effect on the transporter's conformers along the transport cycle, we constructed homology models of the inward facing, and outward facing conformations. In addition, we used mass-spectrometry to study proteins that interact with wild type SLC6A8 and five selected variants in HEK293 cells. In silico models of the protein complexes revealed how two variants impact the interaction interface of SLC6A8 with other proteins and how pathogenic variants lead to an enrichment of ER protein partners. Overall, our integrated analysis disambiguates the pathogenicity of 15 variants of unknown significance revealing diverse mechanisms of pathogenicity, including two previously unreported variants obtained from patients suffering from the creatine deficiency syndrome.
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Affiliation(s)
- Evandro Ferrada
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria.
| | - Tabea Wiedmer
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria
| | - Wen-An Wang
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria
| | - Fabian Frommelt
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria
| | - Barbara Steurer
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria
| | - Christoph Klimek
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria
| | - Sabrina Lindinger
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria
| | | | - Andrea Garofoli
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria
| | | | | | - Jiahui Huang
- Department of Pharmaceutical Sciences, University of Vienna, Vienna, Austria
| | | | | | - Gerhard F Ecker
- Department of Pharmaceutical Sciences, University of Vienna, Vienna, Austria
| | - Anders Malarstig
- Pfizer Worldwide Research, Development and Medical, Stockholm, Sweden
| | - Giulio Superti-Furga
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria; Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria.
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4
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Bian X, Zhu J, Jia X, Liang W, Yu S, Li Z, Zhang W, Rao Y. Suggestion of creatine as a new neurotransmitter by approaches ranging from chemical analysis and biochemistry to electrophysiology. eLife 2023; 12:RP89317. [PMID: 38126335 PMCID: PMC10735228 DOI: 10.7554/elife.89317] [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] [Indexed: 12/23/2023] Open
Abstract
The discovery of a new neurotransmitter, especially one in the central nervous system, is both important and difficult. We have been searching for new neurotransmitters for 12 y. We detected creatine (Cr) in synaptic vesicles (SVs) at a level lower than glutamate and gamma-aminobutyric acid but higher than acetylcholine and 5-hydroxytryptamine. SV Cr was reduced in mice lacking either arginine:glycine amidinotransferase (a Cr synthetase) or SLC6A8, a Cr transporter with mutations among the most common causes of intellectual disability in men. Calcium-dependent release of Cr was detected after stimulation in brain slices. Cr release was reduced in Slc6a8 and Agat mutants. Cr inhibited neocortical pyramidal neurons. SLC6A8 was necessary for Cr uptake into synaptosomes. Cr was found by us to be taken up into SVs in an ATP-dependent manner. Our biochemical, chemical, genetic, and electrophysiological results are consistent with the possibility of Cr as a neurotransmitter, though not yet reaching the level of proof for the now classic transmitters. Our novel approach to discover neurotransmitters is to begin with analysis of contents in SVs before defining their function and physiology.
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Affiliation(s)
- Xiling Bian
- Laboratory of Neurochemical Biology, PKU-IDG/McGovern Institute for Brain Research, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Department of Chemical Biology, College of Chemistry and Chemical Engineering, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking UniversityBeijingChina
- Chinese Institute for Brain Research (CIBR)BeijingChina
| | - Jiemin Zhu
- Laboratory of Neurochemical Biology, PKU-IDG/McGovern Institute for Brain Research, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Department of Chemical Biology, College of Chemistry and Chemical Engineering, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking UniversityBeijingChina
- Chinese Institute for Brain Research (CIBR)BeijingChina
| | - Xiaobo Jia
- Laboratory of Neurochemical Biology, PKU-IDG/McGovern Institute for Brain Research, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Department of Chemical Biology, College of Chemistry and Chemical Engineering, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking UniversityBeijingChina
- Chinese Institute for Brain Research (CIBR)BeijingChina
| | - Wenjun Liang
- Chinese Institutes of Medical Research, Capital Medical UniversityBeijingChina
- Changping Laboratory, Yard 28, Science Park Road, Changping DistrictBeijingChina
| | - Sihan Yu
- Laboratory of Neurochemical Biology, PKU-IDG/McGovern Institute for Brain Research, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Department of Chemical Biology, College of Chemistry and Chemical Engineering, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking UniversityBeijingChina
- Changping Laboratory, Yard 28, Science Park Road, Changping DistrictBeijingChina
| | - Zhiqiang Li
- Laboratory of Neurochemical Biology, PKU-IDG/McGovern Institute for Brain Research, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Department of Chemical Biology, College of Chemistry and Chemical Engineering, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking UniversityBeijingChina
| | - Wenxia Zhang
- Laboratory of Neurochemical Biology, PKU-IDG/McGovern Institute for Brain Research, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Department of Chemical Biology, College of Chemistry and Chemical Engineering, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking UniversityBeijingChina
- Chinese Institutes of Medical Research, Capital Medical UniversityBeijingChina
- Institute of Molecular Physiology, Shenzhen Bay LaboratoryShenzhenChina
| | - Yi Rao
- Laboratory of Neurochemical Biology, PKU-IDG/McGovern Institute for Brain Research, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Department of Chemical Biology, College of Chemistry and Chemical Engineering, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking UniversityBeijingChina
- Chinese Institute for Brain Research (CIBR)BeijingChina
- Chinese Institutes of Medical Research, Capital Medical UniversityBeijingChina
- Changping Laboratory, Yard 28, Science Park Road, Changping DistrictBeijingChina
- Institute of Molecular Physiology, Shenzhen Bay LaboratoryShenzhenChina
- Research Unit of Medical Neurobiology, Chinese Academy of Medical SciencesBeijingChina
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5
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Tiivoja E, Reinson K, Muru K, Rähn K, Muhu K, Mauring L, Kahre T, Pajusalu S, Õunap K. The prevalence of inherited metabolic disorders in Estonian population over 30 years: A significant increase during study period. JIMD Rep 2022; 63:604-613. [PMID: 36341167 PMCID: PMC9626666 DOI: 10.1002/jmd2.12325] [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: 06/29/2022] [Revised: 08/09/2022] [Accepted: 08/10/2022] [Indexed: 11/09/2022] Open
Abstract
Inherited metabolic disorders (IMD) are a group of hereditary diseases wherein the impairment of a biochemical pathway is intrinsic to the pathophysiology of the disease. Estonia's small population and nationwide digitalised healthcare system make it possible to perform an epidemiological study that covers the whole population. A study was performed in Tartu University Hospital, which is the only tertiary care unit in Estonia for diagnosing patients with IMD, to define the prevalence and live birth prevalence of IMDs and the effectiveness of new diagnostic methods on the diagnosis of IMD. During the retrospective study period from 1990 to 2017, 333 patients were diagnosed with IMD. Statistical analysis showed a significant increase in IMD diagnoses per year from 0.47 to 2.51 cases per 100 000 persons (p < 0.0001) during the study period. Live birth prevalence of IMD in Estonia was calculated to be 41.52 cases per 100 000 live births. The most frequently diagnosed IMD groups were disorders of amino acid metabolism, disorders of complex molecule degradation, mitochondrial disorders, and disorders of tetrapyrrole metabolism. Phenylketonuria was the most frequently diagnosed disorder of all IMD (21.6%). Our results correlated well with data from other developed countries and, along with high birth prevalence, add confidence in the effectiveness of our diagnostic yield. Implementation of new diagnostic methods during study period may largely account for the significant increase in the number of IMD diagnoses per year. We conclude that the implementation of new diagnostic methods continues to be important and contributes to better diagnosis of rare diseases.
