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Abstract
Epilepsy, characterized by spontaneous recurrent seizures (SRS), is a serious and common neurological disorder afflicting an estimated 1% of the population worldwide. Animal experiments, especially those utilizing small laboratory rodents, remain essential to understanding the fundamental mechanisms underlying epilepsy and to prevent, diagnose, and treat this disease. While much attention has been focused on epileptogenesis in animal models of epilepsy, there is little discussion on SRS, the hallmark of epilepsy. This is in part due to the technical difficulties of rigorous SRS detection. In this review, we comprehensively summarize both genetic and acquired models of SRS and discuss the methodology used to monitor and detect SRS in mice and rats.
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Affiliation(s)
- Bin Gu
- Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC 27599, USA.
| | - Katherine A Dalton
- Psychology & Neuroscience Program, University of North Carolina, Chapel Hill, NC 27599, USA
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52
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Zhong W, Johnson CM, Cui N, Oginsky MF, Wu Y, Jiang C. Effects of early-life exposure to THIP on brainstem neuronal excitability in the Mecp2-null mouse model of Rett syndrome before and after drug withdrawal. Physiol Rep 2017; 5:5/2/e13110. [PMID: 28108647 PMCID: PMC5269412 DOI: 10.14814/phy2.13110] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2016] [Revised: 12/08/2016] [Accepted: 12/08/2016] [Indexed: 11/24/2022] Open
Abstract
Rett syndrome (RTT) is mostly caused by mutations of the X‐linked MECP2 gene. Although the causal neuronal mechanisms are still unclear, accumulating experimental evidence obtained from Mecp2−/Y mice suggests that imbalanced excitation/inhibition in central neurons plays a major role. Several approaches may help to rebalance the excitation/inhibition, including agonists of GABAA receptors (GABAAR). Indeed, our previous studies have shown that early‐life exposure of Mecp2‐null mice to the extrasynaptic GABAAR agonist THIP alleviates several RTT‐like symptoms including breathing disorders, motor dysfunction, social behaviors, and lifespan. However, how the chronic THIP affects the Mecp2−/Y mice at the cellular level remains elusive. Here, we show that the THIP exposure in early lives markedly alleviated hyperexcitability of two types of brainstem neurons in Mecp2−/Y mice. In neurons of the locus coeruleus (LC), known to be involved in breathing regulation, the hyperexcitability showed clear age‐dependence, which was associated with age‐dependent deterioration of the RTT‐like breathing irregularities. Both the neuronal hyperexcitability and the breathing disorders were relieved with early THIP treatment. In neurons of the mesencephalic trigeminal nucleus (Me5), both the neuronal hyperexcitability and the changes in intrinsic membrane properties were alleviated with the THIP treatment in Mecp2‐null mice. The effects of THIP on both LC and Me5 neuronal excitability remained 1 week after withdrawal. Persistent alleviation of breathing abnormalities in Mecp2−/Y mice was also observed a week after THIP withdrawal. These results suggest that early‐life exposure to THIP, a potential therapeutic medicine, appears capable of controlling neuronal hyperexcitability in Mecp2−/Y mice, which occurs in the absence of THIP in the recording solution, lasts at least 1 week after withdrawal, and may contribute to the RTT‐like symptom mitigation.
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Affiliation(s)
- Weiwei Zhong
- Department of Biology, Georgia State University, Atlanta, Georgia
| | | | - Ningren Cui
- Department of Biology, Georgia State University, Atlanta, Georgia
| | - Max F Oginsky
- Department of Biology, Georgia State University, Atlanta, Georgia
| | - Yang Wu
- Department of Biology, Georgia State University, Atlanta, Georgia
| | - Chun Jiang
- Department of Biology, Georgia State University, Atlanta, Georgia
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53
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Lee LJ, Tsytsarev V, Erzurumlu RS. Structural and functional differences in the barrel cortex of Mecp2 null mice. J Comp Neurol 2017; 525:3951-3961. [PMID: 28857161 DOI: 10.1002/cne.24315] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 07/28/2017] [Accepted: 08/14/2017] [Indexed: 02/06/2023]
Abstract
Functional deficits in sensory systems are commonly noted in neurodevelopmental disorders, such as the Rett syndrome (RTT). Defects in methyl CpG binding protein gene (MECP2) largely accounts for RTT. Manipulations of the Mecp2 gene in mice provide useful models to probe into various aspects of brain development associated with the RTT. In this study, we focused on the somatosensory cortical phenotype in the Bird mouse model of RTT. We used voltage-sensitive dye imaging to evaluate whisker sensory evoked activity in the barrel cortex of mice. We coupled this functional assay with morphological analyses in postnatal mice and investigated the dendritic differentiation of barrel neurons and individual thalamocortical axon (TCA) arbors that synapse with them. We show that in Mecp2-deficient male mice, whisker-evoked activity is roughly topographic but weak in the barrel cortex. At the morphological level, we find that TCA arbors fail to develop into discrete, concentrated patches in barrel hollows, and the complexity of the dendritic branches in layer IV spiny stellate neurons is reduced. Collectively, our results indicate significant structural and functional impairments in the barrel cortex of the Bird mouse line, a popular animal model for the RTT. Such structural and functional anomalies in the primary somatosensory cortex may underlie orofacial tactile sensitivity issues and sensorimotor stereotypies characteristic of RTT.
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Affiliation(s)
- Li-Jen Lee
- Graduate Institute of Anatomy and Cell Biology, National Taiwan University, Taipei, Taiwan, ROC.,Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Vassiliy Tsytsarev
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Reha S Erzurumlu
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland
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54
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Ben-Ari Y. NKCC1 Chloride Importer Antagonists Attenuate Many Neurological and Psychiatric Disorders. Trends Neurosci 2017; 40:536-554. [PMID: 28818303 DOI: 10.1016/j.tins.2017.07.001] [Citation(s) in RCA: 136] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Revised: 07/03/2017] [Accepted: 07/10/2017] [Indexed: 12/23/2022]
Abstract
In physiological conditions, adult neurons have low intracellular Cl- [(Cl-)I] levels underlying the γ-aminobutyric acid (GABA)ergic inhibitory drive. In contrast, neurons have high (Cl-)I levels and excitatory GABA actions in a wide range of pathological conditions including spinal cord lesions, chronic pain, brain trauma, cerebrovascular infarcts, autism, Rett and Down syndrome, various types of epilepsies, and other genetic or environmental insults. The diuretic highly specific NKCC1 chloride importer antagonist bumetanide (PubChem CID: 2461) efficiently restores low (Cl-)I levels and attenuates many disorders in experimental conditions and in some clinical trials. Here, I review the mechanisms of action, therapeutic effects, promises, and pitfalls of bumetanide.
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Affiliation(s)
- Yehezkel Ben-Ari
- New INMED, Aix-Marseille University, Campus Scientifique de Luminy, Marseilles, France.
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55
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Rescue of impaired sociability and anxiety-like behavior in adult cacna1c-deficient mice by pharmacologically targeting eIF2α. Mol Psychiatry 2017; 22:1096-1109. [PMID: 28584287 PMCID: PMC5863913 DOI: 10.1038/mp.2017.124] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Revised: 04/12/2017] [Accepted: 05/04/2017] [Indexed: 12/13/2022]
Abstract
CACNA1C, encoding the Cav1.2 subunit of L-type Ca2+ channels, has emerged as one of the most prominent and highly replicable susceptibility genes for several neuropsychiatric disorders. Cav1.2 channels play a crucial role in calcium-mediated processes involved in brain development and neuronal function. Within the CACNA1C gene, disease-associated single-nucleotide polymorphisms have been associated with impaired social and cognitive processing and altered prefrontal cortical (PFC) structure and activity. These findings suggest that aberrant Cav1.2 signaling may contribute to neuropsychiatric-related disease symptoms via impaired PFC function. Here, we show that mice harboring loss of cacna1c in excitatory glutamatergic neurons of the forebrain (fbKO) that we have previously reported to exhibit anxiety-like behavior, displayed a social behavioral deficit and impaired learning and memory. Furthermore, focal knockdown of cacna1c in the adult PFC recapitulated the social deficit and elevated anxiety-like behavior, but not the deficits in learning and memory. Electrophysiological and molecular studies in the PFC of cacna1c fbKO mice revealed higher E/I ratio in layer 5 pyramidal neurons and lower general protein synthesis. This was concurrent with reduced activity of mTORC1 and its downstream mRNA translation initiation factors eIF4B and 4EBP1, as well as elevated phosphorylation of eIF2α, an inhibitor of mRNA translation. Remarkably, systemic treatment with ISRIB, a small molecule inhibitor that suppresses the effects of phosphorylated eIF2α on mRNA translation, was sufficient to reverse the social deficit and elevated anxiety-like behavior in adult cacna1c fbKO mice. ISRIB additionally normalized the lower protein synthesis and higher E/I ratio in the PFC. Thus this study identifies a novel Cav1.2 mechanism in neuropsychiatric-related endophenotypes and a potential future therapeutic target to explore.
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56
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Hu Y, Le L, Qi LX, Zhao Y, Fu H, Duan C, Wang XY, Hu KP. Comprehensive Evaluation on Effect of IMPX977 on Expression of Methyl-CpG-binding Protein 2 in Rats. CHINESE HERBAL MEDICINES 2017. [DOI: 10.1016/s1674-6384(17)60104-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
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57
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Zhang W, Daly KM, Liang B, Zhang L, Li X, Li Y, Lin DT. BDNF rescues prefrontal dysfunction elicited by pyramidal neuron-specific DTNBP1 deletion in vivo. J Mol Cell Biol 2017; 9:117-131. [PMID: 27330059 DOI: 10.1093/jmcb/mjw029] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Accepted: 05/16/2016] [Indexed: 01/15/2023] Open
Abstract
Dystrobrevin-binding protein 1 (Dtnbp1) is one of the earliest identified schizophrenia susceptibility genes. Reduced expression of DTNBP1 is commonly found in brain areas of schizophrenic patients. Dtnbp1-null mutant mice exhibit abnormalities in behaviors and impairments in neuronal activities. However, how diminished DTNBP1 expression contributes to clinical relevant features of schizophrenia remains to be illustrated. Here, using a conditional Dtnbp1 knockout mouse line, we identified an in vivo schizophrenia-relevant function of DTNBP1 in pyramidal neurons of the medial prefrontal cortex (mPFC). We demonstrated that DTNBP1 elimination specifically in pyramidal neurons of the mPFC impaired mouse pre-pulse inhibition (PPI) behavior and reduced perisomatic GABAergic synapses. We further revealed that loss of DTNBP1 in pyramidal neurons diminished activity-dependent secretion of brain-derived neurotrophic factor (BDNF). Finally, we showed that chronic BDNF infusion in the mPFC fully rescued both GABAergic synaptic dysfunction and PPI behavioral deficit induced by DTNBP1 elimination from pyramidal neurons. Our findings highlight brain region- and cell type-specific functions of DTNBP1 in the pathogenesis of schizophrenia, and underscore BDNF restoration as a potential therapeutic strategy for schizophrenia.
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Affiliation(s)
- Wen Zhang
- Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, 333 Cassell Drive, Baltimore, MD 21224, USA
| | - Kathryn M Daly
- Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, 333 Cassell Drive, Baltimore, MD 21224, USA
| | - Bo Liang
- Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, 333 Cassell Drive, Baltimore, MD 21224, USA
| | - Lifeng Zhang
- Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, 333 Cassell Drive, Baltimore, MD 21224, USA
| | - Xuan Li
- Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, 333 Cassell Drive, Baltimore, MD 21224, USA
| | - Yun Li
- Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, 333 Cassell Drive, Baltimore, MD 21224, USA
| | - Da-Ting Lin
- Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, 333 Cassell Drive, Baltimore, MD 21224, USA.,The Jackson Laboratory, 600 Main Street, Bar Harbor, ME 04609, USA.,The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Baltimore, MD 21205, USA
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58
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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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59
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Maphis NM, Jiang S, Binder J, Wright C, Gopalan B, Lamb BT, Bhaskar K. Whole Genome Expression Analysis in a Mouse Model of Tauopathy Identifies MECP2 as a Possible Regulator of Tau Pathology. Front Mol Neurosci 2017; 10:69. [PMID: 28367114 PMCID: PMC5355442 DOI: 10.3389/fnmol.2017.00069] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Accepted: 02/28/2017] [Indexed: 11/14/2022] Open
Abstract
Increasing evidence suggests that hyperphosphorylation and aggregation of microtubule-associated protein tau (MAPT or tau) correlates with the development of cognitive impairment in Alzheimer’s disease (AD) and related tauopathies. While numerous attempts have been made to model AD-relevant tau pathology in various animal models, there has been very limited success for these models to fully recapitulate the progression of disease as seen in human tauopathies. Here, we performed whole genome gene expression in a genomic mouse model of tauopathy that expressed human MAPT gene under the control of endogenous human MAPT promoter and also were complete knockout for endogenous mouse tau [referred to as ‘hTauMaptKO(Duke)′ mice]. First, whole genome expression analysis revealed 64 genes, which were differentially expressed (32 up-regulated and 32 down-regulated) in the hippocampus of 6-month-old hTauMaptKO(Duke) mice compared to age-matched non-transgenic controls. Genes relevant to neuronal function or neurological disease include up-regulated genes: PKC-alpha (Prkca), MECP2 (Mecp2), STRN4 (Strn4), SLC40a1 (Slc40a1), POLD2 (Pold2), PCSK2 (Pcsk2), and down-regulated genes: KRT12 (Krt12), LASS1 (Cers1), PLAT (Plat), and NRXN1 (Nrxn1). Second, network analysis suggested anatomical structure development, cellular metabolic process, cell death, signal transduction, and stress response were significantly altered biological processes in the hTauMaptKO(Duke) mice as compared to age-matched non-transgenic controls. Further characterization of a sub-group of significantly altered genes revealed elevated phosphorylation of MECP2 (methyl-CpG-binding protein-2), which binds to methylated CpGs and associates with chromatin, in hTauMaptKO(Duke) mice compared to age-matched controls. Third, phoshpho-MECP2 was elevated in autopsy brain samples from human AD compared to healthy controls. Finally, siRNA-mediated knockdown of MECP2 in human tau expressing N2a cells resulted in a significant decrease in total and phosphorylated tau. Together, these results suggest that MECP2 is a potential novel regulator of tau pathology relevant to AD and tauopathies.
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Affiliation(s)
- Nicole M Maphis
- Department of Molecular Genetics and Microbiology, University of New Mexico, Albuquerque NM, USA
| | - Shanya Jiang
- Department of Molecular Genetics and Microbiology, University of New Mexico, Albuquerque NM, USA
| | - Jessica Binder
- Department of Molecular Genetics and Microbiology, University of New Mexico, Albuquerque NM, USA
| | - Carrie Wright
- Lieber Institute for Brain Development, Baltimore MD, USA
| | - Banu Gopalan
- Department of Biostatistics, Cleveland Clinic Foundation Cleveland OH, USA
| | - Bruce T Lamb
- Stark Neurosciences Research Institute, Indiana University, Indianapolis IN, USA
| | - Kiran Bhaskar
- Department of Molecular Genetics and Microbiology, University of New Mexico, Albuquerque NM, USA
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60
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Effects of chronic exposure to low dose THIP on brainstem neuronal excitability in mouse models of Rett syndrome: Evidence from symptomatic females. Neuropharmacology 2017; 116:288-299. [PMID: 28069353 DOI: 10.1016/j.neuropharm.2017.01.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2016] [Revised: 12/10/2016] [Accepted: 01/04/2017] [Indexed: 01/17/2023]
Abstract
Rett Syndrome (RTT) is a neurodevelopmental disorder caused by mutations of the MECP2 gene, affecting predominantly females. One of the characteristic features of the disease is defective brainstem autonomic function. In Mecp2-/Y mice, several groups of brainstem neurons are overly excitable, which causes destabilization of neuronal networks for the autonomic control. We have previously shown that the extrasynaptic GABAA receptor agonist THIP relieves many RTT-like symptoms in Mecp2-/Y mice. Although neuronal activity is inhibited by acute THIP exposure, how a chronic treatment affects neuronal excitability remains elusive. Thus, we performed studies to address whether increased excitability occurs in brainstem neurons of female Mecp2+/- mice, how the MeCP expression affects the neuronal excitability, and whether chronic THIP exposure improves the neuronal hyperexcitability. Symptomatic Mecp2+/- (sMecp2+/-) female mice were identified with a two-step screening system. Whole-cell recording was performed in brain slices after a prior exposure of the sMecp2+/- mice to a 5-week low-dose THIP. Neurons in the locus coeruleus (LC) and the mesencephalic trigeminal nucleus (Me5) showed excessive firing activity in the sMecp2+/- mice. THIP pretreatment reduced the hyperexcitability of both LC and Me5 neurons in the sMecp2+/- mice, to a similar level as their counterparts in Mecp2-/Y mice. In identified LC neurons, the hyperexcitability appeared to be determined by not only the MeCP2 expression, but also their environmental cues. The alleviation of LC neuronal hyperexcitability seems to benefit brainstem autonomic function as THIP also improved breathing abnormalities of these sMecp2+/- mice.
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61
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Tarquinio DC, Hou W, Berg A, Kaufmann WE, Lane JB, Skinner SA, Motil KJ, Neul JL, Percy AK, Glaze DG. Longitudinal course of epilepsy in Rett syndrome and related disorders. Brain 2016; 140:306-318. [PMID: 28007990 DOI: 10.1093/brain/aww302] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Revised: 09/22/2016] [Accepted: 10/10/2016] [Indexed: 01/05/2023] Open
Abstract
Epilepsy is common in Rett syndrome, an X-linked dominant disorder caused by mutations in the MECP2 gene, and in Rett-related disorders, such as MECP2 duplication. However, neither the longitudinal course of epilepsy nor the patterns of seizure onset and remission have been described in Rett syndrome and related conditions. The present study summarizes the findings of the Rett syndrome Natural History study. Participants with clinical Rett syndrome and those with MECP2 mutations without the clinical syndrome were recruited through the Rett Natural History study from 2006 to 2015. Clinical details were collected, and cumulative lifetime prevalence of epilepsy was determined using the Kaplan-Meier estimator. Risk factors for epilepsy were assessed using Cox proportional hazards models. Of 1205 participants enrolled in the study, 922 had classic Rett syndrome, and 778 of these were followed longitudinally for 3939 person-years. The diagnosis of atypical Rett syndrome with a severe clinical phenotype was associated with higher prevalence of epilepsy than those with classic Rett syndrome. While point prevalence of active seizures ranged from 30% to 44%, the estimated cumulative lifetime prevalence of epilepsy using Kaplan-Meier approached 90%. Specific MECP2 mutations were not significantly associated with either seizure prevalence or seizure severity. In contrast, many clinical features were associated with seizure prevalence; frequency of hospitalizations, inability to walk, bradykinesia, scoliosis, gastrostomy feeding, age of seizure onset, and late age of diagnosis were independently associated with higher odds of an individual having epilepsy. Aggressive behaviour was associated with lower odds. Three distinct patterns of seizure prevalence emerged in classic Rett syndrome, including those who did not have seizures throughout the study, those who had frequent relapse and remission, and those who had relentless seizures. Although 248 of those with classic Rett syndrome and a history of seizures were in terminal remission at last contact, only 74 (12% of those with a history of epilepsy) were seizure free and off anti-seizure medication. When studied longitudinally, point prevalence of active seizures is relatively low in Rett syndrome, although lifetime risk of epilepsy is higher than previously reported. While daily seizures are uncommon in Rett syndrome, prolonged remission is less common than in other causes of childhood onset epilepsy. Complete remission off anti-seizure medications is possible, but future efforts should be directed at determining what factors predict when withdrawal of medications in those who are seizure free is propitious.
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Affiliation(s)
| | - Wei Hou
- Stony Brook University Medical Center, Stony Brook, NY, USA
| | - Anne Berg
- Ann and Robert H. Lurie Children's Hospital of Chicago, IL, USA
| | | | - Jane B Lane
- University of Alabama at Birmingham, Birmingham, AL, USA
| | | | | | | | - Alan K Percy
- University of Alabama at Birmingham, Birmingham, AL, USA
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62
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Leonard H, Cobb S, Downs J. Clinical and biological progress over 50 years in Rett syndrome. Nat Rev Neurol 2016; 13:37-51. [PMID: 27934853 DOI: 10.1038/nrneurol.2016.186] [Citation(s) in RCA: 137] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
In the 50 years since Andreas Rett first described the syndrome that came to bear his name, and is now known to be caused by a mutation in the methyl-CpG-binding protein 2 (MECP2) gene, a compelling blend of astute clinical observations and clinical and laboratory research has substantially enhanced our understanding of this rare disorder. Here, we document the contributions of the early pioneers in Rett syndrome (RTT) research, and describe the evolution of knowledge in terms of diagnostic criteria, clinical variation, and the interplay with other Rett-related disorders. We provide a synthesis of what is known about the neurobiology of MeCP2, considering the lessons learned from both cell and animal models, and how they might inform future clinical trials. With a focus on the core criteria, we examine the relationships between genotype and clinical severity. We review current knowledge about the many comorbidities that occur in RTT, and how genotype may modify their presentation. We also acknowledge the important drivers that are accelerating this research programme, including the roles of research infrastructure, international collaboration and advocacy groups. Finally, we highlight the major milestones since 1966, and what they mean for the day-to-day lives of individuals with RTT and their families.
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Affiliation(s)
- Helen Leonard
- Telethon Kids Institute, 100 Roberts Road, Subiaco, Perth, Western Australia 6008, Australia
| | - Stuart Cobb
- Institute of Neuroscience and Psychology, College of Medical, Veterinary and Life Sciences, University of Glasgow, University Avenue, Glasgow G12 8QQ, UK
| | - Jenny Downs
- Telethon Kids Institute, 100 Roberts Road, Subiaco, Perth, Western Australia 6008, Australia
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63
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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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64
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Zhong W, Johnson CM, Wu Y, Cui N, Xing H, Zhang S, Jiang C. Effects of early-life exposure to THIP on phenotype development in a mouse model of Rett syndrome. J Neurodev Disord 2016; 8:37. [PMID: 27777634 PMCID: PMC5069883 DOI: 10.1186/s11689-016-9169-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Accepted: 10/04/2016] [Indexed: 01/15/2023] Open
Abstract
Background Rett syndrome (RTT) is a neurodevelopmental disorder caused mostly by disruptions in the MECP2 gene. MECP2-null mice show imbalances in neuronal excitability and synaptic communications. Several previous studies indicate that augmenting synaptic GABA receptors (GABAARs) can alleviate RTT-like symptoms in mice. In addition to the synaptic GABAARs, there is a group of GABAARs found outside the synaptic cleft with the capability to produce sustained inhibition, which may be potential therapeutic targets for the control of neuronal excitability in RTT. Methods Wild-type and MECP2-null mice were randomly divided into four groups, receiving the extrasynaptic GABAAR agonist 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol hydrochloride (THIP) and vehicle control, respectively. Low-dose THIP was administered to neonatal mice through lactation. RTT-like symptoms including lifespan, breathing, motor function, and social behaviors were studied when mice became mature. Changes in neuronal excitability and norepinephrine biosynthesis enzyme expression were studied in electrophysiology and molecular biology. Results With no evident sedation and other adverse side effects, early-life exposure to THIP extended the lifespan, alleviated breathing abnormalities, enhanced motor function, and improved social behaviors of MECP2-null mice. Such beneficial effects were associated with stabilization of locus coeruleus neuronal excitability and improvement of norepinephrine biosynthesis enzyme expression. Conclusions THIP treatment in early lives might be a therapeutic approach to RTT-like symptoms in MECP2-null mice and perhaps in people with RTT as well.
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Affiliation(s)
- Weiwei Zhong
- Department of Biology, Georgia State University, 100 Piedmont Avenue, Atlanta, GA 30302-4010 USA
| | | | - Yang Wu
- Department of Biology, Georgia State University, 100 Piedmont Avenue, Atlanta, GA 30302-4010 USA
| | - Ningren Cui
- Department of Biology, Georgia State University, 100 Piedmont Avenue, Atlanta, GA 30302-4010 USA
| | - Hao Xing
- Department of Biology, Georgia State University, 100 Piedmont Avenue, Atlanta, GA 30302-4010 USA
| | - Shuang Zhang
- Department of Biology, Georgia State University, 100 Piedmont Avenue, