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Oluigbo DC. Rett Syndrome: A Tale of Altered Genetics, Synaptic Plasticity, and Neurodevelopmental Dynamics. Cureus 2023; 15:e41555. [PMID: 37554594 PMCID: PMC10405636 DOI: 10.7759/cureus.41555] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/07/2023] [Indexed: 08/10/2023] Open
Abstract
Rett syndrome (RTT) is a neurodevelopmental disorder that is a leading cause of severe cognitive and physical impairment. RTT typically occurs in females, although rare cases of males with the disease exist. Its genetic cause, symptoms, and clinical progression timeline have also become well-documented since its initial discovery. However, a relatively late diagnosis and lack of an available cure signify that our understanding of the disease is incomplete. Innovative research methods and tools are thereby helping to fill gaps in our knowledge of RTT. Specifically, mouse models of RTT, video analysis, and retrospective parental analysis are well-established tools that provide valuable insights into RTT. Moreover, current and anticipated treatment options are improving the quality of life of the RTT patient population. Collectively, these developments are creating optimistic future perspectives for RTT.
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Affiliation(s)
- David C Oluigbo
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, USA
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2
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Medina E, Peterson S, Ford K, Singletary K, Peixoto L. Critical periods and Autism Spectrum Disorders, a role for sleep. Neurobiol Sleep Circadian Rhythms 2023; 14:100088. [PMID: 36632570 PMCID: PMC9826922 DOI: 10.1016/j.nbscr.2022.100088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 12/16/2022] [Accepted: 12/19/2022] [Indexed: 12/24/2022] Open
Abstract
Brain development relies on both experience and genetically defined programs. Time windows where certain brain circuits are particularly receptive to external stimuli, resulting in heightened plasticity, are referred to as "critical periods". Sleep is thought to be essential for normal brain development. Importantly, studies have shown that sleep enhances critical period plasticity and promotes experience-dependent synaptic pruning in the developing mammalian brain. Therefore, normal plasticity during critical periods depends on sleep. Problems falling and staying asleep occur at a higher rate in Autism Spectrum Disorder (ASD) relative to typical development. In this review, we explore the potential link between sleep, critical period plasticity, and ASD. First, we review the importance of critical period plasticity in typical development and the role of sleep in this process. Next, we summarize the evidence linking ASD with deficits in synaptic plasticity in rodent models of high-confidence ASD gene candidates. We then show that the high-confidence rodent models of ASD that show sleep deficits also display plasticity deficits. Given how important sleep is for critical period plasticity, it is essential to understand the connections between synaptic plasticity, sleep, and brain development in ASD. However, studies investigating sleep or plasticity during critical periods in ASD mouse models are lacking. Therefore, we highlight an urgent need to consider developmental trajectory in studies of sleep and plasticity in neurodevelopmental disorders.
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Affiliation(s)
- Elizabeth Medina
- Department of Translational Medicine and Physiology, Sleep and Performance Research Center, Elson S. Floyd College of Medicine, Washington State University, Spokane, WA, United States
| | - Sarah Peterson
- Department of Translational Medicine and Physiology, Sleep and Performance Research Center, Elson S. Floyd College of Medicine, Washington State University, Spokane, WA, United States
| | - Kaitlyn Ford
- Department of Translational Medicine and Physiology, Sleep and Performance Research Center, Elson S. Floyd College of Medicine, Washington State University, Spokane, WA, United States
| | - Kristan Singletary
- Department of Translational Medicine and Physiology, Sleep and Performance Research Center, Elson S. Floyd College of Medicine, Washington State University, Spokane, WA, United States
| | - Lucia Peixoto
- Department of Translational Medicine and Physiology, Sleep and Performance Research Center, Elson S. Floyd College of Medicine, Washington State University, Spokane, WA, United States
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3
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Fogarty MJ. Inhibitory Synaptic Influences on Developmental Motor Disorders. Int J Mol Sci 2023; 24:ijms24086962. [PMID: 37108127 PMCID: PMC10138861 DOI: 10.3390/ijms24086962] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Revised: 04/05/2023] [Accepted: 04/06/2023] [Indexed: 04/29/2023] Open
Abstract
During development, GABA and glycine play major trophic and synaptic roles in the establishment of the neuromotor system. In this review, we summarise the formation, function and maturation of GABAergic and glycinergic synapses within neuromotor circuits during development. We take special care to discuss the differences in limb and respiratory neuromotor control. We then investigate the influences that GABAergic and glycinergic neurotransmission has on two major developmental neuromotor disorders: Rett syndrome and spastic cerebral palsy. We present these two syndromes in order to contrast the approaches to disease mechanism and therapy. While both conditions have motor dysfunctions at their core, one condition Rett syndrome, despite having myriad symptoms, has scientists focused on the breathing abnormalities and their alleviation-to great clinical advances. By contrast, cerebral palsy remains a scientific quagmire or poor definitions, no widely adopted model and a lack of therapeutic focus. We conclude that the sheer abundance of diversity of inhibitory neurotransmitter targets should provide hope for intractable conditions, particularly those that exhibit broad spectra of dysfunction-such as spastic cerebral palsy and Rett syndrome.
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Affiliation(s)
- Matthew J Fogarty
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, MN 55902, USA
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Chen C, Ma X, Wei J, Shakir N, Zhang JK, Zhang L, Nehme A, Cui Y, Ferguson D, Bai F, Qiu S. Early impairment of cortical circuit plasticity and connectivity in the 5XFAD Alzheimer's disease mouse model. Transl Psychiatry 2022; 12:371. [PMID: 36075886 PMCID: PMC9458752 DOI: 10.1038/s41398-022-02132-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Revised: 08/16/2022] [Accepted: 08/22/2022] [Indexed: 11/09/2022] Open
Abstract
Genetic risk factors for neurodegenerative disorders, such as Alzheimer's disease (AD), are expressed throughout the life span. How these risk factors affect early brain development and function remain largely unclear. Analysis of animal models with high constructive validity for AD, such as the 5xFAD mouse model, may provide insights on potential early neurodevelopmental effects that impinge on adult brain function and age-dependent degeneration. The 5XFAD mouse model over-expresses human amyloid precursor protein (APP) and presenilin 1 (PS1) harboring five familial AD mutations. It is unclear how the expression of these mutant proteins affects early developing brain circuits. We found that the prefrontal cortex (PFC) layer 5 (L5) neurons in 5XFAD mice exhibit transgenic APP overloading at an early post-weaning age. Impaired synaptic plasticity (long-term potentiation, LTP) was seen at 6-8 weeks age in L5 PFC circuit, which was correlated with increased intracellular APP. APP overloading was also seen in L5 pyramidal neurons in the primary visual cortex (V1) during the critical period of plasticity (4-5 weeks age). Whole-cell patch clamp recording in V1 brain slices revealed reduced intrinsic excitability of L5 neurons in 5XFAD mice, along with decreased spontaneous miniature excitatory and inhibitory inputs. Functional circuit mapping using laser scanning photostimulation (LSPS) combined with glutamate uncaging uncovered reduced excitatory synaptic connectivity onto L5 neurons in V1, and a more pronounced reduction in inhibitory connectivity, indicative of altered excitation and inhibition during VC critical period. Lastly, in vivo single-unit recording in V1 confirmed that monocular visual deprivation-induced ocular dominance plasticity during critical period was impaired in 5XFAD mice. Our study reveals plasticity deficits across multiple cortical regions and indicates altered early cortical circuit developmental trajectory as a result of mutant APP/PS1 over-expression.
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Affiliation(s)
- Chang Chen
- grid.41156.370000 0001 2314 964XDepartment of Neurology, Affiliated Drum Tower Hospital, Medical School of Nanjing University, Nanjing, Jiangsu 210008 China ,grid.134563.60000 0001 2168 186XBasic Medical Sciences, University of Arizona College of Medicine-Phoenix, Phoenix, AZ 85004 USA
| | - Xiaokuang Ma
- grid.134563.60000 0001 2168 186XBasic Medical Sciences, University of Arizona College of Medicine-Phoenix, Phoenix, AZ 85004 USA
| | - Jing Wei
- grid.134563.60000 0001 2168 186XBasic Medical Sciences, University of Arizona College of Medicine-Phoenix, Phoenix, AZ 85004 USA
| | - Neha Shakir
- grid.134563.60000 0001 2168 186XBasic Medical Sciences, University of Arizona College of Medicine-Phoenix, Phoenix, AZ 85004 USA
| | - Jessica K. Zhang
- grid.134563.60000 0001 2168 186XBasic Medical Sciences, University of Arizona College of Medicine-Phoenix, Phoenix, AZ 85004 USA
| | - Le Zhang
- grid.134563.60000 0001 2168 186XBasic Medical Sciences, University of Arizona College of Medicine-Phoenix, Phoenix, AZ 85004 USA
| | - Antoine Nehme
- grid.134563.60000 0001 2168 186XBasic Medical Sciences, University of Arizona College of Medicine-Phoenix, Phoenix, AZ 85004 USA
| | - Yuehua Cui
- grid.134563.60000 0001 2168 186XBasic Medical Sciences, University of Arizona College of Medicine-Phoenix, Phoenix, AZ 85004 USA
| | - Deveroux Ferguson
- grid.134563.60000 0001 2168 186XBasic Medical Sciences, University of Arizona College of Medicine-Phoenix, Phoenix, AZ 85004 USA
| | - Feng Bai
- Department of Neurology, Affiliated Drum Tower Hospital, Medical School of Nanjing University, Nanjing, Jiangsu, 210008, China.
| | - Shenfeng Qiu
- Basic Medical Sciences, University of Arizona College of Medicine-Phoenix, Phoenix, AZ, 85004, USA.
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Horvath PM, Piazza MK, Kavalali ET, Monteggia LM. MeCP2 loss-of-function dysregulates microRNAs regionally and disrupts excitatory/inhibitory synaptic transmission balance. Hippocampus 2022; 32:610-623. [PMID: 35851733 PMCID: PMC9344394 DOI: 10.1002/hipo.23455] [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: 07/19/2021] [Revised: 06/11/2022] [Accepted: 06/25/2022] [Indexed: 11/06/2022]
Abstract
Rett syndrome is a leading cause of intellectual disability in females primarily caused by loss of function mutations in the transcriptional regulator MeCP2. Loss of MeCP2 leads to a host of synaptic phenotypes that are believed to underlie Rett syndrome pathophysiology. Synaptic deficits vary by brain region upon MeCP2 loss, suggesting distinct molecular alterations leading to disparate synaptic outcomes. In this study, we examined the contribution of MeCP2's newly described role in miRNA regulation to regional molecular and synaptic impairments. Two miRNAs, miR-101a and miR-203, were identified and confirmed as upregulated in MeCP2 KO mice in the hippocampus and cortex, respectively. miR-101a overexpression in hippocampal cultures led to opposing effects at excitatory and inhibitory synapses and in spontaneous and evoked neurotransmission, revealing the potential for a single miRNA to broadly regulate synapse function in the hippocampus. These results highlight the importance of regional alterations in miRNA expression and the specific impact on synaptic function with potential implications for Rett syndrome.
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Affiliation(s)
- Patricia M. Horvath
- Department of Pharmacology, Vanderbilt University, Nashville, Tennessee, USA,Department of Neuroscience, The University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Michelle K. Piazza
- Vanderbilt Brain Institute, Vanderbilt University, Nashville, Tennessee, USA,Neuroscience Program, Vanderbilt University, Nashville, Tennessee, USA
| | - Ege T. Kavalali
- Department of Pharmacology, Vanderbilt University, Nashville, Tennessee, USA,Vanderbilt Brain Institute, Vanderbilt University, Nashville, Tennessee, USA
| | - Lisa M. Monteggia
- Department of Pharmacology, Vanderbilt University, Nashville, Tennessee, USA,Vanderbilt Brain Institute, Vanderbilt University, Nashville, Tennessee, USA
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Li W. Excitation and Inhibition Imbalance in Rett Syndrome. Front Neurosci 2022; 16:825063. [PMID: 35250460 PMCID: PMC8894599 DOI: 10.3389/fnins.2022.825063] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Accepted: 01/31/2022] [Indexed: 12/12/2022] Open
Abstract
A loss of the excitation/inhibition (E/I) balance in the neural circuit has emerged as a common neuropathological feature in many neurodevelopmental disorders. Rett syndrome (RTT), a prevalent neurodevelopmental disorder that affects 1:10,000-15,000 women globally, is caused by loss-of-function mutations in the Methyl-CpG-binding Protein-2 (Mecp2) gene. E/I imbalance is recognized as the leading cellular and synaptic hallmark that is fundamental to diverse RTT neurological symptoms, including stereotypic hand movements, impaired motor coordination, breathing irregularities, seizures, and learning/memory dysfunctions. E/I balance in RTT is not homogeneously altered but demonstrates brain region and cell type specificity instead. In this review, I elaborate on the current understanding of the loss of E/I balance in a range of brain areas at molecular and cellular levels. I further describe how the underlying cellular mechanisms contribute to the disturbance of the proper E/I ratio. Last, I discuss current pharmacologic innervations for RTT and their role in modifying the E/I balance.