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Affiliation(s)
- Elis Tiivoja
- Department of Clinical Genetics, Institute of Clinical MedicineUniversity of TartuTartuEstonia
- Department of Clinical Genetics, Genetic and Personalized Medicine ClinicTartu University HospitalTartuEstonia
| | - Karit Reinson
- Department of Clinical Genetics, Institute of Clinical MedicineUniversity of TartuTartuEstonia
- Department of Clinical Genetics, Genetic and Personalized Medicine ClinicTartu University HospitalTartuEstonia
| | - Kai Muru
- Department of Clinical Genetics, Institute of Clinical MedicineUniversity of TartuTartuEstonia
- Department of Clinical Genetics, Genetic and Personalized Medicine ClinicTartu University HospitalTartuEstonia
| | - Kristi Rähn
- Department of Clinical Genetics, Institute of Clinical MedicineUniversity of TartuTartuEstonia
- Department of Clinical Genetics, Genetic and Personalized Medicine ClinicTartu University HospitalTartuEstonia
| | - Kristina Muhu
- Department of Clinical Genetics, Institute of Clinical MedicineUniversity of TartuTartuEstonia
| | - Laura Mauring
- Department of Clinical Genetics, Institute of Clinical MedicineUniversity of TartuTartuEstonia
- Eye ClinicTartu University HospitalTartuEstonia
| | - Tiina Kahre
- Department of Clinical Genetics, Institute of Clinical MedicineUniversity of TartuTartuEstonia
- Department of Laboratory Genetics, Genetic and Personalized Medicine ClinicTartu University HospitalTartuEstonia
| | - Sander Pajusalu
- Department of Clinical Genetics, Institute of Clinical MedicineUniversity of TartuTartuEstonia
- Department of Laboratory Genetics, Genetic and Personalized Medicine ClinicTartu University HospitalTartuEstonia
| | - Katrin Õunap
- Department of Clinical Genetics, Institute of Clinical MedicineUniversity of TartuTartuEstonia
- Department of Clinical Genetics, Genetic and Personalized Medicine ClinicTartu University HospitalTartuEstonia
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6
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Farr CV, El-Kasaby A, Erdem FA, Sucic S, Freissmuth M, Sandtner W. Cooperative Binding of Substrate and Ions Drives Forward Cycling of the Human Creatine Transporter-1. Front Physiol 2022; 13:919439. [PMID: 35837012 PMCID: PMC9273935 DOI: 10.3389/fphys.2022.919439] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Accepted: 06/09/2022] [Indexed: 11/25/2022] Open
Abstract
Creatine serves as an ATP buffer and is thus an integral component of cellular energy metabolism. Most cells maintain their creatine levels via uptake by the creatine transporter (CRT-1, SLC6A8). The activity of CRT-1, therefore, is a major determinant of cytosolic creatine concentrations. We determined the kinetics of CRT-1 in real time by relying on electrophysiological recordings of transport-associated currents. Our analysis revealed that CRT-1 harvested the concentration gradient of NaCl and the membrane potential but not the potassium gradient to achieve a very high concentrative power. We investigated the mechanistic basis for the ability of CRT-1 to maintain the forward cycling mode in spite of high intracellular concentrations of creatine: this is achieved by cooperative binding of substrate and co-substrate ions, which, under physiological ion conditions, results in a very pronounced (i.e. about 500-fold) drop in the affinity of creatine to the inward-facing state of CRT-1. Kinetic estimates were integrated into a mathematical model of the transport cycle of CRT-1, which faithfully reproduced all experimental data. We interrogated the kinetic model to examine the most plausible mechanistic basis of cooperativity: based on this systematic exploration, we conclude that destabilization of binary rather than ternary complexes is necessary for CRT-1 to maintain the observed cytosolic creatine concentrations. Our model also provides a plausible explanation why neurons, heart and skeletal muscle cells must express a creatine releasing transporter to achieve rapid equilibration of the intracellular creatine pool.
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Affiliation(s)
| | | | | | | | - Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
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7
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Ghirardini E, Calugi F, Sagona G, Di Vetta F, Palma M, Battini R, Cioni G, Pizzorusso T, Baroncelli L. The Role of Preclinical Models in Creatine Transporter Deficiency: Neurobiological Mechanisms, Biomarkers and Therapeutic Development. Genes (Basel) 2021; 12:genes12081123. [PMID: 34440297 PMCID: PMC8392480 DOI: 10.3390/genes12081123] [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] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Revised: 07/22/2021] [Accepted: 07/23/2021] [Indexed: 12/12/2022] Open
Abstract
Creatine (Cr) Transporter Deficiency (CTD) is an X-linked metabolic disorder, mostly caused by missense mutations in the SLC6A8 gene and presenting with intellectual disability, autistic behavior, and epilepsy. There is no effective treatment for CTD and patients need lifelong assistance. Thus, the research of novel intervention strategies is a major scientific challenge. Animal models are an excellent tool to dissect the disease pathogenetic mechanisms and drive the preclinical development of therapeutics. This review illustrates the current knowledge about Cr metabolism and CTD clinical aspects, with a focus on mainstay diagnostic and therapeutic options. Then, we discuss the rodent models of CTD characterized in the last decade, comparing the phenotypes expressed within clinically relevant domains and the timeline of symptom development. This analysis highlights that animals with the ubiquitous deletion/mutation of SLC6A8 genes well recapitulate the early onset and the complex pathological phenotype of the human condition. Thus, they should represent the preferred model for preclinical efficacy studies. On the other hand, brain- and cell-specific conditional mutants are ideal for understanding the basis of CTD at a cellular and molecular level. Finally, we explain how CTD models might provide novel insight about the pathogenesis of other disorders, including cancer.
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MESH Headings
- Animals
- Biomarkers/metabolism
- Brain Diseases, Metabolic, Inborn/metabolism
- Brain Diseases, Metabolic, Inborn/pathology
- Brain Diseases, Metabolic, Inborn/therapy
- Central Nervous System/pathology
- Creatine/deficiency
- Creatine/metabolism
- Disease Models, Animal
- Humans
- Mental Retardation, X-Linked/metabolism
- Mental Retardation, X-Linked/pathology
- Mental Retardation, X-Linked/therapy
- Mice
- Plasma Membrane Neurotransmitter Transport Proteins/deficiency
- Plasma Membrane Neurotransmitter Transport Proteins/metabolism
- Rats
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Affiliation(s)
- Elsa Ghirardini
- Department of Developmental Neuroscience, IRCCS Stella Maris Foundation, I-56128 Pisa, Italy; (E.G.); (G.S.); (R.B.); (G.C.)
- Institute of Neuroscience, National Research Council (CNR), I-56124 Pisa, Italy; (F.C.); (F.D.V.); (M.P.); (T.P.)
| | - Francesco Calugi
- Institute of Neuroscience, National Research Council (CNR), I-56124 Pisa, Italy; (F.C.); (F.D.V.); (M.P.); (T.P.)
- Department of Neuroscience, Psychology, Drug Research and Child Health NEUROFARBA, University of Florence, I-50135 Florence, Italy
| | - Giulia Sagona
- Department of Developmental Neuroscience, IRCCS Stella Maris Foundation, I-56128 Pisa, Italy; (E.G.); (G.S.); (R.B.); (G.C.)
- Department of Neuroscience, Psychology, Drug Research and Child Health NEUROFARBA, University of Florence, I-50135 Florence, Italy
| | - Federica Di Vetta
- Institute of Neuroscience, National Research Council (CNR), I-56124 Pisa, Italy; (F.C.); (F.D.V.); (M.P.); (T.P.)
- Department of Biology, University of Pisa, I-56126 Pisa, Italy
| | - Martina Palma
- Institute of Neuroscience, National Research Council (CNR), I-56124 Pisa, Italy; (F.C.); (F.D.V.); (M.P.); (T.P.)
- Department of Neuroscience, Psychology, Drug Research and Child Health NEUROFARBA, University of Florence, I-50135 Florence, Italy
| | - Roberta Battini
- Department of Developmental Neuroscience, IRCCS Stella Maris Foundation, I-56128 Pisa, Italy; (E.G.); (G.S.); (R.B.); (G.C.)
- Department of Clinical and Experimental Medicine, University of Pisa, I-56126 Pisa, Italy
| | - Giovanni Cioni
- Department of Developmental Neuroscience, IRCCS Stella Maris Foundation, I-56128 Pisa, Italy; (E.G.); (G.S.); (R.B.); (G.C.)
- Department of Clinical and Experimental Medicine, University of Pisa, I-56126 Pisa, Italy
| | - Tommaso Pizzorusso
- Institute of Neuroscience, National Research Council (CNR), I-56124 Pisa, Italy; (F.C.); (F.D.V.); (M.P.); (T.P.)
- Department of Neuroscience, Psychology, Drug Research and Child Health NEUROFARBA, University of Florence, I-50135 Florence, Italy
| | - Laura Baroncelli
- Department of Developmental Neuroscience, IRCCS Stella Maris Foundation, I-56128 Pisa, Italy; (E.G.); (G.S.); (R.B.); (G.C.)
- Institute of Neuroscience, National Research Council (CNR), I-56124 Pisa, Italy; (F.C.); (F.D.V.); (M.P.); (T.P.)
- Correspondence:
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8
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Wawro AM, Gajera CR, Baker SA, Nirschl JJ, Vogel H, Montine TJ. Creatine transport and pathological changes in creatine transporter deficient mice. J Inherit Metab Dis 2021; 44:939-948. [PMID: 33389772 DOI: 10.1002/jimd.12358] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 12/29/2020] [Accepted: 12/30/2020] [Indexed: 01/26/2023]
Abstract
The severe impact on brain function and lack of effective therapy for patients with creatine (Cr) transporter deficiency motivated the generation of three ubiquitous Slc6a8 deficient mice (-/y). While each mouse knock-out line has similar behavioral effects at 2 to 3 months of age, other features critical to the efficient use of these mice in drug discovery are unclear or lacking: the concentration of Cr in brain and heart differ widely between mouse lines, there are limited data on histopathologic changes, and no data on Cr uptake. Here, we determined survival, measured endogenous Cr and uptake of its deuterium-labeled analogue Cr-d3 using a liquid chromatography coupled with tandem mass spectrometry assay, and performed comprehensive histopathologic examination on the Slc6a8-/y mouse developed by Skelton et al. Our results show that Slc6a8-/y mice have widely varying organ-specific uptake of Cr-d3, significantly diminished growth with the exception of brain, progressive vacuolar myopathy, and markedly shortened lifespan.
