1
|
Rodnyy AY, Kondaurova EM, Tsybko AS, Popova NK, Kudlay DA, Naumenko VS. The brain serotonin system in autism. Rev Neurosci 2024; 35:1-20. [PMID: 37415576 DOI: 10.1515/revneuro-2023-0055] [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: 05/12/2023] [Accepted: 06/10/2023] [Indexed: 07/08/2023]
Abstract
Autism spectrum disorders (ASDs) are among the most common neurodevelopmental diseases. These disorders are characterized by lack of social interaction, by repetitive behavior, and often anxiety and learning disabilities. The brain serotonin (5-HT) system is known to be crucially implicated in a wide range of physiological functions and in the control of different kinds of normal and pathological behavior. A growing number of studies indicate the involvement of the brain 5-HT system in the mechanisms underlying both ASD development and ASD-related behavioral disorders. There are some review papers describing the role of separate key players of the 5-HT system in an ASD and/or autistic-like behavior. In this review, we summarize existing data on the participation of all members of the brain 5-HT system, namely, 5-HT transporter, tryptophan hydroxylase 2, MAOA, and 5-HT receptors, in autism in human and various animal models. Additionally, we describe the most recent studies involving modern techniques for in vivo regulation of gene expression that are aimed at identifying exact roles of 5-HT receptors, MAOA, and 5-HT transporter in the mechanisms underlying autistic-like behavior. Altogether, results of multiple research articles show that the brain 5-HT system intimately partakes in the control of some types of ASD-related behavior, and that specific changes in a function of a certain 5-HT receptor, transporter, and/or enzyme may normalize this aberrant behavior. These data give hope that some of clinically used 5-HT-related drugs have potential for ASD treatment.
Collapse
Affiliation(s)
- Alexander Ya Rodnyy
- Federal Research Center Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences, Akad. Lavrentyeva Ave. 10, Novosibirsk 630090, Russia
| | - Elena M Kondaurova
- Federal Research Center Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences, Akad. Lavrentyeva Ave. 10, Novosibirsk 630090, Russia
| | - Anton S Tsybko
- Federal Research Center Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences, Akad. Lavrentyeva Ave. 10, Novosibirsk 630090, Russia
| | - Nina K Popova
- Federal Research Center Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences, Akad. Lavrentyeva Ave. 10, Novosibirsk 630090, Russia
| | - Dmitry A Kudlay
- NRC Institute of Immunology FMBA of Russia, Kashirskoe Highway 24, Moscow 115522, Russia
- Sechenov's University, 8-2 Trubetskaya Str., Moscow 119991, Russia
| | - Vladimir S Naumenko
- Federal Research Center Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences, Akad. Lavrentyeva Ave. 10, Novosibirsk 630090, Russia
| |
Collapse
|
2
|
He XB, Guo F, Li K, Yan J, Lee SH. Timing of MeCP2 Expression Determines Midbrain Dopamine Neuron Phenotype Specification. Stem Cells 2022; 40:1043-1055. [PMID: 36041430 DOI: 10.1093/stmcls/sxac061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2022] [Accepted: 08/22/2022] [Indexed: 11/14/2022]
Abstract
Midbrain dopamine (DA) neurons are associated with locomotor and psychiatric disorders. DA phenotype is specified in ancestral neural precursor cells (NPCs) and maintained throughout neuronal differentiation. Here we show that endogenous expression of MeCP2 coincides with DA phenotype specification in mouse mesencephalon, and premature expression of MeCP2 prevents in vitro cultured NPCs from acquiring DA phenotype through interfering NURR1 transactivation of DA phenotype genes. By contrast, ectopic MeCP2 expression does not disturb DA phenotype in the DA neurons. By analyzing the dynamic change of DNA methylation along DA neuronal differentiation at the promoter of DA phenotype gene tyrosine hydroxylase (Th), we show that Th expression is determined by TET1-mediated de-methylation of NURR1 binding sites within Th promoter. Chromatin immunoprecipitation assays demonstrate that premature MeCP2 dominates the DNA binding of the corresponding sites thereby blocking TET1 function in DA NPCs, whereas TET1-mediated de-methylation prevents excessive MeCP2 binding in DA neurons. The significance of temporal DNA methylation status is further confirmed by targeted methylation/demethylation experiments showing that targeted de-methylation in DA NPCs protects DA phenotype specification from ectopic MeCP2 expression, whereas targeted methylation disturbs phenotype maintenance in MeCP2-overexpressed DA neurons. These findings suggest the appropriate timing of MeCP2 expression as a novel determining factor for guiding NPCs into DA lineage.
Collapse
Affiliation(s)
- Xi-Biao He
- Laboratory of Stem Cell Biology and Epigenetics, College of Basic Medical Sciences, Shanghai University of Medicine and Health Sciences, Shanghai, People's Republic of China
| | - Fang Guo
- Laboratory of Stem Cell Biology and Epigenetics, College of Basic Medical Sciences, Shanghai University of Medicine and Health Sciences, Shanghai, People's Republic of China
| | - Kexuan Li
- Laboratory of Stem Cell Biology and Epigenetics, College of Basic Medical Sciences, Shanghai University of Medicine and Health Sciences, Shanghai, People's Republic of China
| | - Jiaqing Yan
- Laboratory of Stem Cell Biology and Epigenetics, College of Basic Medical Sciences, Shanghai University of Medicine and Health Sciences, Shanghai, People's Republic of China
| | - Sang-Hun Lee
- Department of Biochemistry and Molecular Biology, College of Medicine, Hanyang University, Seoul, Republic of Korea
| |
Collapse
|
3
|
Murasawa H, Kobayashi H, Imai J, Nagase T, Soumiya H, Fukumitsu H. Substantial acetylcholine reduction in multiple brain regions of Mecp2-deficient female rats and associated behavioral abnormalities. PLoS One 2021; 16:e0258830. [PMID: 34673817 PMCID: PMC8530288 DOI: 10.1371/journal.pone.0258830] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Accepted: 10/06/2021] [Indexed: 11/24/2022] Open
Abstract
Rett syndrome (RTT) is a neurodevelopmental disorder with X-linked dominant inheritance caused mainly by mutations in the methyl-CpG-binding protein 2 (MECP2) gene. The effects of various Mecp2 mutations have been extensively assessed in mouse models, but none adequately mimic the symptoms and pathological changes of RTT. In this study, we assessed the effects of Mecp2 gene deletion on female rats (Mecp2+/−) and found severe impairments in social behavior [at 8 weeks (w), 12 w, and 23 w of age], motor function [at 16 w and 26 w], and spatial cognition [at 29 w] as well as lower plasma insulin-like growth factor (but not brain-derived neurotrophic factor) and markedly reduced acetylcholine (30%–50%) in multiple brain regions compared to female Mecp2+/+ rats [at 29 w]. Alternatively, changes in brain monoamine levels were relatively small, in contrast to reports on mouse Mecp2 mutants. Female Mecp2-deficient rats express phenotypes resembling RTT and so may provide a robust model for future research on RTT pathobiology and treatment.
