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Loss of MeCP2 from forebrain excitatory neurons leads to cortical hyperexcitation and seizures. J Neurosci 2014; 34:2754-63. [PMID: 24523563 DOI: 10.1523/jneurosci.4900-12.2014] [Citation(s) in RCA: 94] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Mutations of MECP2 cause Rett syndrome (RTT), a neurodevelopmental disorder leading to loss of motor and cognitive functions, impaired social interactions, and seizure at young ages. Defects of neuronal circuit development and function are thought to be responsible for the symptoms of RTT. The majority of RTT patients show recurrent seizures, indicating that neuronal hyperexcitation is a common feature of RTT. However, mechanisms underlying hyperexcitation in RTT are poorly understood. Here we show that deletion of Mecp2 from cortical excitatory neurons but not forebrain inhibitory neurons in the mouse leads to spontaneous seizures. Selective deletion of Mecp2 from excitatory but not inhibitory neurons in the forebrain reduces GABAergic transmission in layer 5 pyramidal neurons in the prefrontal and somatosensory cortices. Loss of MeCP2 from cortical excitatory neurons reduces the number of GABAergic synapses in the cortex, and enhances the excitability of layer 5 pyramidal neurons. Using single-cell deletion of Mecp2 in layer 2/3 pyramidal neurons, we show that GABAergic transmission is reduced in neurons without MeCP2, but is normal in neighboring neurons with MeCP2. Together, these results suggest that MeCP2 in cortical excitatory neurons plays a critical role in the regulation of GABAergic transmission and cortical excitability.
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52
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Xu X, Kozikowski AP, Pozzo-Miller L. A selective histone deacetylase-6 inhibitor improves BDNF trafficking in hippocampal neurons from Mecp2 knockout mice: implications for Rett syndrome. Front Cell Neurosci 2014; 8:68. [PMID: 24639629 PMCID: PMC3945638 DOI: 10.3389/fncel.2014.00068] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2014] [Accepted: 02/17/2014] [Indexed: 12/20/2022] Open
Abstract
Rett syndrome (RTT) is a neurodevelopmental disorder caused by loss-of-function mutations in the transcriptional modulator methyl-CpG-binding protein 2 (MECP2). One of the most prominent gene targets of MeCP2 is brain-derived neurotrophic factor (Bdnf), a potent modulator of activity-dependent synaptic development, function and plasticity. Dysfunctional BDNF signaling has been demonstrated in several pathophysiological mechanisms of RTT disease progression. To evaluate whether the dynamics of BDNF trafficking is affected by Mecp2 deletion, we analyzed movements of BDNF tagged with yellow fluorescent protein (YFP) in cultured hippocampal neurons by time-lapse fluorescence imaging. We found that both anterograde and retrograde vesicular trafficking of BDNF-YFP are significantly impaired in Mecp2 knockout hippocampal neurons. Selective inhibitors of histone deacetylase 6 (HDAC6) show neuroprotective effects in neurodegenerative diseases and stimulate microtubule-dependent vesicular trafficking of BDNF-containing dense core vesicles. Here, we show that the selective HDAC6 inhibitor Tubastatin-A increased the velocity of BDNF-YFP vesicles in Mecp2 knockout neurons in both directions by increasing α–tubulin acetylation. Tubastatin-A also restored activity-dependent BDNF release from Mecp2 knockout neurons to levels comparable to those shown by wildtype neurons. These findings demonstrate that a selective HDAC6 inhibitor is a potential pharmacological strategy to reverse cellular and synaptic impairments in RTT resulting from impaired BDNF signaling.
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Affiliation(s)
- Xin Xu
- Department of Neurobiology, Civitan International Research Center, The University of Alabama at Birmingham Birmingham, AL, USA
| | - Alan P Kozikowski
- Drug Discovery Program, Department of Medicinal Chemistry and Pharmacognosy, University of Illinois at Chicago Chicago, IL, USA
| | - Lucas Pozzo-Miller
- Department of Neurobiology, Civitan International Research Center, The University of Alabama at Birmingham Birmingham, AL, USA
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Abstract
Rett syndrome (RTT) is a devastating neurodevelopmental disorder with autistic features caused by loss-of-function mutations in the gene encoding methyl-CpG-binding protein 2 (MECP2), a transcriptional regulatory protein. RTT has attracted widespread attention not only because of the urgent need for treatments, but also because it has become a window into basic mechanisms underlying epigenetic regulation of neuronal genes, including BDNF. In addition, work in mouse models of the disease has demonstrated the possibility of symptom reversal upon restoration of normal gene function. This latter finding has resulted in a paradigm shift in RTT research and, indeed, in the field of neurodevelopmental disorders as a whole, and spurred the search for potential therapies for RTT and related syndromes. In this context, the discovery that expression of BDNF is dysregulated in RTT and mouse models of the disease has taken on particular importance. This chapter reviews the still evolving story of how MeCP2 might regulate expression of BDNF, the functional consequences of BDNF deficits in Mecp2 mutant mice, and progress in developing BDNF-targeted therapies for the treatment of RTT.