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Affiliation(s)
- Adam M Wawro
- Department of Pathology, Stanford University, Stanford, California, USA
| | | | - Steven A Baker
- Department of Pathology, Stanford University, Stanford, California, USA
| | - Jeffrey J Nirschl
- Department of Pathology, Stanford University, Stanford, California, USA
| | - Hannes Vogel
- Department of Pathology, Stanford University, Stanford, California, USA
| | - Thomas J Montine
- Department of Pathology, Stanford University, Stanford, California, USA
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9
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Farr CV, El-Kasaby A, Freissmuth M, Sucic S. The Creatine Transporter Unfolded: A Knotty Premise in the Cerebral Creatine Deficiency Syndrome. Front Synaptic Neurosci 2020; 12:588954. [PMID: 33192443 PMCID: PMC7644880 DOI: 10.3389/fnsyn.2020.588954] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Accepted: 09/18/2020] [Indexed: 12/16/2022] Open
Abstract
Creatine provides cells with high-energy phosphates for the rapid reconstitution of hydrolyzed adenosine triphosphate. The eponymous creatine transporter (CRT1/SLC6A8) belongs to a family of solute carrier 6 (SLC6) proteins. The key role of CRT1 is to translocate creatine across tissue barriers and into target cells, such as neurons and myocytes. Individuals harboring mutations in the coding sequence of the human CRT1 gene develop creatine transporter deficiency (CTD), one of the pivotal underlying causes of cerebral creatine deficiency syndrome. CTD encompasses an array of clinical manifestations, including severe intellectual disability, epilepsy, autism, development delay, and motor dysfunction. CTD is characterized by the absence of cerebral creatine, which implies an indispensable role for CRT1 in supplying the brain cells with creatine. CTD-associated variants dramatically reduce or abolish creatine transport activity by CRT1. Many of these are point mutations that are known to trigger folding defects, leading to the retention of encoded CRT1 proteins in the endoplasmic reticulum and precluding their delivery to the cell surface. Misfolding of several related SLC6 transporters also gives rise to detrimental pathologic conditions in people; e.g., mutations in the dopamine transporter induce infantile parkinsonism/dystonia, while mutations in the GABA transporter 1 cause treatment-resistant epilepsy. In some cases, folding defects are amenable to rescue by small molecules, known as pharmacological and chemical chaperones, which restore the cell surface expression and transport activity of the previously non-functional proteins. Insights from the recent molecular, animal and human case studies of CTD add toward our understanding of this complex disorder and reveal the wide-ranging effects elicited upon CRT1 dysfunction. This grants novel therapeutic prospects for the treatment of patients afflicted with CTD, e.g., modifying the creatine molecule to facilitate CRT1-independent entry into brain cells, or correcting folding-deficient and loss-of-function CTD variants using pharmacochaperones and/or allosteric modulators. The latter justifies a search for additional compounds with a capacity to correct mutation-specific defects.
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Affiliation(s)
| | | | | | - Sonja Sucic
- Institute of Pharmacology, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
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10
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Arnold GL. Inborn errors of metabolism in the 21 st century: past to present. ANNALS OF TRANSLATIONAL MEDICINE 2018; 6:467. [PMID: 30740398 DOI: 10.21037/atm.2018.11.36] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The 21st century is an exciting time to be in the field of metabolic medicine. As with many fields, one of the keys to anticipating the future is to understand the past. The term "inborn error of metabolism" was first coined in 1908 by Sir Archibald Garrod, in reference to four disorders (alkaptonuria, pentosuria, cystinuria and albinism). The first (and still most definitive) textbook on the subject, "The Metabolic Basis of Inherited Disease" was initially published in 1960 and covered 80 disorders in 1,477 pages. After the eighth edition of this text became unwieldy at 6,338 pages in 4 volumes covering more than 1,000 disorders, the book was changed to an online reference text with 259 chapters and is still growing. Current newborn screening on a few dried blood spots on filter paper identifies more than 1 in 2,000 newborns as having a metabolic disorder. The availability of metabolomic and genomic analyses is resulting in the diagnosis of many new disorders. Enzyme replacement therapy (ERT) has provided treatments for previously untreatable metabolic disorders, and the promise of gene therapy on the near horizon will certainly revolutionize the field.
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Affiliation(s)
- Georgianne L Arnold
- Department of Pediatrics, University of Pittsburgh Medical Center, Pittsburgh, PA, USA
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11
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Wang Q, Yang J, Liu Y, Li X, Luo F, Xie J. A novel SLC6A8 mutation associated with intellectual disabilities in a Chinese family exhibiting creatine transporter deficiency: case report. BMC MEDICAL GENETICS 2018; 19:193. [PMID: 30400883 PMCID: PMC6219255 DOI: 10.1186/s12881-018-0707-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Accepted: 10/22/2018] [Indexed: 12/19/2022]
Abstract
Background X-linked creatine transporter deficiency (OMIM#300036,CRTR-D) is characterized by cerebral creatine deficiency, intellectual disabilities, severe speech impairment, seizures and behavioral problems. Mutations in the creatine transporter gene SLC6A8, a member of the solute-carrier family 6 mapped to Xq28, have been reported to cause the creatine transporter deficiency. Case presentation The proband presented at 5 yrs. 1 month of age with delays in intellectual and development, seizures and behavioral problems. A novel missense mutation, c.1181C > A (p.Thr394Lys), in the SLC6A8 gene (NM_005629.3) was detected via targeted exome sequencing, and then validated by Sanger sequencing. Multiple in silico variant effect analysis methods, including SIFT, PolyPhen2, PROVEAN, and Mutation Taster predicted that this variant was likely damaging or diseasing-causing. This hemizygous variation was also identified in the affected brother with the same clinical condition and inherited from the heterozygous carrier mother. The diagnosis was suggested by increased urinary creatine/creatinine (Cr:Crn) ratio and markedly reduced creatine content peak by brain proton magnetic resonance spectroscopy (MRS). The proband’s mother became pregnant with a 3rd sibling, in whom the Sanger sequencing result of c.1181C > A was negative. Conclusion The novel mutation c.1181C > A in the SLC6A8 gene reported in a Chinese family has expanded the mutation spectrum of CRTR-D. The combination of powerful new technologies such as targeted exome sequencing with thorough systematic clinical evaluation of patients will improve the diagnostic yield, and assist in genetic counselling and prenatal diagnosis for suspected genetic disorders. Electronic supplementary material The online version of this article (10.1186/s12881-018-0707-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Qin Wang
- Shenzhen Maternity and Child Healthcare Hospital, No. 3012, Fuqiang Road, Shenzhen, 518028, Guangdong, China
| | - Jingxin Yang
- Shenzhen Maternity and Child Healthcare Hospital, No. 3012, Fuqiang Road, Shenzhen, 518028, Guangdong, China
| | - Yang Liu
- Shenzhen Maternity and Child Healthcare Hospital, No. 3012, Fuqiang Road, Shenzhen, 518028, Guangdong, China
| | - Xingping Li
- Shenzhen Maternity and Child Healthcare Hospital, No. 3012, Fuqiang Road, Shenzhen, 518028, Guangdong, China
| | - Fuwei Luo
- Shenzhen Maternity and Child Healthcare Hospital, No. 3012, Fuqiang Road, Shenzhen, 518028, Guangdong, China
| | - Jiansheng Xie
- Shenzhen Maternity and Child Healthcare Hospital, No. 3012, Fuqiang Road, Shenzhen, 518028, Guangdong, China.