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Affiliation(s)
- Wei Li
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, AL, United States
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Loss of O-GlcNAcylation on MeCP2 at Threonine 203 Leads to Neurodevelopmental Disorders. Neurosci Bull 2021; 38:113-134. [PMID: 34773221 PMCID: PMC8821740 DOI: 10.1007/s12264-021-00784-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2021] [Accepted: 08/06/2021] [Indexed: 02/03/2023] Open
Abstract
Mutations of the X-linked methyl-CpG-binding protein 2 (MECP2) gene in humans are responsible for most cases of Rett syndrome (RTT), an X-linked progressive neurological disorder. While genome-wide screens in clinical trials have revealed several putative RTT-associated mutations in MECP2, their causal relevance regarding the functional regulation of MeCP2 at the etiologic sites at the protein level requires more evidence. In this study, we demonstrated that MeCP2 was dynamically modified by O-linked-β-N-acetylglucosamine (O-GlcNAc) at threonine 203 (T203), an etiologic site in RTT patients. Disruption of the O-GlcNAcylation of MeCP2 specifically at T203 impaired dendrite development and spine maturation in cultured hippocampal neurons, and disrupted neuronal migration, dendritic spine morphogenesis, and caused dysfunction of synaptic transmission in the developing and juvenile mouse cerebral cortex. Mechanistically, genetic disruption of O-GlcNAcylation at T203 on MeCP2 decreased the neuronal activity-induced induction of Bdnf transcription. Our study highlights the critical role of MeCP2 T203 O-GlcNAcylation in neural development and synaptic transmission potentially via brain-derived neurotrophic factor.
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Yue Y, Xu P, Liu Z, Sun X, Su J, Du H, Chen L, Ash RT, Smirnakis S, Simha R, Kusner L, Zeng C, Lu H. Motor training improves coordination and anxiety in symptomatic Mecp2-null mice despite impaired functional connectivity within the motor circuit. SCIENCE ADVANCES 2021; 7:eabf7467. [PMID: 34678068 PMCID: PMC8535852 DOI: 10.1126/sciadv.abf7467] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Accepted: 09/01/2021] [Indexed: 05/03/2023]
Abstract
Rett syndrome (RTT) is a severe neurodevelopmental disorder caused by loss of function of the X-linked methyl-CpG–binding protein 2 (MECP2). Several case studies report that gross motor function can be improved in children with RTT through treadmill walking, but whether the MeCP2-deficient motor circuit can support actual motor learning remains unclear. We used two-photon calcium imaging to simultaneously observe layer (L) 2/3 and L5a excitatory neuronal activity in the motor cortex (M1) while mice adapted to changing speeds on a computerized running wheel. Despite circuit hypoactivity and weakened functional connectivity across L2/3 and L5a, the Mecp2-null circuit’s firing pattern evolved with improved performance over 2 weeks. Moreover, trained mice became less anxious and lived 20% longer than untrained mice. Because motor deficits and anxiety are core symptoms of RTT, which is not diagnosed until well after symptom onset, these results underscore the benefit of motor learning.
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Affiliation(s)
- Yuanlei Yue
- Department of Pharmacology and Physiology, School of Medicine and Health Sciences, The George Washington University, Washington, DC 20037, USA
| | - Pan Xu
- Department of Pharmacology and Physiology, School of Medicine and Health Sciences, The George Washington University, Washington, DC 20037, USA
| | - Zhichao Liu
- Department of Physics, Columbian College of Arts and Sciences, The George Washington University, Washington, DC 20037, USA
| | - Xiaoqian Sun
- Department of Computer Science, School of Engineering and Applied Science, The George Washington University, Washington, DC 20037, USA
| | - Juntao Su
- Department of Statistics, Columbian College of Arts and Sciences, The George Washington University, Washington, DC 20037, USA
| | - Hongfei Du
- Department of Statistics, Columbian College of Arts and Sciences, The George Washington University, Washington, DC 20037, USA
| | - Lingling Chen
- Department of Pharmacology and Physiology, School of Medicine and Health Sciences, The George Washington University, Washington, DC 20037, USA
| | - Ryan T. Ash
- Department of Psychiatry, Stanford University, Palo Alto, CA 94305, USA
| | - Stelios Smirnakis
- Department of Neurology, Brigham and Women’s Hospital, Jamaica Plain VA Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Rahul Simha
- Department of Computer Science, School of Engineering and Applied Science, The George Washington University, Washington, DC 20037, USA
| | - Linda Kusner
- Department of Pharmacology and Physiology, School of Medicine and Health Sciences, The George Washington University, Washington, DC 20037, USA
| | - Chen Zeng
- Department of Physics, Columbian College of Arts and Sciences, The George Washington University, Washington, DC 20037, USA
| | - Hui Lu
- Department of Pharmacology and Physiology, School of Medicine and Health Sciences, The George Washington University, Washington, DC 20037, USA
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Zhou Q, Tian Y, Xu C, Wang J, Jin Y. Prenatal and postnatal traffic pollution exposure, DNA methylation in Shank3 and MeCP2 promoter regions, H3K4me3 and H3K27me3 and sociability in rats' offspring. Clin Epigenetics 2021; 13:180. [PMID: 34565458 PMCID: PMC8474908 DOI: 10.1186/s13148-021-01170-x] [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: 06/02/2021] [Accepted: 09/13/2021] [Indexed: 11/24/2022] Open
Abstract
Background Road traffic air pollution is linked with an increased risk of autistic spectrum disorder (ASD). The aim of this study is to assess the effect of exposure to prenatal or postnatal traffic-related air pollution combining concomitant noise pollution on ASD-related epigenetic and behavioral alternations on offspring. Methods A 2 × 2 factorial analysis experiment was designed. Wistar rats were exposed at different sites (L group: green space; H group: crossroads) and timings (E group: full gestation; P group: 21 days after birth) at the same time, and air pollutants of nitrogen dioxide (NO2) and fine particles (PM2.5) were meanwhile sampled. On postnatal day 25, brains from offspring of each group were extracted to determine the levels of DNA methylation in Shank3 (three parts: Shank3_01, Shank3_02, Shank3_03) and MeCP2 (two parts: MeCP2_01, MeCP2_02) promoter regions, H3K4me3 and H3K27me3 after three-chamber social test. Meanwhile, the Shank3 and MeCP2 levels were quantified. Results The concentrations of PM2.5 (L: 58.33 µg/m3; H: 88.33 µg/m3, P < 0.05) and NO2 (L: 52.76 µg/m3; H: 146.03 µg/m3, P < 0.01) as well as the intensity of noise pollution (L: 44.4 dB (A); H: 70.1 dB (A), P < 0.001) differed significantly from 18:00 to 19:00 between experimental sites. Traffic pollution exposure (P = 0.006) and neonatal exposure (P = 0.001) led to lower weight of male pups on PND25. Male rats under early-life exposure had increased levels of Shank3 (Shank3_02: timing P < 0.001; site P < 0.05, Shank3_03: timing P < 0.001) and MeCP2 (MeCP2_01: timing P < 0.001, MeCP2_02: timing P < 0.001) methylation and H3K4me3 (EL: 11.94 µg/mg; EH: 11.98; PL: 17.14; PH: 14.78, timing P < 0.05), and reduced levels of H3K27me3 (EL: 71.07 µg/mg; EH: 44.76; PL: 29.15; PH: 28.67, timing P < 0.001; site P < 0.05) in brain compared to those under prenatal exposure. There was, for female pups, a same pattern of Shank3 (Shank3_02: timing P < 0.001; site P < 0.05, Shank3_03: timing P < 0.001) and MeCP2 (MeCP2_01: timing P < 0.05, MeCP2_02: timing P < 0.001) methylation and H3K4me3 (EL: 11.27 µg/mg; EH: 11.55; PL: 16.11; PH: 15.44, timing P < 0.001), but the levels of H3K27me3 exhibited an inverse trend concerning exposure timing. Hypermethylation at the MeCP2 and Shank3 promoter was correlated with the less content of MeCP2 (female: EL: 32.23 ng/mg; EH: 29.58; PL: 25.01; PH: 23.03, timing P < 0.001; site P < 0.05; male: EL: 31.05 ng/mg; EH: 32.75; PL: 23.40; PH: 25.91, timing P < 0.001) and Shank3 (female: EL: 5.10 ng/mg; EH: 5.31; PL: 4.63; PH: 4.82, timing P < 0.001; male: EL: 5.40 ng/mg; EH: 5.48; PL: 4.82; PH: 4.87, timing P < 0.001). Rats with traffic pollution exposure showed aberrant sociability preference and social novelty, while those without it behaved normally. Conclusions Our findings suggest early life under environmental risks is a crucial window for epigenetic perturbations and then abnormalities in protein expression, and traffic pollution impairs behaviors either during pregnancy or after birth. Supplementary Information The online version contains supplementary material available at 10.1186/s13148-021-01170-x.
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Affiliation(s)
- Qinfeng Zhou
- Environmental Epigenetics Laboratory, Department of Environmental Medicine, School of Public Health, Zhejiang University, 866 Yuhangtang Rd, Hangzhou, 310058, Zhejiang Province, People's Republic of China
| | - Yu Tian
- Environmental Epigenetics Laboratory, Department of Environmental Medicine, School of Public Health, Zhejiang University, 866 Yuhangtang Rd, Hangzhou, 310058, Zhejiang Province, People's Republic of China
| | - Chenlu Xu
- Environmental Epigenetics Laboratory, Department of Environmental Medicine, School of Public Health, Zhejiang University, 866 Yuhangtang Rd, Hangzhou, 310058, Zhejiang Province, People's Republic of China
| | - Juling Wang
- Environmental Epigenetics Laboratory, Department of Environmental Medicine, School of Public Health, Zhejiang University, 866 Yuhangtang Rd, Hangzhou, 310058, Zhejiang Province, People's Republic of China
| | - Yongtang Jin
- Environmental Epigenetics Laboratory, Department of Environmental Medicine, School of Public Health, Zhejiang University, 866 Yuhangtang Rd, Hangzhou, 310058, Zhejiang Province, People's Republic of China. .,Department of General Practice, Sir Run Run Shaw Hospital, Medical College of Zhejiang University, Hangzhou, Zhejiang Province, People's Republic of China.
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10
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Distinct Pathogenic Genes Causing Intellectual Disability and Autism Exhibit a Common Neuronal Network Hyperactivity Phenotype. Cell Rep 2021; 30:173-186.e6. [PMID: 31914384 DOI: 10.1016/j.celrep.2019.12.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 10/15/2019] [Accepted: 11/27/2019] [Indexed: 01/31/2023] Open
Abstract
Pathogenic mutations in either one of the epigenetic modifiers EHMT1, MBD5, MLL3, or SMARCB1 have been identified to be causative for Kleefstra syndrome spectrum (KSS), a neurodevelopmental disorder with clinical features of both intellectual disability (ID) and autism spectrum disorder (ASD). To understand how these variants lead to the phenotypic convergence in KSS, we employ a loss-of-function approach to assess neuronal network development at the molecular, single-cell, and network activity level. KSS-gene-deficient neuronal networks all develop into hyperactive networks with altered network organization and excitatory-inhibitory balance. Interestingly, even though transcriptional data reveal distinct regulatory mechanisms, KSS target genes share similar functions in regulating neuronal excitability and synaptic function, several of which are associated with ID and ASD. Our results show that KSS genes mainly converge at the level of neuronal network communication, providing insights into the pathophysiology of KSS and phenotypically congruent disorders.
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11
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Wagner NR, MacDonald JL. Atypical Neocortical Development in the Cited2 Conditional Knockout Leads to Behavioral Deficits Associated with Neurodevelopmental Disorders. Neuroscience 2020; 455:65-78. [PMID: 33346116 DOI: 10.1016/j.neuroscience.2020.12.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 11/13/2020] [Accepted: 12/03/2020] [Indexed: 02/07/2023]
Abstract
The mammalian neocortex develops from a single layer of neuroepithelial cells to form a six-layer heterogeneous mosaic of differentiated neurons and glial cells. This process requires a complex choreography of temporally and spatially restricted transcription factors and epigenetic regulators. Even subtle disruptions in this regulation can alter the way the neocortex forms and functions, leading to a neurodevelopmental disorder. One epigenetic regulator that is essential for the precise development of the neocortex is CITED2 (CBP/p300 Interacting Transactivator with ED-rich termini). Cited2 is highly expressed by intermediate progenitor cells in the subventricular zone during the generation of the superficial layers of the neocortex. A forebrain-specific conditional knockout of Cited2 (cKO) exhibits reduced proliferation of intermediate progenitor cells embryonically, leading to reduced thickness of the superficial layers and reduced corpus callosum (CC) volume postnatally. Further, the Cited2 cKO display disruptions in balanced neocortical arealization, with a specific reduction in the somatosensory neocortical length, and dysregulation of precise, area-specific neuronal connectivity. Here, we explore the behavioral consequences resulting from this aberrant neocortical development. We demonstrate that Cited2 cKO mice display decreased maternal separation-induced ultrasonic vocalizations (USVs) as neonates, and an increase in rearing behavior and lack of habituation following repeated acoustic startle as adults. They do not display alterations in anxiety-like behavior, overall locomotor activity, or social interactions. Together with the morphological, molecular, and connectivity disruptions, these results identify the Cited2 cKO neocortex as an ideal system to study mechanisms underlying neurodevelopmental and neuroanatomical disruptions with relevance to human neurodevelopmental disorders.
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Affiliation(s)
- Nikolaus R Wagner
- Department of Biology, Program in Neuroscience, Syracuse University, Syracuse NY, United States
| | - Jessica L MacDonald
- Department of Biology, Program in Neuroscience, Syracuse University, Syracuse NY, United States.
