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Arefieva AB, Komleva PD, Naumenko VS, Khotskin NV, Kulikov AV. In Vitro and In Vivo Chaperone Effect of (R)-2-amino-6-(1R, 2S)-1,2-dihydroxypropyl)-5,6,7,8-tetrahydropterin-4(3H)-one on the C1473G Mutant Tryptophan Hydroxylase 2. Biomolecules 2023; 13:1458. [PMID: 37892138 PMCID: PMC10604173 DOI: 10.3390/biom13101458] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Revised: 09/14/2023] [Accepted: 09/17/2023] [Indexed: 10/29/2023] Open
Abstract
Tryptophan hydroxylase 2 (TPH2) is the key and rate-limiting enzyme of serotonin (5-HT) synthesis in the mammalian brain. The 1473G mutation in the Tph2 gene decreases TPH2 activity in the mouse brain by twofold. (R)-2-amino-6-(1R, 2S)-1,2-dihydroxypropyl)-5,6,7,8-tetrahydropterin-4(3H)-one (BH4) is a pharmacological chaperone for aromatic amino acid hydroxylases. In the present study, chaperone effects of BH4 on the mutant C1473G TPH2 were investigated in vitro and in vivo. In vitro BH4 increased the thermal stability (T50 value) of mutant and wild-type TPH2 molecules. At the same time, neither chronic (twice per day for 7 days) intraperitoneal injection of 48.3 mg/kg of BH4 nor a single intraventricular administration of 60 μg of the drug altered the mutant TPH2 activity in the brain of Balb/c mice. This result indicates that although BH4 shows a chaperone effect in vitro, it is unable to increase the activity of mutant TPH2 in vivo.
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Affiliation(s)
- Alla B. Arefieva
- Department of Genetic Collections of Neural Disorders, Federal Research Center Institute of Cytology and Genetic Siberian Branch of Russian Academy of Sciences, 630090 Novosibirsk, Russia; (A.B.A.); (N.V.K.)
| | - Polina D. Komleva
- Department of Psychoneuropharmacology, Federal Research Center Institute of Cytology and Genetic Siberian Branch of Russian Academy of Sciences, 630090 Novosibirsk, Russia; (P.D.K.); (V.S.N.)
| | - Vladimir S. Naumenko
- Department of Psychoneuropharmacology, Federal Research Center Institute of Cytology and Genetic Siberian Branch of Russian Academy of Sciences, 630090 Novosibirsk, Russia; (P.D.K.); (V.S.N.)
- Departments of Behavioral Neurogenomics, Federal Research Center Institute of Cytology and Genetic Siberian Branch of Russian Academy of Sciences, 630090 Novosibirsk, Russia
| | - Nikita V. Khotskin
- Department of Genetic Collections of Neural Disorders, Federal Research Center Institute of Cytology and Genetic Siberian Branch of Russian Academy of Sciences, 630090 Novosibirsk, Russia; (A.B.A.); (N.V.K.)
| | - Alexander V. Kulikov
- Department of Genetic Collections of Neural Disorders, Federal Research Center Institute of Cytology and Genetic Siberian Branch of Russian Academy of Sciences, 630090 Novosibirsk, Russia; (A.B.A.); (N.V.K.)
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2
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Carkaci-Salli N, Bewley MC, Tekin I, Flanagan JM, Vrana KE. The A328 V/E (rs2887147) polymorphisms in human tryptophan hydroxylase 2 compromise enzyme activity. Biochem Biophys Rep 2023; 35:101527. [PMID: 37608910 PMCID: PMC10440358 DOI: 10.1016/j.bbrep.2023.101527] [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: 06/20/2023] [Revised: 08/03/2023] [Accepted: 08/03/2023] [Indexed: 08/24/2023] Open
Abstract
Human tryptophan hydroxylase 2 (hTPH2) is the rate-limiting enzyme for serotonin biosynthesis in the brain. A number of naturally-occurring single nucleotide polymorphisms (SNPs) have been reported for hTPH2. We investigated the activity and kinetic characteristics of the most common missense polymorphism rs2887147 (A328 V/E; 0.92% allelic frequency for the two different reported SNPs at the same site) using bacterially expressed hTPH2. The recombinant full-length enzyme A328E had no measurable enzyme activity, but A328V displayed decreased enzyme activity (Vmax). A328V also displayed substrate inhibition and decreased stability compared to the wild-type enzyme. By contrast, in constructs lacking the N-terminal 150 amino acid regulatory domain, the A328V substitution had no effect; that is, there was no substrate inhibition, enzyme stabilities (for wild-type and A328V) were dramatically increased, and Vmax values were not different (while the A328E variant remained inactive). These findings, in combination with molecular modeling, suggest that substitutions at A328 affect catalytic activity by altering the conformational freedom of the regulatory domain. The reduced activity and substrate inhibition resulting from these polymorphisms may ultimately reduce serotonin synthesis and contribute to behavioral perturbations, emotional stress, and eating disorders.