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Stockebrand M, Sasani A, Das D, Hornig S, Hermans-Borgmeyer I, Lake HA, Isbrandt D, Lygate CA, Heerschap A, Neu A, Choe CU. A Mouse Model of Creatine Transporter Deficiency Reveals Impaired Motor Function and Muscle Energy Metabolism. Front Physiol 2018; 9:773. [PMID: 30013483 PMCID: PMC6036259 DOI: 10.3389/fphys.2018.00773] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Accepted: 06/04/2018] [Indexed: 11/22/2022] Open
Abstract
Creatine serves as fast energy buffer in organs of high-energy demand such as brain and skeletal muscle. L-Arginine:glycine amidinotransferase (AGAT) and guanidinoacetate N-methyltransferase are responsible for endogenous creatine synthesis. Subsequent uptake into target organs like skeletal muscle, heart and brain is mediated by the creatine transporter (CT1, SLC6A8). Creatine deficiency syndromes are caused by defects of endogenous creatine synthesis or transport and are mainly characterized by intellectual disability, behavioral abnormalities, poorly developed muscle mass, and in some cases also muscle weakness. CT1-deficiency is estimated to be among the most common causes of X-linked intellectual disability and therefore the brain phenotype was the main focus of recent research. Unfortunately, very limited data concerning muscle creatine levels and functions are available from patients with CT1 deficiency. Furthermore, different CT1-deficient mouse models yielded conflicting results and detailed analyses of their muscular phenotype are lacking. Here, we report the generation of a novel CT1-deficient mouse model and characterized the effects of creatine depletion in skeletal muscle. HPLC-analysis showed strongly reduced total creatine levels in skeletal muscle and heart. MR-spectroscopy revealed an almost complete absence of phosphocreatine in skeletal muscle. Increased AGAT expression in skeletal muscle was not sufficient to compensate for insufficient creatine transport. CT1-deficient mice displayed profound impairment of skeletal muscle function and morphology (i.e., reduced strength, reduced endurance, and muscle atrophy). Furthermore, severely altered energy homeostasis was evident on magnetic resonance spectroscopy. Strongly reduced phosphocreatine resulted in decreased ATP/Pi levels despite an increased inorganic phosphate to ATP flux. Concerning glucose metabolism, we show increased glucose transporter type 4 expression in muscle and improved glucose clearance in CT1-deficient mice. These metabolic changes were associated with activation of AMP-activated protein kinase – a central regulator of energy homeostasis. In summary, creatine transporter deficiency resulted in a severe muscle weakness and atrophy despite different compensatory mechanisms.
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Affiliation(s)
- Malte Stockebrand
- German Center for Neurodegenerative Diseases, Bonn, Germany.,Institute for Molecular and Behavioral Neuroscience, University of Cologne, Cologne, Germany
| | - Ali Sasani
- Department of Neurology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.,Experimental Neuropediatrics, Department of Pediatrics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Devashish Das
- Department of Radiology, Radboud University Nijmegen Medical Center, Nijmegen, Netherlands
| | - Sönke Hornig
- Experimental Neuropediatrics, Department of Pediatrics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Irm Hermans-Borgmeyer
- Transgenic Mouse Unit, Center for Molecular Neurobiology Hamburg, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Hannah A Lake
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine, BHF Centre of Research Excellence, University of Oxford, Oxford, United Kingdom.,Wellcome Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
| | - Dirk Isbrandt
- German Center for Neurodegenerative Diseases, Bonn, Germany
| | - Craig A Lygate
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine, BHF Centre of Research Excellence, University of Oxford, Oxford, United Kingdom.,Wellcome Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
| | - Arend Heerschap
- Department of Radiology, Radboud University Nijmegen Medical Center, Nijmegen, Netherlands
| | - Axel Neu
- Experimental Neuropediatrics, Department of Pediatrics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Chi-Un Choe
- Department of Neurology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
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13
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Uemura T, Ito S, Ohta Y, Tachikawa M, Wada T, Terasaki T, Ohtsuki S. Abnormal N-Glycosylation of a Novel Missense Creatine Transporter Mutant, G561R, Associated with Cerebral Creatine Deficiency Syndromes Alters Transporter Activity and Localization. Biol Pharm Bull 2017; 40:49-55. [PMID: 28049948 DOI: 10.1248/bpb.b16-00582] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cerebral creatine deficiency syndromes (CCDSs) are caused by loss-of-function mutations in creatine transporter (CRT, SLC6A8), which transports creatine at the blood-brain barrier and into neurons of the central nervous system (CNS). This results in low cerebral creatine levels, and patients exhibit mental retardation, poor language skills and epilepsy. We identified a novel human CRT gene missense mutation (c.1681 G>C, G561R) in Japanese CCDSs patients. The purpose of the present study was to evaluate the reduction of creatine transport in G561R-mutant CRT-expressing 293 cells, and to clarify the mechanism of its functional attenuation. G561R-mutant CRT exhibited greatly reduced creatine transport activity compared to wild-type CRT (WT-CRT) when expressed in 293 cells. Also, the mutant protein is localized mainly in intracellular membrane fraction, while WT-CRT is localized in plasma membrane. Western blot analysis revealed a 68 kDa band of WT-CRT protein in plasma membrane fraction, while G561R-mutant CRT protein predominantly showed bands at 55, 110 and 165 kDa in crude membrane fraction. The bands of both WT-CRT and G561R-mutant CRT were shifted to 50 kDa by N-glycosidase treatment. Our results suggest that the functional impairment of G561R-mutant CRT was probably caused by incomplete N-linked glycosylation due to misfolding during protein maturation, leading to oligomer formation and changes of cellular localization.
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Affiliation(s)
- Tatsuki Uemura
- Department of Pharmaceutical Microbiology, Graduate School of Pharmaceutical Sciences, Kumamoto University
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14
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Laboratory diagnosis of creatine deficiency syndromes: a technical standard and guideline of the American College of Medical Genetics and Genomics. Genet Med 2017; 19:256-263. [PMID: 28055022 DOI: 10.1038/gim.2016.203] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Accepted: 11/11/2016] [Indexed: 01/29/2023] Open
Abstract
Disclaimer: These ACMG Standards and Guidelines are intended as an educational resource for clinical laboratory geneticists to help them provide quality clinical laboratory genetic services. Adherence to these standards and guidelines is voluntary and does not necessarily assure a successful medical outcome. These Standards and Guidelines should not be considered inclusive of all proper procedures and tests or exclusive of others that are reasonably directed to obtaining the same results. In determining the propriety of any specific procedure or test, clinical laboratory geneticists should apply their professional judgment to the specific circumstances presented by the patient or specimen. Clinical laboratory geneticists are encouraged to document in the patient's record the rationale for the use of a particular procedure or test, whether or not it is in conformance with these Standards and Guidelines. They also are advised to take notice of the date any particular guideline was adopted, and to consider other relevant medical and scientific information that becomes available after that date. It also would be prudent to consider whether intellectual property interests may restrict the performance of certain tests and other procedures.Cerebral creatine deficiency syndromes are neurometabolic conditions characterized by intellectual disability, seizures, speech delay, and behavioral abnormalities. Several laboratory methods are available for preliminary and confirmatory diagnosis of these conditions, including measurement of creatine and related metabolites in biofluids using liquid chromatography-tandem mass spectrometry or gas chromatography-mass spectrometry, enzyme activity assays in cultured cells, and DNA sequence analysis. These guidelines are intended to standardize these procedures to help optimize the diagnosis of creatine deficiency syndromes. While biochemical methods are emphasized, considerations for confirmatory molecular testing are also discussed, along with variables that influence test results and interpretation.Genet Med 19 2, 256-263.
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15
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Abstract
Creatine deficiency syndromes are a group of disorders of creatine (Cr) synthesis and transport characterized by intellectual disability, language delay, epilepsy, autism spectrum disorder, and movement disorders secondary to decrease of Cr concentration in the brain. Synthesis defects are treatable, therefore an early diagnosis and treatment is essential. The aim of this article is to review the Cr metabolism and function in the central nervous system. We describe the optimal diagnostic protocol in Cr deficiency syndromes based on biochemical methods, neuroradiological (1H-MRS), and molecular analysis. Finally, a treatment approach of the different Cr deficiency syndromes is described.
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Affiliation(s)
- Carmen Fons
- From the Pediatric Neurology Department, Sant Joan de Déu Hospital, Barcelona University, Barcelona, Spain.
| | - Jaume Campistol
- From the Pediatric Neurology Department, Sant Joan de Déu Hospital, Barcelona University, Barcelona, Spain
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16
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Baroncelli L, Molinaro A, Cacciante F, Alessandrì MG, Napoli D, Putignano E, Tola J, Leuzzi V, Cioni G, Pizzorusso T. A mouse model for creatine transporter deficiency reveals early onset cognitive impairment and neuropathology associated with brain aging. Hum Mol Genet 2016; 25:4186-4200. [DOI: 10.1093/hmg/ddw252] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2016] [Revised: 07/17/2016] [Accepted: 07/18/2016] [Indexed: 01/11/2023] Open
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17
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Ardon O, Procter M, Mao R, Longo N, Landau Y, Shilon-Hadass A, Gabis L, Hoffmann C, Tzadok M, Heimer G, Sada S, Ben-Zeev B, Anikster Y. Creatine transporter deficiency: Novel mutations and functional studies. Mol Genet Metab Rep 2016; 8:20-3. [PMID: 27408820 PMCID: PMC4932609 DOI: 10.1016/j.ymgmr.2016.06.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2016] [Revised: 06/24/2016] [Accepted: 06/24/2016] [Indexed: 12/31/2022] Open
Abstract
X-linked cerebral creatine deficiency (MIM 300036) is caused by deficiency of the creatine transporter encoded by the SLC6A8 gene. Here we report three patients with this condition from Israel. These unrelated patients were evaluated for global developmental delays and language apraxia. Borderline microcephaly was noted in one of them. Diagnosis was prompted by brain magnetic resonance imaging and spectroscopy which revealed normal white matter distribution, but absence of the creatine peak in all three patients. Biochemical testing indicated normal plasma levels of creatine and guanidinoacetate, but an increased urine creatine/creatinine ratio. The diagnosis was confirmed by demonstrating absent ([14])C-creatine transport in fibroblasts. Molecular studies indicated that the first patient is hemizygous for a single nucleotide change substituting a single amino acid (c.619 C > T, p.R207W). Expression studies in HeLa cells confirmed the causative role of the R207W substitution. The second patient had a three base pair deletion in the SLC6A8 gene (c.1222_1224delTTC, p.F408del) as well as a single base change (c.1254 + 1G > A) at a splicing site in the intron-exon junction of exon 8, the latter occurring de novo. The third patient, had a three base pair deletion (c.1006_1008delAAC, p.N336del) previously reported in other patients with creatine transporter deficiency. These three patients are the first reported cases of creatine transporter deficiency in Israel.