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12
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Ramirez JM, Karlen-Amarante M, Wang JDJ, Bush NE, Carroll MS, Weese-Mayer DE, Huff A. The Pathophysiology of Rett Syndrome With a Focus on Breathing Dysfunctions. Physiology (Bethesda) 2020; 35:375-390. [PMID: 33052774 PMCID: PMC7864239 DOI: 10.1152/physiol.00008.2020] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Revised: 06/21/2020] [Accepted: 06/22/2020] [Indexed: 02/07/2023] Open
Abstract
Rett syndrome (RTT), an X-chromosome-linked neurological disorder, is characterized by serious pathophysiology, including breathing and feeding dysfunctions, and alteration of cardiorespiratory coupling, a consequence of multiple interrelated disturbances in the genetic and homeostatic regulation of central and peripheral neuronal networks, redox state, and control of inflammation. Characteristic breath-holds, obstructive sleep apnea, and aerophagia result in intermittent hypoxia, which, combined with mitochondrial dysfunction, causes oxidative stress-an important driver of the clinical presentation of RTT.
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Affiliation(s)
- Jan-Marino Ramirez
- Center for Integrative Brain Research, Seattle Children's Research Institute, University of Washington School of Medicine, Seattle, Washington
- Departments of Neurological Surgery and Pediatrics, University of Washington School of Medicine, Seattle, Washington
| | - Marlusa Karlen-Amarante
- Center for Integrative Brain Research, Seattle Children's Research Institute, University of Washington School of Medicine, Seattle, Washington
- Department of Physiology and Pathology, School of Dentistry of Araraquara, São Paulo State University (UNESP), Araraquara, Brazil
| | - Jia-Der Ju Wang
- Center for Integrative Brain Research, Seattle Children's Research Institute, University of Washington School of Medicine, Seattle, Washington
| | - Nicholas E Bush
- Center for Integrative Brain Research, Seattle Children's Research Institute, University of Washington School of Medicine, Seattle, Washington
| | - Michael S Carroll
- Data Analytics and Reporting, Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, Illinois
- Department of Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, Illinois
- Division of Autonomic Medicine, Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, Illinois
| | - Debra E Weese-Mayer
- Department of Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, Illinois
- Division of Autonomic Medicine, Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, Illinois
| | - Alyssa Huff
- Center for Integrative Brain Research, Seattle Children's Research Institute, University of Washington School of Medicine, Seattle, Washington
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13
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Vitamin D Supplementation Rescues Aberrant NF-κB Pathway Activation and Partially Ameliorates Rett Syndrome Phenotypes in Mecp2 Mutant Mice. eNeuro 2020; 7:ENEURO.0167-20.2020. [PMID: 32393583 PMCID: PMC7253640 DOI: 10.1523/eneuro.0167-20.2020] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Accepted: 04/30/2020] [Indexed: 01/28/2023] Open
Abstract
Rett syndrome (RTT) is a severe, progressive X-linked neurodevelopmental disorder caused by mutations in the transcriptional regulator MECP2. We previously identified aberrant NF-κB pathway upregulation in brains of Mecp2-null mice and demonstrated that genetically attenuating NF-κB rescues some characteristic neuronal RTT phenotypes. These results raised the intriguing question of whether NF-κB pathway inhibitors might provide a therapeutic avenue in RTT. Here, we investigate whether the known NF-κB pathway inhibitor vitamin D ameliorates neuronal phenotypes in Mecp2-mutant mice. Vitamin D deficiency is prevalent among RTT patients, and we find that Mecp2-null mice similarly have significantly reduced 25(OH)D serum levels compared with wild-type littermates. We identify that vitamin D rescues aberrant NF-κB pathway activation and reduced neurite outgrowth of Mecp2 knock-down cortical neurons in vitro. Further, dietary supplementation with vitamin D in early symptomatic male Mecp2 hemizygous null and female Mecp2 heterozygous mice ameliorates reduced neocortical dendritic morphology and soma size phenotypes and modestly improves reduced lifespan of Mecp2-nulls. These results elucidate fundamental neurobiology of RTT and provide foundation that NF-κB pathway inhibition might be a therapeutic target for RTT.
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14
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Sysoeva OV, Smirnov K, Stroganova TA. Sensory evoked potentials in patients with Rett syndrome through the lens of animal studies: Systematic review. Clin Neurophysiol 2019; 131:213-224. [PMID: 31812082 DOI: 10.1016/j.clinph.2019.11.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 11/07/2019] [Accepted: 11/11/2019] [Indexed: 01/04/2023]
Abstract
OBJECTIVE Systematically review the abnormalities in event related potential (ERP) recorded in Rett Syndrome (RTT) patients and animals in search of translational biomarkers of deficits related to the particular neurophysiological processes of known genetic origin (MECP2 mutations). METHODS Pubmed, ISI Web of Knowledge and BIORXIV were searched for the relevant articles according to PRISMA standards. RESULTS ERP components are generally delayed across all sensory modalities both in RTT patients and its animal model, while findings on ERPs amplitude strongly depend on stimulus properties and presentation rate. Studies on RTT animal models uncovered the abnormalities in the excitatory and inhibitory transmission as critical mechanisms underlying the ERPs changes, but showed that even similar ERP alterations in auditory and visual domains have a diverse neural basis. A range of novel approaches has been developed in animal studies bringing along the meaningful neurophysiological interpretation of ERP measures in RTT patients. CONCLUSIONS While there is a clear evidence for sensory ERPs abnormalities in RTT, to further advance the field there is a need in a large-scale ERP studies with the functionally-relevant experimental paradigms. SIGNIFICANCE The review provides insights into domain-specific neural basis of the ERP abnormalities and promotes clinical application of the ERP measures as the non-invasive functional biomarkers of RTT pathophysiology.
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Affiliation(s)
- Olga V Sysoeva
- The Cognitive Neurophysiology Laboratory, Department of Pediatrics, Albert Einstein College of Medicine & Montefiore Medical Center, Bronx, New York, USA; The Cognitive Neurophysiology Laboratory, Ernest J. Del Monte Institute for Neuroscience, Department of Neuroscience, University of Rochester School of Medicine and Dentistry, Rochester, New York, USA; The Laboratory of Human Higher Nervous Activity, Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow, Russia.
| | - Kirill Smirnov
- Department of Neuroontogenesis, Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Science, Moscow, Russia.
| | - Tatiana A Stroganova
- Center for Neurocognitive Research (MEG-Center), Moscow State University of Psychology and Education (MSUPE), Moscow, Russia; Autism Research Laboratory, Moscow State University of Psychology and Education (MSUPE), Moscow, Russia.
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15
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Rademacher S, Eickholt BJ. PTEN in Autism and Neurodevelopmental Disorders. Cold Spring Harb Perspect Med 2019; 9:cshperspect.a036780. [PMID: 31427284 DOI: 10.1101/cshperspect.a036780] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Phosphatase and tensin homolog (PTEN) is a classical tumor suppressor that antagonizes phosphatidylinositol 3-phosphate kinase (PI3K)/AKT signaling. Although there is a strong association of PTEN germline mutations with cancer syndromes, they have also been described in a subset of patients with autism spectrum disorders with macrocephaly characterized by impairments in social interactions and communication, repetitive behavior and, occasionally, epilepsy. To investigate PTEN's role during neurodevelopment and its implication for autism, several conditional Pten knockout mouse models have been generated. These models are valuable tools to understand PTEN's spatiotemporal roles during neurodevelopment. In this review, we will highlight the anatomical and phenotypic results from animal studies and link them to cellular and molecular findings.
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Affiliation(s)
- Sebastian Rademacher
- Institute of Biochemistry, Charité - Universitätsmedizin Berlin, 10117 Berlin, Germany
| | - Britta J Eickholt
- Institute of Biochemistry, Charité - Universitätsmedizin Berlin, 10117 Berlin, Germany
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16
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Banerjee A, Miller MT, Li K, Sur M, Kaufmann WE. Towards a better diagnosis and treatment of Rett syndrome: a model synaptic disorder. Brain 2019; 142:239-248. [PMID: 30649225 DOI: 10.1093/brain/awy323] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Accepted: 10/31/2018] [Indexed: 12/21/2022] Open
Abstract
With the recent 50th anniversary of the first publication on Rett syndrome, and the almost 20 years since the first report on the link between Rett syndrome and MECP2 mutations, it is important to reflect on the tremendous advances in our understanding and their implications for the diagnosis and treatment of this neurodevelopmental disorder. Rett syndrome features an interesting challenge for biologists and clinicians, as the disorder lies at the intersection of molecular mechanisms of epigenetic regulation and neurophysiological alterations in synapses and circuits that together contribute to severe pathophysiological endophenotypes. Genetic, clinical, and neurobiological evidences support the notion that Rett syndrome is primarily a synaptic disorder, and a disease model for both intellectual disability and autism spectrum disorder. This review examines major developments in both recent neurobiological and preclinical findings of Rett syndrome, and to what extent they are beginning to impact our understanding and management of the disorder. It also discusses potential applications of knowledge on synaptic plasticity abnormalities in Rett syndrome to its diagnosis and treatment.
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Affiliation(s)
- Abhishek Banerjee
- Laboratory of Neural Circuit Dynamics, Brain Research Institute, University of Zürich, Zürich, Switzerland
| | - Meghan T Miller
- Roche Pharma Research and Early Development, Roche Innovation Center, F. Hoffman-La Roche, Basel, Switzerland
| | - Keji Li
- Department of Brain and Cognitive Sciences, Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge MA, USA
| | - Mriganka Sur
- Department of Brain and Cognitive Sciences, Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge MA, USA
| | - Walter E Kaufmann
- Department of Human Genetics, Emory University School of Medicine, Atlanta GA, USA
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17
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Ma X, Chen K, Lu Z, Piechowicz M, Liu Q, Wu J, Qiu S. Disruption of MET Receptor Tyrosine Kinase, an Autism Risk Factor, Impairs Developmental Synaptic Plasticity in the Hippocampus. Dev Neurobiol 2019; 79:36-50. [PMID: 30304576 PMCID: PMC6397659 DOI: 10.1002/dneu.22645] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Revised: 09/21/2018] [Accepted: 10/10/2018] [Indexed: 02/05/2023]
Abstract
As more genes conferring risks to neurodevelopmental disorders are identified, translating these genetic risk factors into biological mechanisms that impact the trajectory of the developing brain is a critical next step. Here, we report that disrupted signaling mediated MET receptor tyrosine kinase (RTK), an established risk factor for autism spectrum disorders, in the developing hippocampus glutamatergic circuit leads to profound deficits in neural development, synaptic transmission, and plasticity. In cultured hippocampus slices prepared from neonatal mice, pharmacological inhibition of MET kinase activity suppresses dendritic arborization and disrupts normal dendritic spine development. In addition, single-neuron knockdown (RNAi) or overexpression of Met in the developing hippocampal CA1 neurons leads to alterations, opposite in nature, in basal synaptic transmission and long-term plasticity. In forebrain-specific Met conditional knockout mice (Metfx/fx ;emx1cre ), an enhanced long-term potentiation (LTP) and long-term depression (LTD) were observed at early developmental stages (P12-14) at the Schaffer collateral to CA1 synapses compared with wild-type littermates. In contrast, LTP and LTD were markedly reduced at young adult stage (P56-70) during which wild-type mice show robust LTP and LTD. The altered trajectory of synaptic plasticity revealed by this study indicate that temporally regulated MET signaling as an intrinsic, cell autonomous, and pleiotropic mechanism not only critical for neuronal growth and functional maturation, but also for the timing of synaptic plasticity during forebrain glutamatergic circuits development.
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Affiliation(s)
- Xiaokuang Ma
- Basic Medical Sciences, University of Arizona College of Medicine-Phoenix, Phoenix, Arizona, 85004
- Department of Pharmacology, Shantou University Medical College, Shantou, Guangdong, 515041, China
| | - Ke Chen
- Basic Medical Sciences, University of Arizona College of Medicine-Phoenix, Phoenix, Arizona, 85004
- MOE Key Laboratory for NeuroInformation, The Clinical Hospital of Chengdu Brain Sciences Institute, University of Electronic Science and Technology of China, Chengdu, Sichuan, 610054, China
| | - Zhongming Lu
- Basic Medical Sciences, University of Arizona College of Medicine-Phoenix, Phoenix, Arizona, 85004
| | - Mariel Piechowicz
- Basic Medical Sciences, University of Arizona College of Medicine-Phoenix, Phoenix, Arizona, 85004
| | - Qiang Liu
- Barrow Neurological Institute, St. Joseph's Hospital Medical Center, Phoenix, Arizona, 85013
| | - Jie Wu
- Basic Medical Sciences, University of Arizona College of Medicine-Phoenix, Phoenix, Arizona, 85004
- Barrow Neurological Institute, St. Joseph's Hospital Medical Center, Phoenix, Arizona, 85013
- Department of Pharmacology, Shantou University Medical College, Shantou, Guangdong, 515041, China
| | - Shenfeng Qiu
- Basic Medical Sciences, University of Arizona College of Medicine-Phoenix, Phoenix, Arizona, 85004
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18
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MeCP2 Deficiency Leads to Loss of Glial Kir4.1. eNeuro 2018; 5:eN-NWR-0194-17. [PMID: 29464197 PMCID: PMC5818552 DOI: 10.1523/eneuro.0194-17.2018] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Revised: 02/01/2018] [Accepted: 02/08/2018] [Indexed: 01/05/2023] Open
Abstract
Rett syndrome (RTT) is an X-linked neurodevelopmental disorder usually caused by mutations in methyl-CpG-binding protein 2 (MeCP2). RTT is typified by apparently normal development until 6-18 mo of age, when motor and communicative skills regress and hand stereotypies, autonomic symptoms, and seizures present. Restoration of MeCP2 function selectively to astrocytes reversed several deficits in a murine model of RTT, but the mechanism of this rescue is unknown. Astrocytes carry out many essential functions required for normal brain functioning, including extracellular K+ buffering. Kir4.1, an inwardly rectifying K+ channel, is largely responsible for the channel-mediated K+ regulation by astrocytes. Loss-of-function mutations in Kir4.1 in human patients result in a severe neurodevelopmental disorder termed EAST or SESAME syndrome. Here, we evaluated astrocytic Kir4.1 expression in a murine model of Rett syndrome. We demonstrate by chromatin immunoprecipitation analysis that Kir4.1 is a direct molecular target of MeCP2. Astrocytes from Mecp2-deficient mice express significantly less Kir4.1 mRNA and protein, which translates into a >50% deficiency in Ba2+-sensitive Kir4.1-mediated currents, and impaired extracellular potassium dynamics. By examining astrocytes in isolation, we demonstrate that loss of Kir4.1 is cell autonomous. Assessment through postnatal development revealed that Kir4.1 expression in Mecp2-deficient animals never reaches adult, wild-type levels, consistent with a neurodevelopmental disorder. These are the first data implicating a direct MeCP2 molecular target in astrocytes and provide novel mechanistic insight explaining a potential mechanism by which astrocytic dysfunction may contribute to RTT.