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Affiliation(s)
- D M Katz
- Department of Neurosciences, Case Western Reserve University School of Medicine, 10900 Euclid Avenue, Cleveland, OH, 44106, USA,
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54
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Ong HL, de Souza LB, Cheng KT, Ambudkar IS. Physiological functions and regulation of TRPC channels. Handb Exp Pharmacol 2014; 223:1005-34. [PMID: 24961978 DOI: 10.1007/978-3-319-05161-1_12] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The TRP-canonical (TRPC) subfamily, which consists of seven members (TRPC1-TRPC7), are Ca(2+)-permeable cation channels that are activated in response to receptor-mediated PIP2 hydrolysis via store-dependent and store-independent mechanisms. These channels are involved in a variety of physiological functions in different cell types and tissues. Of these, TRPC6 has been linked to a channelopathy resulting in human disease. Two key players of the store-dependent regulatory pathway, STIM1 and Orai1, interact with some TRPC channels to gate and regulate channel activity. The Ca(2+) influx mediated by TRPC channels generates distinct intracellular Ca(2+) signals that regulate downstream signaling events and consequent cell functions. This requires localization of TRPC channels in specific plasma membrane microdomains and precise regulation of channel function which is coordinated by various scaffolding, trafficking, and regulatory proteins.
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Affiliation(s)
- Hwei Ling Ong
- Secretory Physiology Section, Molecular Physiology and Therapeutics Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, 20892, USA
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Lindner R, Puttagunta R, Di Giovanni S. Epigenetic regulation of axon outgrowth and regeneration in CNS injury: the first steps forward. Neurotherapeutics 2013; 10:771-81. [PMID: 23881454 PMCID: PMC3805867 DOI: 10.1007/s13311-013-0203-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Inadequate axonal sprouting and lack of regeneration limit functional recovery following neurologic injury, such as stroke, brain, and traumatic spinal cord injury. Recently, the enhancement of the neuronal regenerative program has led to promising improvements in axonal sprouting and regeneration in animal models of axonal injury. However, precise knowledge of the essential molecular determinants of this regenerative program remains elusive, thus limiting the choice of fully effective therapeutic strategies. Given that molecular regulation of axonal outgrowth and regeneration requires carefully orchestrated waves of gene expression, both temporally and spatially, epigenetic changes may be an ideal regulatory mechanism to address this unique need. While recent evidence suggests that epigenetic modifications could contribute to the regulation of axonal outgrowth and regeneration following axonal injury in models of stroke, and spinal cord and optic nerve injury, a number of unanswered questions remain. Such questions require systematic investigation of the epigenetic landscape between regenerative and non-regenerative conditions for the potential translation of this knowledge into regenerative strategies in human spinal and brain injury, as well as stroke.
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Affiliation(s)
- Ricco Lindner
- Laboratory for NeuroRegeneration and Repair, Center for Neurology, Hertie Institute for Clinical Brain Research, University of Tuebingen, Otfried-Mueller Strasse 27, 72076 Tuebingen, Germany
| | - Radhika Puttagunta
- Laboratory for NeuroRegeneration and Repair, Center for Neurology, Hertie Institute for Clinical Brain Research, University of Tuebingen, Otfried-Mueller Strasse 27, 72076 Tuebingen, Germany
| | - Simone Di Giovanni
- Laboratory for NeuroRegeneration and Repair, Center for Neurology, Hertie Institute for Clinical Brain Research, University of Tuebingen, Otfried-Mueller Strasse 27, 72076 Tuebingen, Germany
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56
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Larimore J, Ryder PV, Kim KY, Ambrose LA, Chapleau C, Calfa G, Gross C, Bassell GJ, Pozzo-Miller L, Smith Y, Talbot K, Park IH, Faundez V. MeCP2 regulates the synaptic expression of a Dysbindin-BLOC-1 network component in mouse brain and human induced pluripotent stem cell-derived neurons. PLoS One 2013; 8:e65069. [PMID: 23750231 PMCID: PMC3672180 DOI: 10.1371/journal.pone.0065069] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Accepted: 04/22/2013] [Indexed: 02/06/2023] Open
Abstract
Clinical, epidemiological, and genetic evidence suggest overlapping pathogenic mechanisms between autism spectrum disorder (ASD) and schizophrenia. We tested this hypothesis by asking if mutations in the ASD gene MECP2 which cause Rett syndrome affect the expression of genes encoding the schizophrenia risk factor dysbindin, a subunit of the biogenesis of lysosome-related organelles complex-1 (BLOC-1), and associated interacting proteins. We measured mRNA and protein levels of key components of a dysbindin interaction network by, quantitative real time PCR and quantitative immunohistochemistry in hippocampal samples of wild-type and Mecp2 mutant mice. In addition, we confirmed results by performing immunohistochemistry of normal human hippocampus and quantitative qRT-PCR of human inducible pluripotent stem cells (iPSCs)-derived human neurons from Rett syndrome patients. We defined the distribution of the BLOC-1 subunit pallidin in human and mouse hippocampus and contrasted this distribution with that of symptomatic Mecp2 mutant mice. Neurons from mutant mice and Rett syndrome patients displayed selectively reduced levels of pallidin transcript. Pallidin immunoreactivity decreased in the hippocampus of symptomatic Mecp2 mutant mice, a feature most prominent at asymmetric synapses as determined by immunoelectron microcopy. Pallidin immunoreactivity decreased concomitantly with reduced BDNF content in the hippocampus of Mecp2 mice. Similarly, BDNF content was reduced in the hippocampus of BLOC-1 deficient mice suggesting that genetic defects in BLOC-1 are upstream of the BDNF phenotype in Mecp2 deficient mice. Our results demonstrate that the ASD-related gene Mecp2 regulates the expression of components belonging to the dysbindin interactome and these molecular differences may contribute to synaptic phenotypes that characterize Mecp2 deficiencies and ASD.
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Affiliation(s)
- Jennifer Larimore
- Department of Biology, Agnes Scott College, Decatur, Georgia, United States of America
| | - Pearl V. Ryder
- Cell Biology, Emory University, Atlanta, Georgia, United States of America
| | - Kun-Yong Kim
- Department of Genetics, Yale Stem Cell Center, Yale School of Medicine, New Haven, Connecticut, United States of America
| | - L. Alex Ambrose
- Department of Biology, Agnes Scott College, Decatur, Georgia, United States of America
| | - Christopher Chapleau
- Department of Neurobiology, The University of Alabama, Birmingham, Alabama, United States of America
| | - Gaston Calfa
- Department of Neurobiology, The University of Alabama, Birmingham, Alabama, United States of America
| | - Christina Gross
- Cell Biology, Emory University, Atlanta, Georgia, United States of America
| | - Gary J. Bassell
- Cell Biology, Emory University, Atlanta, Georgia, United States of America
| | - Lucas Pozzo-Miller
- Department of Neurobiology, The University of Alabama, Birmingham, Alabama, United States of America
| | - Yoland Smith
- Department of Neurology, Emory University, Atlanta, Georgia, United States of America
- Yerkes National Primate Center, Emory University, Atlanta, Georgia, United States of America
| | - Konrad Talbot
- Center for Neurobiology and Behavior, Department of Psychiatry, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - In-Hyun Park
- Department of Genetics, Yale Stem Cell Center, Yale School of Medicine, New Haven, Connecticut, United States of America
| | - Victor Faundez
- Cell Biology, Emory University, Atlanta, Georgia, United States of America
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Katz DM, Berger-Sweeney JE, Eubanks JH, Justice MJ, Neul JL, Pozzo-Miller L, Blue ME, Christian D, Crawley JN, Giustetto M, Guy J, Howell CJ, Kron M, Nelson SB, Samaco RC, Schaevitz LR, St Hillaire-Clarke C, Young JL, Zoghbi HY, Mamounas LA. Preclinical research in Rett syndrome: setting the foundation for translational success. Dis Model Mech 2013; 5:733-45. [PMID: 23115203 PMCID: PMC3484856 DOI: 10.1242/dmm.011007] [Citation(s) in RCA: 155] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
In September of 2011, the National Institute of Neurological Disorders and Stroke (NINDS), the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), the International Rett Syndrome Foundation (IRSF) and the Rett Syndrome Research Trust (RSRT) convened a workshop involving a broad cross-section of basic scientists, clinicians and representatives from the National Institutes of Health (NIH), the US Food and Drug Administration (FDA), the pharmaceutical industry and private foundations to assess the state of the art in animal studies of Rett syndrome (RTT). The aim of the workshop was to identify crucial knowledge gaps and to suggest scientific priorities and best practices for the use of animal models in preclinical evaluation of potential new RTT therapeutics. This review summarizes outcomes from the workshop and extensive follow-up discussions among participants, and includes: (1) a comprehensive summary of the physiological and behavioral phenotypes of RTT mouse models to date, and areas in which further phenotypic analyses are required to enhance the utility of these models for translational studies; (2) discussion of the impact of genetic differences among mouse models, and methodological differences among laboratories, on the expression and analysis, respectively, of phenotypic traits; and (3) definitions of the standards that the community of RTT researchers can implement for rigorous preclinical study design and transparent reporting to ensure that decisions to initiate costly clinical trials are grounded in reliable preclinical data.