Collapse
Affiliation(s)
- Hiroyasu Murasawa
- Laboratory of Molecular Biology, Department of Biofunctional Analysis, Gifu Pharmaceutical University, Gifu, Japan
- Hashima Laboratory, Nihon Bioresearch Inc, Gifu, Japan
| | - Hiroyuki Kobayashi
- Laboratory of Molecular Biology, Department of Biofunctional Analysis, Gifu Pharmaceutical University, Gifu, Japan
- Hashima Laboratory, Nihon Bioresearch Inc, Gifu, Japan
| | - Jun Imai
- Hashima Laboratory, Nihon Bioresearch Inc, Gifu, Japan
| | | | - Hitomi Soumiya
- Laboratory of Molecular Biology, Department of Biofunctional Analysis, Gifu Pharmaceutical University, Gifu, Japan
| | - Hidefumi Fukumitsu
- Laboratory of Molecular Biology, Department of Biofunctional Analysis, Gifu Pharmaceutical University, Gifu, Japan
- * E-mail:
| |
Collapse
|
4
|
Kosillo P, Bateup HS. Dopaminergic Dysregulation in Syndromic Autism Spectrum Disorders: Insights From Genetic Mouse Models. Front Neural Circuits 2021; 15:700968. [PMID: 34366796 PMCID: PMC8343025 DOI: 10.3389/fncir.2021.700968] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Accepted: 06/21/2021] [Indexed: 12/12/2022] Open
Abstract
Autism spectrum disorder (ASD) is a neurodevelopmental disorder defined by altered social interaction and communication, and repetitive, restricted, inflexible behaviors. Approximately 1.5-2% of the general population meet the diagnostic criteria for ASD and several brain regions including the cortex, amygdala, cerebellum and basal ganglia have been implicated in ASD pathophysiology. The midbrain dopamine system is an important modulator of cellular and synaptic function in multiple ASD-implicated brain regions via anatomically and functionally distinct dopaminergic projections. The dopamine hypothesis of ASD postulates that dysregulation of dopaminergic projection pathways could contribute to the behavioral manifestations of ASD, including altered reward value of social stimuli, changes in sensorimotor processing, and motor stereotypies. In this review, we examine the support for the idea that cell-autonomous changes in dopaminergic function are a core component of ASD pathophysiology. We discuss the human literature supporting the involvement of altered dopamine signaling in ASD including genetic, brain imaging and pharmacologic studies. We then focus on genetic mouse models of syndromic neurodevelopmental disorders in which single gene mutations lead to increased risk for ASD. We highlight studies that have directly examined dopamine neuron number, morphology, physiology, or output in these models. Overall, we find considerable support for the idea that the dopamine system may be dysregulated in syndromic ASDs; however, there does not appear to be a consistent signature and some models show increased dopaminergic function, while others have deficient dopamine signaling. We conclude that dopamine dysregulation is common in syndromic forms of ASD but that the specific changes may be unique to each genetic disorder and may not account for the full spectrum of ASD-related manifestations.
Collapse
Affiliation(s)
- Polina Kosillo
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, United States
| | - Helen S. Bateup
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, United States
- Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA, United States
- Chan Zuckerberg Biohub, San Francisco, CA, United States
| |
Collapse
|
5
|
Fluoxetine rescues rotarod motor deficits in Mecp2 heterozygous mouse model of Rett syndrome via brain serotonin. Neuropharmacology 2020; 176:108221. [PMID: 32652084 DOI: 10.1016/j.neuropharm.2020.108221] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2019] [Revised: 05/24/2020] [Accepted: 06/20/2020] [Indexed: 01/28/2023]
Abstract
Motor skill is a specific area of disability of Rett syndrome (RTT), a rare disorder occurring almost exclusively in girls, caused by loss-of-function mutations of the X-linked methyl-CpG-binding protein2 (MECP2) gene, encoding the MECP2 protein, a member of the methyl-CpG-binding domain nuclear proteins family. Brain 5-HT, which is defective in RTT patients and Mecp2 mutant mice, regulates motor circuits and SSRIs enhance motor skill learning and plasticity. In the present study, we used heterozygous (Het) Mecp2 female and Mecp2-null male mice to investigate whether fluoxetine, a SSRI with pleiotropic effects on neuronal circuits, rescues motor coordination deficits. Repeated administration of 10 mg/kg fluoxetine fully rescued rotarod deficit in Mecp2 Het mice regardless of age, route of administration or pre-training to rotarod. The motor improvement was confirmed in the beam walking test while no effect was observed in the hanging-wire test, suggesting a preferential action of fluoxetine on motor coordination. Citalopram mimicked the effects of fluoxetine, while the inhibition of 5-HT synthesis abolished the fluoxetine-induced improvement of motor coordination. Mecp2 null mice, which responded poorly to fluoxetine in the rotarod, showed reduced 5-HT synthesis in the prefrontal cortex, hippocampus and striatum, and reduced efficacy of fluoxetine in raising extracellular 5-HT as compared to female mutants. No sex differences were observed in the ability of fluoxetine to desensitize 5-HT1A autoreceptors upon repeated administration. These findings indicate that fluoxetine rescues motor coordination in Mecp2 Het mice through its ability to enhance brain 5-HT and suggest that drugs enhancing 5-HT neurotransmission may have beneficial effects on motor symptoms of RTT.
Collapse
|
6
|
Cosentino L, Vigli D, Franchi F, Laviola G, De Filippis B. Rett syndrome before regression: A time window of overlooked opportunities for diagnosis and intervention. Neurosci Biobehav Rev 2019; 107:115-135. [PMID: 31108160 DOI: 10.1016/j.neubiorev.2019.05.013] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 05/10/2019] [Accepted: 05/15/2019] [Indexed: 11/29/2022]
Abstract
Rett syndrome (RTT) is a rare neurological disorder primarily affecting females, causing severe cognitive, social, motor and physiological impairments for which no cure currently exists. RTT clinical diagnosis is based on the peculiar progression of the disease, since patients show an apparently normal initial development with a subsequent sudden regression at around 2 years of age. Accumulating evidences are rising doubts regarding the absence of early impairments, hence questioning the concept of regression. We reviewed the published literature addressing the pre-symptomatic stage of the disease in both patients and animal models with a particular focus on behavioral, physiological and brain abnormalities. The emerging picture delineates subtle, but reliable impairments that precede the onset of overt symptoms whose bases are likely set up already during embryogenesis. Some of the outlined alterations appear transient, suggesting compensatory mechanisms to occur in the course of development. There is urgent need for more systematic developmental analyses able to detect early pathological markers to be used as diagnostic tools and precocious targets of time-specific interventions.