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19
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Gulmez Karaca K, Brito DVC, Zeuch B, Oliveira AMM. Adult hippocampal MeCP2 preserves the genomic responsiveness to learning required for long-term memory formation. Neurobiol Learn Mem 2018; 149:84-97. [PMID: 29438740 DOI: 10.1016/j.nlm.2018.02.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Revised: 02/04/2018] [Accepted: 02/09/2018] [Indexed: 01/09/2023]
Abstract
MeCP2 is required both during postnatal neurodevelopment and throughout the adult life for brain function. Although it is well accepted that MeCP2 in the maturing nervous system is critical for establishing normal development, the functions of MeCP2 during adulthood are poorly understood. Particularly, the requirement of hippocampal MeCP2 for cognitive abilities in the adult is not studied. To characterize the role of MeCP2 in adult neuronal function and cognition, we used a temporal and region-specific disruption of MeCP2 expression in the hippocampus of adult male mice. We found that MeCP2 is required for long-term memory formation and that it controls the learning-induced transcriptional response of hippocampal neurons required for memory consolidation. Furthermore, we uncovered MeCP2 functions in the adult hippocampus that may underlie cognitive integrity. We showed that MeCP2 maintains the developmentally established chromatin configuration and epigenetic landscape of CA1 neurons throughout the adulthood, and that it regulates the expression of neuronal and immune-related genes in the adult hippocampus. Overall, our findings identify MeCP2 as a maintenance factor in the adult hippocampus that preserves signal responsiveness of the genome and allows for integrity of cognitive functions. This study provides new insight into how MeCP2 maintains adult brain functions, but also into the mechanisms underlying the cognitive impairments observed in RTT patients and highlights the understudied role of DNA methylation interpretation in adult cognitive processes.
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Affiliation(s)
- Kubra Gulmez Karaca
- Department of Neurobiology, Interdisciplinary Centre for Neurosciences (IZN), University of Heidelberg, INF 364, 69120 Heidelberg, Germany
| | - David V C Brito
- Department of Neurobiology, Interdisciplinary Centre for Neurosciences (IZN), University of Heidelberg, INF 364, 69120 Heidelberg, Germany
| | - Benjamin Zeuch
- Department of Neurobiology, Interdisciplinary Centre for Neurosciences (IZN), University of Heidelberg, INF 364, 69120 Heidelberg, Germany
| | - Ana M M Oliveira
- Department of Neurobiology, Interdisciplinary Centre for Neurosciences (IZN), University of Heidelberg, INF 364, 69120 Heidelberg, Germany.
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20
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Tatti R, Haley MS, Swanson O, Tselha T, Maffei A. Neurophysiology and Regulation of the Balance Between Excitation and Inhibition in Neocortical Circuits. Biol Psychiatry 2017; 81:821-831. [PMID: 27865453 PMCID: PMC5374043 DOI: 10.1016/j.biopsych.2016.09.017] [Citation(s) in RCA: 105] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Revised: 08/25/2016] [Accepted: 09/15/2016] [Indexed: 12/18/2022]
Abstract
Brain function relies on the ability of neural networks to maintain stable levels of activity, while experiences sculpt them. In the neocortex, the balance between activity and stability relies on the coregulation of excitatory and inhibitory inputs onto principal neurons. Shifts of excitation or inhibition result in altered excitability impaired processing of incoming information. In many neurodevelopmental and neuropsychiatric disorders, the excitability of local circuits is altered, suggesting that their pathophysiology may involve shifts in synaptic excitation, inhibition, or both. Most studies focused on identifying the cellular and molecular mechanisms controlling network excitability to assess whether they may be altered in animal models of disease. The impact of changes in excitation/inhibition balance on local circuit and network computations is not clear. Here we report findings on the integration of excitatory and inhibitory inputs in healthy cortical circuits and discuss how shifts in excitation/inhibition balance may relate to pathological phenotypes.
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Affiliation(s)
- Roberta Tatti
- Dept. of Neurobiology and Behavior, SUNY-Stony Brook, Stony Brook, NY 11794
| | - Melissa S. Haley
- Dept. of Neurobiology and Behavior, SUNY-Stony Brook, Stony Brook, NY 11794
| | - Olivia Swanson
- Dept. of Neurobiology and Behavior, SUNY-Stony Brook, Stony Brook, NY 11794
| | - Tenzin Tselha
- Dept. of Neurobiology and Behavior, SUNY-Stony Brook, Stony Brook, NY 11794
| | - Arianna Maffei
- Department of Neurobiology and Behavior, Stony Brook University, The State University of New York, Stony Brook, New York.
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21
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The Crucial Role of DNA Methylation and MeCP2 in Neuronal Function. Genes (Basel) 2017; 8:genes8050141. [PMID: 28505093 PMCID: PMC5448015 DOI: 10.3390/genes8050141] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Revised: 04/25/2017] [Accepted: 05/05/2017] [Indexed: 12/16/2022] Open
Abstract
A neuron is unique in its ability to dynamically modify its transcriptional output in response to synaptic activity while maintaining a core gene expression program that preserves cellular identity throughout a lifetime that is longer than almost every other cell type in the body. A contributing factor to the immense adaptability of a neuron is its unique epigenetic landscape that elicits locus-specific alterations in chromatin architecture, which in turn influences gene expression. One such epigenetic modification that is sensitive to changes in synaptic activity, as well as essential for maintaining cellular identity, is DNA methylation. The focus of this article is on the importance of DNA methylation in neuronal function, summarizing recent studies on critical players in the establishment of (the “writing”), the modification or erasure of (the “editing”), and the mediation of (the “reading”) DNA methylation in neurodevelopment and neuroplasticity. One “reader” of DNA methylation in particular, methyl-CpG-binding protein 2 (MeCP2), is highlighted, given its undisputed importance in neuronal function.
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22
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Jointly reduced inhibition and excitation underlies circuit-wide changes in cortical processing in Rett syndrome. Proc Natl Acad Sci U S A 2016; 113:E7287-E7296. [PMID: 27803317 DOI: 10.1073/pnas.1615330113] [Citation(s) in RCA: 113] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Rett syndrome (RTT) arises from loss-of-function mutations in methyl-CpG binding protein 2 gene (Mecp2), but fundamental aspects of its physiological mechanisms are unresolved. Here, by whole-cell recording of synaptic responses in MeCP2 mutant mice in vivo, we show that visually driven excitatory and inhibitory conductances are both reduced in cortical pyramidal neurons. The excitation-to-inhibition (E/I) ratio is increased in amplitude and prolonged in time course. These changes predict circuit-wide reductions in response reliability and selectivity of pyramidal neurons to visual stimuli, as confirmed by two-photon imaging. Targeted recordings reveal that parvalbumin-expressing (PV+) interneurons in mutant mice have reduced responses. PV-specific MeCP2 deletion alone recapitulates effects of global MeCP2 deletion on cortical circuits, including reduced pyramidal neuron responses and reduced response reliability and selectivity. Furthermore, MeCP2 mutant mice show reduced expression of the cation-chloride cotransporter KCC2 (K+/Cl- exporter) and a reduced KCC2/NKCC1 (Na+/K+/Cl- importer) ratio. Perforated patch recordings demonstrate that the reversal potential for GABA is more depolarized in mutant mice, but is restored by application of the NKCC1 inhibitor bumetanide. Treatment with recombinant human insulin-like growth factor-1 restores responses of PV+ and pyramidal neurons and increases KCC2 expression to normalize the KCC2/NKCC1 ratio. Thus, loss of MeCP2 in the brain alters both excitation and inhibition in brain circuits via multiple mechanisms. Loss of MeCP2 from a specific interneuron subtype contributes crucially to the cell-specific and circuit-wide deficits of RTT. The joint restoration of inhibition and excitation in cortical circuits is pivotal for functionally correcting the disorder.
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23
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Yamawaki N, Suter BA, Wickersham IR, Shepherd GMG. Combining Optogenetics and Electrophysiology to Analyze Projection Neuron Circuits. Cold Spring Harb Protoc 2016; 2016:2016/10/pdb.prot090084. [PMID: 27698240 PMCID: PMC5476926 DOI: 10.1101/pdb.prot090084] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
A set of methods is described for channelrhodopsin-2 (ChR2)-based synaptic circuit analysis that combines photostimulation of virally transfected presynaptic neurons' axons with whole-cell electrophysiological recordings from retrogradely labeled postsynaptic neurons. The approach exploits the preserved photoexcitability of ChR2-expressing axons in brain slices and can be used to assess either local or long-range functional connections. Stereotaxic injections are used both to express ChR2 selectively in presynaptic axons of interest (using rabies virus [RV] or adeno-associated virus [AAV]) and to label two types of postsynaptic projection neurons of interest with fluorescent retrograde tracers. In brain slices, tracer-labeled postsynaptic neurons are targeted for whole-cell electrophysiological recordings, and synaptic connections are assessed by sampling voltage or current responses to light-emitting diode (LED) photostimulation of ChR2-expressing axons. The data are analyzed to estimate the relative amplitude of synaptic input and other connectivity parameters. Pharmacological and electrophysiological manipulations extend the versatility of the basic approach, allowing the dissection of monosynaptic versus disynaptic responses, excitatory versus inhibitory responses, and more. The method enables rapid, quantitative characterization of synaptic connectivity between defined pre- and postsynaptic classes of neurons.
