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Pérez-Sala D, Pajares MA. Appraising the Role of Astrocytes as Suppliers of Neuronal Glutathione Precursors. Int J Mol Sci 2023; 24:ijms24098059. [PMID: 37175763 PMCID: PMC10179008 DOI: 10.3390/ijms24098059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Revised: 04/25/2023] [Accepted: 04/25/2023] [Indexed: 05/15/2023] Open
Abstract
The metabolism and intercellular transfer of glutathione or its precursors may play an important role in cellular defense against oxidative stress, a common hallmark of neurodegeneration. In the 1990s, several studies in the Neurobiology field led to the widely accepted notion that astrocytes produce large amounts of glutathione that serve to feed neurons with precursors for glutathione synthesis. This assumption has important implications for health and disease since a reduction in this supply from astrocytes could compromise the capacity of neurons to cope with oxidative stress. However, at first glance, this shuttling would imply a large energy expenditure to get to the same point in a nearby cell. Thus, are there additional underlying reasons for this expensive mechanism? Are neurons unable to import and/or synthesize the three non-essential amino acids that are the glutathione building blocks? The rather oxidizing extracellular environment favors the presence of cysteine (Cys) as cystine (Cis), less favorable for neuronal import. Therefore, it has also been proposed that astrocytic GSH efflux could induce a change in the redox status of the extracellular space nearby the neurons, locally lowering the Cis/Cys ratio. This astrocytic glutathione release would also increase their demand for precursors, stimulating Cis uptake, which these cells can import, further impacting the local decline of the Cis/Cys ratio, in turn, contributing to a more reduced extracellular environment and subsequently favoring neuronal Cys import. Here, we revisit the experimental evidence that led to the accepted hypothesis of astrocytes acting as suppliers of neuronal glutathione precursors, considering recent data from the Human Protein Atlas. In addition, we highlight some potential drawbacks of this hypothesis, mainly supported by heterogeneous cellular models. Finally, we outline additional and more cost-efficient possibilities by which astrocytes could support neuronal glutathione levels, including its shuttling in extracellular vesicles.
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Affiliation(s)
- Dolores Pérez-Sala
- Department of Structural and Chemical Biology, Centro de Investigaciones Biológicas Margarita Salas (CSIC), Ramiro de Maeztu 9, 28040 Madrid, Spain
| | - María A Pajares
- Department of Structural and Chemical Biology, Centro de Investigaciones Biológicas Margarita Salas (CSIC), Ramiro de Maeztu 9, 28040 Madrid, Spain
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2
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Huynh MT, Landais E, Agathe JMDS, Panchout A, Caroline DVDBL, Bruel H. Novel homozygous GLDC variant causing late-onset glycine encephalopathy: A case report and updated review of the literature. Mol Genet Metab Rep 2023; 34:100959. [PMID: 36817643 PMCID: PMC9932748 DOI: 10.1016/j.ymgmr.2023.100959] [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: 12/30/2022] [Revised: 01/31/2023] [Accepted: 01/31/2023] [Indexed: 02/08/2023] Open
Abstract
Glycine encephalopathy (MIM #605899) is an autosomal recessive inborn error of metabolism caused by pathogenic variants in three genes GLDC, AMT, GCSH encoding glycine cleavage enzyme system. We report an 8-year-old boy with late-onset glycine encephalopathy who harbors a novel homozygous GLDC likely pathogenic variant c.707G > A p.(Arg236Gln). Polyhydramnios was noted at fetal ultrasound. He displayed global developmental delay, craniofacial dysmorphism, convulsions. Our report expands the phenotypic and genetic spectrum of late-onset nonketotic hyperglycinemia.
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Affiliation(s)
- Minh-Tuan Huynh
- Medical Genetics Department, Vinmec Times City International Hospital-Times City, HaNoi, Viet Nam
- Centre Hospitalier du Havre, Unité de Génétique Clinique, 29 Avenue Pierre Mendès-France, 76290 Montivilliers, France
- Corresponding author at: Medical Genetics Department, Vinmec Times City International Hospital-Times City, 458 Minh Khai, Hai Ba Trung District, VietNam.
| | - Emilie Landais
- Laboratoire de Génétique, CHRU de Reims, 45 rue Cognacq-Jay, 51092 Reims, France
| | | | - Anne Panchout
- Centre Hospitalier du Havre, Service de Gynécologie, 29 Avenue Pierre Mendès-France, 76290 Montivilliers, France
| | | | - Henri Bruel
- Centre Hospitalier du Havre, Service de Néonatologie, 29 Avenue Pierre Mendès-France, 76290 Montivilliers, France
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3
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MYCN and Metabolic Reprogramming in Neuroblastoma. Cancers (Basel) 2022; 14:cancers14174113. [PMID: 36077650 PMCID: PMC9455056 DOI: 10.3390/cancers14174113] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 08/15/2022] [Accepted: 08/22/2022] [Indexed: 11/17/2022] Open
Abstract
Neuroblastoma is a pediatric cancer responsible for approximately 15% of all childhood cancer deaths. Aberrant MYCN activation, as a result of genomic MYCN amplification, is a major driver of high-risk neuroblastoma, which has an overall survival rate of less than 50%, despite the best treatments currently available. Metabolic reprogramming is an integral part of the growth-promoting program driven by MYCN, which fuels cell growth and proliferation by increasing the uptake and catabolism of nutrients, biosynthesis of macromolecules, and production of energy. This reprogramming process also generates metabolic vulnerabilities that can be exploited for therapy. In this review, we present our current understanding of metabolic reprogramming in neuroblastoma, focusing on transcriptional regulation as a key mechanism in driving the reprogramming process. We also highlight some important areas that need to be explored for the successful development of metabolism-based therapy against high-risk neuroblastoma.