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Affiliation(s)
- O. Ardon
- Research and Development, ARUP Laboratories, Salt Lake City, UT, USA
- Division of Medical Genetics, Department of Pediatrics, University of Utah, Salt Lake City, UT, USA
- Department of Pathology, University of Utah, Salt Lake City, UT, USA
| | - M. Procter
- Research and Development, ARUP Laboratories, Salt Lake City, UT, USA
| | - R. Mao
- Research and Development, ARUP Laboratories, Salt Lake City, UT, USA
- Division of Medical Genetics, Department of Pediatrics, University of Utah, Salt Lake City, UT, USA
- Department of Pathology, University of Utah, Salt Lake City, UT, USA
| | - N. Longo
- Research and Development, ARUP Laboratories, Salt Lake City, UT, USA
- Division of Medical Genetics, Department of Pediatrics, University of Utah, Salt Lake City, UT, USA
- Department of Pathology, University of Utah, Salt Lake City, UT, USA
- Corresponding author at: Division of Medical Genetics, Department of Pediatrics, University of Utah, 295 Chipeta Way, Salt Lake City, UT 84108, USA.Division of Medical GeneticsDepartment of PediatricsUniversity of Utah295 Chipeta WaySalt Lake CityUT84108USA
| | - Y.E. Landau
- Edmond and Lily Safra Children's hospital and Sackler Faculty of Medicine, TAU, Sheba Medical Center, Israel
| | - A. Shilon-Hadass
- Edmond and Lily Safra Children's hospital and Sackler Faculty of Medicine, TAU, Sheba Medical Center, Israel
| | - L.V. Gabis
- Edmond and Lily Safra Children's hospital and Sackler Faculty of Medicine, TAU, Sheba Medical Center, Israel
| | - C. Hoffmann
- Edmond and Lily Safra Children's hospital and Sackler Faculty of Medicine, TAU, Sheba Medical Center, Israel
| | - M. Tzadok
- Edmond and Lily Safra Children's hospital and Sackler Faculty of Medicine, TAU, Sheba Medical Center, Israel
| | - G. Heimer
- Edmond and Lily Safra Children's hospital and Sackler Faculty of Medicine, TAU, Sheba Medical Center, Israel
- Pediatric Neurology Unit, Edmond and Lily Safra Children's Hospital and The Dr. Pinchas Borenstein Talpiot Medical Leadership Program, Sheba Medical Center, Tel-Hashomer, Israel
| | - S. Sada
- Department of Pathology, University of Utah, Salt Lake City, UT, USA
- Edmond and Lily Safra Children's hospital and Sackler Faculty of Medicine, TAU, Sheba Medical Center, Israel
| | - B. Ben-Zeev
- Edmond and Lily Safra Children's hospital and Sackler Faculty of Medicine, TAU, Sheba Medical Center, Israel
| | - Y. Anikster
- Edmond and Lily Safra Children's hospital and Sackler Faculty of Medicine, TAU, Sheba Medical Center, Israel
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Creatine Transporter Deficiency: Screening of Males with Neurodevelopmental Disorders and Neurocognitive Characterization of a Case. J Dev Behav Pediatr 2016; 37:322-6. [PMID: 27096572 PMCID: PMC4907372 DOI: 10.1097/dbp.0000000000000299] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
OBJECTIVE Creatine transporter deficiency (CTD) is an X-linked, neurometabolic disorder associated with intellectual disability that is characterized by brain creatine (Cr) deficiency and caused by mutations in SLC6A8, the Cr transporter 1 protein gene. CTD is identified by elevated urine creatine/creatinine (Cr/Crn) ratio or reduced Cr peak on brain magnetic resonance spectroscopy; the diagnosis is confirmed by decreased Cr uptake in cultured fibroblasts, and/or identification of a mutation in the SLC6A8 gene. Prevalence studies suggest this disorder may be underdiagnosed. We sought to identify cases from a well-characterized cohort of children diagnosed with neurodevelopmental disorders. METHOD Urine screening for CTD was performed on a cohort of 46 males with autism spectrum disorder (ASD) and 9 males with a history of non-ASD developmental delay (DD) classified with intellectual disability. RESULTS We identified 1 patient with CTD in the cohort based on abnormal urine Cr/Crn, and confirmed the diagnosis by the identification of a novel frameshift mutation in the SLC6A8 gene. This patient presented without ASD but with intellectual disability, and was characterized by a nonspecific phenotype of early language delay and DD that persisted into moderate-to-severe intellectual disability, consistent with previous descriptions of CTD. CONCLUSION Identification of patients with CTD is possible by measuring urine Cr and Crn levels and the current case adds to the growing literature of neurocognitive deficits associated with the disorder that affect cognition, language and behavior in childhood.
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DesRoches CL, Patel J, Wang P, Minassian B, Salomons GS, Marshall CR, Mercimek-Mahmutoglu S. Estimated carrier frequency of creatine transporter deficiency in females in the general population using functional characterization of novel missense variants in the SLC6A8 gene. Gene 2015; 565:187-91. [PMID: 25861866 DOI: 10.1016/j.gene.2015.04.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Revised: 04/02/2015] [Accepted: 04/06/2015] [Indexed: 01/01/2023]
Abstract
Creatine transporter deficiency (CRTR-D) is an X-linked inherited disorder of creatine transport. All males and about 50% of females have intellectual disability or cognitive dysfunction. Creatine deficiency on brain proton magnetic resonance spectroscopy and elevated urinary creatine to creatinine ratio are important biomarkers. Mutations in the SLC6A8 gene occur de novo in 30% of males. Despite reports of high prevalence of CRTR-D in males with intellectual disability, there are no true prevalence studies in the general population. To determine carrier frequency of CRTR-D in the general population we studied the variants in the SLC6A8 gene reported in the Exome Variant Server database and performed functional characterization of missense variants. We also analyzed synonymous and intronic variants for their predicted pathogenicity using in silico analysis tools. Nine missense variants were functionally analyzed using transient transfection by site-directed mutagenesis with In-Fusion HD Cloning in HeLa cells. Creatine uptake was measured by liquid chromatography tandem mass spectrometry for creatine measurement. The c.1654G>T (p.Val552Leu) variant showed low residual creatine uptake activity of 35% of wild type transfected HeLa cells and was classified as pathogenic. Three variants (c.808G>A; p.Val270Met, c.942C>G; p.Phe314Leu and c.952G>A; p.Ala318Thr) were predicted to be pathogenic based on in silico analysis, but proved to be non-pathogenic by our functional analysis. The estimated carrier frequency of CRTR-D was 0.024% in females in the general population. We recommend functional studies for all novel missense variants by transient transfection followed by creatine uptake measurement by liquid chromatography tandem mass spectrometry as fast and cost effective method for the functional analysis of missense variants in the SLC6A8 gene.
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Affiliation(s)
- Caro-Lyne DesRoches
- Genetics and Genome Biology Research Program, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Jaina Patel
- Genetics and Genome Biology Research Program, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Peixiang Wang
- Genetics and Genome Biology Research Program, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Berge Minassian
- Genetics and Genome Biology Research Program, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada; Division of Neurology, Department of Paediatrics, University of Toronto, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Gajja S Salomons
- Metabolic Laboratory, Department of Clinical Chemistry, VU University Medical Center, Neuroscience Campus, Amsterdam, The Netherlands
| | - Christian R Marshall
- Genetics and Genome Biology Research Program, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada; Genome Diagnostics, Department of Paediatric Laboratory Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Saadet Mercimek-Mahmutoglu
- Genetics and Genome Biology Research Program, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada; Division of Clinical and Metabolic Genetics, Department of Pediatrics, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada.
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20
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Clark JF, Cecil KM. Diagnostic methods and recommendations for the cerebral creatine deficiency syndromes. Pediatr Res 2015; 77:398-405. [PMID: 25521922 DOI: 10.1038/pr.2014.203] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Accepted: 09/15/2014] [Indexed: 12/29/2022]
Abstract
Primary care pediatricians and a variety of specialist physicians strive to define an accurate diagnosis for children presenting with impairment of expressive speech and delay in achieving developmental milestones. Within the past two decades, a group of disorders featuring this presentation have been identified as cerebral creatine deficiency syndromes (CCDS). Patients with these disorders were initially discerned using proton magnetic resonance spectroscopy of the brain within a magnetic resonance imaging (MRI) examination. The objective of this review is to provide the clinician with an overview of the current information available on identifying and treating these conditions. We explain the salient features of creatine metabolism, synthesis, and transport required for normal development. We propose diagnostic approaches for confirming a CCDS diagnosis. Finally, we describe treatment approaches for managing patients with these conditions.
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Affiliation(s)
- Joseph F Clark
- Department of Neurology, University of Cincinnati College of Medicine, Cincinnati, Ohio
| | - Kim M Cecil
- 1] Department of Radiology, University of Cincinnati College of Medicine, Cincinnati, Ohio [2] Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio [3] Department of Environmental Health, University of Cincinnati College of Medicine, Cincinnati, Ohio [4] Department of Radiology and Medical Imaging, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
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21
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Fezai M, Elvira B, Borras J, Ben-Attia M, Hoseinzadeh Z, Lang F. Negative regulation of the creatine transporter SLC6A8 by SPAK and OSR1. Kidney Blood Press Res 2014; 39:546-54. [PMID: 25531585 DOI: 10.1159/000368465] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/06/2014] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND/AIMS Transport regulation involves several kinases including SPAK (SPS1-related proline/alanine-rich kinase) and OSR1 (oxidative stress-responsive kinase 1), which are under control of WNK (with-no-K[Lys]) kinases. The present study explored whether SPAK and/or OSR1 participate in the regulation of the creatine transporter CreaT (SLC6A8), which accomplishes Na+ coupled cellular uptake of creatine in several tissues including kidney, intestine, heart, skeletal muscle and brain. METHODS cRNA encoding SLC6A8 was injected into Xenopus laevis oocytes with or without additional injection of cRNA encoding wild-type SPAK, constitutively active (T233E)SPAK, WNK insensitive (T233A)SPAK, catalytically inactive (D212A)SPAK, wild-type OSR1, constitutively active (T185E)OSR1, WNK insensitive (T185A)OSR1 and catalytically inactive (D164A)OSR1. Transporter activity was determined from creatine (1 mM) induced current utilizing dual electrode voltage clamp. RESULTS Coexpression of wild-type SPAK and of (T233E)SPAK, but not of (T233A)SPAK or of (D212A)SPAK was followed by a significant decrease of creatine induced current in SLC6A8 expressing oocytes. Coexpression of SPAK significantly decreased maximal transport rate. Coexpression of wild-type OSR1, (T185E)OSR1 and (T185A)OSR1 but not of (D164A)OSR1 significantly negatively regulated SLC6A8 activity. OSR1 again decreased significantly maximal transport rate. CONCLUSIONS Both, SPAK and OSR1, are negative regulators of the creatine transporter SLC6A8.
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Affiliation(s)
- Myriam Fezai
- Department of Physiology I, University of Tübingen, Tübingen, Germany
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Almilaji A, Sopjani M, Elvira B, Borras J, Dërmaku-Sopjani M, Munoz C, Warsi J, Lang UE, Lang F. Upregulation of the creatine transporter Slc6A8 by Klotho. Kidney Blood Press Res 2014; 39:516-25. [PMID: 25531216 DOI: 10.1159/000368462] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/08/2014] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND/AIMS The transmembrane Klotho protein contributes to inhibition of 1,25(OH)2D3 formation. The extracellular domain of Klotho protein could function as an enzyme with e.g. β-glucuronidase activity, be cleaved off and be released into blood and cerebrospinal fluid. Klotho regulates several cellular transporters. Klotho protein deficiency accelerates the appearance of age related disorders including neurodegeneration and muscle wasting and eventually leads to premature death. The main site of Klotho protein expression is the kidney. Klotho protein is also appreciably expressed in other tissues including chorioid plexus. The present study explored the effect of Klotho protein on the creatine transporter CreaT (Slc6A8), which participates in the maintenance of neuronal function and survival. METHODS To this end cRNA encoding Slc6A8 was injected into Xenopus oocytes with and without additional injection of cRNA encoding Klotho protein. Creatine transporter CreaT (Slc6A8) activity was estimated from creatine induced current determined by two-electrode voltage-clamp. RESULTS Coexpression of Klotho protein significantly increased creatine-induced current in Slc6A8 expressing Xenopus oocytes. Coexpression of Klotho protein delayed the decline of creatine induced current following inhibition of carrier insertion into the cell membrane by brefeldin A (5 µM). The increase of creatine induced current by coexpression of Klotho protein in Slc6A8 expressing Xenopus oocytes was reversed by β-glucuronidase inhibitor (DSAL). Similarly, treatment of Slc6A8 expressing Xenopus oocytes with recombinant human alpha Klotho protein significantly increased creatine induced current. CONCLUSION Klotho protein up-regulates the activity of creatine transporter CreaT (Slc6A8) by stabilizing the carrier protein in the cell membrane, an effect requiring β-glucuronidase activity of Klotho protein.
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Affiliation(s)
- Ahmad Almilaji
- Department of Physiology, Gmelinstr. 5, University of Tübingen, D-72076 Tübingen, Germany
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23
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van de Kamp JM, Mancini GM, Salomons GS. X-linked creatine transporter deficiency: clinical aspects and pathophysiology. J Inherit Metab Dis 2014; 37:715-33. [PMID: 24789340 DOI: 10.1007/s10545-014-9713-8] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Revised: 03/27/2014] [Accepted: 04/01/2014] [Indexed: 12/22/2022]
Abstract
Creatine transporter deficiency was discovered in 2001 as an X-linked cause of intellectual disability characterized by cerebral creatine deficiency. This review describes the current knowledge regarding creatine metabolism, the creatine transporter and the clinical aspects of creatine transporter deficiency. The condition mainly affects the brain while other creatine requiring organs, such as the muscles, are relatively spared. Recent studies have provided strong evidence that creatine synthesis also occurs in the brain, leading to the intriguing question of why cerebral creatine is deficient in creatine transporter deficiency. The possible mechanisms explaining the cerebral creatine deficiency are discussed. The creatine transporter knockout mouse provides a good model to study the disease. Over the past years several treatment options have been explored but no treatment has been proven effective. Understanding the pathogenesis of creatine transporter deficiency is of paramount importance in the development of an effective treatment.