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Affiliation(s)
- Naoki Yamawaki
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611
| | - Benjamin A Suter
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611
| | - Ian R Wickersham
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Gordon M G Shepherd
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611
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24
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Schafer DP, Heller CT, Gunner G, Heller M, Gordon C, Hammond T, Wolf Y, Jung S, Stevens B. Microglia contribute to circuit defects in Mecp2 null mice independent of microglia-specific loss of Mecp2 expression. eLife 2016; 5. [PMID: 27458802 PMCID: PMC4961457 DOI: 10.7554/elife.15224] [Citation(s) in RCA: 105] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2016] [Accepted: 06/14/2016] [Indexed: 12/25/2022] Open
Abstract
Microglia, the resident CNS macrophages, have been implicated in the pathogenesis of Rett Syndrome (RTT), an X-linked neurodevelopmental disorder. However, the mechanism by which microglia contribute to the disorder is unclear and recent data suggest that microglia do not play a causative role. Here, we use the retinogeniculate system to determine if and how microglia contribute to pathogenesis in a RTT mouse model, the Mecp2 null mouse (Mecp2tm1.1Bird/y). We demonstrate that microglia contribute to pathogenesis by excessively engulfing, thereby eliminating, presynaptic inputs at end stages of disease (≥P56 Mecp2 null mice) concomitant with synapse loss. Furthermore, loss or gain of Mecp2 expression specifically in microglia (Cx3cr1CreER;Mecp2fl/yor Cx3cr1CreER; Mecp2LSL/y) had little effect on excessive engulfment, synapse loss, or phenotypic abnormalities. Taken together, our data suggest that microglia contribute to end stages of disease by dismantling neural circuits rendered vulnerable by loss of Mecp2 in other CNS cell types. DOI:http://dx.doi.org/10.7554/eLife.15224.001 Rett Syndrome is a neurodevelopmental disorder with symptoms that typically begin in girls between 6 and 18 months old. Those affected developmentally stagnate and regress – during which they lose some of their previously acquired skills and develop an array of physical impairments. Mutations in a gene called Mecp2 on the X chromosome cause most cases of Rett Syndrome. Mice that lack the Mecp2 gene develop symptoms similar to those seen in people with Rett Syndrome, and so such “Mecp2 null” mice are often used to study the disorder. Microglia, the resident immune cells of the central nervous system, have been implicated in the development of Rett Syndrome. Introducing microglia that carry the Mecp2 gene into Mecp2 null mice has been shown to reduce several disease-associated abnormalities. However, exactly how microglia contribute to these changes remains unknown. In addition, a more recent report failed to reproduce these findings, and instead obtained results suggesting that microglia do not affect the development of Rett syndrome. Schafer et al. now use the mouse visual system as a model to determine if and how microglia contribute to the development of Rett Syndrome. Like many other brain regions, the developing visual system initially has a surplus of connections between neurons, or synapses, which are subsequently pruned back. Schafer et al. previously showed in the developing visual system of early postnatal (5 days after birth) control mice (who express the Mecp2 gene) that microglia contribute to this pruning by engulfing and eliminating a subset of these excessive synaptic connections. The new experiments by Schafer et al. show that another wave of microglia-mediated synaptic pruning occurs in 40-day-old juvenile control mice. Because Mecp2 null mice begin to display features of Rett Syndrome when they’re about 40 days old, Schafer et al. tested whether the microglia of these animals inappropriately prune synaptic connections. While this process occurred normally in neonatal and juvenile Mecp2 null mice, microglia began to excessively engulf cells in Mecp2 null mice when they were around 56 days old. Unexpectedly, deleting or reintroducing the Mecp2 gene solely in the microglia of these mice had little effect on pruning activity of the microglia, and failed to affect Rett-syndrome-like symptoms in the mice. Taken together, the data presented by Schafer et al. suggest how microglia contribute to the final stages of Rett Syndrome: by dismantling circuits of neurons that are rendered vulnerable by the loss of the Mecp2 gene in other cell types. DOI:http://dx.doi.org/10.7554/eLife.15224.002
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Affiliation(s)
- Dorothy P Schafer
- FM Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, United States.,Department of Neurobiology, University of Massachusetts Medical School, Worcester, United States
| | - Christopher T Heller
- FM Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, United States.,Department of Neurobiology, University of Massachusetts Medical School, Worcester, United States
| | - Georgia Gunner
- FM Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, United States.,Department of Neurobiology, University of Massachusetts Medical School, Worcester, United States
| | - Molly Heller
- FM Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, United States
| | - Christopher Gordon
- FM Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, United States
| | - Timothy Hammond
- FM Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, United States
| | - Yochai Wolf
- Department of Immunology, The Weizmann Institute of Science, Rehovot, Israel
| | - Steffen Jung
- Department of Immunology, The Weizmann Institute of Science, Rehovot, Israel
| | - Beth Stevens
- FM Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, United States.,Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, United States
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25
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Peng Y, Lu Z, Li G, Piechowicz M, Anderson M, Uddin Y, Wu J, Qiu S. The autism-associated MET receptor tyrosine kinase engages early neuronal growth mechanism and controls glutamatergic circuits development in the forebrain. Mol Psychiatry 2016; 21:925-35. [PMID: 26728565 PMCID: PMC4914424 DOI: 10.1038/mp.2015.182] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Revised: 07/30/2015] [Accepted: 09/08/2015] [Indexed: 12/18/2022]
Abstract
The human MET gene imparts a replicated risk for autism spectrum disorder (ASD), and is implicated in the structural and functional integrity of brain. MET encodes a receptor tyrosine kinase, MET, which has a pleiotropic role in embryogenesis and modifies a large number of neurodevelopmental events. Very little is known, however, on how MET signaling engages distinct cellular events to collectively affect brain development in ASD-relevant disease domains. Here, we show that MET protein expression is dynamically regulated and compartmentalized in developing neurons. MET is heavily expressed in neuronal growth cones at early developmental stages and its activation engages small GTPase Cdc42 to promote neuronal growth, dendritic arborization and spine formation. Genetic ablation of MET signaling in mouse dorsal pallium leads to altered neuronal morphology indicative of early functional maturation. In contrast, prolonged activation of MET represses the formation and functional maturation of glutamatergic synapses. Moreover, manipulating MET signaling levels in vivo in the developing prefrontal projection neurons disrupts the local circuit connectivity made onto these neurons. Therefore, normal time-delimited MET signaling is critical in regulating the timing of neuronal growth, glutamatergic synapse maturation and cortical circuit function. Dysregulated MET signaling may lead to pathological changes in forebrain maturation and connectivity, and thus contribute to the emergence of neurological symptoms associated with ASD.
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Affiliation(s)
- Yun Peng
- Department of Basic Medical Sciences, University of Arizona College of Medicine-Phoenix, Phoenix, AZ 85004
| | - Zhongming Lu
- Department of Basic Medical Sciences, University of Arizona College of Medicine-Phoenix, Phoenix, AZ 85004,Jiangsu Provincial Center for Disease Control and Prevention, Nanjing, China, 210009
| | - Guohui Li
- Department of Basic Medical Sciences, University of Arizona College of Medicine-Phoenix, Phoenix, AZ 85004,Interdisciplinary Graduate Program in Neuroscience, School of Life Science, Arizona State University. Tempe, AZ 85287
| | - Mariel Piechowicz
- Department of Basic Medical Sciences, University of Arizona College of Medicine-Phoenix, Phoenix, AZ 85004
| | - Miranda Anderson
- Department of Basic Medical Sciences, University of Arizona College of Medicine-Phoenix, Phoenix, AZ 85004
| | - Yasin Uddin
- Department of Basic Medical Sciences, University of Arizona College of Medicine-Phoenix, Phoenix, AZ 85004
| | - Jie Wu
- Division of Neurology, Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, AZ 85013
| | - Shenfeng Qiu
- Department of Basic Medical Sciences, University of Arizona College of Medicine-Phoenix, Phoenix, AZ 85004,Interdisciplinary Graduate Program in Neuroscience, School of Life Science, Arizona State University. Tempe, AZ 85287
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26
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Meng X, Wang W, Lu H, He LJ, Chen W, Chao ES, Fiorotto ML, Tang B, Herrera JA, Seymour ML, Neul JL, Pereira FA, Tang J, Xue M, Zoghbi HY. Manipulations of MeCP2 in glutamatergic neurons highlight their contributions to Rett and other neurological disorders. eLife 2016; 5. [PMID: 27328325 PMCID: PMC4946906 DOI: 10.7554/elife.14199] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Accepted: 06/01/2016] [Indexed: 12/20/2022] Open
Abstract
Many postnatal onset neurological disorders such as autism spectrum disorders (ASDs) and intellectual disability are thought to arise largely from disruption of excitatory/inhibitory homeostasis. Although mouse models of Rett syndrome (RTT), a postnatal neurological disorder caused by loss-of-function mutations in MECP2, display impaired excitatory neurotransmission, the RTT phenotype can be largely reproduced in mice simply by removing MeCP2 from inhibitory GABAergic neurons. To determine what role excitatory signaling impairment might play in RTT pathogenesis, we generated conditional mouse models with Mecp2 either removed from or expressed solely in glutamatergic neurons. MeCP2 deficiency in glutamatergic neurons leads to early lethality, obesity, tremor, altered anxiety-like behaviors, and impaired acoustic startle response, which is distinct from the phenotype of mice lacking MeCP2 only in inhibitory neurons. These findings reveal a role for excitatory signaling impairment in specific neurobehavioral abnormalities shared by RTT and other postnatal neurological disorders.
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Affiliation(s)
- Xiangling Meng
- Department of Neuroscience, Baylor College of Medicine, Houston, United States.,Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, United States
| | - Wei Wang
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, United States.,Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, United States
| | - Hui Lu
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, United States.,Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, United States
| | - Ling-Jie He
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, United States.,Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, United States.,Howard Hughes Medical Institute, Baylor College of Medicine, Houston, United States
| | - Wu Chen
- Department of Neuroscience, Baylor College of Medicine, Houston, United States.,The Cain Foundation Laboratories, Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, United States
| | - Eugene S Chao
- Department of Neuroscience, Baylor College of Medicine, Houston, United States.,The Cain Foundation Laboratories, Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, United States
| | - Marta L Fiorotto
- Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, United States
| | - Bin Tang
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, United States.,Department of Pediatrics, Baylor College of Medicine, Houston, United States
| | - Jose A Herrera
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, United States.,Interdepartmental Program in Translational Biology and Molecular Medicine, Baylor College of Medicine, Houston, United States
| | - Michelle L Seymour
- Huffington Center on Aging, Baylor College of Medicine, Houston, United States.,Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, United States
| | - Jeffrey L Neul
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, United States
| | - Fred A Pereira
- Huffington Center on Aging, Baylor College of Medicine, Houston, United States.,Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, United States.,Bobby R Alford Department of Otolaryngology - Head and Neck Surgery, Baylor College of Medicine, Houston, United States
| | - Jianrong Tang
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, United States.,Department of Pediatrics, Baylor College of Medicine, Houston, United States
| | - Mingshan Xue
- Department of Neuroscience, Baylor College of Medicine, Houston, United States.,The Cain Foundation Laboratories, Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, United States
| | - Huda Y Zoghbi
- Department of Neuroscience, Baylor College of Medicine, Houston, United States.,Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, United States.,Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, United States.,Howard Hughes Medical Institute, Baylor College of Medicine, Houston, United States
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27
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Cell-Specific Regulation of N-Methyl-D-Aspartate Receptor Maturation by Mecp2 in Cortical Circuits. Biol Psychiatry 2016; 79:746-754. [PMID: 26185009 PMCID: PMC4670611 DOI: 10.1016/j.biopsych.2015.05.018] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Revised: 04/29/2015] [Accepted: 05/20/2015] [Indexed: 11/20/2022]
Abstract
BACKGROUND Early postnatal experience shapes N-methyl-D-aspartate receptor (NMDAR) subunit composition and kinetics at excitatory synapses onto pyramidal cells; however, little is known about NMDAR maturation onto inhibitory interneurons. METHODS We combined whole-cell patch clamp recordings (n = 440) of NMDAR-mediated currents from layer-4-to-layer-2/3 synapses onto pyramidal and green fluorescent protein labeled parvalbumin-positive (PV) interneurons in visual cortex at three developmental ages (15, 30, and 45 postnatal days) with array tomography three-dimensional reconstructions of NMDAR subunits GluN2A- and GluN2B-positive synapses onto PV cells. RESULTS We show that the trajectory of the NMDAR subunit switch is slower in PV interneurons than in excitatory pyramidal cells in visual cortex. Notably, this differential time course is reversed in the absence of methyl-CpG-binding protein, MECP2, the molecular basis for cognitive decline in Rett syndrome and some cases of autism. Additional genetic reduction of GluN2A subunits, which prevents regression of vision in Mecp2-knockout mice, specifically rescues the accelerated NMDAR maturation in PV cells. CONCLUSIONS We demonstrate 1) the time course of NMDAR maturation is cell-type specific, and 2) a new cell-type specific role for Mecp2 in the development of NMDAR subunit composition. Reducing GluN2A expression in Mecp2-knockout mice, which prevents the decline in visual cortical function, also prevents the premature NMDAR maturation in PV cells. Thus, circuit-based therapies targeting NMDAR subunit composition on PV cells may provide novel treatments for Rett syndrome.
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28
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Patrizi A, Picard N, Simon AJ, Gunner G, Centofante E, Andrews NA, Fagiolini M. Chronic Administration of the N-Methyl-D-Aspartate Receptor Antagonist Ketamine Improves Rett Syndrome Phenotype. Biol Psychiatry 2016; 79:755-764. [PMID: 26410354 PMCID: PMC7410367 DOI: 10.1016/j.biopsych.2015.08.018] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Revised: 08/13/2015] [Accepted: 08/13/2015] [Indexed: 12/26/2022]
Abstract
BACKGROUND Rett syndrome (RTT) is a neurological disorder caused by mutation of the X-linked MECP2 gene, which results in the progressive disruption of excitatory and inhibitory neuronal circuits. To date, there is no effective treatment available for the disorder. Studies conducted in RTT patients and murine models have shown altered expression of N-methyl-D-aspartate receptors (NMDARs). Genetic deletion of the NMDAR subunit, GluN2A, in mice lacking Mecp2 is sufficient to prevent RTT phenotypes, including regression of vision. METHODS We performed a systematic, randomized preclinical trial of chronic administration of low-dose (8 mg/kg, intraperitoneal) ketamine, an NMDAR antagonist, starting either early in development or at the onset of RTT phenotype in Mecp2-null mice. RESULTS Daily exposure to ketamine ameliorated RTT symptoms and extended the life span of treated Mecp2-null mice without adverse side effects. Furthermore, significant improvement was observed in cortical processing and connectivity, which were fully restored to a wild-type level, particularly when treatment was started at the onset of regression. CONCLUSIONS Our findings provide strong evidence that targeting NMDA receptors can be a safe and effective treatment for RTT.
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Affiliation(s)
- Annarita Patrizi
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Nathalie Picard
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Alex Joseph Simon
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Georgia Gunner
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Eleonora Centofante
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Nick Arthur Andrews
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Michela Fagiolini
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts.