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4
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Kuseyri Hübschmann O, Palacios NAJ, Olivella M, Guder P, Zafeiriou DI, Horvath G, Kulhánek J, Pearson TS, Kuster A, Cortès-Saladelafont E, Ibáñez S, García-Jiménez MC, Honzík T, Santer R, Jeltsch K, Garbade SF, Hoffmann GF, Opladen T, García-Cazorla Á. An integrative approach to predict severity in nonketotic hyperglycinemia. Ann Neurol 2022; 92:292-303. [PMID: 35616651 DOI: 10.1002/ana.26423] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Revised: 05/19/2022] [Accepted: 05/23/2022] [Indexed: 11/11/2022]
Abstract
OBJECTIVE Glycine encephalopathy, also known as nonketotic hyperglycinemia (NKH), is an inherited neurometabolic disorder with variable clinical course and severity, ranging from infantile epileptic encephalopathy to psychiatric disorders. A precise phenotypic characterization and an evaluation of predictive approaches are needed. METHODS Longitudinal clinical and biochemical data of 25 individuals with NKH from the patient registry of International Working Group on Neurotransmitter related Disorders were studied with in silico analyses, pathogenicity scores and molecular modeling of GLDC and AMT variants. RESULTS Symptom onset (p<0· 01) and diagnosis occur earlier in life in severe NKH (p<0· 01). Presenting symptoms affect the age at diagnosis. Psychiatric problems occur predominantly in attenuated NKH. Onset-age ≥3 months (66% specificity, 100% sensitivity, AUC = 0·87) and cerebrospinal fluid (CSF)/plasma glycine ratio ≤0· 09 (57% specificity, 100% sensitivity, AUC = 0·88) are sensitive indicators for attenuated NKH while CSF glycine concentration ≥116· 5 μmol/L (100% specificity, 93% sensitivity, AUC = 0·97) and CSF/plasma glycine ratio ≥0· 15 (100% specificity, 64% sensitivity, AUC = 0·88) are specific for severe forms. A ratio threshold of 0· 128 discriminates the overlapping range. We present ten new GLDC variants. Two mild variants resulted in attenuated, while two severe variants or one mild and one severe variant lead to severe phenotype. Based on clinical, biochemical and genetic parameter we propose a severity prediction model. INTERPRETATION This study widens the phenotypic spectrum of attenuated NKH and expands the number of pathogenic variants. The multiparametric approach provides a promising tool to predict disease severity, helping to improve clinical management strategies. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Oya Kuseyri Hübschmann
- University Children's Hospital Heidelberg, Division of Child Neurology and Metabolic Disorders, Heidelberg, Germany
| | - Natalia Alexandra Julia Palacios
- Inborn errors of metabolism Unit, Department of Neurology, Institut de Recerca Sant Joan de Déu, CIBERER-ISCIII and MetabERN, Barcelona, Spain
| | - Mireia Olivella
- Bioinformatics and Medical Statistics Group. Facultat de Ciències i Tecnologia. Universitat de Vic - Universitat Central de Catalunya (UVic-UCC), Vic, Barcelona, Spain
| | - Philipp Guder
- Children's Hospital, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Dimitrios I Zafeiriou
- First Department of Pediatrics Aristotle University of Thessaloniki Egnatia St. 106 54622, Thessaloniki, Greece
| | - Gabriella Horvath
- University of British Columbia, Department of Pediatrics, Division of Biochemical Genetics, BC Children's Hospital, Vancouver, BC, Canada
| | - Jan Kulhánek
- Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University and General University Hospital in Prague, Prague, Czech Republic
| | - Toni S Pearson
- Department of Neurology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Alice Kuster
- Department of Neurometabolism and Metabolic Disorders, University Hospital of Nantes, Nantes, France
| | - Elisenda Cortès-Saladelafont
- Inborn errors of metabolism Unit, Department of Neurology, Institut de Recerca Sant Joan de Déu, CIBERER-ISCIII and MetabERN, Barcelona, Spain.,Inborn Errors of Metabolism and Child Neurology Unit, Department of Pediatrics, Hospital Germans Trias i Pujol, Badalona and Faculty of Medicine, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Salvador Ibáñez
- Department of Pediatric Neurology, Hospital Virgen de la Arrixaca, Murcia, Spain
| | | | - Tomáš Honzík
- Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University and General University Hospital in Prague, Prague, Czech Republic
| | - René Santer
- Children's Hospital, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Kathrin Jeltsch
- University Children's Hospital Heidelberg, Division of Child Neurology and Metabolic Disorders, Heidelberg, Germany
| | - Sven F Garbade
- University Children's Hospital Heidelberg, Dietmar-Hopp Metabolic Center, Heidelberg, Germany
| | - Georg F Hoffmann
- University Children's Hospital Heidelberg, Division of Child Neurology and Metabolic Disorders, Heidelberg, Germany
| | - Thomas Opladen
- University Children's Hospital Heidelberg, Division of Child Neurology and Metabolic Disorders, Heidelberg, Germany
| | - Ángeles García-Cazorla
- Inborn errors of metabolism Unit, Department of Neurology, Institut de Recerca Sant Joan de Déu, CIBERER-ISCIII and MetabERN, Barcelona, Spain
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5
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Bayrak H, Yıldız Y, Olgaç A, Kasapkara ÇS, Küçükcongar A, Zenciroğlu A, Yüksel D, Ceylaner S, Kılıç M. Genotypic and phenotypic features in Turkish patients with classic nonketotic hyperglycinemia. Metab Brain Dis 2021; 36:1213-1222. [PMID: 33791923 DOI: 10.1007/s11011-021-00718-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Accepted: 03/14/2021] [Indexed: 10/21/2022]
Abstract
Nonketotic hyperglycinemia is an autosomal recessive inborn error of glycine metabolism, characterized by deficient activity of the glycine cleavage enzyme system. Classic nonketotic hyperglycinemia is caused by mutations or genomic changes in genes that encode the protein components of the glycine cleavage enzyme system. We aimed to investigate clinical, biochemical, radiological findings and molecular genetic data in ten Turkish patients with classic nonketotic hyperglycinemia. Ten Turkish patients who were diagnosed with classic nonketotic hyperglycinemia in a single center from 2013 to 2019 were included in this study. Their clinical, radiological, electrophysiological and laboratory data were collected retrospectively. Sixty percent of the patients were in neonatal group, while 40 % of the patients were infantile. There were no late-onset patients. 90 % of the patients had the severe form. All patients had developmental delay and seizures. Mortality ratio was 30 % in all groups and 50 % in the neonatal group, while no mortality was seen in infantile group. Median (range) values of cerebrospinal fluid (CSF) glycine levels, plasma glycine levels and CSF/plasma glycine ratios were 148 (15-320) µmol/L, 896 (87-1910) µmol/L, 0.17 (0.09-0.21) respectively. Diffuse hypomyelination and corpus callosum anomaly were the most common cranial MRI findings and multifocal epileptic activity and burst supression pattern were the most common electroencephalographic findings. Six patients had variants in GLDC gene and four in AMT gene; five novel variants including AMT gene deletion were detected. Prognosis was poor and treatment was not effective, especially in the severe form. Classic nonketotic hyperglycinemia causes high morbidity and mortality. Neonatal-onset disease was more common and severe than infantile-onset disease. The ratio of AMT gene variants might be higher in Turkey than other countries. AMT gene deletion also plays a role in the etiology of classic nonketotic hyperglycinemia.
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Affiliation(s)
- Harun Bayrak
- Department of Pediatrics, Sami Ulus Children Hospital, Ankara, Turkey
| | - Yılmaz Yıldız
- Metabolism Unit, Sami Ulus Children Hospital, Babur cad. No: 44, Altındağ, Ankara, 06080, Turkey
| | - Asburçe Olgaç
- Metabolism Unit, Sami Ulus Children Hospital, Babur cad. No: 44, Altındağ, Ankara, 06080, Turkey
| | - Çiğdem Seher Kasapkara
- Metabolism Unit, Sami Ulus Children Hospital, Babur cad. No: 44, Altındağ, Ankara, 06080, Turkey
| | | | | | - Deniz Yüksel
- Neurology Unit, Sami Ulus Children Hospital, Ankara, Turkey
| | - Serdar Ceylaner
- Intergen, Genetic and Rare Disease Diagnosis and Research Center, Genetic Laboratory, Ankara, Turkey
| | - Mustafa Kılıç
- Metabolism Unit, Sami Ulus Children Hospital, Babur cad. No: 44, Altındağ, Ankara, 06080, Turkey.
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Cao Y, Meng L, Zhang Y, Jiao J, Pu W, Ma L. Novel GLDC Compound Heterozygous Variant Leading to Nonketotic Hyperglycinemia: Case Report and Literature Review. Front Pediatr 2021; 9:725930. [PMID: 34513771 PMCID: PMC8432289 DOI: 10.3389/fped.2021.725930] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Accepted: 08/06/2021] [Indexed: 12/21/2022] Open
Abstract
Nonketotic hyperglycinemia (NKH) is a lethal autosomal recessive disease resulting from alterations in glycine metabolism, commonly caused by mutations in glycine decarboxylase (GLDC). The symptoms of NKH usually manifest in the neonatal period, and can be categorized into severe NKH and attenuated NKH based on the clinical outcome. To date, only a few NKH cases have been reported in China. We here report a case of a neonate with severe NKH carrying a novel compound heterozygous variant in GLDC. The patient was a 68-h-old girl who had progressive lethargy, no crying, and poor sucking ability from birth, and was therefore transferred to our department. On admission, the patient was supported by intubation and ventilation and presented with profound coma. Metabolic investigation indicated a markedly increased glycine concentration both in the plasma and cerebrospinal fluid (CSF). Symptomatic treatments were administered, but the patient's condition did not improve substantially. Whole-exome sequencing identified compound heterozygous mutations (c.1261G>C, p.G421R and c.450 C>G, p.N150K) in GLDC, which were inherited from the mother and the father, respectively. The patient was hospitalized for 8 days in our department and died 2 days after discharge. We further summarize the clinical features, genetic characteristics, administered treatment, and prognosis of previously reported Chinese NKH patients for context. Our results highlight that due to the non-specific clinical phenotypes of NKH and difficulty in obtaining CSF samples, genetic testing is a crucial tool, not only for a diagnosis but also for predicting the clinical outcome and can potentially help to determine the optimal therapeutic strategy.
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Affiliation(s)
- Yanyan Cao
- Institute of Pediatric Research, Children's Hospital of Hebei Province, Shijiazhuang, China
| | - Lingzhi Meng
- Department of Neonatology, Children's Hospital of Hebei Province, Shijiazhuang, China
| | - Yudong Zhang
- Department of Neonatology, Children's Hospital of Hebei Province, Shijiazhuang, China
| | - Jiancheng Jiao
- Department of Neonatology, Children's Hospital of Hebei Province, Shijiazhuang, China
| | - Weicong Pu
- Department of Neonatology, Children's Hospital of Hebei Province, Shijiazhuang, China
| | - Li Ma
- Department of Neonatology, Children's Hospital of Hebei Province, Shijiazhuang, China
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7
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Manta-Vogli PD, Schulpis KH, Loukas YL, Dotsikas Y. Birth weight related essential, non-essential and conditionally essential amino acid blood concentrations in 12,000 breastfed full-term infants perinatally. Scandinavian Journal of Clinical and Laboratory Investigation 2020; 80:571-579. [DOI: 10.1080/00365513.2020.1818280] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Penelope D. Manta-Vogli
- Department of Clinical Nutrition & Dietetics, Agia Sofia Children’s Hospital, Athens, Greece
| | | | - Yannis L. Loukas
- Laboratory of Pharmaceutical Analysis, Department of Pharmacy, National and Kapodistrian University of Athens, Athens, Greece
| | - Yannis Dotsikas
- Laboratory of Pharmaceutical Analysis, Department of Pharmacy, National and Kapodistrian University of Athens, Athens, Greece
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8
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Large scale analyses of genotype-phenotype relationships of glycine decarboxylase mutations and neurological disease severity. PLoS Comput Biol 2020; 16:e1007871. [PMID: 32421718 PMCID: PMC7259800 DOI: 10.1371/journal.pcbi.1007871] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 05/29/2020] [Accepted: 04/13/2020] [Indexed: 12/14/2022] Open
Abstract
Monogenetic diseases provide unique opportunity for studying complex, clinical states that underlie neurological severity. Loss of glycine decarboxylase (GLDC) can severely impact neurological development as seen in non-ketotic hyperglycinemia (NKH). NKH is a neuro-metabolic disorder lacking quantitative predictors of disease states. It is characterized by elevation of glycine, seizures and failure to thrive, but glycine reduction often fails to confer neurological benefit, suggesting need for alternate tools to distinguish severe from attenuated disease. A major challenge has been that there are 255 unique disease-causing missense mutations in GLDC, of which 206 remain entirely uncharacterized. Here we report a Multiparametric Mutation Score (MMS) developed by combining in silico predictions of stability, evolutionary conservation and protein interaction models and suitable to assess 251 of 255 mutations. In addition, we created a quantitative scale of clinical disease severity comprising of four major disease domains (seizure, cognitive failure, muscular and motor control and brain-malformation) to comprehensively score patient symptoms identified in 131 clinical reports published over the last 15 years. The resulting patient Clinical Outcomes Scores (COS) were used to optimize the MMS for biological and clinical relevance and yield a patient Weighted Multiparametric Mutation Score (WMMS) that separates severe from attenuated neurological disease (p = 1.2 e-5). Our study provides understanding for developing quantitative tools to predict clinical severity of neurological disease and a clinical scale that advances monitoring disease progression needed to evaluate new treatments for NKH. Neurodegenerative disorders frequently have diverse, severe symptoms and health outcomes that can be difficult to predict. The rare disease non-ketotic hyperglycinemia (NKH) additionally has a wide range of disease-causing mutations in glycine decarboxylase (GLDC), a protein that breaks down glycine. But measuring glycine is not sufficient to foretell disease outcome. A method to predict whether a mutation will cause severe or more mild forms of NKH would be very helpful to both understanding the disease as well as developing treatments for it. We used computation-based approaches to develop a mutation score that comprehensively predicts how mutations decrease GLDC function. After training against clinical data, the score was able to predict whether a mutation will cause severe or attenuated disease. This study utilizes the power of computational and multidisciplinary analyses to advance understanding and treatment of genetically caused neurodegenerative diseases.
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9
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Alptekin A, Ye B, Yu Y, Poole CJ, van Riggelen J, Zha Y, Ding HF. Glycine decarboxylase is a transcriptional target of MYCN required for neuroblastoma cell proliferation and tumorigenicity. Oncogene 2019; 38:7504-7520. [PMID: 31444411 PMCID: PMC6908766 DOI: 10.1038/s41388-019-0967-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Revised: 08/05/2019] [Accepted: 08/09/2019] [Indexed: 12/12/2022]
Abstract
Genomic amplification of the oncogene MYCN is a major driver in the development of high-risk neuroblastoma, a pediatric cancer with poor prognosis. Given the challenge in targeting MYCN directly for therapy, we sought to identify MYCN-dependent metabolic vulnerabilities that can be targeted therapeutically. Here, we report that the gene encoding glycine decarboxylase (GLDC), which catalyzes the first and rate-limiting step in glycine breakdown with the production of the one-carbon unit 5,10-methylene-tetrahydrofolate, is a direct transcriptional target of MYCN. As a result, GLDC expression is markedly elevated in MYCN-amplified neuroblastoma tumors and cell lines. This transcriptional upregulation of GLDC expression is of functional significance, as GLDC depletion by RNA interference inhibits the proliferation and tumorigenicity of MYCN-amplified neuroblastoma cell lines by inducing G1 arrest. Metabolomic profiling reveals that GLDC knockdown disrupts purine and central carbon metabolism and reduces citrate production, leading to a decrease in the steady-state levels of cholesterol and fatty acids. Moreover, blocking purine or cholesterol synthesis recapitulates the growth inhibitory effect of GLDC knockdown. These findings reveal a critical role of GLDC in sustaining the proliferation of neuroblastoma cells with high-level GLDC expression and suggest that MYCN amplification is a biomarker for GLDC-based therapeutic strategies against high-risk neuroblastoma.
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Affiliation(s)
- Ahmet Alptekin
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta University, Augusta, GA, 30912, USA.,Georgia Cancer Center, Medical College of Georgia, Augusta University, Augusta, GA, 30912, USA
| | - Bingwei Ye
- Georgia Cancer Center, Medical College of Georgia, Augusta University, Augusta, GA, 30912, USA
| | - Yajie Yu
- Institute of Neural Regeneration and Repair and Department of Neurology, The First Hospital of Yichang, Three Gorges University College of Medicine, 443000, Yichang, China
| | - Candace J Poole
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta University, Augusta, GA, 30912, USA.,Georgia Cancer Center, Medical College of Georgia, Augusta University, Augusta, GA, 30912, USA
| | - Jan van Riggelen
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta University, Augusta, GA, 30912, USA.,Georgia Cancer Center, Medical College of Georgia, Augusta University, Augusta, GA, 30912, USA
| | - Yunhong Zha
- Institute of Neural Regeneration and Repair and Department of Neurology, The First Hospital of Yichang, Three Gorges University College of Medicine, 443000, Yichang, China
| | - Han-Fei Ding
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta University, Augusta, GA, 30912, USA. .,Georgia Cancer Center, Medical College of Georgia, Augusta University, Augusta, GA, 30912, USA. .,Department of Pathology, Medical College of Georgia, Augusta University, Augusta, GA, 30912, USA.
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10
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Clinical heterogeneity of glycine encephalopathy in three Palestinian siblings: A novel mutation in the glycine decarboxylase (GLDC) gene. Brain Dev 2017; 39:601-605. [PMID: 28325525 DOI: 10.1016/j.braindev.2017.03.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 02/02/2017] [Accepted: 03/02/2017] [Indexed: 12/31/2022]
Abstract
INTRODUCTION Glycine encephalopathy (GE), also known as non-ketotic hyperglycinemia (NKH), is a rare inborn error of glycine metabolism caused by a defect in glycine cleavage system, a multi-enzyme complex located in mitochondrial membrane. This defect results in elevated glycine concentration in plasma and cerebrospinal fluid (CSF). Clinical manifestations vary from severe lethargy, hypoactivity and apneic episodes in the neonatal form, mild or moderate psychomotor delay and seizures in the infantile form, and abnormal behaviors, ataxia and choreoathetoid movements in late onset form. More than 50 GLDC mutations were found, reflecting large heterogeneity of the gene. METHODS We describe the clinical, biochemical and molecular characteristics of three Palestinian siblings who have distinct clinical phenotypes. Molecular study was performed utilizing standard Polymerase Chain Reaction (PCR) amplification then direct DNA sequencing for the affected family members. RESULTS Their phenotypes included severe symptoms in neonatal period, infantile onset of seizure and psychomotor delay and a mild late-onset form with speech delay at age 20months. All siblings were homozygous for a novel mutation Y164H in exon 4 of GLDC gene. The described novel homozygous variant in our study is predicted deleterious and pathogenic. CONCLUSIONS This article further expands the genetic spectrum of glycine encephalopathy and adds an evidence of the clinical heterogeneity of glycine encephalopathy even in siblings with identical mutation.
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11
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Bravo-Alonso I, Navarrete R, Arribas-Carreira L, Perona A, Abia D, Couce ML, García-Cazorla A, Morais A, Domingo R, Ramos MA, Swanson MA, Van Hove JLK, Ugarte M, Pérez B, Pérez-Cerdá C, Rodríguez-Pombo P. Nonketotic hyperglycinemia: Functional assessment of missense variants in GLDC to understand phenotypes of the disease. Hum Mutat 2017; 38:678-691. [PMID: 28244183 DOI: 10.1002/humu.23208] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Revised: 02/22/2017] [Accepted: 02/23/2017] [Indexed: 11/08/2022]
Abstract
The rapid analysis of genomic data is providing effective mutational confirmation in patients with clinical and biochemical hallmarks of a specific disease. This is the case for nonketotic hyperglycinemia (NKH), a Mendelian disorder causing seizures in neonates and early-infants, primarily due to mutations in the GLDC gene. However, understanding the impact of missense variants identified in this gene is a major challenge for the application of genomics into clinical practice. Herein, a comprehensive functional and structural analysis of 19 GLDC missense variants identified in a cohort of 26 NKH patients was performed. Mutant cDNA constructs were expressed in COS7 cells followed by enzymatic assays and Western blot analysis of the GCS P-protein to assess the residual activity and mutant protein stability. Structural analysis, based on molecular modeling of the 3D structure of GCS P-protein, was also performed. We identify hypomorphic variants that produce attenuated phenotypes with improved prognosis of the disease. Structural analysis allows us to interpret the effects of mutations on protein stability and catalytic activity, providing molecular evidence for clinical outcome and disease severity. Moreover, we identify an important number of mutants whose loss-of-functionality is associated with instability and, thus, are potential targets for rescue using folding therapeutic approaches.
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Affiliation(s)
- Irene Bravo-Alonso
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular Severo Ochoa, CBM-CSIC, Departamento de Biología Molecular, Universidad Autónoma Madrid, Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), IDIPAZ, Madrid, Spain
| | - Rosa Navarrete
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular Severo Ochoa, CBM-CSIC, Departamento de Biología Molecular, Universidad Autónoma Madrid, Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), IDIPAZ, Madrid, Spain
| | - Laura Arribas-Carreira
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular Severo Ochoa, CBM-CSIC, Departamento de Biología Molecular, Universidad Autónoma Madrid, Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), IDIPAZ, Madrid, Spain
| | | | - David Abia
- Servicio de Bioinformática, Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Madrid, Spain
| | - María Luz Couce
- Unit of Diagnosis and Treatment of Congenital Metabolic Diseases, Service of Neonatology, Department of Pediatrics, Hospital Clínico Universitario de Santiago, CIBERER, Health Research Institute of Santiago de Compostela (IDIS), Santiago de Compostela, Spain
| | - Angels García-Cazorla
- Institut de Recerca Pediàtrica-Hospital Sant Joan de Déu (IRP-HSJD), Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Instituto de Salud Carlos III, Barcelona, Spain
| | - Ana Morais
- Unidad de Nutrición Infantil y Enfermedades Metabólicas, Hospital Universitario Infantil La Paz, Madrid, Spain
| | - Rosario Domingo
- Servicio de Pediatría, Hospital Virgen de la Arrixaca, Murcia, Spain
| | - María Antonia Ramos
- Servicio de Genética, Hospital B del Complejo Hospitalario de Navarra, Pamplona, Navarra, Spain
| | - Michael A Swanson
- Department of Pediatrics, Section of Clinical Genetics and Metabolism, University of Colorado, Aurora, Colorado
| | - Johan L K Van Hove
- Department of Pediatrics, Section of Clinical Genetics and Metabolism, University of Colorado, Aurora, Colorado
| | - Magdalena Ugarte
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular Severo Ochoa, CBM-CSIC, Departamento de Biología Molecular, Universidad Autónoma Madrid, Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), IDIPAZ, Madrid, Spain
| | - Belén Pérez
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular Severo Ochoa, CBM-CSIC, Departamento de Biología Molecular, Universidad Autónoma Madrid, Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), IDIPAZ, Madrid, Spain
| | - Celia Pérez-Cerdá
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular Severo Ochoa, CBM-CSIC, Departamento de Biología Molecular, Universidad Autónoma Madrid, Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), IDIPAZ, Madrid, Spain
| | - Pilar Rodríguez-Pombo
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular Severo Ochoa, CBM-CSIC, Departamento de Biología Molecular, Universidad Autónoma Madrid, Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), IDIPAZ, Madrid, Spain
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Li HF. [Clinical and molecular genetic characteristics of nonketotic hyperglycinemia]. ZHONGGUO DANG DAI ER KE ZA ZHI = CHINESE JOURNAL OF CONTEMPORARY PEDIATRICS 2017; 19:272-274. [PMID: 28302195 PMCID: PMC7390138 DOI: 10.7499/j.issn.1008-8830.2017.03.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Received: 11/06/2016] [Accepted: 12/20/2016] [Indexed: 06/06/2023]
Affiliation(s)
- Hai-Feng Li
- Department of Rehabilitation, Children's Hospital, Zhejiang University School of Medicine, Hangzhou 310003, China
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13
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Multifarious Beneficial Effect of Nonessential Amino Acid, Glycine: A Review. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2017; 2017:1716701. [PMID: 28337245 PMCID: PMC5350494 DOI: 10.1155/2017/1716701] [Citation(s) in RCA: 109] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Revised: 02/07/2017] [Accepted: 02/07/2017] [Indexed: 02/06/2023]
Abstract
Glycine is most important and simple, nonessential amino acid in humans, animals, and many mammals. Generally, glycine is synthesized from choline, serine, hydroxyproline, and threonine through interorgan metabolism in which kidneys and liver are the primarily involved. Generally in common feeding conditions, glycine is not sufficiently synthesized in humans, animals, and birds. Glycine acts as precursor for several key metabolites of low molecular weight such as creatine, glutathione, haem, purines, and porphyrins. Glycine is very effective in improving the health and supports the growth and well-being of humans and animals. There are overwhelming reports supporting the role of supplementary glycine in prevention of many diseases and disorders including cancer. Dietary supplementation of proper dose of glycine is effectual in treating metabolic disorders in patients with cardiovascular diseases, several inflammatory diseases, obesity, cancers, and diabetes. Glycine also has the property to enhance the quality of sleep and neurological functions. In this review we will focus on the metabolism of glycine in humans and animals and the recent findings and advances about the beneficial effects and protection of glycine in different disease states.