Collapse
Affiliation(s)
- Livia Cosentino
- Center for Behavioral Sciences and Mental Health, Istituto Superiore di Sanità, Viale Regina Elena, 299, 00161 Rome, Italy
| | - Daniele Vigli
- Center for Behavioral Sciences and Mental Health, Istituto Superiore di Sanità, Viale Regina Elena, 299, 00161 Rome, Italy
| | - Francesca Franchi
- Center for Behavioral Sciences and Mental Health, Istituto Superiore di Sanità, Viale Regina Elena, 299, 00161 Rome, Italy
| | - Giovanni Laviola
- Center for Behavioral Sciences and Mental Health, Istituto Superiore di Sanità, Viale Regina Elena, 299, 00161 Rome, Italy
| | - Bianca De Filippis
- Center for Behavioral Sciences and Mental Health, Istituto Superiore di Sanità, Viale Regina Elena, 299, 00161 Rome, Italy.
| |
Collapse
|
7
|
Are dopamine receptor and transporter changes in Rett syndrome reflected in Mecp2-deficient mice? Exp Neurol 2018; 307:74-81. [PMID: 29782864 DOI: 10.1016/j.expneurol.2018.05.019] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Revised: 04/27/2018] [Accepted: 05/17/2018] [Indexed: 11/20/2022]
Abstract
We tested the claim that the dopaminergic dysfunction of Rett Syndrome (RTT) also occurs in Mecp2-deficient mice that serve as a model of the syndrome. We used positron emission tomography (PET) to image dopamine D2 receptors (D2R) and transporters (DAT) in women with RTT and in Mecp2-deficient mice, and D1R and D2R density was measured in postmortem human tissue by autoradiography. Results showed 1) significantly reduced D2R density in the striatum of women with RTT compared to control subjects. 2) PET imaging of mouse striatum similarly demonstrated significant reductions in D2R density of 7-10 week-old hemizygous (Mecp2-null) and heterozygous (HET) mice compared to wild type (WT) mice. With age, the density of D2R declined in WT mice but not HET mice. 3) In contrast, postmortem autoradiography revealed no group differences in the density of D1R and D2R in the caudate and putamen of RTT versus normal control subjects. 4) In humans and in the mouse model, PET revealed only marginal group differences in DAT. The results confirm that dopaminergic dysfunction in RTT is also present in Mecp2-deficient mice and that reductions in D2R more likely explain the impaired ambulation and progressive rigidity observed rather than alterations in DAT.
Collapse
|
8
|
Abstract
Although serotonin neurotransmission has been implicated in several neurodevelopmental and psychological disorders, the factors that drive dysfunction of the serotonin system are poorly understood. Current research regarding the serotonin system revolves around its dysfunction in neuropsychiatric disorders, but there is no database collating genetic mutations that result in serotonin abnormalities. To bridge this gap, we developed a list of genes in mice that, when perturbed, result in altered levels of serotonin either in brain or blood. Due to the intrinsic limitations of search, the current list should be considered a preliminary subset of all relevant cases. Nevertheless, it offered an opportunity to gain insight into what types of genes have the potential to impact serotonin by using gene ontology (GO). This analysis found that genes associated with monoamine metabolism were more often associated with increases in brain serotonin than decreases. Speculatively, this could be because several pathways (and therefore many genes) are responsible for the clearance and metabolism of serotonin whereas only one pathway (and therefore fewer genes) is directly involved in the synthesis of serotonin. Another contributor could be cross talk between monoamine systems such as dopamine. In contrast, genes that were associated with decreases in brain serotonin were more likely linked to a developmental process. Sensitivity of serotonin neurons to developmental perturbations could be due to their complicated neuroanatomy or possibly they may be negatively regulated by dysfunction of their innervation targets. Thus, these observations suggest hypotheses regarding the mechanisms underlying the vulnerability of brain serotonin neurotransmission.
Collapse
Affiliation(s)
- Richard C. Tenpenny
- Department of Anesthesiology, Perioperative, and Pain
Medicine, Boston Children’s Hospital and Department of Anesthesia,
Harvard Medical School, 300 Longwood
Avenue, Boston, Massachusetts 02115, United States
| | - Kathryn G. Commons
- Department of Anesthesiology, Perioperative, and Pain
Medicine, Boston Children’s Hospital and Department of Anesthesia,
Harvard Medical School, 300 Longwood
Avenue, Boston, Massachusetts 02115, United States
| |
Collapse
|
9
|
Ehrhart F, Coort SLM, Cirillo E, Smeets E, Evelo CT, Curfs LMG. Rett syndrome - biological pathways leading from MECP2 to disorder phenotypes. Orphanet J Rare Dis 2016; 11:158. [PMID: 27884167 PMCID: PMC5123333 DOI: 10.1186/s13023-016-0545-5] [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: 09/22/2016] [Accepted: 11/17/2016] [Indexed: 02/07/2023] Open
Abstract
Rett syndrome (RTT) is a rare disease but still one of the most abundant causes for intellectual disability in females. Typical symptoms are onset at month 6-18 after normal pre- and postnatal development, loss of acquired skills and severe intellectual disability. The type and severity of symptoms are individually highly different. A single mutation in one gene, coding for methyl-CpG-binding protein 2 (MECP2), is responsible for the disease. The most important action of MECP2 is regulating epigenetic imprinting and chromatin condensation, but MECP2 influences many different biological pathways on multiple levels although the molecular pathways from gene to phenotype are currently not fully understood. In this review the known changes in metabolite levels, gene expression and biological pathways in RTT are summarized, discussed how they are leading to some characteristic RTT phenotypes and therefore the gaps of knowledge are identified. Namely, which phenotypes have currently no mechanistic explanation leading back to MECP2 related pathways? As a result of this review the visualization of the biologic pathways showing MECP2 up- and downstream regulation was developed and published on WikiPathways which will serve as template for future omics data driven research. This pathway driven approach may serve as a use case for other rare diseases, too.
Collapse
Affiliation(s)
- Friederike Ehrhart
- Governor Kremers Centre - Rett Expertise Centre, Maastricht University Medical Center, Maastricht, The Netherlands. .,Department of Bioinformatics, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University, Maastricht, The Netherlands.
| | - Susan L M Coort
- Department of Bioinformatics, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University, Maastricht, The Netherlands
| | - Elisa Cirillo
- Department of Bioinformatics, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University, Maastricht, The Netherlands
| | - Eric Smeets
- Governor Kremers Centre - Rett Expertise Centre, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Chris T Evelo
- Governor Kremers Centre - Rett Expertise Centre, Maastricht University Medical Center, Maastricht, The Netherlands.,Department of Bioinformatics, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University, Maastricht, The Netherlands
| | - Leopold M G Curfs
- Governor Kremers Centre - Rett Expertise Centre, Maastricht University Medical Center, Maastricht, The Netherlands
| |
Collapse
|
10
|
Wood KH, Johnson BS, Welsh SA, Lee JY, Cui Y, Krizman E, Brodkin ES, Blendy JA, Robinson MB, Bartolomei MS, Zhou Z. Tagging methyl-CpG-binding domain proteins reveals different spatiotemporal expression and supports distinct functions. Epigenomics 2016; 8:455-73. [PMID: 27066839 DOI: 10.2217/epi-2015-0004] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
AIM DNA methylation is recognized by methyl-CpG-binding domain (MBD) proteins. Multiple MBDs are linked to neurodevelopmental disorders in humans and mice. However, the functions of MBD2 are poorly understood. We characterized Mbd2 knockout mice and determined spatiotemporal expression of MBDs and MBD2-NuRD (nucleosome remodeling deacetylase) interactions. EXPERIMENTAL PROCEDURES We analyzed behavioral phenotypes, generated biotin-tagged MBD1 and MBD2 knockin mice, and performed biochemical studies of MBD2-NuRD. RESULTS Most behavioral measures are minimally affected in Mbd2 knockout mice. In contrast to other MBDs, MBD2 shows distinct expression patterns. CONCLUSION Unlike most MBDs, MBD2 is ubiquitously expressed in all tissues examined and appears dispensable for brain functions measured in this study. We provide novel genetic tools and reveal new directions to investigate MBD2 functions in vivo.
Collapse
Affiliation(s)
- Kathleen H Wood
- Department of Genetics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Brian S Johnson
- Department of Genetics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Sarah A Welsh
- Department of Genetics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Jun Y Lee
- Department of Genetics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Yue Cui
- Department of Genetics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Elizabeth Krizman
- Children's Hospital of Philadelphia Research Institute, Philadelphia, PA 19104, USA
| | - Edward S Brodkin
- Department of Psychiatry, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Julie A Blendy
- Department of Pharmacology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Michael B Robinson
- Children's Hospital of Philadelphia Research Institute, Philadelphia, PA 19104, USA.,Department of Pediatrics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Marisa S Bartolomei
- Department of Cell & Developmental Biology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Zhaolan Zhou
- Department of Genetics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| |
Collapse
|
11
|
Abstract
Two severe, progressive neurological disorders characterized by intellectual disability, autism, and developmental regression, Rett syndrome and MECP2 duplication syndrome, result from loss and gain of function, respectively, of the same critical gene, methyl-CpG-binding protein 2 (MECP2). Neurons acutely require the appropriate dose of MECP2 to function properly but do not die in its absence or overexpression. Instead, neuronal dysfunction can be reversed in a Rett syndrome mouse model if MeCP2 function is restored. Thus, MECP2 disorders provide a unique window into the delicate balance of neuronal health, the power of mouse models, and the importance of chromatin regulation in mature neurons. In this Review, we will discuss the clinical profiles of MECP2 disorders, the knowledge acquired from mouse models of the syndromes, and how that knowledge is informing current and future clinical studies.
Collapse
|
12
|
Herrera JA, Ward CS, Pitcher MR, Percy AK, Skinner S, Kaufmann WE, Glaze DG, Wehrens XHT, Neul JL. Treatment of cardiac arrhythmias in a mouse model of Rett syndrome with Na+-channel-blocking antiepileptic drugs. Dis Model Mech 2015; 8:363-71. [PMID: 25713300 PMCID: PMC4381335 DOI: 10.1242/dmm.020131] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Accepted: 02/12/2015] [Indexed: 12/11/2022] Open
Abstract
One quarter of deaths associated with Rett syndrome (RTT), an X-linked neurodevelopmental disorder, are sudden and unexpected. RTT is associated with prolonged QTc interval (LQT), and LQT-associated cardiac arrhythmias are a potential cause of unexpected death. The standard of care for LQT in RTT is treatment with β-adrenergic antagonists; however, recent work indicates that acute treatment of mice with RTT with a β-antagonist, propranolol, does not prevent lethal arrhythmias. In contrast, acute treatment with the Na+ channel blocker phenytoin prevented arrhythmias. Chronic dosing of propranolol may be required for efficacy; therefore, we tested the efficacy of chronic treatment with either propranolol or phenytoin on RTT mice. Phenytoin completely abolished arrhythmias, whereas propranolol showed no benefit. Surprisingly, phenytoin also normalized weight and activity, but worsened breathing patterns. To explore the role of Na+ channel blockers on QT in people with RTT, we performed a retrospective analysis of QT status before and after Na+ channel blocker antiepileptic therapies. Individuals with RTT and LQT significantly improved their QT interval status after being started on Na+ channel blocker antiepileptic therapies. Thus, Na+ channel blockers should be considered for the clinical management of LQT in individuals with RTT.
Collapse
Affiliation(s)
- José A Herrera
- Interdepartmental Program in Translational Biology and Molecular Medicine, Baylor College of Medicine, Houston, TX 77030, USA. Jan and Duncan Neurological Research Institute, Texas Children's Hospital, Houston, TX, USA
| | - Christopher S Ward
- Jan and Duncan Neurological Research Institute, Texas Children's Hospital, Houston, TX, USA
| | - Meagan R Pitcher
- Interdepartmental Program in Translational Biology and Molecular Medicine, Baylor College of Medicine, Houston, TX 77030, USA. Jan and Duncan Neurological Research Institute, Texas Children's Hospital, Houston, TX, USA
| | - Alan K Percy
- Department of Pediatrics, University of Alabama at Birmingham, Birmingham, AL, USA
| | | | - Walter E Kaufmann
- Department of Neurology, Boston Children's Hospital, Boston, MA 02115, USA
| | - Daniel G Glaze
- Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Xander H T Wehrens
- Interdepartmental Program in Translational Biology and Molecular Medicine, Baylor College of Medicine, Houston, TX 77030, USA. Cardiovascular Research Institute, Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Jeffrey L Neul
- Interdepartmental Program in Translational Biology and Molecular Medicine, Baylor College of Medicine, Houston, TX 77030, USA. Jan and Duncan Neurological Research Institute, Texas Children's Hospital, Houston, TX, USA. Department of Pediatrics, University of Alabama at Birmingham, Birmingham, AL, USA. Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA. Cardiovascular Research Institute, Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX 77030, USA.