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29
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Lo FS, Blue ME, Erzurumlu RS. Enhancement of postsynaptic GABAA and extrasynaptic NMDA receptor-mediated responses in the barrel cortex of Mecp2-null mice. J Neurophysiol 2016; 115:1298-306. [PMID: 26683074 PMCID: PMC4808090 DOI: 10.1152/jn.00944.2015] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Accepted: 12/15/2015] [Indexed: 12/12/2022] Open
Abstract
Rett syndrome (RTT) is a neurodevelopmental disorder that results from mutations in the X-linked gene for methyl-CpG-binding protein 2 (MECP2). The underlying cellular mechanism for the sensory deficits in patients with RTT is largely unknown. This study used the Bird mouse model of RTT to investigate sensory thalamocortical synaptic transmission in the barrel cortex of Mecp2-null mice. Electrophysiological results showed an excitation/inhibition imbalance, biased toward inhibition, due to an increase in efficacy of postsynaptic GABAA receptors rather than alterations in inhibitory network and presynaptic release properties. Enhanced inhibition impaired the transmission of tonic sensory signals from the thalamus to the somatosensory cortex. Previous morphological studies showed an upregulation of NMDA receptors in the neocortex of both RTT patients and Mecp2-null mice at early ages [Blue ME, Naidu S, Johnston MV. Ann Neurol 45: 541-545, 1999; Blue ME, Kaufmann WE, Bressler J, Eyring C, O'Driscoll C, Naidu S, Johnston MV. Anat Rec (Hoboken) 294: 1624-1634, 2011]. Although AMPA and NMDA receptor-mediated excitatory synaptic transmission was not altered in the barrel cortex of Mecp2-null mice, extrasynaptic NMDA receptor-mediated responses increased markedly. These responses were blocked by memantine, suggesting that extrasynaptic NMDA receptors play an important role in the pathogenesis of RTT. The results suggest that enhancement of postsynaptic GABAA and extrasynaptic NMDA receptor-mediated responses may underlie impaired somatosensation and that pharmacological blockade of extrasynaptic NMDA receptors may have therapeutic value for RTT.
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Affiliation(s)
- Fu-Sun Lo
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland; and
| | - Mary E Blue
- Hugo W. Moser Research Institute at Kennedy Krieger, Inc. and Departments of Neurology and Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Reha S Erzurumlu
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland; and
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30
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Developmental Dynamics of Rett Syndrome. Neural Plast 2016; 2016:6154080. [PMID: 26942018 PMCID: PMC4752981 DOI: 10.1155/2016/6154080] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2015] [Revised: 12/23/2015] [Accepted: 12/31/2015] [Indexed: 12/31/2022] Open
Abstract
Rett Syndrome was long considered to be simply a disorder of postnatal development, with phenotypes that manifest only late in development and into adulthood. A variety of recent evidence demonstrates that the phenotypes of Rett Syndrome are present at the earliest stages of brain development, including developmental stages that define neurogenesis, migration, and patterning in addition to stages of synaptic and circuit development and plasticity. These phenotypes arise from the pleotropic effects of MeCP2, which is expressed very early in neuronal progenitors and continues to be expressed into adulthood. The effects of MeCP2 are mediated by diverse signaling, transcriptional, and epigenetic mechanisms. Attempts to reverse the effects of Rett Syndrome need to take into account the developmental dynamics and temporal impact of MeCP2 loss.
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31
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Kishi N, MacDonald JL, Ye J, Molyneaux BJ, Azim E, Macklis JD. Reduction of aberrant NF-κB signalling ameliorates Rett syndrome phenotypes in Mecp2-null mice. Nat Commun 2016; 7:10520. [PMID: 26821816 PMCID: PMC4740176 DOI: 10.1038/ncomms10520] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Accepted: 12/22/2015] [Indexed: 12/21/2022] Open
Abstract
Mutations in the transcriptional regulator Mecp2 cause the severe X-linked neurodevelopmental disorder Rett syndrome (RTT). In this study, we investigate genes that function downstream of MeCP2 in cerebral cortex circuitry, and identify upregulation of Irak1, a central component of the NF-κB pathway. We show that overexpression of Irak1 mimics the reduced dendritic complexity of Mecp2-null cortical callosal projection neurons (CPN), and that NF-κB signalling is upregulated in the cortex with Mecp2 loss-of-function. Strikingly, we find that genetically reducing NF-κB signalling in Mecp2-null mice not only ameliorates CPN dendritic complexity but also substantially extends their normally shortened lifespan, indicating broader roles for NF-κB signalling in RTT pathogenesis. These results provide new insight into both the fundamental neurobiology of RTT, and potential therapeutic strategies via NF-κB pathway modulation. Rett syndrome is a neurodevelopmental disorder caused by mutations in Mecp2. Here the authors show that Mecp2 loss-of-function leads to upregulation of the NF-κB pathway, and that reducing NF-κB signalling ameliorates phenotypes of Mecp2-null mice, thus offering a potential therapeutic strategy.
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Affiliation(s)
- Noriyuki Kishi
- Department of Stem Cell and Regenerative Biology, Center for Brain Science, and Harvard Stem Cell Institute, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Jessica L MacDonald
- Department of Stem Cell and Regenerative Biology, Center for Brain Science, and Harvard Stem Cell Institute, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Julia Ye
- Department of Stem Cell and Regenerative Biology, Center for Brain Science, and Harvard Stem Cell Institute, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Bradley J Molyneaux
- Department of Stem Cell and Regenerative Biology, Center for Brain Science, and Harvard Stem Cell Institute, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Eiman Azim
- Department of Stem Cell and Regenerative Biology, Center for Brain Science, and Harvard Stem Cell Institute, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Jeffrey D Macklis
- Department of Stem Cell and Regenerative Biology, Center for Brain Science, and Harvard Stem Cell Institute, Harvard University, Cambridge, Massachusetts 02138, USA
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32
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Sahin M, Sur M. Genes, circuits, and precision therapies for autism and related neurodevelopmental disorders. Science 2015; 350:aab3897. [PMID: 26472761 PMCID: PMC4739545 DOI: 10.1126/science.aab3897] [Citation(s) in RCA: 192] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Research in the genetics of neurodevelopmental disorders such as autism suggests that several hundred genes are likely risk factors for these disorders. This heterogeneity presents a challenge and an opportunity at the same time. Although the exact identity of many of the genes remains to be discovered, genes identified to date encode proteins that play roles in certain conserved pathways: protein synthesis, transcriptional and epigenetic regulation, and synaptic signaling. The next generation of research in neurodevelopmental disorders must address the neural circuitry underlying the behavioral symptoms and comorbidities, the cell types playing critical roles in these circuits, and common intercellular signaling pathways that link diverse genes. Results from clinical trials have been mixed so far. Only when we can leverage the heterogeneity of neurodevelopmental disorders into precision medicine will the mechanism-based therapeutics for these disorders start to unlock success.
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Affiliation(s)
- Mustafa Sahin
- F. M. Kirby Center for Neurobiology, Translational Neuroscience Center, Department of Neurology, Boston Children's Hospital, Boston, MA 02115, USA.
| | - Mriganka Sur
- Simons Center for the Social Brain, Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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33
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Cuddapah VA, Sinifunanya EN, Percy AK, Olsen ML. MeCP2 in the regulation of neural activity: Rett syndrome pathophysiological perspectives. Degener Neurol Neuromuscul Dis 2015; 5:103-116. [PMID: 32669918 PMCID: PMC7337177 DOI: 10.2147/dnnd.s61269] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Accepted: 04/23/2015] [Indexed: 11/23/2022] Open
Abstract
Rett syndrome (RTT), an X-linked neurodevelopment disorder, occurs in approximately one out of 10,000 females. Individuals afflicted by RTT display a constellation of signs and symptoms, affecting nearly every organ system. Most striking are the neurological manifestations, including regression of language and motor skills, increased seizure activity, autonomic dysfunction, and aberrant regulation of breathing patterns. The majority of girls with RTT have mutations in the gene encoding for methyl-CpG binding protein 2 (MeCP2). Since the discovery of this genetic cause of RTT in 1999, there has been an accelerated pace of research seeking to understand the role of MeCP2 in the brain in the hope of developing a disease-modifying therapy for RTT. In this study, we review the clinical features of RTT and then explore the latest mechanistic studies in order to explain how a mutation in MeCP2 leads to these unique features. We cover in detail studies examining the role of MeCP2 in neuronal physiology, as well as recent evidence that implicates a key role for glia in the pathogenesis of RTT. In the past 20 years, these basic and clinical studies have yielded an extraordinary understanding of RTT; as such, we end this narrative review considering the translation of these studies into clinical trials for the treatment of RTT.
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Affiliation(s)
| | | | - Alan K Percy
- Civitan International Research Center, University of Alabama at Birmingham, Birmingham, AL, USA
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34
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Li Q, Loh DH, Kudo T, Truong D, Derakhshesh M, Kaswan ZM, Ghiani CA, Tsoa R, Cheng Y, Sun YE, Colwell CS. Circadian rhythm disruption in a mouse model of Rett syndrome circadian disruption in RTT. Neurobiol Dis 2015; 77:155-64. [PMID: 25779967 DOI: 10.1016/j.nbd.2015.03.009] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2014] [Revised: 03/08/2015] [Accepted: 03/09/2015] [Indexed: 12/14/2022] Open
Abstract
Disturbances in the sleep/wake cycle are prevalent in patients with Rett syndrome (RTT). We sought to determine whether the circadian system is disrupted in a RTT model, Mecp2(-/y) mice. We found that MeCP2 mutants showed decreased strength and precision of daily rhythms of activity coupled with extremely fragmented sleep. The central circadian clock (suprachiasmatic nucleus) exhibited significant reduction in the number of neurons expressing vasoactive intestinal peptide (VIP) as well as compromised spontaneous neural activity. The molecular clockwork was disrupted both centrally in the SCN and in peripheral organs, indicating a general disorganization of the circadian system. Disruption of the molecular clockwork was observed in fibroblasts of RTT patients. Finally, MeCP2 mutant mice were vulnerable to circadian disruption as chronic jet lag accelerated mortality. Our finds suggest an integral role of MeCP2 in the circadian timing system and provides a possible mechanistic explanation for the sleep/wake distrubances observed in RTT patients. The work raises the possibility that RTT patients may benefit from a temporally structured environment.
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Affiliation(s)
- Quan Li
- Laboratory of Circadian and Sleep Medicine, Department of Psychiatry, University of California, Los Angeles, 760 Westwood Plaza, Los Angeles 90095-1759, USA; Department of Psychiatry, University of California, Los Angeles, Box 957332, 635 S. Charles E. Young Dr, Los Angeles, CA 90095-7332, USA; Molecular, Cellular and Integrative Physiology Program, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Dawn H Loh
- Laboratory of Circadian and Sleep Medicine, Department of Psychiatry, University of California, Los Angeles, 760 Westwood Plaza, Los Angeles 90095-1759, USA
| | - Takashi Kudo
- Laboratory of Circadian and Sleep Medicine, Department of Psychiatry, University of California, Los Angeles, 760 Westwood Plaza, Los Angeles 90095-1759, USA
| | - Danny Truong
- Laboratory of Circadian and Sleep Medicine, Department of Psychiatry, University of California, Los Angeles, 760 Westwood Plaza, Los Angeles 90095-1759, USA
| | - Matthew Derakhshesh
- Laboratory of Circadian and Sleep Medicine, Department of Psychiatry, University of California, Los Angeles, 760 Westwood Plaza, Los Angeles 90095-1759, USA
| | - Zoë MacDowell Kaswan
- Laboratory of Circadian and Sleep Medicine, Department of Psychiatry, University of California, Los Angeles, 760 Westwood Plaza, Los Angeles 90095-1759, USA
| | - Cristina A Ghiani
- Laboratory of Circadian and Sleep Medicine, Department of Psychiatry, University of California, Los Angeles, 760 Westwood Plaza, Los Angeles 90095-1759, USA
| | - Rosemarie Tsoa
- Department of Psychiatry, University of California, Los Angeles, Box 957332, 635 S. Charles E. Young Dr, Los Angeles, CA 90095-7332, USA
| | - Yin Cheng
- Department of Psychiatry, University of California, Los Angeles, Box 957332, 635 S. Charles E. Young Dr, Los Angeles, CA 90095-7332, USA
| | - Yi E Sun
- Department of Psychiatry, University of California, Los Angeles, Box 957332, 635 S. Charles E. Young Dr, Los Angeles, CA 90095-7332, USA.
| | - Christopher S Colwell
- Laboratory of Circadian and Sleep Medicine, Department of Psychiatry, University of California, Los Angeles, 760 Westwood Plaza, Los Angeles 90095-1759, USA.
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35
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Suter BA, Shepherd GMG. Reciprocal interareal connections to corticospinal neurons in mouse M1 and S2. J Neurosci 2015; 35:2959-74. [PMID: 25698734 PMCID: PMC4331623 DOI: 10.1523/jneurosci.4287-14.2015] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2014] [Revised: 12/18/2014] [Accepted: 01/05/2015] [Indexed: 01/13/2023] Open
Abstract
Primary motor (M1) and secondary somatosensory (S2) cortices, although anatomically and functionally distinct, share an intriguing cellular component: corticospinal neurons (CSP) in layer 5B. Here, we investigated the long-range circuits of CSPs in mouse forelimb-M1 and S2. We found that interareal projections (S2 → M1 and M1 → S2) monosynaptically excited pyramidal neurons across multiple layers, including CSPs. Area-specific differences were observed in the relative strengths of inputs to subsets of CSPs and other cell types, but the general patterns were similar. Furthermore, subcellular mapping of the dendritic distributions of these corticocortical excitatory synapses onto CSPs in both areas also showed similar patterns. Because layer 5B is particularly thick in M1, but not S2, we studied M1-CSPs at different cortical depths, quantifying their dendritic morphology and mapping inputs from additional cortical (M2, contralateral M1, and local layer 2/3) and thalamic (VL nucleus) sources. These results indicated that CSPs exhibit area-specific modifications on an otherwise conserved synaptic organization, and that different afferents innervate M1-CSP dendritic domains in a source-specific manner. In the cervical spinal cord, CSP axons from S2 and M1 partly converged on middle layers, but S2-CSP axons extended further dorsally, and M1-CSP axons ventrally. Thus, our findings identify many shared features in the circuits of M1 and S2 and show that these areas communicate via mutual projections that give each area monosynaptic access to the other area's CSPs. These interareally yoked CSP circuits may enable M1 and S2 to operate in a coordinated yet differentiated manner in the service of sensorimotor integration.