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Trujillano D, Oprea GE, Schmitz Y, Bertoli-Avella AM, Abou Jamra R, Rolfs A. A comprehensive global genotype-phenotype database for rare diseases. Mol Genet Genomic Med 2016; 5:66-75. [PMID: 28116331 PMCID: PMC5241210 DOI: 10.1002/mgg3.262] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Revised: 10/03/2016] [Accepted: 11/01/2016] [Indexed: 12/20/2022] Open
Abstract
Background The ability to discover genetic variants in a patient runs far ahead of the ability to interpret them. Databases with accurate descriptions of the causal relationship between the variants and the phenotype are valuable since these are critical tools in clinical genetic diagnostics. Here, we introduce a comprehensive and global genotype–phenotype database focusing on rare diseases. Methods This database (CentoMD®) is a browser‐based tool that enables access to a comprehensive, independently curated system utilizing stringent high‐quality criteria and a quickly growing repository of genetic and human phenotype ontology (HPO)‐based clinical information. Its main goals are to aid the evaluation of genetic variants, to enhance the validity of the genetic analytical workflow, to increase the quality of genetic diagnoses, and to improve evaluation of treatment options for patients with hereditary diseases. The database software correlates clinical information from consented patients and probands of different geographical backgrounds with a large dataset of genetic variants and, when available, biomarker information. An automated follow‐up tool is incorporated that informs all users whenever a variant classification has changed. These unique features fully embedded in a CLIA/CAP‐accredited quality management system allow appropriate data quality and enhanced patient safety. Results More than 100,000 genetically screened individuals are documented in the database, resulting in more than 470 million variant detections. Approximately, 57% of the clinically relevant and uncertain variants in the database are novel. Notably, 3% of the genetic variants identified and previously reported in the literature as being associated with a particular rare disease were reclassified, based on internal evidence, as clinically irrelevant. Conclusions The database offers a comprehensive summary of the clinical validity and causality of detected gene variants with their associated phenotypes, and is a valuable tool for identifying new disease genes through the correlation of novel genetic variants with specific, well‐defined phenotypes.
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Affiliation(s)
| | | | | | | | - Rami Abou Jamra
- Centogene AGRostockGermany; Institute of Human GeneticsUniversity of Leipzig Hospitals and ClinicsLeipzigGermany
| | - Arndt Rolfs
- Centogene AGRostockGermany; Albrecht-Kossel-Institute for NeuroregenerationMedical University RostockRostockGermany
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15
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The genetic basis of classic nonketotic hyperglycinemia due to mutations in GLDC and AMT. Genet Med 2016; 19:104-111. [PMID: 27362913 DOI: 10.1038/gim.2016.74] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 04/25/2016] [Indexed: 11/09/2022] Open
Abstract
PURPOSE The study's purpose was to delineate the genetic mutations that cause classic nonketotic hyperglycinemia (NKH). METHODS Genetic results, parental phase, ethnic origin, and gender data were collected from subjects suspected to have classic NKH. Mutations were compared with those in the existing literature and to the population frequency from the Exome Aggregation Consortium (ExAC) database. RESULTS In 578 families, genetic analyses identified 410 unique mutations, including 246 novel mutations. 80% of subjects had mutations in GLDC. Missense mutations were noted in 52% of all GLDC alleles, most private. Missense mutations were 1.5 times as likely to be pathogenic in the carboxy terminal of GLDC than in the amino-terminal part. Intragenic copy-number variations (CNVs) in GLDC were noted in 140 subjects, with biallelic CNVs present in 39 subjects. The position and frequency of the breakpoint for CNVs correlated with intron size and presence of Alu elements. Missense mutations, most often recurring, were the most common type of disease-causing mutation in AMT. Sequencing and CNV analysis identified biallelic pathogenic mutations in 98% of subjects. Based on genotype, 15% of subjects had an attenuated phenotype. The frequency of NKH is estimated at 1:76,000. CONCLUSION The 484 unique mutations now known in classic NKH provide a valuable overview for the development of genotype-based therapies.Genet Med 19 1, 104-111.
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Nickerson SL, Balasubramaniam S, Dryland PA, Love JM, Kava MP, Love DR, Prosser DO. Two Novel GLDC Mutations in a Neonate with Nonketotic Hyperglycinemia. J Pediatr Genet 2016; 5:174-80. [PMID: 27617160 DOI: 10.1055/s-0036-1584358] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Accepted: 09/09/2015] [Indexed: 10/21/2022]
Abstract
Nonketotic hyperglycinemia, also known as glycine encephalopathy (OMIM #605899), is an autosomal recessive disorder of glycine metabolism resulting from a defect in the glycine cleavage system. We report two novel mutations of the glycine decarboxylase (GLDC) gene observed in a compound heterozygous state in a neonate of mixed Maori and Caucasian parentage: c.395C>T p.(Ser132Leu) in exon 3, and c.256-?_334+?del p.(Ser86Valfs*119), resulting in an out-of-frame deletion of exon 2. Additionally, we describe our experience of implementing the ketogenic diet, alongside standard pharmacological therapy, and highlight its potential therapeutic benefit in severe nonketotic hyperglycinemia, particularly in seizure management.
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Affiliation(s)
- Sarah L Nickerson
- Diagnostic Genetics, LabPLUS, Auckland City Hospital, Auckland, New Zealand
| | - Shanti Balasubramaniam
- Metabolic Unit, Department of Rheumatology/Metabolic Medicine, Princess Margaret Hospital, Perth, WA, Australia; School of Paediatrics and Child Health, University of Western Australia, WA, Australia
| | - Philippa A Dryland
- Diagnostic Genetics, LabPLUS, Auckland City Hospital, Auckland, New Zealand
| | - Jennifer M Love
- Diagnostic Genetics, LabPLUS, Auckland City Hospital, Auckland, New Zealand
| | - Maina P Kava
- School of Paediatrics and Child Health, University of Western Australia, WA, Australia; Department of Paediatric Neurology, Princess Margaret Hospital for Children, Perth, WA, Australia
| | - Donald R Love
- Diagnostic Genetics, LabPLUS, Auckland City Hospital, Auckland, New Zealand
| | - Debra O Prosser
- Diagnostic Genetics, LabPLUS, Auckland City Hospital, Auckland, New Zealand
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17
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Bjoraker KJ, Swanson MA, Coughlin CR, Christodoulou J, Tan ES, Fergeson M, Dyack S, Ahmad A, Friederich MW, Spector EB, Creadon-Swindell G, Hodge MA, Gaughan S, Burns C, Van Hove JLK. Neurodevelopmental Outcome and Treatment Efficacy of Benzoate and Dextromethorphan in Siblings with Attenuated Nonketotic Hyperglycinemia. J Pediatr 2016; 170:234-9. [PMID: 26749113 DOI: 10.1016/j.jpeds.2015.12.027] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Revised: 10/05/2015] [Accepted: 12/08/2015] [Indexed: 11/18/2022]
Abstract
OBJECTIVE To evaluate the impact of sodium benzoate and dextromethorphan treatment on patients with the attenuated form of nonketotic hyperglycinemia. STUDY DESIGN Families were recruited with 2 siblings both affected with attenuated nonketotic hyperglycinemia. Genetic mutations were expressed to identify residual activity. The outcome on developmental progress and seizures was compared between the first child diagnosed and treated late with the second child diagnosed at birth and treated aggressively from the newborn period using dextromethorphan and benzoate at dosing sufficient to normalize plasma glycine levels. Both siblings were evaluated with similar standardized neurodevelopmental measures. RESULTS In each sibling set, the second sibling treated from the neonatal period achieved earlier and more developmental milestones, and had a higher developmental quotient. In 3 of the 4 sibling pairs, the younger sibling had no seizures whereas the first child had a seizure disorder. The adaptive behavior subdomains of socialization and daily living skills improved more than motor skills and communication. CONCLUSIONS Early treatment with dextromethorphan and sodium benzoate sufficient to normalize plasma glycine levels is effective at improving outcome if used in children with attenuated disease with mutations providing residual activity and when started from the neonatal period.
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Affiliation(s)
| | | | | | - John Christodoulou
- Western Sydney Genetics Program, Children's Hospital at Westmead, and Disciplines of Pediatrics and Child Health and Genetic Medicine, Sydney Medical School, University of Sydney, Sydney, New South Wales, Australia
| | - Ee S Tan
- Western Sydney Genetics Program, Children's Hospital at Westmead, and Disciplines of Pediatrics and Child Health and Genetic Medicine, Sydney Medical School, University of Sydney, Sydney, New South Wales, Australia
| | - Mark Fergeson
- Department of Pediatrics, Oklahoma University, Oklahoma City, OK
| | - Sarah Dyack
- Department of Pediatrics, Dalhousie University, IWK Health Centre, Halifax, Nova Scotia, Canada
| | - Ayesha Ahmad
- Division of Pediatric Genetics, University of Michigan, Ann Arbor, MI
| | | | | | | | - M Antoinette Hodge
- Child Development Unit, Children's Hospital at Westmead, Sydney, New South Wales, Australia
| | - Sommer Gaughan
- Department of Pediatrics, University of Colorado, Aurora, CO
| | - Casey Burns
- Department of Pediatrics, University of Colorado, Aurora, CO
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18
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Swanson MA, Coughlin CR, Scharer GH, Szerlong HJ, Bjoraker KJ, Spector EB, Creadon-Swindell G, Mahieu V, Matthijs G, Hennermann JB, Applegarth DA, Toone JR, Tong S, Williams K, Van Hove JLK. Biochemical and molecular predictors for prognosis in nonketotic hyperglycinemia. Ann Neurol 2015; 78:606-18. [PMID: 26179960 PMCID: PMC4767401 DOI: 10.1002/ana.24485] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Revised: 07/14/2015] [Accepted: 07/14/2015] [Indexed: 12/22/2022]
Abstract
Objective Nonketotic hyperglycinemia is a neurometabolic disorder characterized by intellectual disability, seizures, and spasticity. Patients with attenuated nonketotic hyperglycinemia make variable developmental progress. Predictive factors have not been systematically assessed. Methods We reviewed 124 patients stratified by developmental outcome for biochemical and molecular predictive factors. Missense mutations were expressed to quantify residual activity using a new assay. Results Patients with severe nonketotic hyperglycinemia required multiple anticonvulsants, whereas patients with developmental quotient (DQ) > 30 did not require anticonvulsants. Brain malformations occurred mainly in patients with severe nonketotic hyperglycinemia (71%) but rarely in patients with attenuated nonketotic hyperglycinemia (7.5%). Neonatal presentation did not correlate with outcome, but age at onset ≥ 4 months was associated with attenuated nonketotic hyperglycinemia. Cerebrospinal fluid (CSF) glycine levels and CSF:plasma glycine ratio correlated inversely with DQ; CSF glycine > 230 μM indicated severe outcome and CSF:plasma glycine ratio ≤ 0.08 predicted attenuated outcome. The glycine index correlated strongly with outcome. Molecular analysis identified 99% of mutant alleles, including 96 novel mutations. Mutations near the active cleft of the P‐protein maintained stable protein levels. Presence of 1 mutation with residual activity was necessary but not sufficient for attenuated outcome; 2 such mutations conferred best outcome. Divergent outcomes for the same genotype indicate a contribution of other genetic or nongenetic factors. Interpretation Accurate prediction of outcome is possible in most patients. A combination of 4 factors available neonatally predicted 78% of severe and 49% of attenuated patients, and a score based on mutation severity predicted outcome with 70% sensitivity and 97% specificity. Ann Neurol 2015;78:606–618
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Affiliation(s)
| | | | | | | | | | | | | | - Vincent Mahieu
- Center for Human Genetics, University of Leuven, Leuven, Belgium
| | - Gert Matthijs
- Center for Human Genetics, University of Leuven, Leuven, Belgium
| | - Julia B Hennermann
- Department of Pediatric and Adolescent Medicine, University Medical Center Mainz, Mainz, Germany
| | - Derek A Applegarth
- Department of Pediatrics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Jennifer R Toone
- Department of Pediatrics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Suhong Tong
- Department of Pediatrics, University of Colorado, Aurora, CO
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Azize NAA, Ngah WZW, Othman Z, Md Desa N, Chin CB, Md Yunus Z, Mohan A, Hean TS, Syed Zakaria SZ, Lock-Hock N. Mutation analysis of glycine decarboxylase, aminomethyltransferase and glycine cleavage system protein-H genes in 13 unrelated families with glycine encephalopathy. J Hum Genet 2014; 59:593-7. [DOI: 10.1038/jhg.2014.69] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Revised: 07/11/2014] [Accepted: 07/17/2014] [Indexed: 01/28/2023]
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20
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Badenhorst CPS, Erasmus E, van der Sluis R, Nortje C, van Dijk AA. A new perspective on the importance of glycine conjugation in the metabolism of aromatic acids. Drug Metab Rev 2014; 46:343-61. [PMID: 24754494 DOI: 10.3109/03602532.2014.908903] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
A number of endogenous and xenobiotic organic acids are conjugated to glycine, in animals ranging from mosquitoes to humans. Glycine conjugation has generally been assumed to be a detoxification mechanism, increasing the water solubility of organic acids in order to facilitate urinary excretion. However, the recently proposed glycine deportation hypothesis states that the role of the amino acid conjugations, including glycine conjugation, is to regulate systemic levels of amino acids that are also utilized as neurotransmitters in the central nervous systems of animals. This hypothesis is based on the observation that, compared to glucuronidation, glycine conjugation does not significantly increase the water solubility of aromatic acids. In this review it will be argued that the major role of glycine conjugation is to dispose of the end products of phenylpropionate metabolism. Furthermore, glucuronidation, which occurs in the endoplasmic reticulum, would not be ideal for the detoxification of free benzoate, which has been shown to accumulate in the mitochondrial matrix. Glycine conjugation, however, prevents accumulation of benzoic acid in the mitochondrial matrix by forming hippurate, a less lipophilic conjugate that can be more readily transported out of the mitochondria. Finally, it will be explained that the glycine conjugation of benzoate, a commonly used preservative, exacerbates the dietary deficiency of glycine in humans. Because the resulting shortage of glycine can negatively influence brain neurochemistry and the synthesis of collagen, nucleic acids, porphyrins, and other important metabolites, the risks of using benzoate as a preservative should not be underestimated.
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Glycine transporters as novel therapeutic targets in schizophrenia, alcohol dependence and pain. Nat Rev Drug Discov 2014; 12:866-85. [PMID: 24172334 DOI: 10.1038/nrd3893] [Citation(s) in RCA: 153] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Glycine transporters are endogenous regulators of the dual functions of glycine, which acts as a classical inhibitory neurotransmitter at glycinergic synapses and as a modulator of neuronal excitation mediated by NMDA (N-methyl-D-aspartate) receptors at glutamatergic synapses. The two major subtypes of glycine transporters, GlyT1 and GlyT2, have been linked to the pathogenesis and/or treatment of central and peripheral nervous system disorders, including schizophrenia and related affective and cognitive disturbances, alcohol dependence, pain, epilepsy, breathing disorders and startle disease (also known as hyperekplexia). This Review examines the rationale for the therapeutic potential of GlyT1 and GlyT2 inhibition, and surveys the latest advances in the biology of glycine reuptake and transport as well as the drug discovery and clinical development of compounds that block glycine transporters.
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22
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Glycine metabolism in animals and humans: implications for nutrition and health. Amino Acids 2013; 45:463-77. [PMID: 23615880 DOI: 10.1007/s00726-013-1493-1] [Citation(s) in RCA: 432] [Impact Index Per Article: 39.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Accepted: 04/02/2013] [Indexed: 01/01/2023]
Abstract
Glycine is a major amino acid in mammals and other animals. It is synthesized from serine, threonine, choline, and hydroxyproline via inter-organ metabolism involving primarily the liver and kidneys. Under normal feeding conditions, glycine is not adequately synthesized in birds or in other animals, particularly in a diseased state. Glycine degradation occurs through three pathways: the glycine cleavage system (GCS), serine hydroxymethyltransferase, and conversion to glyoxylate by peroxisomal D-amino acid oxidase. Among these pathways, GCS is the major enzyme to initiate glycine degradation to form ammonia and CO2 in animals. In addition, glycine is utilized for the biosynthesis of glutathione, heme, creatine, nucleic acids, and uric acid. Furthermore, glycine is a significant component of bile acids secreted into the lumen of the small intestine that is necessary for the digestion of dietary fat and the absorption of long-chain fatty acids. Glycine plays an important role in metabolic regulation, anti-oxidative reactions, and neurological function. Thus, this nutrient has been used to: (1) prevent tissue injury; (2) enhance anti-oxidative capacity; (3) promote protein synthesis and wound healing; (4) improve immunity; and (5) treat metabolic disorders in obesity, diabetes, cardiovascular disease, ischemia-reperfusion injuries, cancers, and various inflammatory diseases. These multiple beneficial effects of glycine, coupled with its insufficient de novo synthesis, support the notion that it is a conditionally essential and also a functional amino acid for mammals (including pigs and humans).
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Mulligan JL. Neonatal nonketotic hyperglycinemia: a case study and review of management for the advanced practice nurse. Neonatal Netw 2013; 32:95-103. [PMID: 23477976 DOI: 10.1891/0730-0832.32.2.95] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Nonketotic hyperglycinemia (NKH) is an autosomal recessive inborn error of glycine metabolism. In this article, I will present the case of baby girl S. who presented to the emergency room on Day 4 of life with severe lethargy, seizures, and respiratory depression requiring mechanical ventilation. A diagnosis of NKH was made secondary to elevated plasma and cerebrospinal fluid glycine concentrations. I will review the pathophysiology of NKH, methods of diagnosis, and the differential diagnosis. There are a variety of different pharmacologic and alternative therapies for NKH. Despite these treatments, the prognosis for infants with NKH is poor, with severe neurologic impairment, intractable seizures, and death common before 5 years of age. I will address the role of the advanced practice nurse in caring for an infant with NKH including clinical, educational, and research implications.
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Williams LH, Miller KA, Dahl HHM, Manji SSM. Characterization of a novel ENU-generated myosin VI mutant mouse strain with congenital deafness and vestibular dysfunction. Hear Res 2013; 299:53-62. [PMID: 23485424 DOI: 10.1016/j.heares.2013.02.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Revised: 02/12/2013] [Accepted: 02/15/2013] [Indexed: 11/30/2022]
Abstract
Myosin VI (Myo6) is known to play an important role in the mammalian auditory and vestibular systems. We have identified a novel N-ethyl-N-nitrosourea mutagenised mouse strain, charlie, carrying an intronic Myo6 splice site mutation. This mutation (IVS5+5G > A) results in skipping of exon 5, and is predicted to cause a frameshift and premature termination of the protein. We detected essentially no Myo6 transcript in tissue from charlie homozygous mutant mice (Myo6(chl/chl)). Myo6(chl/chl) mice exhibit vestibular dysfunction and profound hearing impairment when first tested at four weeks of age. Analysis of vestibular and cochlear hair cells by scanning electron microscopy and immunohistochemistry revealed highly disorganised hair bundles with irregular orientation and kinocilium position at postnatal stage P2-P3. Within a few weeks, the majority of hair cell stereocilia are missing, or fused and elongated, and degeneration of the sensory epithelium occurs. This novel mouse strain will be an important resource in elucidating the role myosin VI plays in the mammalian auditory system, as well as its non-auditory functions.
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Affiliation(s)
- Louise H Williams
- Genetic Hearing Research Laboratory, Murdoch Childrens Research Institute, Royal Children's Hospital, Parkville, Victoria 3052, Australia.
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25
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Yoon IA, Lee NM, Yoo BH, Lee BS, Yoo HW. Two novel missense mutations observed in nonketotic hyperglycinemia. Pediatr Neurol 2012; 46:401-3. [PMID: 22633639 DOI: 10.1016/j.pediatrneurol.2012.03.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2012] [Accepted: 03/08/2012] [Indexed: 11/15/2022]
Abstract
Nonketotic hyperglycinemia, also known as glycine encephalopathy, is an autosomal recessive disorder of an inborn error of the glycine metabolism, caused by deficiency in the mitochondrial glycine cleavage enzyme. The majority of cases are caused by mutations in P-protein, one of the four components of the glycine cleavage enzyme, glycine decarboxylase. We describe a male neonate with hypotonia, hiccups, and persistent apnea, but without seizures. The patient's glycine level in cerebrospinal fluid and plasma was 328.3 nmol/mL (reference value, 2.2-14.2 nmol/mL) and 1439 nmol/mL (reference value, 232-740 nmol/mL), respectively. The cerebrospinal fluid/plasma ratio of 0.228 represented an increase (normal range, <0.04). Two novel heterozygous missense mutations (c.1130C>T (p.A377V) and c.2081_2088del (p.A694DfsX11) in exons 8 and 18) in the glycine decarboxylase gene confirmed the diagnosis of nonketotic hyperglycinemia.
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Affiliation(s)
- In Ae Yoon
- Department of Pediatrics, College of Medicine, Chung-Ang University, Dongjak-gu, Seoul, Korea
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26
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Rodríguez-Benítez V, Arranz JA, Mata C, Pérez-Navero JL, Gil-Campos M. [A new mutation in the GLDC gene in non-ketotic hyperglycinaemia]. An Pediatr (Barc) 2011; 80:e7-8. [PMID: 22206881 DOI: 10.1016/j.anpedi.2011.11.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2011] [Revised: 09/24/2011] [Accepted: 11/13/2011] [Indexed: 10/14/2022] Open
Affiliation(s)
| | - J A Arranz
- Unidad Metabólica, Hospital Universitario Vall d'Hebron, Barcelona, España
| | - C Mata
- Unidad de Neonatología, Hospital Universitario Reina Sofía, Córdoba, España
| | - J L Pérez-Navero
- Unidad de Metabolismo e Investigación Pediátrica, Hospital Universitario Reina Sofía, Córdoba, España. Instituto Maimónides de Investigación Biomédica, Córdoba (IMIBIC), España
| | - M Gil-Campos
- Unidad de Metabolismo e Investigación Pediátrica, Hospital Universitario Reina Sofía, Córdoba, España. Instituto Maimónides de Investigación Biomédica, Córdoba (IMIBIC), España.
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Meyer S, Acquaviva C, Shamdeen MG, Haas D, Vianey-Saban C. A novel missense mutation in a neonate with nonketotic hyperglycinemia. Pediatr Neurol 2010; 43:363-7. [PMID: 20933183 DOI: 10.1016/j.pediatrneurol.2010.05.025] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/11/2010] [Revised: 04/15/2010] [Accepted: 05/24/2010] [Indexed: 11/19/2022]
Abstract
Nonketotic hyperglycinemia (OMIM #605899), also known as glycine encephalopathy, is an autosomal recessive disorder of glycine metabolism caused by a defect in the glycine cleavage system. A term neonate developed progressive lethargy, muscular hypotonia, and respiratory insufficiency on day 2 after birth, but no overt clinical seizures. Amplitude-integrated electroencephalography indicated a continuous burst-suppression pattern. The diagnosis of nonketotic hyperglycinemia was made biochemically and was confirmed by genetic studies, which revealed two missense mutations (one not previously described) within the glycine decarboxylase gene, GLDC. Nonketotic hyperglycinemia should be incorporated into the differential diagnosis of neonatal hypotonia, to avoid an erroneous diagnosis of sepsis or hypoxic ischemic injury. Amplitude-integrated electroencephalography may be helpful in the initial assessment of severely sick and hypotonic neonates without overt clinical seizures, and may direct further diagnostic evaluation.
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Affiliation(s)
- Sascha Meyer
- Department of Pediatric and Neonatal Intensive Care Medicine, University Hospital of Saarland, Homburg, Germany.
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Hellani A, Sammour A, Johansson L, El-Sheikh A. Delivery of a normal baby after preimplantation genetic diagnosis for non-ketotic hyperglycinaemia. Reprod Biomed Online 2008; 16:893-7. [PMID: 18549703 DOI: 10.1016/s1472-6483(10)60158-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Non-ketotic hyperglycinaemia (NKH), or glycine encephalopathy, is an autosomal recessive neurometabolic disease caused by defective activity of the glycine cleavage system. Up to 80% of NKH cases are caused by mutations in the P protein encoded by the glycine decarboxylase (GLDC) gene. GLDC deletions were identified in approximately 20% of NKH mutant alleles and resulted in a severe neonatal form of the disease. Given the difficult management of NKH caused by GLDC deletion, it was decided to adopt a preventative approach in a family with a history of this disease by using preimplantation genetic diagnosis (PGD). In this family, there is a deletion in the 5' UTR (untranslated region) up to the third intron of GLDC. PGD was carried out using multiple displacement amplification (MDA) and fluorescent polymerase chain reaction (PCR). This resulted in a singleton pregnancy after transfer of three unaffected embryos. Post-natal DNA testing of the newborn confirmed the PGD result. This is the first report of a successful PGD cycle intended to prevent the occurrence of NKH in a family with a history of the disease. The use of MDA coupled with fluorescent PCR is a very encouraging strategy leading to both low allele drop-out (2/40) and failure of amplification (0/40) rates.
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Affiliation(s)
- Ali Hellani
- Saad Specialist Hospital, Al-Khobar, 31952, Kingdom of Saudi Arabia.
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Harvey RJ, Carta E, Pearce BR, Chung SK, Supplisson S, Rees MI, Harvey K. A critical role for glycine transporters in hyperexcitability disorders. Front Mol Neurosci 2008; 1:1. [PMID: 18946534 PMCID: PMC2526004 DOI: 10.3389/neuro.02.001.2008] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2008] [Accepted: 01/30/2008] [Indexed: 11/13/2022] Open
Abstract
Defects in mammalian glycinergic neurotransmission result in a complex motor disorder characterized by neonatal hypertonia and an exaggerated startle reflex, known as hyperekplexia (OMIM 149400). This affects newborn children and is characterized by noise or touch-induced seizures that result in muscle stiffness and breath-holding episodes. Although rare, this disorder can have serious consequences, including brain damage and/or sudden infant death. The primary cause of hyperekplexia is missense and non-sense mutations in the glycine receptor (GlyR) α1 subunit gene (GLRA1) on chromosome 5q33.1, although we have also discovered rare mutations in the genes encoding the GlyR β subunit (GLRB) and the GlyR clustering proteins gephyrin (GPNH) and collybistin (ARHGEF9). Recent studies of the Na+/Cl−-dependent glycine transporters GlyT1 and GlyT2 using mouse knockout models and human genetics have revealed that mutations in GlyT2 are a second major cause of hyperekplexia, while the phenotype of the GlyT1 knockout mouse resembles a devastating neurological disorder known as glycine encephalopathy (OMIM 605899). These findings highlight the importance of these transporters in regulating the levels of synaptic glycine.
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Affiliation(s)
- Robert J Harvey
- Department of Pharmacology, The School of Pharmacy London, UK
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Abstract
Glycine encephalopathy (GCE) is an autosomal recessive error of glycine degradation, resulting in a poor outcome with severe mental retardation, intractable seizures and spasticity. Milder variants with a significantly better outcome have been reported, but an early prediction of the long-term outcome is not yet possible. With regard to the long-term outcome, the data reported in the literature of children with different GCE forms were compared. Determination of cerebrospinal fluid and plasma glycine concentrations at the time of diagnosis were not useful in differentiating mild and severe outcomes. By contrast, several clinical parameters correlate with a poor outcome: spastic quadriparesis, truncal hypotonia, typical electroencephalography patterns, congenital and cerebral malformations (e.g., corpus callosum hypoplasia). Hyperactivity, behavioral problems and choreiform movement disorders are associated with a milder outcome. Thus, prediction of the outcome of GCE may be facilitated by searching for selected clinical parameters. In addition, early neuroimaging may be a valuable tool in predicting the outcome of GCE.
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Affiliation(s)
- Julia B Hennermann
- Otto Heubner Center for Pediatric & Adolescent Medicine, Charité Universitätsmedizin Berlin Augustenburger Platz 1, 13353 Berlin, Germany
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