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MESH Headings
- Amino Acid Metabolism, Inborn Errors/diagnosis
- Amino Acid Metabolism, Inborn Errors/drug therapy
- Amino Acid Metabolism, Inborn Errors/genetics
- Amino Acid Metabolism, Inborn Errors/pathology
- Animals
- Brain Diseases, Metabolic, Inborn/complications
- Brain Diseases, Metabolic, Inborn/genetics
- Brain Diseases, Metabolic, Inborn/physiopathology
- Creatine/deficiency
- Creatine/genetics
- Genetic Diseases, X-Linked/genetics
- Humans
- Intellectual Disability/etiology
- Intellectual Disability/genetics
- Membrane Transport Proteins/deficiency
- Membrane Transport Proteins/genetics
- Mental Retardation, X-Linked/complications
- Mental Retardation, X-Linked/genetics
- Mental Retardation, X-Linked/physiopathology
- Mice
- Plasma Membrane Neurotransmitter Transport Proteins/deficiency
- Plasma Membrane Neurotransmitter Transport Proteins/genetics
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Affiliation(s)
- Jiddeke M van de Kamp
- Department of Clinical Genetics, VU University Medical Center, P.O. Box 7057, 1007 MB, Amsterdam, The Netherlands,
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24
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van de Kamp JM, Betsalel OT, Mercimek-Mahmutoglu S, Abulhoul L, Grünewald S, Anselm I, Azzouz H, Bratkovic D, de Brouwer A, Hamel B, Kleefstra T, Yntema H, Campistol J, Vilaseca MA, Cheillan D, D’Hooghe M, Diogo L, Garcia P, Valongo C, Fonseca M, Frints S, Wilcken B, von der Haar S, Meijers-Heijboer HE, Hofstede F, Johnson D, Kant SG, Lion-Francois L, Pitelet G, Longo N, Maat-Kievit JA, Monteiro JP, Munnich A, Muntau AC, Nassogne MC, Osaka H, Ounap K, Pinard JM, Quijano-Roy S, Poggenburg I, Poplawski N, Abdul-Rahman O, Ribes A, Arias A, Yaplito-Lee J, Schulze A, Schwartz CE, Schwenger S, Soares G, Sznajer Y, Valayannopoulos V, Van Esch H, Waltz S, Wamelink MMC, Pouwels PJW, Errami A, van der Knaap MS, Jakobs C, Mancini GM, Salomons GS. Phenotype and genotype in 101 males with X-linked creatine transporter deficiency. J Med Genet 2013; 50:463-72. [DOI: 10.1136/jmedgenet-2013-101658] [Citation(s) in RCA: 101] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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25
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Valayannopoulos V, Bakouh N, Mazzuca M, Nonnenmacher L, Hubert L, Makaci FL, Chabli A, Salomons GS, Mellot-Draznieks C, Brulé E, de Lonlay P, Toulhoat H, Munnich A, Planelles G, de Keyzer Y. Functional and electrophysiological characterization of four non-truncating mutations responsible for creatine transporter (SLC6A8) deficiency syndrome. J Inherit Metab Dis 2013; 36:103-12. [PMID: 22644605 DOI: 10.1007/s10545-012-9495-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/11/2012] [Revised: 04/24/2012] [Accepted: 05/03/2012] [Indexed: 12/27/2022]
Abstract
Intellectual disability coupled with epilepsy are clinical hallmarks of the creatine (Cr) transporter deficiency syndrome resulting from mutations in the SLC6A8 gene. So far characterization of pathogenic mutations of SLC6A8 has been limited to Cr uptake. The aim of our study was to characterize the electrogenic and pharmacological properties of non truncating SLC6A8 mutations identified in patients presenting variable clinical severity. Electrophysiological and pharmacological properties of four mutants (including two novel ones) were studied in X. laevis oocyte expression system. Creatine uptake was assessed with [(14)C]-Cr in X. laevis and patients' fibroblasts. Subcellular localization was determined by immunofluorescence and western blot. All mutants were properly targeted to the plasma membrane in both systems. Mutations led to the complete loss of both electrogenic and transport activities in X. laevis and Cr uptake in patients' fibroblasts. Among the Cr analogs tested, guanidinopropionate induced an electrogenic activity with the normal SLC6A8 transporter similar to creatine whereas a phosphocreatine derivative, PCr-Mg-CPLX, resulted in partial activity. SLC6A8 mutants displayed no electrogenic activity with all Cr analogs tested in X. laevis oocytes. Although the mutations altered various domains of SLC6A8 Cr uptake and electrogenic properties were completely inhibited and could not be dissociated. Besides the metabolic functions of Cr, the loss of SLC6A8 electrogenic activity, demonstrated here for the first time, may also play a role in the altered brain functions of the patients.
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Affiliation(s)
- Vassili Valayannopoulos
- INSERM U781 and Paris-Descartes University, Necker-Enfants Malades Hospital, 149 rue de Sèvres, 75743 Paris cedex 15, France
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26
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Kurosawa Y, DeGrauw TJ, Lindquist DM, Blanco VM, Pyne-Geithman GJ, Daikoku T, Chambers JB, Benoit SC, Clark JF. Cyclocreatine treatment improves cognition in mice with creatine transporter deficiency. J Clin Invest 2012; 122:2837-46. [PMID: 22751104 PMCID: PMC3408730 DOI: 10.1172/jci59373] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Accepted: 05/23/2012] [Indexed: 01/06/2023] Open
Abstract
The second-largest cause of X-linked mental retardation is a deficiency in creatine transporter (CRT; encoded by SLC6A8), which leads to speech and language disorders with severe cognitive impairment. This syndrome, caused by the absence of creatine in the brain, is currently untreatable because CRT is required for creatine entry into brain cells. Here, we developed a brain-specific Slc6a8 knockout mouse (Slc6a8-/y) as an animal model of human CRT deficiency in order to explore potential therapies for this syndrome. The phenotype of the Slc6a8-/y mouse was comparable to that of human patients. We successfully treated the Slc6a8-/y mice with the creatine analog cyclocreatine. Brain cyclocreatine and cyclocreatine phosphate were detected after 9 weeks of cyclocreatine treatment in Slc6a8-/y mice, in contrast to the same mice treated with creatine or placebo. Cyclocreatine-treated Slc6a8-/y mice also exhibited a profound improvement in cognitive abilities, as seen with novel object recognition as well as spatial learning and memory tests. Thus, cyclocreatine appears promising as a potential therapy for CRT deficiency.
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Affiliation(s)
- Yuko Kurosawa
- Department of Neurology, University of Cincinnati, Cincinnati, Ohio, USA.
Division of Neurology and
Department of Radiology and Imaging Research Center, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, USA.
Department of Emergency Medicine and
Department of Neurosurgery, University of Cincinnati, Cincinnati, Ohio, USA.
Division of Reproductive Science, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, USA.
Department of Psychiatry and Behavior Neuroscience, University of Cincinnati, Cincinnati, Ohio, USA
| | - Ton J. DeGrauw
- Department of Neurology, University of Cincinnati, Cincinnati, Ohio, USA.
Division of Neurology and
Department of Radiology and Imaging Research Center, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, USA.
Department of Emergency Medicine and
Department of Neurosurgery, University of Cincinnati, Cincinnati, Ohio, USA.
Division of Reproductive Science, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, USA.
Department of Psychiatry and Behavior Neuroscience, University of Cincinnati, Cincinnati, Ohio, USA
| | - Diana M. Lindquist
- Department of Neurology, University of Cincinnati, Cincinnati, Ohio, USA.
Division of Neurology and
Department of Radiology and Imaging Research Center, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, USA.
Department of Emergency Medicine and
Department of Neurosurgery, University of Cincinnati, Cincinnati, Ohio, USA.
Division of Reproductive Science, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, USA.
Department of Psychiatry and Behavior Neuroscience, University of Cincinnati, Cincinnati, Ohio, USA
| | - Victor M. Blanco
- Department of Neurology, University of Cincinnati, Cincinnati, Ohio, USA.
Division of Neurology and
Department of Radiology and Imaging Research Center, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, USA.
Department of Emergency Medicine and
Department of Neurosurgery, University of Cincinnati, Cincinnati, Ohio, USA.
Division of Reproductive Science, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, USA.
Department of Psychiatry and Behavior Neuroscience, University of Cincinnati, Cincinnati, Ohio, USA
| | - Gail J. Pyne-Geithman
- Department of Neurology, University of Cincinnati, Cincinnati, Ohio, USA.
Division of Neurology and
Department of Radiology and Imaging Research Center, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, USA.
Department of Emergency Medicine and
Department of Neurosurgery, University of Cincinnati, Cincinnati, Ohio, USA.
Division of Reproductive Science, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, USA.
Department of Psychiatry and Behavior Neuroscience, University of Cincinnati, Cincinnati, Ohio, USA
| | - Takiko Daikoku
- Department of Neurology, University of Cincinnati, Cincinnati, Ohio, USA.
Division of Neurology and
Department of Radiology and Imaging Research Center, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, USA.
Department of Emergency Medicine and
Department of Neurosurgery, University of Cincinnati, Cincinnati, Ohio, USA.
Division of Reproductive Science, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, USA.
Department of Psychiatry and Behavior Neuroscience, University of Cincinnati, Cincinnati, Ohio, USA
| | - James B. Chambers
- Department of Neurology, University of Cincinnati, Cincinnati, Ohio, USA.
Division of Neurology and
Department of Radiology and Imaging Research Center, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, USA.
Department of Emergency Medicine and
Department of Neurosurgery, University of Cincinnati, Cincinnati, Ohio, USA.
Division of Reproductive Science, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, USA.
Department of Psychiatry and Behavior Neuroscience, University of Cincinnati, Cincinnati, Ohio, USA
| | - Stephen C. Benoit
- Department of Neurology, University of Cincinnati, Cincinnati, Ohio, USA.
Division of Neurology and
Department of Radiology and Imaging Research Center, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, USA.
Department of Emergency Medicine and
Department of Neurosurgery, University of Cincinnati, Cincinnati, Ohio, USA.
Division of Reproductive Science, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, USA.
Department of Psychiatry and Behavior Neuroscience, University of Cincinnati, Cincinnati, Ohio, USA
| | - Joseph F. Clark
- Department of Neurology, University of Cincinnati, Cincinnati, Ohio, USA.
Division of Neurology and
Department of Radiology and Imaging Research Center, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, USA.
Department of Emergency Medicine and
Department of Neurosurgery, University of Cincinnati, Cincinnati, Ohio, USA.
Division of Reproductive Science, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, USA.
Department of Psychiatry and Behavior Neuroscience, University of Cincinnati, Cincinnati, Ohio, USA
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27
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Osaka H, Takagi A, Tsuyusaki Y, Wada T, Iai M, Yamashita S, Shimbo H, Saitsu H, Salomons GS, Jakobs C, Aida N, Toshihiro S, Kuhara T, Matsumoto N. Contiguous deletion of SLC6A8 and BAP31 in a patient with severe dystonia and sensorineural deafness. Mol Genet Metab 2012; 106:43-7. [PMID: 22472424 DOI: 10.1016/j.ymgme.2012.02.018] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Revised: 02/25/2012] [Accepted: 02/25/2012] [Indexed: 12/28/2022]
Abstract
We report here a 6-year-old boy exhibiting severe dystonia, profound intellectual and developmental disability with liver disease, and sensorineural deafness. A deficient creatine peak in brain (1)H-MR spectroscopy and high ratio of creatine/creatinine concentration in his urine lead us to suspect a creatine transporter (solute carrier family 6, member 8; SLC6A8) deficiency, which was confirmed by the inability to take up creatine into fibroblasts. We found a large ~19 kb deletion encompassing exons 5-13 of SLC6A8 and exons 5-8 of the B-cell receptor-associated protein (BAP31) gene. This case is the first report in which the SLC6A8 and BAP31 genes are both deleted. The phenotype of BAP31 mutations has been reported only as a part of Xq28 deletion syndrome or contiguous ATP-binding cassette, sub-family D, member 1 (ABCD1)/DXS1375E (BAP31) deletion syndrome [MIM ID #300475], where liver dysfunction and sensorineural deafness have been suggested to be attributed to the loss of function of BAP31. Our case supports the idea that the loss of BAP31 is related to liver dysfunction and hearing loss.
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Affiliation(s)
- Hitoshi Osaka
- Division of Neurology, Kanagawa Children's Medical Center, Yokohama, Japan.
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28
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Downregulation of the Creatine Transporter SLC6A8 by JAK2. J Membr Biol 2012; 245:157-63. [DOI: 10.1007/s00232-012-9424-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2011] [Accepted: 02/16/2012] [Indexed: 12/20/2022]
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29
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Wong ACY, Velamoor S, Skelton MR, Thorne PR, Vlajkovic SM. Expression and distribution of creatine transporter and creatine kinase (brain isoform) in developing and mature rat cochlear tissues. Histochem Cell Biol 2012; 137:599-613. [PMID: 22307408 DOI: 10.1007/s00418-012-0922-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/13/2012] [Indexed: 02/07/2023]
Abstract
Physiological processes in the cochlea associated with sound transduction and maintenance of the unique electrochemical environment are metabolically demanding. Creatine maintains ATP homeostasis by providing high-energy phosphates for ATP regeneration which is catalyzed by creatine kinase (CK). Cellular uptake of creatine requires a specific high affinity sodium- and chloride-dependent creatine transporter (CRT). This study postulates that this CRT is developmentally regulated in the rat cochlea. CRT expression was measured by quantitative real-time RT-PCR and immunohistochemistry in the postnatal (P0-P14) and adult (P22-P56) rat cochlea. The maximum CRT expression was reached at the onset of hearing (P12), and this level was maintained through to adulthood. CRT immunoreactivity was strongest in the sensory inner hair cells, supporting cells and the spiral ganglion neurons. Cochlear distribution of the CK brain isoform (CKB) was also assessed by immunohistochemistry and compared with the distribution of CRT in the developing and adult cochlea. CKB was immunolocalized in the organ of Corti supporting cells, and the lateral wall tissues involved in K(+) cycling, including stria vascularis and spiral ligament fibrocytes. Similar to CRT, CKB reached peak expression after the onset of hearing. Differential spatial and temporal expression of CRT and CK in cochlear tissues during development may reflect differential requirements for creatine-phosphocreatine buffering to replenish ATP consumed during energy-dependent metabolic processes, especially around the period when the cochlea becomes responsive to airborne sound.
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Affiliation(s)
- Ann Chi Yan Wong
- Translational Neuroscience Facility, School of Medical Sciences, University of New South Wales, Sydney, Australia.
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30
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Wada T, Shimbo H, Osaka H. A simple screening method using ion chromatography for the diagnosis of cerebral creatine deficiency syndromes. Amino Acids 2011; 43:993-7. [PMID: 22080216 DOI: 10.1007/s00726-011-1146-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2011] [Accepted: 11/01/2011] [Indexed: 11/24/2022]
Abstract
Cerebral creatine deficiency syndromes (CCDS) are caused by genetic defects in L-arginine:glycine amidinotransferase, guanidinoacetate methyltransferase or creatine transporter 1. CCDS are characterized by abnormal concentrations of urinary creatine (CR), guanidinoacetic acid (GA), or creatinine (CN). In this study, we describe a simple HPLC method to determine the concentrations of CR, GA, and CN using a weak-acid ion chromatography column with a UV detector without any derivatization. CR, GA, and CN were separated clearly with the retention times (mean ± SD, n = 3) of 5.54 ± 0.0035 min for CR, 6.41 ± 0.0079 min for GA, and 13.53 ± 0.046 min for CN. This new method should provide a simple screening test for the diagnosis of CCDS.
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Affiliation(s)
- Takahito Wada
- Division of Neurology, Kanagawa Children's Medical Center, 2-138-4 Mutsukawa, Minami-ku, Yokohama, Kanagawa 232-8555, Japan
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31
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Mencarelli MA, Tassini M, Pollazzon M, Vivi A, Calderisi M, Falco M, Fichera M, Monti L, Buoni S, Mari F, Engelke U, Wevers RA, Hayek J, Renieri A. Creatine transporter defect diagnosed by proton NMR spectroscopy in males with intellectual disability. Am J Med Genet A 2011; 155A:2446-52. [PMID: 21910234 PMCID: PMC3306553 DOI: 10.1002/ajmg.a.34208] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2011] [Accepted: 06/23/2011] [Indexed: 11/09/2022]
Abstract
Creatine deficiency syndrome due to mutations in X-linked SLC6A8 gene results in nonspecific intellectual disability (ID). Diagnosis cannot be established on clinical grounds and is often based on the assessment of brain creatine levels by magnetic resonance spectroscopy (MRS). Considering high costs of MRS and necessity of sedation, this technique cannot be used as a first level-screening test. Likewise, gene test analysis is time consuming and not easily accessible to all laboratories. In this article feasibility of urine analysis (creatine/creatinine (Cr/Crn) ratio) performed by nuclear magnetic resonance (NMR) as a first level-screening test is explored. Before running a systematic selection of cases a preliminary study for further molecular analysis is shown. NMR urine spectra (n = 1,347) of male patients with an ID without a clinically recognizable syndrome were measured. On the basis of abnormal Cr/Crn ratio, three patients with the highest values were selected for molecular analysis. A confirmatory second urine test was positive in two patients and diagnosis was further confirmed by a decreased brain creatine level and by SLC6A8 gene analysis. A de novo mutation was identified in one. Another patient inherited a novel mutation from the mother who also has a mild ID. A repeat urine test was negative in the third patient and accordingly creatine level in the brain and SLC6A8 gene analysis both gave a normal result. We conclude that Cr/Crn ratio measured by NMR for male patients represents a rapid and useful first level screening test preceding molecular analysis.
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Skelton MR, Schaefer TL, Graham DL, Degrauw TJ, Clark JF, Williams MT, Vorhees CV. Creatine transporter (CrT; Slc6a8) knockout mice as a model of human CrT deficiency. PLoS One 2011; 6:e16187. [PMID: 21249153 PMCID: PMC3020968 DOI: 10.1371/journal.pone.0016187] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2010] [Accepted: 12/09/2010] [Indexed: 11/18/2022] Open
Abstract
Mutations in the creatine (Cr) transporter (CrT; Slc6a8) gene lead to absence of brain Cr and intellectual disabilities, loss of speech, and behavioral abnormalities. To date, no mouse model of CrT deficiency exists in which to understand and develop treatments for this condition. The purpose of this study was to generate a mouse model of human CrT deficiency. We created mice with exons 2–4 of Slc6a8 flanked by loxP sites and crossed these to Cre:CMV mice to create a line of ubiquitous CrT knockout expressing mice. Mice were tested for learning and memory deficits and assayed for Cr and neurotransmitter levels. Male CrT−/y (affected) mice lack Cr in the brain and muscle with significant reductions of Cr in other tissues including heart and testes. CrT−/y mice showed increased path length during acquisition and reversal learning in the Morris water maze. During probe trials, CrT−/y mice showed increased average distance from the platform site. CrT−/y mice showed reduced novel object recognition and conditioned fear memory compared to CrT+/y. CrT−/y mice had increased serotonin and 5-hydroxyindole acetic acid in the hippocampus and prefrontal cortex. Ubiquitous CrT knockout mice have learning and memory deficits resembling human CrT deficiency and this model should be useful in understanding this disorder.
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Affiliation(s)
- Matthew R Skelton
- Division of Neurology, Cincinnati Children's Research Foundation, and Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America.
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