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Affiliation(s)
- David M Katz
- Department of Neurosciences, Case Western Reserve University School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44120, USA.
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Li W, Pozzo-Miller L. BDNF deregulation in Rett syndrome. Neuropharmacology 2013; 76 Pt C:737-46. [PMID: 23597512 DOI: 10.1016/j.neuropharm.2013.03.024] [Citation(s) in RCA: 114] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Revised: 02/25/2013] [Accepted: 03/15/2013] [Indexed: 12/21/2022]
Abstract
BDNF is the best-characterized neurotrophin in terms of its gene structure and modulation, secretion processing, and signaling cascades following its release. In addition to diverse features at the genetic and molecular levels, the abundant expression in several regions of the central nervous system has implicated BDNF as a potent modulator in many aspects of neuronal development, as well as synaptic transmission and plasticity. Impairments in any of these critical functions likely contribute to a wide array of neurodevelopmental, neurodegenerative, and neuropsychiatric diseases. In this review, we focus on a prevalent neurodevelopmental disorder, Rett syndrome (RTT), which afflicts 1:15,000 women world-wide. We describe the consequences of loss-of-function mutations in the gene encoding the transcription factor methyl-CpG binding protein 2 (MeCP2) in RTT, and then elaborate on the current understanding of how MeCP2 controls BDNF expression. Finally, we discuss the literature regarding alterations in BDNF levels in RTT individuals and MeCP2-based mouse models, as well as recent progress in searching for rational therapeutic interventions. This article is part of the Special Issue entitled 'BDNF Regulation of Synaptic Structure, Function, and Plasticity'.
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Affiliation(s)
- Wei Li
- Department of Neurobiology, Civitan International Research Center, The University of Alabama at Birmingham, Birmingham, AL 35294, USA
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59
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Gapp K, Woldemichael BT, Bohacek J, Mansuy IM. Epigenetic regulation in neurodevelopment and neurodegenerative diseases. Neuroscience 2012; 264:99-111. [PMID: 23256926 DOI: 10.1016/j.neuroscience.2012.11.040] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Revised: 11/08/2012] [Accepted: 11/21/2012] [Indexed: 01/25/2023]
Abstract
From fertilization throughout development and until death, cellular programs in individual cells are dynamically regulated to fulfill multiple functions ranging from cell lineage specification to adaptation to internal and external stimuli. Such regulation is of major importance in brain cells, because the brain continues to develop long after birth and incorporates information from the environment across life. When compromised, these regulatory mechanisms can have detrimental consequences on neurodevelopment and lead to severe brain pathologies and neurodegenerative diseases in the adult individual. Elucidating these processes is essential to better understand their implication in disease etiology. Because they are strongly influenced by environmental factors, they have been postulated to depend on epigenetic mechanisms. This review describes recent studies that have identified epigenetic dysfunctions in the pathophysiology of several neurodevelopmental and neurodegenerative diseases. It discusses currently known pathways and molecular targets implicated in pathologies including imprinting disorders, Rett syndrome, and Alzheimer's, Parkinson's and Hungtinton's disease, and their relevance to these diseases.
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Affiliation(s)
- K Gapp
- Brain Research Institute, Medical Faculty of the University of Zürich and Swiss Federal Institute of Technology, Neuroscience Center Zürich, Zürich, Switzerland
| | - B T Woldemichael
- Brain Research Institute, Medical Faculty of the University of Zürich and Swiss Federal Institute of Technology, Neuroscience Center Zürich, Zürich, Switzerland
| | - J Bohacek
- Brain Research Institute, Medical Faculty of the University of Zürich and Swiss Federal Institute of Technology, Neuroscience Center Zürich, Zürich, Switzerland
| | - I M Mansuy
- Brain Research Institute, Medical Faculty of the University of Zürich and Swiss Federal Institute of Technology, Neuroscience Center Zürich, Zürich, Switzerland.
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