| |
Collapse
|
13
|
Oginsky MF, Cui N, Zhong W, Johnson CM, Jiang C. Alterations in the cholinergic system of brain stem neurons in a mouse model of Rett syndrome. Am J Physiol Cell Physiol 2014; 307:C508-20. [PMID: 25009110 DOI: 10.1152/ajpcell.00035.2014] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Rett syndrome is an autism-spectrum disorder resulting from mutations to the X-linked gene, methyl-CpG binding protein 2 (MeCP2), which causes abnormalities in many systems. It is possible that the body may develop certain compensatory mechanisms to alleviate the abnormalities. The norepinephrine system originating mainly in the locus coeruleus (LC) is defective in Rett syndrome and Mecp2-null mice. LC neurons are subject to modulation by GABA, glutamate, and acetylcholine (ACh), providing an ideal system to test the compensatory hypothesis. Here we show evidence for potential compensatory modulation of LC neurons by post- and presynaptic ACh inputs. We found that the postsynaptic currents of nicotinic ACh receptors (nAChR) were smaller in amplitude and longer in decay time in the Mecp2-null mice than in the wild type. Single-cell PCR analysis showed a decrease in the expression of α3-, α4-, α7-, and β3-subunits and an increase in the α5- and α6-subunits in the mutant mice. The α5-subunit was present in many of the LC neurons with slow-decay nAChR currents. The nicotinic modulation of spontaneous GABAA-ergic inhibitory postsynaptic currents in LC neurons was enhanced in Mecp2-null mice. In contrast, the nAChR manipulation of glutamatergic input to LC neurons was unaffected in both groups of mice. Our current-clamp studies showed that the modulation of LC neurons by ACh input was reduced moderately in Mecp2-null mice, despite the major decrease in nAChR currents, suggesting possible compensatory processes may take place, thus reducing the defects to a lesser extent in LC neurons.
Collapse
Affiliation(s)
- Max F Oginsky
- Department of Biology, Georgia State University, Atlanta, Georgia
| | - Ningren Cui
- Department of Biology, Georgia State University, Atlanta, Georgia
| | - Weiwei Zhong
- Department of Biology, Georgia State University, Atlanta, Georgia
| | | | - Chun Jiang
- Department of Biology, Georgia State University, Atlanta, Georgia
| |
Collapse
|
14
|
Abdala AP, Lioy DT, Garg SK, Knopp SJ, Paton JFR, Bissonnette JM. Effect of Sarizotan, a 5-HT1a and D2-like receptor agonist, on respiration in three mouse models of Rett syndrome. Am J Respir Cell Mol Biol 2014; 50:1031-9. [PMID: 24351104 PMCID: PMC4068914 DOI: 10.1165/rcmb.2013-0372oc] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2013] [Accepted: 12/10/2013] [Indexed: 01/06/2023] Open
Abstract
Disturbances in respiration are common and debilitating features of Rett syndrome (RTT). A previous study showed that the 5-HT1a receptor agonist (R)-(+)-8-hydroxy-dipropyl-2-aminotetralin hydrobromide (8-OH-DPAT) significantly reduced the incidence of apnea and the irregular breathing pattern in a mouse model of the disorder. 8-OH-DPAT, however, is not available for clinical practice. Sarizotan, a full 5-HT1a agonist and a dopamine D2-like agonist/partial agonist, has been used in clinical trials for the treatment of l-dopa-induced dyskinesia. The purpose of this study was to evaluate the effects of sarizotan on respiration and locomotion in mouse models of RTT. Studies were performed in Bird and Jaenisch strains of methyl-CpG-binding protein 2--deficient heterozygous female and Jaenisch strain Mecp2 null male mice and in knock-in heterozygous female mice of a common nonsense mutation (R168X). Respiratory pattern was determined with body plethysmography, and locomotion was determined with open-field recording. Sarizotan or vehicle was administered 20 minutes before a 30-minute recording of respiratory pattern or motor behavior. In separate studies, a crossover design was used to administer the drug for 7 and for 14 days. Sarizotan reduced the incidence of apnea in all three RTT mouse models to approximately 15% of their pretreatment levels. The irregular breathing pattern was corrected to that of wild-type littermates. When administered for 7 or 14 days, apnea decreased to 25 to 33% of the incidence seen with vehicle. This study indicates that the clinically approved drug sarizotan is an effective treatment for respiratory disorders in mouse models of RTT.
Collapse
Affiliation(s)
- Ana P. Abdala
- Department of Physiology and Pharmacology, Medical Sciences Building, University of Bristol, Bristol, United Kingdom; and
| | | | | | | | - Julian F. R. Paton
- Department of Physiology and Pharmacology, Medical Sciences Building, University of Bristol, Bristol, United Kingdom; and
| | - John M. Bissonnette
- Departments of Obstetrics & Gynecology, and
- Cell & Developmental Biology, Oregon Health and Science University, Portland, Oregon
| |
Collapse
|
15
|
Bellot B, Peyronnet-Roux J, Gire C, Simeoni U, Vinay L, Viemari JC. Deficits of brainstem and spinal cord functions after neonatal hypoxia-ischemia in mice. Pediatr Res 2014; 75:723-30. [PMID: 24618565 DOI: 10.1038/pr.2014.42] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/23/2013] [Accepted: 12/30/2013] [Indexed: 01/18/2023]
Abstract
BACKGROUND Perinatal cerebral hypoxia-ischemia (HI) can lead to severe neurodevelopmental disorders. Studies in humans and animal models mainly focused on cerebral outcomes, and little is known about the mechanisms that may affect the brainstem and the spinal cord. Dysfunctions of neuromodulatory systems, such as the serotonergic (5-HT) projections, critical for the development of neural networks, have been postulated to underlie behavioral and motor deficits, as well as metabolic changes. METHODS The aim of this study was to investigate brainstem and spinal cord functions by means of plethysmography and sensorimotor tests in a neonatal Rice-Vanucci model of HI in mice. We also evaluated bioaminergic contents in central regions dedicated to the motor control of autonomic functions. RESULTS Mice with cerebral infarct expressed motor disturbances and had a lower body weight and a decreased respiratory frequency than SHAM, suggesting defects of brainstem neural network involved in the motor control of feeding, suckling, swallowing, and respiration. Moreover, our study revealed changes of monoamine and amino acid contents in the brainstem and the spinal cord of HI mice. CONCLUSION Our results suggest that monoaminergic neuromodulation plays an important role in the physiopathology of HI brain injury that may represent a good therapeutic target.