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Affiliation(s)
- Nurgul Carkaci-Salli
- Departments of Pharmacology, Pennsylvania State University College of Medicine, Hershey, PA, 17033, USA
| | - Maria C. Bewley
- Biochemistry and Molecular Biology, Pennsylvania State University College of Medicine, Hershey, PA, 17033, USA
| | - Izel Tekin
- Departments of Pharmacology, Pennsylvania State University College of Medicine, Hershey, PA, 17033, USA
| | - John M. Flanagan
- Biochemistry and Molecular Biology, Pennsylvania State University College of Medicine, Hershey, PA, 17033, USA
| | - Kent E. Vrana
- Departments of Pharmacology, Pennsylvania State University College of Medicine, Hershey, PA, 17033, USA
- Pennsylvania State University College of Medicine, Hershey, PA, 17033, USA
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3
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Pereira GRC, Tavares GDB, de Freitas MC, De Mesquita JF. In silico analysis of the tryptophan hydroxylase 2 (TPH2) protein variants related to psychiatric disorders. PLoS One 2020; 15:e0229730. [PMID: 32119710 PMCID: PMC7051086 DOI: 10.1371/journal.pone.0229730] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Accepted: 02/12/2020] [Indexed: 11/19/2022] Open
Abstract
The tryptophan hydroxylase 2 (TPH2) enzyme catalyzes the first step of serotonin biosynthesis. Serotonin is known for its role in several homeostatic systems related to sleep, mood, and food intake. As the reaction catalyzed by TPH2 is the rate-limiting step of serotonin biosynthesis, mutations in TPH2 have been associated with several psychiatric disorders (PD). This work undertakes an in silico analysis of the effects of genetic mutations in the human TPH2 protein. Ten algorithms were used to predict the functional and stability effects of the TPH2 mutations. ConSurf was used to estimate the evolutionary conservation of TPH2 amino acids. GROMACS was used to perform molecular dynamics (MD) simulations of TPH2 WT and P260S, R303W, and R441H, which had already been associated with the development of PD. Forty-six TPH2 variants were compiled from the literature. Among the analyzed variants, those occurring at the catalytic domain were shown to be more damaging to protein structure and function. The ConSurf analysis indicated that the mutations affecting the catalytic domain were also more conserved throughout evolution. The variants S364K and S383F were predicted to be deleterious by all the functional algorithms used and occurred at conserved positions, suggesting that they might be deleterious. The MD analyses indicate that the mutations P206S, R303W, and R441H affect TPH2 flexibility and essential mobility at the catalytic and oligomerization domains. The variants P206S, R303W, and R441H also exhibited alterations in dimer binding affinity and stability throughout the simulations. Thus, these mutations may impair TPH2 functional interactions and, consequently, its function, leading to the development of PD. Furthermore, we developed a database, SNPMOL (http://www.snpmol.org/), containing the results presented in this paper. Understanding the effects of TPH2 mutations on protein structure and function may lead to improvements in existing treatments for PD and facilitate the design of further experiments.
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Affiliation(s)
- Gabriel Rodrigues Coutinho Pereira
- Bioinformatics and Computational Biology Laboratory, Department of Genetics and Molecular Biology, Federal University of the State of Rio de Janeiro (UNIRIO), Rio de Janeiro, Rio de Janeiro, Brazil
| | - Gustavo Duarte Bocayuva Tavares
- Bioinformatics and Computational Biology Laboratory, Department of Genetics and Molecular Biology, Federal University of the State of Rio de Janeiro (UNIRIO), Rio de Janeiro, Rio de Janeiro, Brazil
| | - Marta Costa de Freitas
- Bioinformatics and Computational Biology Laboratory, Department of Genetics and Molecular Biology, Federal University of the State of Rio de Janeiro (UNIRIO), Rio de Janeiro, Rio de Janeiro, Brazil
| | - Joelma Freire De Mesquita
- Bioinformatics and Computational Biology Laboratory, Department of Genetics and Molecular Biology, Federal University of the State of Rio de Janeiro (UNIRIO), Rio de Janeiro, Rio de Janeiro, Brazil
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4
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Zhao ZM, Campbell MC, Li N, Lee DSW, Zhang Z, Townsend JP. Detection of Regional Variation in Selection Intensity within Protein-Coding Genes Using DNA Sequence Polymorphism and Divergence. Mol Biol Evol 2018; 34:3006-3022. [PMID: 28962009 DOI: 10.1093/molbev/msx213] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Numerous approaches have been developed to infer natural selection based on the comparison of polymorphism within species and divergence between species. These methods are especially powerful for the detection of uniform selection operating across a gene. However, empirical analyses have demonstrated that regions of protein-coding genes exhibiting clusters of amino acid substitutions are subject to different levels of selection relative to other regions of the same gene. To quantify this heterogeneity of selection within coding sequences, we developed Model Averaged Site Selection via Poisson Random Field (MASS-PRF). MASS-PRF identifies an ensemble of intragenic clustering models for polymorphic and divergent sites. This ensemble of models is used within the Poisson Random Field framework to estimate selection intensity on a site-by-site basis. Using simulations, we demonstrate that MASS-PRF has high power to detect clusters of amino acid variants in small genic regions, can reliably estimate the probability of a variant occurring at each nucleotide site in sequence data and is robust to historical demographic trends and recombination. We applied MASS-PRF to human gene polymorphism derived from the 1,000 Genomes Project and divergence data from the common chimpanzee. On the basis of this analysis, we discovered striking regional variation in selection intensity, indicative of positive or negative selection, in well-defined domains of genes that have previously been associated with neurological processing, immunity, and reproduction. We suggest that amino acid-altering substitutions within these regions likely are or have been selectively advantageous in the human lineage, playing important roles in protein function.
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Affiliation(s)
- Zi-Ming Zhao
- Department of Biostatistics, Yale University, New Haven, CT
| | - Michael C Campbell
- Department of Biostatistics, Yale University, New Haven, CT.,Department of Biology, Howard University, Washington, DC
| | - Ning Li
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT
| | - Daniel S W Lee
- Department of Biostatistics, Yale University, New Haven, CT
| | - Zhang Zhang
- CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, China
| | - Jeffrey P Townsend
- Department of Biostatistics, Yale University, New Haven, CT.,Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT.,Program in Computational Biology and Bioinformatics, Yale University, New Haven, CT
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Mora-Villalobos JA, Zeng AP. Protein and pathway engineering for the biosynthesis of 5-hydroxytryptophan in Escherichia coli. Eng Life Sci 2017; 17:892-899. [PMID: 32624837 DOI: 10.1002/elsc.201700064] [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: 03/15/2017] [Revised: 05/16/2017] [Accepted: 05/29/2017] [Indexed: 11/06/2022] Open
Abstract
The hydroxylation of tryptophan is an important reaction in the biosynthesis of natural products. 5-Hydroxytryptophan (5HTP) is not only an important compound for its pharmaceutical value but also because it is the precursor of other molecules, such as serotonin. In this study, we have extended the metabolism of an E. coli strain to produce 5HTP. Aromatic amino acid hydroxylase from Cupriavidus taiwanensis (CtAAAH) was selected using an in silico structure-based approach. We have predicted and selected several substrate-determining residues using sequence, phylogenetic and functional divergence analyses; we also did rational design on CtAAAH to shift the enzyme preference from phenylalanine to tryptophan. Whole cell bioconversion assays were used to show the effect of predicted sites. In general, all of them decreased the preference toward phenylalanine and increased the tryptophan synthesis activity. The best performer, CtAAAH-W192F, was transformed into a strain that had the tryptophanase gene disrupted and carried a human tetrahydrobiopterin (BH4) regeneration pathway. The resulting strain was capable of synthesizing 2.5 mM 5HTP after 24 hours. This work demonstrates the application of computational approaches for protein engineering and further coupling with the bacterial metabolism.
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Affiliation(s)
- José-Aníbal Mora-Villalobos
- Institute of Bioprocess and Biosystems Engineering Hamburg University of Technology Hamburg Germany.,Centro Nacional de Innovaciones Biotecnológicas Centro Nacional de Alta Tecnología San Jose Costa Rica
| | - An-Ping Zeng
- Institute of Bioprocess and Biosystems Engineering Hamburg University of Technology Hamburg Germany
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6
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Martinez AF, Abe Y, Hong S, Molyneux K, Yarnell D, Löhr H, Driever W, Acosta MT, Arcos-Burgos M, Muenke M. An Ultraconserved Brain-Specific Enhancer Within ADGRL3 (LPHN3) Underpins Attention-Deficit/Hyperactivity Disorder Susceptibility. Biol Psychiatry 2016; 80:943-954. [PMID: 27692237 PMCID: PMC5108697 DOI: 10.1016/j.biopsych.2016.06.026] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Revised: 06/28/2016] [Accepted: 06/30/2016] [Indexed: 12/22/2022]
Abstract
BACKGROUND Genetic factors predispose individuals to attention-deficit/hyperactivity disorder (ADHD). Previous studies have reported linkage and association to ADHD of gene variants within ADGRL3. In this study, we functionally analyzed noncoding variants in this gene as likely pathological contributors. METHODS In silico, in vitro, and in vivo approaches were used to identify and characterize evolutionary conserved elements within the ADGRL3 linkage region (~207 Kb). Family-based genetic analyses of 838 individuals (372 affected and 466 unaffected patients) identified ADHD-associated single nucleotide polymorphisms harbored in some of these conserved elements. Luciferase assays and zebrafish green fluorescent protein transgenesis tested conserved elements for transcriptional enhancer activity. Electromobility shift assays were used to verify transcription factor-binding disruption by ADHD risk alleles. RESULTS An ultraconserved element was discovered (evolutionary conserved region 47) that functions as a transcriptional enhancer. A three-variant ADHD risk haplotype in evolutionary conserved region 47, formed by rs17226398, rs56038622, and rs2271338, reduced enhancer activity by 40% in neuroblastoma and astrocytoma cells (pBonferroni < .0001). This enhancer also drove green fluorescent protein expression in the zebrafish brain in a tissue-specific manner, sharing aspects of endogenous ADGRL3 expression. The rs2271338 risk allele disrupts binding of YY1 transcription factor, an important factor in the development and function of the central nervous system. Expression quantitative trait loci analysis of postmortem human brain tissues revealed an association between rs2271338 and reduced ADGRL3 expression in the thalamus. CONCLUSIONS These results uncover the first functional evidence of common noncoding variants with potential implications for the pathology of ADHD.
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7
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Pelosi B, Pratelli M, Migliarini S, Pacini G, Pasqualetti M. Generation of a Tph2 Conditional Knockout Mouse Line for Time- and Tissue-Specific Depletion of Brain Serotonin. PLoS One 2015; 10:e0136422. [PMID: 26291320 PMCID: PMC4546246 DOI: 10.1371/journal.pone.0136422] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Accepted: 08/03/2015] [Indexed: 11/29/2022] Open
Abstract
Serotonin has been gaining increasing attention during the last two decades due to the dual function of this monoamine as key regulator during critical developmental events and as neurotransmitter. Importantly, unbalanced serotonergic levels during critical temporal phases might contribute to the onset of neuropsychiatric disorders, such as schizophrenia and autism. Despite increasing evidences from both animal models and human genetic studies have underpinned the importance of serotonin homeostasis maintenance during central nervous system development and adulthood, the precise role of this molecule in time-specific activities is only beginning to be elucidated. Serotonin synthesis is a 2-step process, the first step of which is mediated by the rate-limiting activity of Tph enzymes, belonging to the family of aromatic amino acid hydroxylases and existing in two isoforms, Tph1 and Tph2, responsible for the production of peripheral and brain serotonin, respectively. In the present study, we generated and validated a conditional knockout mouse line, Tph2flox/flox, in which brain serotonin can be effectively ablated with time specificity. We demonstrated that the Cre-mediated excision of the third exon of Tph2 gene results in the production of a Tph2null allele in which we observed the near-complete loss of brain serotonin, as well as the growth defects and perinatal lethality observed in serotonin conventional knockouts. We also revealed that in mice harbouring the Tph2null allele, but not in wild-types, two distinct Tph2 mRNA isoforms are present, namely Tph2Δ3 and Tph2Δ3Δ4, with the latter showing an in-frame deletion of amino acids 84–178 and coding a protein that could potentially retain non-negligible enzymatic activity. As we could not detect Tph1 expression in the raphe, we made the hypothesis that the Tph2Δ3Δ4 isoform can be at the origin of the residual, sub-threshold amount of serotonin detected in the brain of Tph2null/null mice. Finally, we set up a tamoxifen administration protocol that allows an efficient, time-specific inactivation of brain serotonin synthesis. On the whole, we generated a suitable genetic tool to investigate how serotonin depletion impacts on time-specific events during central nervous system development and adulthood life.
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Affiliation(s)
- Barbara Pelosi
- Department of Biology, Unit of Cell and Developmental Biology, University of Pisa, S.S.12 Abetone e Brennero 4, 56127, Pisa, Italy
| | - Marta Pratelli
- Department of Biology, Unit of Cell and Developmental Biology, University of Pisa, S.S.12 Abetone e Brennero 4, 56127, Pisa, Italy
| | - Sara Migliarini
- Department of Biology, Unit of Cell and Developmental Biology, University of Pisa, S.S.12 Abetone e Brennero 4, 56127, Pisa, Italy
| | - Giulia Pacini
- Department of Biology, Unit of Cell and Developmental Biology, University of Pisa, S.S.12 Abetone e Brennero 4, 56127, Pisa, Italy
| | - Massimo Pasqualetti
- Department of Biology, Unit of Cell and Developmental Biology, University of Pisa, S.S.12 Abetone e Brennero 4, 56127, Pisa, Italy
- Center for Neuroscience and Cognitive Systems@UniTn, Istituto Italiano di Tecnologia, Via Bettini 31, 38068, Rovereto (TN), Italy
- * E-mail:
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8
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Kulikov AV, Popova NK. Tryptophan hydroxylase 2 in seasonal affective disorder: underestimated perspectives? Rev Neurosci 2015; 26:679-90. [DOI: 10.1515/revneuro-2015-0013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Accepted: 05/26/2015] [Indexed: 01/14/2023]
Abstract
AbstractSeasonal affective disorder (SAD) is characterized by recurrent depression occurring generally in fall/winter. Numerous pieces of evidence indicate the association of SAD with decreased brain neurotransmitter serotonin (5-HT) system functioning. Tryptophan hydroxylase 2 (TPH2) is the key and rate-limiting enzyme in 5-HT synthesis in the brain. This paper concentrates on the relationship between TPH2 activity and mood disturbances, the association between human
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Carkaci-Salli N, Salli U, Tekin I, Hengst JA, Zhao MK, Gilman TL, Andrews AM, Vrana KE. Functional characterization of the S41Y (C2755A) polymorphism of tryptophan hydroxylase 2. J Neurochem 2014; 130:748-58. [PMID: 24899127 DOI: 10.1111/jnc.12779] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Accepted: 05/23/2014] [Indexed: 01/11/2023]
Abstract
Human TPH2 (hTPH2) catalyzes the rate-limiting step in CNS serotonin biosynthesis. We characterized a single-nucleotide polymorphism (C2755A) in the hTPH2 gene that substitutes tyrosine for serine at position 41 in the regulatory domain of the enzyme. This polymorphism is associated with bipolar disorder and peripartum depression in a Chinese population. Recombinant h TPH2 human proteins were expressed in bacteria and also stably expressed in PC12 cells. Following bacterial expression and purification, the tyrosine for serine substitution at position 41 (S41Y) polymorphic enzyme displayed increased Vmax with unchanged Km values. By contrast, enzyme stability was decreased in vitro from 32 min to 4 min (37 °C) for the S41Y enzyme (as compared to the wild-type enzyme). The S41Y polymorphism decreased cyclic AMP-dependent protein kinase A-mediated phosphorylation ~ 50% relative to wild-type hTPH2, suggesting that the S41Y mutation may disrupt the post-translational regulation of this enzyme. Transfected PC12 cells expressed hTPH2 mRNA, active protein, and synthesized and released serotonin. Paradoxically, while S41Y-transfected PC12 cells expressed higher levels of hTPH2 than wild type, they synthesized less serotonin. These findings suggest a modified regulation of the S41Y gene variant leading to altered regulation and reduced neurotransmitter synthesis that may contribute to association of the polymorphism with bipolar disorder and depression. We report the functional implications of a polymorphic human tryptophan hydroxylase-2 gene associated with depression and bipolar disorder. The polymorphic enzyme (serine-41 converted to tyrosine) has increased activity, but decreased enzyme stability and serotonin production. Moreover, cyclic AMP-dependent protein kinase (PKA)-mediated phosphorylation of the mutant enzyme is decreased suggesting modified regulation of the S41Y variant leading to altered serotonin.
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Affiliation(s)
- Nurgul Carkaci-Salli
- Department of Pharmacology, Penn State College of Medicine, Hershey, Pennsylvania, USA
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10
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Fossbakk A, Kleppe R, Knappskog PM, Martinez A, Haavik J. Functional studies of tyrosine hydroxylase missense variants reveal distinct patterns of molecular defects in Dopa-responsive dystonia. Hum Mutat 2014; 35:880-90. [PMID: 24753243 PMCID: PMC4312968 DOI: 10.1002/humu.22565] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2014] [Accepted: 04/10/2014] [Indexed: 11/23/2022]
Abstract
Congenital tyrosine hydroxylase deficiency (THD) is found in autosomal-recessive Dopa-responsive dystonia and related neurological syndromes. The clinical manifestations of THD are variable, ranging from early-onset lethal disease to mild Parkinson disease-like symptoms appearing in adolescence. Until 2014, approximately 70 THD patients with a total of 40 different disease-related missense mutations, five nonsense mutations, and three mutations in the promoter region of the tyrosine hydroxylase (TH) gene have been reported. We collected clinical and biochemical data in the literature for all variants, and also generated mutant forms of TH variants previously not studied (N = 23). We compared the in vitro solubility, thermal stability, and kinetic properties of the TH variants to determine the cause(s) of their impaired enzyme activity, and found great heterogeneity in all these properties among the mutated forms. Some TH variants had specific kinetic anomalies and phenylalanine hydroxylase, and Dopa oxidase activities were measured for variants that showed signs of altered substrate binding. p.Arg233His, p.Gly247Ser, and p.Phe375Leu had shifted substrate specificity from tyrosine to phenylalanine and Dopa, whereas p.Cys359Phe had an impaired activity toward these substrates. The new data about pathogenic mechanisms presented are expected to contribute to develop individualized therapy for THD patients.
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Affiliation(s)
- Agnete Fossbakk
- Department of Biomedicine, University of Bergen, Bergen, Norway; K. G. Jebsen Centre for Research on Neuropsychiatric Disorders, University of Bergen, Bergen, Norway
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11
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Siesser WB, Sachs BD, Ramsey AJ, Sotnikova TD, Beaulieu JM, Zhang X, Caron MG, Gainetdinov RR. Chronic SSRI treatment exacerbates serotonin deficiency in humanized Tph2 mutant mice. ACS Chem Neurosci 2013; 4:84-8. [PMID: 23336047 DOI: 10.1021/cn300127h] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Accepted: 10/01/2012] [Indexed: 01/12/2023] Open
Abstract
Selective serotonin reuptake inhibitors (SSRIs) are a major class of antidepressants that act by blocking inward transport of serotonin (5-HT) into presynaptic neurons mediated by the serotonin transporter (SERT). Both reuptake and ongoing synthesis are essential in supporting intraneuronal serotonin concentrations in serotonergic neurons. A rare mutation in tryptophan hydroxylase 2 (Tph2), the rate limiting enzyme for 5-HT synthesis, was identified in several patients with major depression, and knock-in mice expressing the analogous mutation (R439H Tph2 KI) show 80% reduction in 5-HT synthesis and tissue levels. Chronic treatment with SSRIs (fluoxetine and paroxetine) resulted in a dramatic further depletion of 5-HT tissue levels in R439H Tph2 KI mice (down to 1-3% of wild type levels) while having little effects in wild-type controls. Treatment with the 5-HT precursor 5-hydroxytryptophan (5-HTP) restored 5-HT tissue content in mutant mice, and cotreatment with 5-HTP and fluoxetine essentially prevented the depleting effect of a chronic SSRI. These data demonstrate that chronic SSRI treatment could further exacerbate the 5-HT deficiency in Tph2 mutation carriers, and this can be prevented by 5-HTP supplementation.
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Affiliation(s)
- William B. Siesser
- Department of Cell Biology, Duke University, Durham, North Carolina 27710, United
States
| | - Benjamin D. Sachs
- Department of Cell Biology, Duke University, Durham, North Carolina 27710, United
States
| | - Amy J. Ramsey
- Department of Pharmacology
and
Toxicology, University of Toronto, ON,
Canada M5S 1A8
| | - Tatyana D. Sotnikova
- Department
of Neuroscience and
Brain Technologies, Istituto Italiano di Tecnologia (IIT), Via Morego 30, Genova, 16163 Italy
| | - Jean-Martin Beaulieu
- Department of Psychiatry and
Neuroscience, Université Laval/IUSMQ, Québec, Canada
| | - Xiaodong Zhang
- Neuroscience & Behavioral Disorders Program, Duke−NUS Graduate Medical School Singapore, Singapore
- Department of Physiology, National University of Singapore, Singapore
- Department
of Psychiatry and
Behavioral Sciences, Duke University Medical Center, Durham, North Carolina 27710, United States
| | - Marc G. Caron
- Department of Cell Biology, Duke University, Durham, North Carolina 27710, United
States
- Department of Neurobiology, Duke University Medical Center, Durham, North Carolina
27710, United States
| | - Raul R. Gainetdinov
- Department of Cell Biology, Duke University, Durham, North Carolina 27710, United
States
- Department
of Neuroscience and
Brain Technologies, Istituto Italiano di Tecnologia (IIT), Via Morego 30, Genova, 16163 Italy
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12
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Jacobsen JPR, Medvedev IO, Caron MG. The 5-HT deficiency theory of depression: perspectives from a naturalistic 5-HT deficiency model, the tryptophan hydroxylase 2Arg439His knockin mouse. Philos Trans R Soc Lond B Biol Sci 2012; 367:2444-59. [PMID: 22826344 DOI: 10.1098/rstb.2012.0109] [Citation(s) in RCA: 124] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
A decreased level of brain 5-hydroxytryptamine (5-HT) has been theorized to be a core pathogenic factor in depression for half a century. The theory arose from clinical observations that drugs enhancing extracellular levels of 5-HT (5-HT(Ext)) have antidepressant effects in many patients. However, whether such drugs indeed correct a primary deficit remains unresolved. Still, a number of anomalies in putative biomarkers of central 5-HT function have been repeatedly reported in depression patients over the past 40 years, collectively indicating that 5-HT deficiency could be present in depression, particularly in severely ill and/or suicidal patients. This body of literature on putative 5-HT biomarker anomalies and depression has recently been corroborated by data demonstrating that such anomalies indeed occur consequent to severely reduced 5-HT(Ext) levels in a mouse model of naturalistic 5-HT deficiency, the tryptophan hydroxylase 2 His(439) knockin (Tph2KI) mouse. In this review, we will critically assess the evidence for 5-HT deficiency in depression and the possible role of polymorphisms in the Tph2 gene as a causal factor in 5-HT deficiency, the latter investigated from a clinical as well as preclinical angle.
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Affiliation(s)
- Jacob P R Jacobsen
- Department of Cell Biology, Duke University Medical Center, , Durham, NC 27710, USA.
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Lesch KP, Araragi N, Waider J, van den Hove D, Gutknecht L. Targeting brain serotonin synthesis: insights into neurodevelopmental disorders with long-term outcomes related to negative emotionality, aggression and antisocial behaviour. Philos Trans R Soc Lond B Biol Sci 2012; 367:2426-43. [PMID: 22826343 DOI: 10.1098/rstb.2012.0039] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Aggression, which comprises multi-faceted traits ranging from negative emotionality to antisocial behaviour, is influenced by an interaction of biological, psychological and social variables. Failure in social adjustment, aggressiveness and violence represent the most detrimental long-term outcome of neurodevelopmental disorders. With the exception of brain-specific tryptophan hydroxylase-2 (Tph2), which generates serotonin (5-HT) in raphe neurons, the contribution of gene variation to aggression-related behaviour in genetically modified mouse models has been previously appraised (Lesch 2005 Novartis Found Symp. 268, 111-140; Lesch & Merschdorf 2000 Behav. Sci. Law 18, 581-604). Genetic inactivation of Tph2 function in mice led to the identification of phenotypic changes, ranging from growth retardation and late-onset obesity, to enhanced conditioned fear response, increased aggression and depression-like behaviour. This spectrum of consequences, which are amplified by stress-related epigenetic interactions, are attributable to deficient brain 5-HT synthesis during development and adulthood. Human data relating altered TPH2 function to personality traits of negative emotionality and neurodevelopmental disorders characterized by deficits in cognitive control and emotion regulation are based on genetic association and are therefore not as robust as the experimental mouse results. Mouse models in conjunction with approaches focusing on TPH2 variants in humans provide unexpected views of 5-HT's role in brain development and in disorders related to negative emotionality, aggression and antisocial behaviour.
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Affiliation(s)
- Klaus-Peter Lesch
- Division of Molecular Psychiatry (MP), Laboratory of Translational Neuroscience (LTN), Department of Psychiatry, Psychosomatics, and Psychotherapy, University of Wuerzburg, , Fuechsleinstrasse 15, 97080 Wuerzburg, Germany.
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14
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Su G, Xia J, Liu H, Lam MHW, Yu H, Giesy JP, Zhang X. Dioxin-like potency of HO- and MeO- analogues of PBDEs' the potential risk through consumption of fish from eastern China. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2012; 46:10781-10788. [PMID: 22954249 DOI: 10.1021/es302317y] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Polybrominated diphenyl ethers (PBDEs) and their analogues, such as hydroxylated PBDE (HO-PBDEs) and methoxylated PBDE (MeO-PBDEs) are of interest due to their wide distribution, bioaccumulation and potential toxicity to humans and wildlife. While information on the toxicity/biological potencies of PBDEs was available, information on analogues of PBDEs was limited. Dioxin-like toxicity of 34 PBDEs analogues was evaluated by use of the H4IIE-luc, rat hepatoma transactivation bioassay in 384-well plate format at concentrations ranging from 0 to 10 000 ng/mL. Among the 34 target analogues of PBDEs studied here, 19 activated the aryl hydrocarbon receptor (AhR) and induced significant dioxin-like responses in H4IIE-luc cells. Efficacies of the analogues of PBDEs ranged from 5.0% to 101.8% of the maximum response caused by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD-max) and their respective 2,3,7,8-TCDD potency factors (ReP(H4IIE-luc)) ranged from 7.35 × 10(-12) to 4.00 × 10(-4), some of which were equal to or more potent than some mono-ortho-substituted PCBs (TEF-(WHO) = 3 × 10(-5)). HO-PBDEs exhibited greater dioxin-like activity than did the corresponding MeO-PBDEs. Analogues of PBDEs were detected mostly in marine organisms. Of these 11 detected analogues of PBDEs, 6 were found to have measurable dioxin-like potency. Though some analogues of PBDEs exhibited significant dioxin-like potency as measured by responses of the H4IIE-luc transactivation assay, concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) equivalents ((PBDEs analogues)TEQ(H4IIE-luc)), calculated as the sum of the product of concentrations of individual PBDE and their ReP(H4IIE-luc), were less than the tolerance limit proposed by European Union and the oral reference dose (RfD) derived by U.S. Environmental Protection Agency, respectively. (Hazard Quotients (HQ) < 0.005) Additional investigations should be conducted to evaluate the toxic potencies of these chemicals, especially for 2'-MeO-BDE-28, 4-HO-BDE-90, 6-HO-BDE-47, and 6-MeO-BDE-47, which had been detected in other environmental media, including human blood.
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Affiliation(s)
- Guanyong Su
- State Key Laboratory of Pollution Control and Resource Reuse & School of the Environment, Nanjing University, Nanjing, China
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15
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Berger SM, Weber T, Perreau-Lenz S, Vogt MA, Gartside SE, Maser-Gluth C, Lanfumey L, Gass P, Spanagel R, Bartsch D. A functional Tph2 C1473G polymorphism causes an anxiety phenotype via compensatory changes in the serotonergic system. Neuropsychopharmacology 2012; 37:1986-98. [PMID: 22491354 PMCID: PMC3398728 DOI: 10.1038/npp.2012.46] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The association of single-nucleotide polymorphisms (SNPs) in the human tryptophan hydroxylase 2 (TPH2) gene with anxiety traits and depression has been inconclusive. Observed inconsistencies might result from the fact that TPH2 polymorphisms have been studied in a genetically heterogeneous human population. A defined genetic background, control over environmental factors, and the ability to analyze the molecular and neurochemical consequences of introduced genetic alterations constitute major advantages of investigating SNPs in inbred laboratory mouse strains. To investigate the behavioral and neurochemical consequences of a functional C1473G SNP in the mouse Tph2 gene, we generated congenic C57BL/6N mice homozygous for the Tph2 1473G allele. The Arg(447) substitution in the TPH2 enzyme resulted in a significant reduction of the brain serotonin (5-HT) in vivo synthesis rate. Despite decreased 5-HT synthesis, we could detect neither a reduction of brain region-specific 5-HT concentrations nor changes in baseline and stress-induced 5-HT release using a microdialysis approach. However, using a [(35)S]GTP-γ-S binding assay and 5-HT(1A) receptor autoradiography, a functional desensitization of 5-HT(1A) autoreceptors could be identified. Furthermore, behavioral analysis revealed a distinct anxiety phenotype in homozygous Tph2 1473G mice, which could be reversed with chronic escitalopram treatment. Alterations in depressive-like behavior could not be detected under baseline conditions or after chronic mild stress. These findings provide evidence for an involvement of functional Tph2 polymorphisms in anxiety-related behaviors, which are likely not caused directly by alterations in 5-HT content or release but are rather due to compensatory changes during development involving functional desensitization of 5-HT(1A) autoreceptors.
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Affiliation(s)
- Stefan M Berger
- Department of Molecular Biology, Central Institute of Mental Health, Medical Faculty Mannheim/Heidelberg University, Mannheim, Germany
| | - Tillmann Weber
- Department of Molecular Biology, Central Institute of Mental Health, Medical Faculty Mannheim/Heidelberg University, Mannheim, Germany,Department of Addictive Behavior and Addiction Medicine, Central Institute of Mental Health, Medical Faculty Mannheim/Heidelberg University, Mannheim, Germany,Department of Psychiatry and Psychotherapy, Central Institute of Mental Health, Medical Faculty Mannheim/Heidelberg University, Mannheim, Germany
| | - Stephanie Perreau-Lenz
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim/Heidelberg University, Mannheim, Germany
| | - Miriam A Vogt
- Department of Psychiatry and Psychotherapy, Research Group Animal Models in Psychiatry, Central Institute of Mental Health, Medical Faculty Mannheim/Heidelberg University, Mannheim, Germany
| | - Sarah E Gartside
- Institute of Neuroscience, The Medical School, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Christiane Maser-Gluth
- Steroid Laboratory, Department of Pharmacology, University of Heidelberg, Heidelberg, Germany
| | - Laurence Lanfumey
- INSERM UMRS894, CPN, Université Pierre and Marie Curie, Paris, France
| | - Peter Gass
- Department of Psychiatry and Psychotherapy, Research Group Animal Models in Psychiatry, Central Institute of Mental Health, Medical Faculty Mannheim/Heidelberg University, Mannheim, Germany
| | - Rainer Spanagel
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim/Heidelberg University, Mannheim, Germany
| | - Dusan Bartsch
- Department of Molecular Biology, Central Institute of Mental Health, Medical Faculty Mannheim/Heidelberg University, Mannheim, Germany,Department of Molecular Biology, Central Institute of Mental Health, Medical Faculty Mannheim/Heidelberg University, J-5, 68159 Mannheim, Germany, Tel: +49 621 1703 6202, Fax: +49 621 1703 6205, E-mail:
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Egawa J, Watanabe Y, Nunokawa A, Endo T, Kaneko N, Tamura R, Sugiyama T, Someya T. A detailed association analysis between the tryptophan hydroxylase 2 (TPH2) gene and autism spectrum disorders in a Japanese population. Psychiatry Res 2012; 196:320-2. [PMID: 22361444 DOI: 10.1016/j.psychres.2011.09.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/26/2011] [Revised: 08/11/2011] [Accepted: 09/01/2011] [Indexed: 12/23/2022]
Abstract
We conducted a detailed association analysis between the tryptophan hydroxylase 2 gene and autism spectrum disorders in a Japanese population using 19 markers, including tagging single nucleotide polymorphisms and a novel missense variation, p.R225Q, identified through exon resequencing. However, we failed to obtain supportive evidence for an association.
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Affiliation(s)
- Jun Egawa
- Department of Psychiatry, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
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Haavik J, Halmøy A, Hegvik TA, Johansson S. Maternal genotypes as predictors of offspring mental health: the next frontier of genomic medicine? FUTURE NEUROLOGY 2011. [DOI: 10.2217/fnl.11.54] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Multiple lines of evidence have suggested that the in utero microenvironment is influenced by the maternal genotype and that such genetic differences can affect the prenatal development and long-term health of the offspring. This article reviews recent evidence for such effects on offspring mental health, with an emphasis on common neurodevelopmental disorders, such as attention deficit–hyperactivity disorder, autism and schizophrenia. We conclude that prenatal programming of offspring behavior has been found to be important both in humans and animal models and that this mechanism may explain some of the ‘missing heritability’ reported for genetic studies of complex disorders. Combining genetic and epidemiological research strategies, it is possible to disentangle the different effects of prenatal environmental and genetic exposures, which are particularly attractive candidates for primary prevention and early intervention strategies, for instance by correcting for metabolic deficiencies during critical weeks of prenatal development. Combined with advancing DNA sequencing and genotyping technologies, this knowledge may gradually transform our approach to psychiatric diagnostics, prevention and therapy.
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Affiliation(s)
| | - Anne Halmøy
- Department of Biomedicine, University of Bergen, 5009 Bergen, Norway
- Division of Psychiatry, Haukeland University Hospital, 5021 Bergen, Norway
- KG Jebsen Centre for Research on Neuropsychiatric Disorders, University of Bergen, Norway
| | - Tor-Arne Hegvik
- Department of Biomedicine, University of Bergen, 5009 Bergen, Norway
- KG Jebsen Centre for Research on Neuropsychiatric Disorders, University of Bergen, Norway
| | - Stefan Johansson
- Department of Biomedicine, University of Bergen, 5009 Bergen, Norway
- KG Jebsen Centre for Research on Neuropsychiatric Disorders, University of Bergen, Norway
- Center of Medical Genetics & Molecular Medicine, Haukeland University Hospital, 5021 Bergen, Norway
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Fernandez SP, Gaspar P. Investigating anxiety and depressive-like phenotypes in genetic mouse models of serotonin depletion. Neuropharmacology 2011; 62:144-54. [PMID: 21945798 DOI: 10.1016/j.neuropharm.2011.08.049] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Revised: 08/25/2011] [Accepted: 08/29/2011] [Indexed: 01/24/2023]
Abstract
Emotional disorders such as depression, panic attacks, generalized anxiety, phobias and post-traumatic stress have been associated to decreased serotonin (5-HT) function, based on the positive effects of treatments that enhance 5-HT neurotransmission. However, it has been difficult to establish a primary role for 5-HT deficiency in these diseases, making preclinical models particularly useful. Over the last ten years a variety of genetic mouse models of 5-HT depletion have been produced, complementing previous pharmacologically-based models. Initial models hindered the differentiation of the raphe 5-HT neurons, while more recently produced models suppressed 5-HT production or incapacitated 5-HT vesicular packaging and release in normally developed raphe neurons. Here, we provide an overview of 11 genetic mouse models with lowered 5-HT transmission and summarize the available behavioural investigations concerning their anxiety and depression phenotypes. Although these studies are still ongoing, some common anxiety-related traits and behavioural phenotypes have emerged. Most studies have reported decreased innate anxiety to novelty but heightened fear responses to conditioned aversive cues. This complex phenotype is in general agreement with the proposed dual function of 5-HT in modulating different defensive behaviours. Surprisingly, the depressive-like behaviours have been less studied and, so far, did not yield a consistent phenotype in standard tests. Future studies should be conducted using more ethological relevant models to conclude on the causal role of 5-HT depletion in depression. This review also describes the differences in level and regional distribution of 5-HT depletion among the available mouse models, which could contribute to the diverse phenotypes observed. This article is part of a Special Issue entitled 'Anxiety and Depression'.
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19
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Vega AI, Pérez-Cerdá C, Abia D, Gámez A, Briones P, Artuch R, Desviat LR, Ugarte M, Pérez B. Expression analysis revealing destabilizing mutations in phosphomannomutase 2 deficiency (PMM2-CDG): expression analysis of PMM2-CDG mutations. J Inherit Metab Dis 2011; 34:929-39. [PMID: 21541725 DOI: 10.1007/s10545-011-9328-2] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/27/2010] [Revised: 03/23/2011] [Accepted: 03/28/2011] [Indexed: 01/19/2023]
Abstract
Deficiency of phosphomannomutase (PMM2, MIM#601785) is the most common congenital disorder of glycosylation. Herein we report the genetic analysis of 22 Spanish PMM2 deficient patients and the functional analysis of 14 nucleotide changes in a prokaryotic expression system in order to elucidate their molecular pathogenesis. PMM2 activity assay revealed the presence of six protein changes with no enzymatic activities (p.R123Q, p.R141H, p.F157S, p.P184T, p.F207S and p.D209G) and seven mild protein changes with residual activities ranging from 16 to 54% (p.L32R, p.V44A p.D65Y, p.P113L p.T118S, p.T237M and p.C241S) and also one variant change with normal activity (p.E197A). The results obtained from Western blot analysis, degradation time courses of 11 protein changes and structural analysis of the PMM2 protein, suggest that the loss-of-function of most mutant proteins is based on their increased susceptibility to degradation or aggregation compared to the wild type protein, considering PMM2 deficiency as a conformational disease. We have identified exclusively catalytic protein change (p.D209G), catalytic protein changes affecting protein stability (p.R123Q and p.R141H), two protein changes disrupting the dimer interface (p.P113L and p.T118S) and several misfolding changes (p.L32R, p.V44A, p.D65Y, p.F157S, p.P184T, p.F207S, p.T237M and p.C241S). Our current work opens a promising therapeutic option using pharmacological chaperones to revert the effect of the characterized misfolding mutations identified in a wide range of PMM2 deficient patients.
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Affiliation(s)
- Ana Isabel Vega
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular-SO UAM-CSIC, Universidad Autónoma de Madrid, Campus de Cantoblanco, 28049 Madrid / Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
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20
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Waider J, Araragi N, Gutknecht L, Lesch KP. Tryptophan hydroxylase-2 (TPH2) in disorders of cognitive control and emotion regulation: a perspective. Psychoneuroendocrinology 2011; 36:393-405. [PMID: 21257271 DOI: 10.1016/j.psyneuen.2010.12.012] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2010] [Revised: 12/22/2010] [Accepted: 12/23/2010] [Indexed: 01/24/2023]
Abstract
Based on genetic variation, there is accumulating evidence that altered function of tryptophan hydroxylase-2 (TPH2), the enzyme critical for synthesis of serotonin (5-HT) in the brain, plays a role in anxiety-, aggression- and depression-related personality traits and in the pathogenesis of disorders featuring deficits in cognitive control and emotion regulation. Here, we appraise the genetic and neurobiological evidence to illustrate the critical role of TPH2 in central 5-HT system function and in the pathophysiology of a wide spectrum of disorders of cognitive control and emotion regulation, ranging from depression to attention-deficit/hyperactivity disorder (ADHD), a phenotype commonly associated with difficulties in the control of emotion and with a high co-morbidity of depression. Findings from psychophysiological and functional imaging studies are indicative of various TPH2 polymorphisms directly influencing serotonergic function and thus impacting on mood disorders and on the response to antidepressant treatment. Especially a combination with uncontrollable stress seems to potentiate these effects linking gene-environment interaction directly with behavioral dysfunction in human and animal models. TPH2-deficient mice display alterations in anxiety-like behavior which is accompanied by adaptational changes of 5-HT(1A) receptors and its associated signaling pathway. Mouse models in conjunction with cognitive neuroscience approaches in humans are providing unexpected results and it may well be that future research on TPH2 will provide an entirely new view of 5-HT in brain development and function related to neuropsychiatric disorders.
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Affiliation(s)
- Jonas Waider
- Molecular Psychiatry, Laboratory of Translational Neuroscience, Department of Psychiatry, Psychosomatics, and Psychotherapy, University of Wuerzburg, Fuechsleinstrasse 15, 97080 Wuerzburg, Germany
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21
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Popova NK, Kulikov AV. Targeting tryptophan hydroxylase 2 in affective disorder. Expert Opin Ther Targets 2010; 14:1259-71. [DOI: 10.1517/14728222.2010.524208] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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22
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Osipova DV, Kulikov AV, Mekada K, Yoshiki A, Moshkin MP, Kotenkova EV, Popova NK. Distribution of the C1473G polymorphism in tryptophan hydroxylase 2 gene in laboratory and wild mice. GENES BRAIN AND BEHAVIOR 2010; 9:537-43. [PMID: 20398061 DOI: 10.1111/j.1601-183x.2010.00586.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The neurotransmitter serotonin is implicated in the regulation of various forms of behavior, including aggression, sexual behavior and stress response. The rate of brain serotonin synthesis is determined by the activity of neuronal-specific enzyme tryptophan hydroxylase 2. The missense C1473G substitution in mouse tryptophan hydroxylase 2 gene has been shown to lower the enzyme activity and brain serotonin level. Here, the C1473G polymorphism was investigated in 84 common laboratory inbred strains, 39 inbred and semi-inbred strains derived from wild ancestors (mostly from Eurasia) and in 75 wild mice trapped in different locations in Russia and Armenia. Among all the classical inbred strains studied, only substrains of BALB/c, A and DBA, as well as the IITES/Nga and NZW/NSlc strains were homozygous for the 1473G allele. In contrast to laboratory strains, the 1473G allele was not present in any of the samples from wild and wild-derived mice, although the wild mice varied substantially in the C1477T neutral substitution closely linked to the C1473G polymorphism. According to these results, the frequency of the 1473G allele in natural populations does not exceed 0.5%, and the C1473G polymorphism is in fact a rare mutation that is possibly eliminated by the forces of natural selection.
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Affiliation(s)
- D V Osipova
- Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
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