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Affiliation(s)
- Benjamin A Suter
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611
| | - Gordon M G Shepherd
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611
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36
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Sceniak MP, Lang M, Enomoto AC, James Howell C, Hermes DJ, Katz DM. Mechanisms of Functional Hypoconnectivity in the Medial Prefrontal Cortex of Mecp2 Null Mice. Cereb Cortex 2015; 26:1938-1956. [PMID: 25662825 DOI: 10.1093/cercor/bhv002] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Frontal cortical dysfunction is thought to contribute to cognitive and behavioral features of autism spectrum disorders; however, underlying mechanisms are poorly understood. The present study sought to define how loss of Mecp2, the gene mutated in Rett syndrome (RTT), disrupts function in the murine medial prefrontal cortex (mPFC) using acute brain slices and behavioral testing. Compared with wildtype, pyramidal neurons in the Mecp2 null mPFC exhibit significant reductions in excitatory postsynaptic currents, the duration of excitatory UP-states, evoked population activity, and the ratio of NMDA:AMPA currents, as well as an increase in the relative fraction of NR2B currents. These functional changes are associated with reductions in the density of excitatory dendritic spines, the ratio of vesicular glutamate to GABA transporters and GluN1 expression. In contrast to recent reports on circuit defects in other brain regions, we observed no effect of Mecp2 loss on inhibitory synaptic currents or expression of the inhibitory marker parvalbumin. Consistent with mPFC hypofunction, Mecp2 nulls exhibit respiratory dysregulation in response to behavioral arousal. Our data highlight functional hypoconnectivity in the mPFC as a potential substrate for behavioral disruption in RTT and other disorders associated with reduced expression of Mecp2 in frontal cortical regions.
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Affiliation(s)
- Michael P Sceniak
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Min Lang
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Addison C Enomoto
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - C James Howell
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Douglas J Hermes
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - David M Katz
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
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Yamawaki N, Shepherd GMG. Synaptic circuit organization of motor corticothalamic neurons. J Neurosci 2015; 35:2293-307. [PMID: 25653383 PMCID: PMC4315846 DOI: 10.1523/jneurosci.4023-14.2015] [Citation(s) in RCA: 86] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2014] [Revised: 11/24/2014] [Accepted: 12/27/2014] [Indexed: 01/07/2023] Open
Abstract
Corticothalamic (CT) neurons in layer 6 constitute a large but enigmatic class of cortical projection neurons. How they are integrated into intracortical and thalamo-cortico-thalamic circuits is incompletely understood, especially outside of sensory cortex. Here, we investigated CT circuits in mouse forelimb motor cortex (M1) using multiple circuit-analysis methods. Stimulating and recording from CT, intratelencephalic (IT), and pyramidal tract (PT) projection neurons, we found strong CT↔ CT and CT↔ IT connections; however, CT→IT connections were limited to IT neurons in layer 6, not 5B. There was strikingly little CT↔ PT excitatory connectivity. Disynaptic inhibition systematically accompanied excitation in these pathways, scaling with the amplitude of excitation according to both presynaptic (class-specific) and postsynaptic (cell-by-cell) factors. In particular, CT neurons evoked proportionally more inhibition relative to excitation (I/E ratio) than IT neurons. Furthermore, the amplitude of inhibition was tuned to match the amount of excitation at the level of individual neurons; in the extreme, neurons receiving no excitation received no inhibition either. Extending these studies to dissect the connectivity between cortex and thalamus, we found that M1-CT neurons and thalamocortical neurons in the ventrolateral (VL) nucleus were remarkably unconnected in either direction. Instead, VL axons in the cortex excited both IT and PT neurons, and CT axons in the thalamus excited other thalamic neurons, including those in the posterior nucleus, which additionally received PT excitation. These findings, which contrast in several ways with previous observations in sensory areas, illuminate the basic circuit organization of CT neurons within M1 and between M1 and thalamus.
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Affiliation(s)
- Naoki Yamawaki
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611
| | - Gordon M G Shepherd
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611
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Yamawaki N, Borges K, Suter BA, Harris KD, Shepherd GMG. A genuine layer 4 in motor cortex with prototypical synaptic circuit connectivity. eLife 2014; 3:e05422. [PMID: 25525751 PMCID: PMC4290446 DOI: 10.7554/elife.05422] [Citation(s) in RCA: 85] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Accepted: 12/18/2014] [Indexed: 12/28/2022] Open
Abstract
The motor cortex (M1) is classically considered an agranular area, lacking a distinct layer 4 (L4). Here, we tested the idea that M1, despite lacking a cytoarchitecturally visible L4, nevertheless possesses its equivalent in the form of excitatory neurons with input–output circuits like those of the L4 neurons in sensory areas. Consistent with this idea, we found that neurons located in a thin laminar zone at the L3/5A border in the forelimb area of mouse M1 have multiple L4-like synaptic connections: excitatory input from thalamus, largely unidirectional excitatory outputs to L2/3 pyramidal neurons, and relatively weak long-range corticocortical inputs and outputs. M1-L4 neurons were electrophysiologically diverse but morphologically uniform, with pyramidal-type dendritic arbors and locally ramifying axons, including branches extending into L2/3. Our findings therefore identify pyramidal neurons in M1 with the expected prototypical circuit properties of excitatory L4 neurons, and question the traditional assumption that motor cortex lacks this layer. DOI:http://dx.doi.org/10.7554/eLife.05422.001 In 1909, a German scientist called Korbinian Brodmann published the first map of the outer layer of the human brain. After staining neurons with a dye and studying the structures of the cells and how they were organized, he realized that he could divide the cortex into 43 numbered regions. Most Brodmann areas can be divided into a number of horizontal layers, with layer 1 being closest to the surface of the brain. Neurons in the different layers form distinct sets of connections, and the relative thickness of the layers has implications for the function carried out by that area. It is thought, for example, that the motor cortex does not have a layer 4, which suggests that the neural circuitry that controls movement differs from that in charge of vision, hearing, and other functions. Yamawaki et al. now challenge this view by providing multiple lines of evidence for the existence of layer 4 in the motor cortex in mice. Neurons at the border between layer 3 and layer 5A in the motor cortex possess many of the same properties as the neurons in layer 4 in sensory cortex. In particular, they receive inputs from a brain region called the thalamus, and send outputs to neurons in layers 2 and 3. Yamawaki et al. go on to characterize some of the properties of the neurons in the putative layer 4 of the motor cortex, finding that they do not look like the specialized ‘stellate’ cells that are found in some other areas of the cortex. Instead, they resemble the ‘pyramidal’ type of neuron that is found in all layers and areas of the cortex. The discovery that the motor cortex is more similar in its circuit connections to other area of the cortex than previously thought has important implications for our understanding of this region of the brain. DOI:http://dx.doi.org/10.7554/eLife.05422.002
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Affiliation(s)
- Naoki Yamawaki
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - Katharine Borges
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - Benjamin A Suter
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - Kenneth D Harris
- Institute of Neurology, University College London, London, United Kingdom
| | - Gordon M G Shepherd
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, United States
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In vivo interrogation of gene function in the mammalian brain using CRISPR-Cas9. Nat Biotechnol 2014; 33:102-6. [PMID: 25326897 DOI: 10.1038/nbt.3055] [Citation(s) in RCA: 561] [Impact Index Per Article: 56.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Accepted: 10/02/2014] [Indexed: 12/16/2022]
Abstract
Probing gene function in the mammalian brain can be greatly assisted with methods to manipulate the genome of neurons in vivo. The clustered, regularly interspaced, short palindromic repeats (CRISPR)-associated endonuclease (Cas)9 from Streptococcus pyogenes (SpCas9) can be used to edit single or multiple genes in replicating eukaryotic cells, resulting in frame-shifting insertion/deletion (indel) mutations and subsequent protein depletion. Here, we delivered SpCas9 and guide RNAs using adeno-associated viral (AAV) vectors to target single (Mecp2) as well as multiple genes (Dnmt1, Dnmt3a and Dnmt3b) in the adult mouse brain in vivo. We characterized the effects of genome modifications in postmitotic neurons using biochemical, genetic, electrophysiological and behavioral readouts. Our results demonstrate that AAV-mediated SpCas9 genome editing can enable reverse genetic studies of gene function in the brain.
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Song C, Feodorova Y, Guy J, Peichl L, Jost KL, Kimura H, Cardoso MC, Bird A, Leonhardt H, Joffe B, Solovei I. DNA methylation reader MECP2: cell type- and differentiation stage-specific protein distribution. Epigenetics Chromatin 2014; 7:17. [PMID: 25170345 PMCID: PMC4148084 DOI: 10.1186/1756-8935-7-17] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2014] [Accepted: 07/23/2014] [Indexed: 11/21/2022] Open
Abstract
Background Methyl-CpG binding protein 2 (MECP2) is a protein that specifically binds methylated DNA, thus regulating transcription and chromatin organization. Mutations in the gene have been identified as the principal cause of Rett syndrome, a severe neurological disorder. Although the role of MECP2 has been extensively studied in nervous tissues, still very little is known about its function and cell type specific distribution in other tissues. Results Using immunostaining on tissue cryosections, we characterized the distribution of MECP2 in 60 cell types of 16 mouse neuronal and non-neuronal tissues. We show that MECP2 is expressed at a very high level in all retinal neurons except rod photoreceptors. The onset of its expression during retina development coincides with massive synapse formation. In contrast to astroglia, retinal microglial cells lack MECP2, similar to microglia in the brain, cerebellum, and spinal cord. MECP2 is also present in almost all non-neural cell types, with the exception of intestinal epithelial cells, erythropoietic cells, and hair matrix keratinocytes. Our study demonstrates the role of MECP2 as a marker of the differentiated state in all studied cells other than oocytes and spermatogenic cells. MECP2-deficient male (Mecp2-/y) mice show no apparent defects in the morphology and development of the retina. The nuclear architecture of retinal neurons is also unaffected as the degree of chromocenter fusion and the distribution of major histone modifications do not differ between Mecp2-/y and Mecp2wt mice. Surprisingly, the absence of MECP2 is not compensated by other methyl-CpG binding proteins. On the contrary, their mRNA levels were downregulated in Mecp2-/y mice. Conclusions MECP2 is almost universally expressed in all studied cell types with few exceptions, including microglia. MECP2 deficiency does not change the nuclear architecture and epigenetic landscape of retinal cells despite the missing compensatory expression of other methyl-CpG binding proteins. Furthermore, retinal development and morphology are also preserved in Mecp2-null mice. Our study reveals the significance of MECP2 function in cell differentiation and sets the basis for future investigations in this direction.
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Affiliation(s)
- Congdi Song
- Department of Biology II, Center for Integrated Protein Science Munich (CIPSM), Ludwig Maximilians University Munich, Grosshadernerstrasse 2, 82152 Planegg-Martinsried, Germany
| | - Yana Feodorova
- Department of Biology II, Center for Integrated Protein Science Munich (CIPSM), Ludwig Maximilians University Munich, Grosshadernerstrasse 2, 82152 Planegg-Martinsried, Germany
| | - Jacky Guy
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, EH9 3JR Edinburgh, UK
| | - Leo Peichl
- Max Planck Institute for Brain Research, Max-von-Laue-Str. 4, Frankfurt am Main 60438, Germany
| | - Katharina Laurence Jost
- Cell Biology and Epigenetics, Department of Biology, Technische Universität Darmstadt, Schnittspahnstr. 10, Darmstadt 64287, Germany
| | - Hiroshi Kimura
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, 565-0871 Suita, Osaka, Japan
| | - Maria Cristina Cardoso
- Cell Biology and Epigenetics, Department of Biology, Technische Universität Darmstadt, Schnittspahnstr. 10, Darmstadt 64287, Germany
| | - Adrian Bird
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, EH9 3JR Edinburgh, UK
| | - Heinrich Leonhardt
- Department of Biology II, Center for Integrated Protein Science Munich (CIPSM), Ludwig Maximilians University Munich, Grosshadernerstrasse 2, 82152 Planegg-Martinsried, Germany
| | - Boris Joffe
- Department of Biology II, Center for Integrated Protein Science Munich (CIPSM), Ludwig Maximilians University Munich, Grosshadernerstrasse 2, 82152 Planegg-Martinsried, Germany
| | - Irina Solovei
- Department of Biology II, Center for Integrated Protein Science Munich (CIPSM), Ludwig Maximilians University Munich, Grosshadernerstrasse 2, 82152 Planegg-Martinsried, Germany
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Abstract
The methyl-DNA binding protein MeCP2 is emerging as an important regulator of drug reinforcement processes. Psychostimulants induce phosphorylation of MeCP2 at Ser421; however, the functional significance of this posttranslational modification for addictive-like behaviors was unknown. Here we show that MeCP2 Ser421Ala knock-in mice display both a reduced threshold for the induction of locomotor sensitization by investigator-administered amphetamine and enhanced behavioral sensitivity to the reinforcing properties of self-administered cocaine. These behavioral differences were accompanied in the knock-in mice by changes in medium spiny neuron intrinsic excitability and nucleus accumbens gene expression typically observed in association with repeated exposure to these drugs. These data show that phosphorylation of MeCP2 at Ser421 functions to limit the circuit plasticities in the nucleus accumbens that underlie addictive-like behaviors.
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Barth L, Sütterlin R, Nenniger M, Vogt KE. Reduced synaptic activity in neuronal networks derived from embryonic stem cells of murine Rett syndrome model. Front Cell Neurosci 2014; 8:79. [PMID: 24723848 PMCID: PMC3972477 DOI: 10.3389/fncel.2014.00079] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Accepted: 02/26/2014] [Indexed: 12/23/2022] Open
Abstract
Neurodevelopmental diseases such as the Rett syndrome (RTT) have received renewed attention, since the mechanisms involved may underlie a broad range of neuropsychiatric disorders such as schizophrenia and autism. In vertebrates early stages in the functional development of neurons and neuronal networks are difficult to study. Embryonic stem cell-derived neurons provide an easily accessible tool to investigate neuronal differentiation and early network formation. We used in vitro cultures of neurons derived from murine embryonic stem cells missing the methyl-CpG-binding protein 2 (MECP2) gene (MeCP2-/y) and from wild type cells of the corresponding background. Cultures were assessed using whole-cell patch-clamp electrophysiology and immunofluorescence. We studied the functional maturation of developing neurons and the activity of the synaptic connections they formed. Neurons exhibited minor differences in the developmental patterns for their intrinsic parameters, such as resting membrane potential and excitability; with the MeCP2-/y cells showing a slightly accelerated development, with shorter action potential half-widths at early stages. There was no difference in the early phase of synapse development, but as the cultures matured, significant deficits became apparent, particularly for inhibitory synaptic activity. MeCP2-/y embryonic stem cell-derived neuronal cultures show clear developmental deficits that match phenotypes observed in slice preparations and thus provide a compelling tool to further investigate the mechanisms behind RTT pathophysiology.
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Affiliation(s)
- Lydia Barth
- Neurobiology and Pharmacology, Biozentrum, University of Basel Basel, Switzerland
| | - Rosmarie Sütterlin
- Neurobiology and Pharmacology, Biozentrum, University of Basel Basel, Switzerland
| | - Markus Nenniger
- Neurobiology and Pharmacology, Biozentrum, University of Basel Basel, Switzerland
| | - Kaspar E Vogt
- Neurobiology and Pharmacology, Biozentrum, University of Basel Basel, Switzerland
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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.
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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:
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Ho ECY, Eubanks JH, Zhang L, Skinner FK. Network models predict that reduced excitatory fluctuations can give rise to hippocampal network hyper-excitability in MeCP2-null mice. PLoS One 2014; 9:e91148. [PMID: 24642514 PMCID: PMC3958347 DOI: 10.1371/journal.pone.0091148] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Accepted: 02/07/2014] [Indexed: 11/18/2022] Open
Abstract
Rett syndrome is a severe pediatric neurological disorder caused by loss of function mutations within the gene encoding methyl CpG-binding protein 2 (MeCP2). Although MeCP2 is expressed near ubiquitously, the primary pathophysiology of Rett syndrome stems from impairments of nervous system function. One alteration within different regions of the MeCP2-deficient brain is the presence of hyper-excitable network responses. In the hippocampus, such responses exist despite there being an overall decrease in spontaneous excitatory drive within the network. In this study, we generated and used mathematical, neuronal network models to resolve this apparent paradox. We did this by taking advantage of previous mathematical modelling insights that indicated that decreased excitatory fluctuations, but not mean excitatory drive, more critically explain observed changes in hippocampal network oscillations from MeCP2-null mouse slices. Importantly, reduced excitatory fluctuations could also bring about hyper-excitable responses in our network models. Therefore, these results indicate that diminished excitatory fluctuations may be responsible for the hyper-excitable state of MeCP2-deficient hippocampal circuitry.
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Affiliation(s)
- Ernest C. Y. Ho
- Toronto Western Research Institute, University Health Network, Toronto, Ontario, Canada
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
| | - James H. Eubanks
- Toronto Western Research Institute, University Health Network, Toronto, Ontario, Canada
- Department of Surgery (Neurosurgery), University of Toronto, Toronto, Ontario, Canada
| | - Liang Zhang
- Toronto Western Research Institute, University Health Network, Toronto, Ontario, Canada
- Department of Medicine (Neurology), University of Toronto, Toronto, Ontario, Canada
| | - Frances K. Skinner
- Toronto Western Research Institute, University Health Network, Toronto, Ontario, Canada
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
- Department of Medicine (Neurology), University of Toronto, Toronto, Ontario, Canada
- * E-mail:
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Abstract
The role of epigenetics in human disease has become an area of increased research interest. Collaborative efforts from scientists and clinicians have led to a better understanding of the molecular mechanisms by which epigenetic regulation is involved in the pathogenesis of many human diseases. Several neurological and non-neurological disorders are associated with mutations in genes that encode for epigenetic factors. One of the most studied proteins that impacts human disease and is associated with deregulation of epigenetic processes is Methyl CpG binding protein 2 (MeCP2). MeCP2 is an epigenetic regulator that modulates gene expression by translating epigenetic DNA methylation marks into appropriate cellular responses. In order to highlight the importance of epigenetics to development and disease, we will discuss how MeCP2 emerges as a key epigenetic player in human neurodevelopmental, neurological, and non-neurological disorders. We will review our current knowledge on MeCP2-related diseases, including Rett Syndrome, Angelman Syndrome, Fetal Alcohol Spectrum Disorder, Hirschsprung disease, and Cancer. Additionally, we will briefly discuss about the existing MeCP2 animal models that have been generated for a better understanding of how MeCP2 impacts certain human diseases.
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Affiliation(s)
| | - Mojgan Rastegar
- Author to whom correspondence should be addressed; ; Tel.: +204-272-3108; Fax: +204-789-3900
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46
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MeCP2 is required for activity-dependent refinement of olfactory circuits. Mol Cell Neurosci 2014; 59:63-75. [PMID: 24472844 DOI: 10.1016/j.mcn.2014.01.005] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2013] [Revised: 01/15/2014] [Accepted: 01/20/2014] [Indexed: 01/06/2023] Open
Abstract
Methyl CpG binding protein 2 (MeCP2) is a structural chromosomal protein involved in the regulation of gene expression. Alterations in the levels of MeCP2 have been related to neurodevelopmental disorders. Studies in mouse models of MeCP2 deficiency have demonstrated that this protein is important for neuronal maturation, neurite complexity, synaptogenesis, and synaptic plasticity. However, the mechanisms by which MeCP2 dysfunction leads to neurodevelopmental defects, and the role of activity, remain unclear, as most studies examine the adult nervous system, which may obfuscate the primary consequences of MeCP2 mutation. We hypothesize that MeCP2 plays a role during the formation and activity-driven maturation of neural circuits at early postnatal stages. To test this hypothesis, we use the olfactory system as a neurodevelopmental model. This system undergoes postnatal neurogenesis; axons from olfactory neurons form highly stereotyped projections to higher-order neurons, facilitating the detection of possible defects in the establishment of connectivity. In vivo olfactory stimulation paradigms were used to produce physiological synaptic activity in gene-targeted mice in which specific olfactory circuits are visualized. Our results reveal defective postnatal refinement of olfactory circuits in Mecp2 knock out (KO) mice after sensory (odorant) stimulation. This failure in refinement was associated with deficits in the normal responses to odorants, including brain-derived neurotrophic factor (BDNF) production, as well as changes in adhesion molecules known to regulate axonal convergence. The defective refinement observed in Mecp2 KO mice was prevented by daily treatment with ampakine beginning after the first postnatal week. These observations indicate that increasing synaptic activity at early postnatal stage might circumvent the detrimental effect of MeCP2 deficiency on circuitry maturation. The present results provide in vivo evidence in real time for the role of MeCP2 in activity-dependent maturation of olfactory circuitry, with implications for understanding the mechanism of MeCP2 mutations in the development of neural connectivity.
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Kao FC, Su SH, Carlson GC, Liao W. MeCP2-mediated alterations of striatal features accompany psychomotor deficits in a mouse model of Rett syndrome. Brain Struct Funct 2013; 220:419-34. [PMID: 24218106 DOI: 10.1007/s00429-013-0664-x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Accepted: 10/15/2013] [Indexed: 12/15/2022]
Abstract
Rett Syndrome (RTT) is a neurodevelopmental disorder caused by mutations in the methyl-CpG-binding protein 2 (MECP2) gene. Affected individuals develop motor deficits including stereotypic hand movements, impaired motor learning and difficulties with movement. To understand the neural mechanisms of motor deficits in RTT, we characterized the molecular and cellular phenotypes in the striatum, the major input nucleus of the basal ganglia that controls psychomotor function, in mice carrying a null allele of Mecp2. These mice showed significant hypoactivity associated with impaired motor coordination and motor skill learning. We found that dopamine content was significantly reduced in the striatum of Mecp2 null mice. Reduced dopamine was accompanied by down-regulation of tyrosine hydroxylase and up-regulation of dopamine D2 receptors, particularly in the rostral striatum. We also observed that loss of MeCP2 induced compartment-specific alterations in the striatum, including reduced expression of μ-opioid receptors in the striosomes and increased number of calbindin-positive neurons in the striatal matrix. The total number of parvalbumin-positive interneurons and their dendritic arborization were also significantly increased in the striatum of Mecp2 null mice. Together, our findings support that MeCP2 regulates a unique set of genes critical for modulating motor output of the striatum, and that aberrant structure and function of the striatum due to MeCP2 deficiency may underlie the motor deficits in RTT.
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Affiliation(s)
- Fang-Chi Kao
- Institute of Neuroscience, National Cheng-Chi University, 64, Sec. 2, Chi-Nan Road, Wen-Shan District, Taipei, 11605, Taiwan
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Della Sala G, Pizzorusso T. Synaptic plasticity and signaling in Rett syndrome. Dev Neurobiol 2013; 74:178-96. [PMID: 23908158 DOI: 10.1002/dneu.22114] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2012] [Revised: 06/28/2013] [Accepted: 07/22/2013] [Indexed: 12/11/2022]
Abstract
Rett syndrome (RTT) is a disorder that is caused in the majority of cases by mutations in the gene methyl-CpG-binding protein-2 (MeCP2). Children with RTT are generally characterized by normal development up to the first year and a half of age, after which they undergo a rapid regression marked by a deceleration of head growth, the onset of stereotyped hand movements, irregular breathing, and seizures. Animal models of RTT with good construct and face validity are available. Their analysis showed that homeostatic regulation of MeCP2 gene is necessary for normal CNS functioning and that multiple complex pathways involving different neuronal and glial cell types are disrupted in RTT models. However, it is increasingly clear that RTT pathogenetic mechanisms converge at synaptic level impairing synaptic transmission and plasticity. We review novel findings showing how specific synaptic mechanisms and related signaling pathways are affected in RTT models.
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Affiliation(s)
- Grazia Della Sala
- Department of Neuroscience, Psychology, Drug Research and Child Health NEUROFARBA, University of Florence, Florence, Italy
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Kaneko T. Local connections of excitatory neurons in motor-associated cortical areas of the rat. Front Neural Circuits 2013; 7:75. [PMID: 23754982 PMCID: PMC3664775 DOI: 10.3389/fncir.2013.00075] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Accepted: 04/03/2013] [Indexed: 11/30/2022] Open
Abstract
In spite of recent progress in brain sciences, the local circuit of the cerebral neocortex, including motor areas, still remains elusive. Morphological works on excitatory cortical circuitry from thalamocortical (TC) afferents to corticospinal neurons (CSNs) in motor-associated areas are reviewed here. First, TC axons of motor thalamic nuclei have been re-examined by the single-neuron labeling method. There are middle layer (ML)-targeting and layer (L) 1-preferring TC axon types in motor-associated areas, being analogous to core and matrix types, respectively, of Jones (1998) in sensory areas. However, the arborization of core-like motor TC axons spreads widely and disregards the columnar structure that is the basis of information processing in sensory areas, suggesting that motor areas adopt a different information-processing framework such as area-wide laminar organization. Second, L5 CSNs receive local excitatory inputs not only from L2/3 pyramidal neurons but also from ML spiny neurons, the latter directly processing cerebellar information of core-like TC neurons (TCNs). In contrast, basal ganglia information is targeted to apical dendrites of L2/3 and L5 pyramidal neurons through matrix TCNs. Third, L6 corticothalamic neurons (CTNs) are most densely innervated by ML spiny neurons located just above CTNs. Since CTNs receive only weak connections from L2/3 and L5 pyramidal neurons, the TC recurrent circuit composed of TCNs, ML spiny neurons and CTNs appears relatively independent of the results of processing in L2/3 and L5. It is proposed that two circuits sharing the same TC projection and ML neurons are embedded in the neocortex: one includes L2/3 and L5 neurons, processes afferent information in a feedforward way and sends the processed information to other cortical areas and subcortical regions; and the other circuit participates in a dynamical system of the TC recurrent circuit and may serve as the basis of autonomous activity of the neocortex.
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Affiliation(s)
- Takeshi Kaneko
- Department of Morphological Brain Science, Graduate School of Medicine, Kyoto University Kyoto, Japan
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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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