Collapse
Affiliation(s)
- Blandine Bellot
- 1] Institut de Neurosciences de la Timone (P3M Team), UMR 7289, CNRS, Aix Marseille Université, Marseille, France [2] Pôle de Médecine et Réanimation Néonatales, Assistance Publique Hôpitaux de Marseille, Marseille, France
| | - Julie Peyronnet-Roux
- Institut de Neurosciences de la Timone (P3M Team), UMR 7289, CNRS, Aix Marseille Université, Marseille, France
| | - Catherine Gire
- Pôle de Médecine et Réanimation Néonatales, Assistance Publique Hôpitaux de Marseille, Marseille, France
| | - Umberto Simeoni
- 1] Pôle de Médecine et Réanimation Néonatales, Assistance Publique Hôpitaux de Marseille, Marseille, France [2] Aix Marseille Université, Marseille, France
| | - Laurent Vinay
- Institut de Neurosciences de la Timone (P3M Team), UMR 7289, CNRS, Aix Marseille Université, Marseille, France
| | - Jean-Charles Viemari
- Institut de Neurosciences de la Timone (P3M Team), UMR 7289, CNRS, Aix Marseille Université, Marseille, France
| |
Collapse
|
16
|
El-Khoury R, Panayotis N, Matagne V, Ghata A, Villard L, Roux JC. GABA and glutamate pathways are spatially and developmentally affected in the brain of Mecp2-deficient mice. PLoS One 2014; 9:e92169. [PMID: 24667344 PMCID: PMC3965407 DOI: 10.1371/journal.pone.0092169] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Accepted: 02/19/2014] [Indexed: 02/03/2023] Open
Abstract
Proper brain functioning requires a fine-tuning between excitatory and inhibitory neurotransmission, a balance maintained through the regulation and release of glutamate and GABA. Rett syndrome (RTT) is a rare genetic disorder caused by mutations in the methyl-CpG binding protein 2 (MECP2) gene affecting the postnatal brain development. Dysfunctions in the GABAergic and glutamatergic systems have been implicated in the neuropathology of RTT and a disruption of the balance between excitation and inhibition, together with a perturbation of the electrophysiological properties of GABA and glutamate neurons, were reported in the brain of the Mecp2-deficient mouse. However, to date, the extent and the nature of the GABA/glutamate deficit affecting the Mecp2-deficient mouse brain are unclear. In order to better characterize these deficits, we simultaneously analyzed the GABA and glutamate levels in Mecp2-deficient mice at 2 different ages (P35 and P55) and in several brain areas. We used a multilevel approach including the quantification of GABA and glutamate levels, as well as the quantification of the mRNA and protein expression levels of key genes involved in the GABAergic and glutamatergic pathways. Our results show that Mecp2-deficient mice displayed regional- and age-dependent variations in the GABA pathway and, to a lesser extent, in the glutamate pathway. The implication of the GABA pathway in the RTT neuropathology was further confirmed using an in vivo treatment with a GABA reuptake inhibitor that significantly improved the lifespan of Mecp2-deficient mice. Our results confirm that RTT mouse present a deficit in the GABAergic pathway and suggest that GABAergic modulators could be interesting therapeutic agents for this severe neurological disorder.
Collapse
Affiliation(s)
- Rita El-Khoury
- Aix Marseille Université, GMGF, Marseille, France
- Inserm, UMR_S 910, Marseille, France
| | - Nicolas Panayotis
- Aix Marseille Université, GMGF, Marseille, France
- Inserm, UMR_S 910, Marseille, France
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, Israel
| | - Valérie Matagne
- Aix Marseille Université, GMGF, Marseille, France
- Inserm, UMR_S 910, Marseille, France
| | - Adeline Ghata
- Aix Marseille Université, GMGF, Marseille, France
- Inserm, UMR_S 910, Marseille, France
| | - Laurent Villard
- Aix Marseille Université, GMGF, Marseille, France
- Inserm, UMR_S 910, Marseille, France
| | - Jean-Christophe Roux
- Aix Marseille Université, GMGF, Marseille, France
- Inserm, UMR_S 910, Marseille, France
- * E-mail:
| |
Collapse
|
17
|
When norepinephrine becomes a driver of breathing irregularities: how intermittent hypoxia fundamentally alters the modulatory response of the respiratory network. J Neurosci 2014; 34:36-50. [PMID: 24381266 DOI: 10.1523/jneurosci.3644-12.2014] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Neuronal networks are endogenously modulated by aminergic and peptidergic substances. These modulatory processes are critical for maintaining normal activity and adapting networks to changes in metabolic, behavioral, and environmental conditions. However, disturbances in neuromodulation have also been associated with pathologies. Using whole animals (in vivo) and functional brainstem slices (in vitro) from mice, we demonstrate that exposure to acute intermittent hypoxia (AIH) leads to fundamental changes in the neuromodulatory response of the respiratory network located within the preBötzinger complex (preBötC), an area critical for breathing. Norepinephrine, which normally regularizes respiratory activity, renders respiratory activity irregular after AIH. Respiratory irregularities are caused both in vitro and in vivo by AIH, which increases synaptic inhibition within the preBötC when norepinephrine is endogenously or exogenously increased. These irregularities are prevented by blocking synaptic inhibition before AIH. However, regular breathing cannot be reestablished if synaptic inhibition is blocked after AIH. We conclude that subtle changes in synaptic transmission can have dramatic consequences at the network level as endogenously released neuromodulators that are normally adaptive become the drivers of irregularity. Moreover, irregularities in the preBötC result in irregularities in the motor output in vivo and in incomplete transmission of inspiratory activity to the hypoglossus motor nucleus. Our finding has basic science implications for understanding network functions in general, and it may be clinically relevant for understanding pathological disturbances associated with hypoxic episodes such as those associated with myocardial infarcts, obstructive sleep apneas, apneas of prematurity, Rett syndrome, and sudden infant death syndrome.
Collapse
|
18
|
Moroto M, Nishimura A, Morimoto M, Isoda K, Morita T, Yoshida M, Morioka S, Tozawa T, Hasegawa T, Chiyonobu T, Yoshimoto K, Hosoi H. Altered somatosensory barrel cortex refinement in the developing brain of Mecp2-null mice. Brain Res 2013; 1537:319-26. [DOI: 10.1016/j.brainres.2013.09.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Revised: 09/13/2013] [Accepted: 09/16/2013] [Indexed: 12/13/2022]
|
19
|
Sanchez-Mut JV, Aso E, Panayotis N, Lott I, Dierssen M, Rabano A, Urdinguio RG, Fernandez AF, Astudillo A, Martin-Subero JI, Balint B, Fraga MF, Gomez A, Gurnot C, Roux JC, Avila J, Hensch TK, Ferrer I, Esteller M. DNA methylation map of mouse and human brain identifies target genes in Alzheimer's disease. ACTA ACUST UNITED AC 2013; 136:3018-27. [PMID: 24030951 PMCID: PMC3784285 DOI: 10.1093/brain/awt237] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The central nervous system has a pattern of gene expression that is closely regulated with respect to functional and anatomical regions. DNA methylation is a major regulator of transcriptional activity, and aberrations in the distribution of this epigenetic mark may be involved in many neurological disorders, such as Alzheimer’s disease. Herein, we have analysed 12 distinct mouse brain regions according to their CpG 5’-end gene methylation patterns and observed their unique epigenetic landscapes. The DNA methylomes obtained from the cerebral cortex were used to identify aberrant DNA methylation changes that occurred in two mouse models of Alzheimer’s disease. We were able to translate these findings to patients with Alzheimer’s disease, identifying DNA methylation-associated silencing of three targets genes: thromboxane A2 receptor (TBXA2R), sorbin and SH3 domain containing 3 (SORBS3) and spectrin beta 4 (SPTBN4). These hypermethylation targets indicate that the cyclic AMP response element-binding protein (CREB) activation pathway and the axon initial segment could contribute to the disease.
Collapse
Affiliation(s)
- Jose V Sanchez-Mut
- 1 Cancer Epigenetics and Biology Program (PEBC), Bellvitge Biomedical Research Institute (IDIBELL), 08908 L'Hospitalet, Barcelona, Catalonia, Spain
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
20
|
Pietri T, Roman AC, Guyon N, Romano SA, Washbourne P, Moens CB, de Polavieja GG, Sumbre G. The first mecp2-null zebrafish model shows altered motor behaviors. Front Neural Circuits 2013; 7:118. [PMID: 23874272 PMCID: PMC3712905 DOI: 10.3389/fncir.2013.00118] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Accepted: 06/21/2013] [Indexed: 11/13/2022] Open
Abstract
Rett syndrome (RTT) is an X-linked neurodevelopmental disorder and one of the most common causes of mental retardation in affected girls. Other symptoms include a rapid regression of motor and cognitive skills after an apparently early normal development. Sporadic mutations in the transcription factor MECP2 has been shown to be present in more than 90% of the patients and several models of MeCP2-deficient mice have been created to understand the role of this gene. These models have pointed toward alterations in the maintenance of the central nervous system rather than its development, in line with the late onset of the disease in humans. However, the exact functions of MeCP2 remain difficult to delineate and the animal models have yielded contradictory results. Here, we present the first mecp2-null allele mutation zebrafish model. Surprisingly and in contrast to MeCP2-null mouse models, mecp2-null zebrafish are viable and fertile. They present nonetheless clear behavioral alterations during their early development, including spontaneous and sensory-evoked motor anomalies, as well as defective thigmotaxis.
Collapse
Affiliation(s)
- Thomas Pietri
- Ecole Normale Supérieure, Institut de Biologie de l'ENS Paris, France ; Inserm, U1024 Paris, France ; CNRS, UMR 8197 Paris, France
| | | | | | | | | | | | | | | |
Collapse
|
21
|
Ramirez JM, Ward CS, Neul JL. Breathing challenges in Rett syndrome: lessons learned from humans and animal models. Respir Physiol Neurobiol 2013; 189:280-7. [PMID: 23816600 DOI: 10.1016/j.resp.2013.06.022] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Revised: 06/21/2013] [Accepted: 06/24/2013] [Indexed: 01/17/2023]
Abstract
Breathing disturbances are a major challenge in Rett Syndrome (RTT). These disturbances are more pronounced during wakefulness; but irregular breathing occurs also during sleep. During the day patients can exhibit alternating bouts of hypoventilation and irregular hyperventilation. But there is significant individual variability in severity, onset, duration and type of breathing disturbances. Research in mouse models of RTT suggests that different areas in the ventrolateral medulla and pons give rise to different aspects of this breathing disorder. Pre-clinical experiments in mouse models that target different neuromodulatory and neurotransmitter receptors and MeCP2 function within glia cells can partly reverse breathing abnormalities. The success in animal models raises optimism that one day it will be possible to control or potentially cure the devastating symptoms also in human patients with RTT.
Collapse
Affiliation(s)
- Jan-Marino Ramirez
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA 98101, USA; Department of Neurological Surgery, University of Washington, Seattle, WA 98101, USA.
| | | | | |
Collapse
|
22
|
Tsai SJ. Peripheral administration of brain-derived neurotrophic factor to Rett syndrome animal model: a possible approach for the treatment of Rett syndrome. Med Sci Monit 2012; 18:HY33-36. [PMID: 22847207 PMCID: PMC3560688 DOI: 10.12659/msm.883251] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Rett syndrome (RTT) is a postnatal, severe, disabling neurodevelopmental disorder occurring almost exclusively in females and is the second most common cause for genetic mental retardation in girls. In the majority of cases it is caused by mutations in gene (MECP2) encoding methyl-CpG-binding protein 2. Brain-derived neurotrophic factor (BDNF) is a neurotrophic factor playing a major role in neuronal survival, neurogenesis and plasticity. Animal studies suggested that abnormalities in BDNF homeostasis may contribute to the pathogenesis in Mecp2 null mice, and BDNF administration in the Mecp2 mutant brain led to later onset/slower disease progression, suggesting that increased BDNF in the brain could be therapeutic for this disease. Mature BDNF is a 14 kDa protein that may have poor blood-brain barrier penetrability. However, recent animal studies demonstrated that peripheral administration of BDNF, either by intravenous injection or intranasal delivery, could increase BDNF levels in the brain. Thus it is proposed that peripheral administration of BDNF in the early stage could have therapeutic potential for RTT subjects. Furthermore, the combination use of mannitol may temporarily open the blood-brain barrier and facilitate the entry of BDNF into brain. The potential therapeutic effect of peripheral BDNF administration could be tested in RTT animal models such as Mecp2 KO mice, which may provide a new intervention for this devastating disease.
Collapse
Affiliation(s)
- Shih-Jen Tsai
- Department of Psychiatry, Taipei Veterans General Hospital, Taipei, Taiwan
| |
Collapse
|
23
|
Toward MA, Abdala AP, Knopp SJ, Paton JFR, Bissonnette JM. Increasing brain serotonin corrects CO2 chemosensitivity in methyl-CpG-binding protein 2 (Mecp2)-deficient mice. Exp Physiol 2012. [PMID: 23180809 DOI: 10.1113/expphysiol.2012.069872] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Mice deficient in the transcription factor methyl-CpG-binding protein 2 (Mecp2), a mouse model of Rett syndrome, display reduced CO2 chemosensitivity, which may contribute to their breathing abnormalities. In addition, patients with Rett syndrome and male mice that are null for Mecp2 show reduced levels of brain serotonin (5-HT). Serotonin is known to play a role in central chemosensitivity, and we hypothesized that increasing the availability of 5-HT in this mouse model would improve their respiratory response to CO2. Here we determined the apnoeic threshold in heterozygous Mecp2-deficient female mice and examined the effects of blocking 5-HT reuptake on the CO2 response in Mecp2-null male mice. Studies were performed in B6.129P2(C)-Mecp2(τm1.1Bird) null males and heterozygous females. In an in situ preparation, seven of eight Mecp2-deficient heterozygous females showed arrest of phrenic nerve activity when arterial CO2 was lowered to 3%, whereas the wild-types maintained phrenic nerve amplitude at 53 ± 3% of maximal. In vivo plethysmography studies were used to determine CO2 chemosensitivity in null males. These mice were exposed sequentially to 1, 3 and 5% CO2. The percentage increase in minute ventilation in response to increased inspired CO2 was less in Mecp2(-/y) than in Mecp2(+/y) mice. Pretreatment with citalopram, a selective 5-HT reuptake inhibitor (2.5 mg kg(-1) i.p.), 40 min prior to CO2 exposure, in Mecp2(-/y) mice resulted in an improvement in CO2 chemosensitivity to wild-type levels. These results suggest that decreased 5-HT in Mecp2-deficient mice reduces CO2 chemosensitivity, and restoring 5-HT levels can reverse this effect.
Collapse
Affiliation(s)
- Marie A Toward
- Department of Obstetrics and Gynecology, Oregon Health and Science University, Portland, OR 97239, USA
| | | | | | | | | |
Collapse
|
24
|
Ricceri L, De Filippis B, Laviola G. Rett syndrome treatment in mouse models: searching for effective targets and strategies. Neuropharmacology 2012; 68:106-15. [PMID: 22940001 DOI: 10.1016/j.neuropharm.2012.08.010] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2012] [Revised: 08/08/2012] [Accepted: 08/13/2012] [Indexed: 11/24/2022]
Abstract
Rett syndrome (RTT) is a pervasive developmental disorder, primarily affecting girls with a prevalence of 1 in every 10,000 births; it represents the second most common cause of intellectual disability in females. Mutations in the gene encoding methyl-CpG-binding protein 2 (MECP2) have been identified as clear etiological factors in more than 90% of classical RTT cases. Whereas the mechanisms leading to the severe, progressive and specific neurological dysfunctions when this gene is mutated still remain to be elucidated, a series of different mouse models have been generated, bearing different Mecp2 mutation. Neurobehavioural analysis in these mouse lines have been carried out and phenotyping analysis can be now utilised to preclinically evaluate the effects of potential RTT treatments. This review summarizes the different results achieved in this research field taking into account different key targets identified to ameliorate RTT phenotype in mouse models, including those not directly downstream of MeCP2 and those limited to the early phases of postnatal development. This article is part of the Special Issue entitled 'Neurodevelopmental Disorders'.
Collapse
Affiliation(s)
- Laura Ricceri
- Section of Neurotoxicology and Neuroendocrinology, Dept. Cell Biology and Neurosciences, Istituto Superiore di Sanità, Viale Regina Elena, 299, I-00161 Roma, Italy
| | | | | |
Collapse
|
25
|
Dichter GS, Damiano CA, Allen JA. Reward circuitry dysfunction in psychiatric and neurodevelopmental disorders and genetic syndromes: animal models and clinical findings. J Neurodev Disord 2012; 4:19. [PMID: 22958744 PMCID: PMC3464940 DOI: 10.1186/1866-1955-4-19] [Citation(s) in RCA: 199] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2012] [Accepted: 05/02/2012] [Indexed: 02/07/2023] Open
Abstract
This review summarizes evidence of dysregulated reward circuitry function in a range of neurodevelopmental and psychiatric disorders and genetic syndromes. First, the contribution of identifying a core mechanistic process across disparate disorders to disease classification is discussed, followed by a review of the neurobiology of reward circuitry. We next consider preclinical animal models and clinical evidence of reward-pathway dysfunction in a range of disorders, including psychiatric disorders (i.e., substance-use disorders, affective disorders, eating disorders, and obsessive compulsive disorders), neurodevelopmental disorders (i.e., schizophrenia, attention-deficit/hyperactivity disorder, autism spectrum disorders, Tourette's syndrome, conduct disorder/oppositional defiant disorder), and genetic syndromes (i.e., Fragile X syndrome, Prader-Willi syndrome, Williams syndrome, Angelman syndrome, and Rett syndrome). We also provide brief overviews of effective psychopharmacologic agents that have an effect on the dopamine system in these disorders. This review concludes with methodological considerations for future research designed to more clearly probe reward-circuitry dysfunction, with the ultimate goal of improved intervention strategies.
Collapse
Affiliation(s)
- Gabriel S Dichter
- Carolina Institute for Developmental Disabilities, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC, USA
- Department of Psychiatry, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC, USA
- Department of Psychology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Department of Psychiatry, University of North Carolina School of Medicine, CB# 7255, 101 Manning Drive, Chapel Hill, NC, 275997255, USA
| | - Cara A Damiano
- Department of Psychology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - John A Allen
- Neuroscience Research Unit Pfizer Global Research and Development, Groton, CT 06340, USA
| |
Collapse
|
26
|
Pan CH, Tsai S. Early intervention with psychostimulants or antidepressants to increase methyl-CpG-binding protein 2 (MeCP2) expressions: a potential therapy for Rett syndrome. Med Sci Monit 2012; 18:HY1-3. [PMID: 22207122 PMCID: PMC3560675 DOI: 10.12659/msm.882183] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Rett syndrome (RTT) is a severe X-linked postnatal neurodevelopmental disorder. The syndrome is caused primarily by mutations in the methyl CpG binding protein 2 (MeCP2) gene on Xq28. Most individuals with RTT are female, and female RTT is normally heterozygous for mutations in MeCP2. Patients with RTT display a normal period of development prior to the onset of symptoms, at which point they undergo a period of regression. Currently, no effective medication is available for this disorder, although animal studies have suggested that RTT symptoms are potentially reversible. For females with RTT, the severity of symptoms and progression of the disease varies a great deal, despite its homogenous genetic origin. These differences could be attributed to differences in the mutation points of MeCP2 and the skew caused by X-chromosome inactivation. Thus, the increased expression in the normal MeCP2 gene could decrease the severity of the disease. Based on findings from studies on animals indicating that fluoxetine (an antidepressant) and cocaine (a psychostimulant) can increase MeCP2 expression in the brain, it is suggested that early intervention with antidepressants or psychostimulants could increase the normal MeCP2 expression in females with RTT, who are normally heterozygous. This therapeutic hypothesis could be tested in an RTT animal model. Following the identification of the antidepressants or psychostimulants with the greatest influence on MeCP2 expression, a combination of early detection of the disorder with early intervention may result in improved therapeutic outcomes. Furthermore, a trial investigating the effects of antidepressants or psychostimulants on MeCP2 expression in lymphocyte culture from patients with RTT is suggested for clinical therapeutic prediction.
Collapse
Affiliation(s)
- Chia-Ho Pan
- Department of Psychiatry, Shin Kong Wu Ho-Su Memorial Hospital, Taipei, Taiwan
| | | |
Collapse
|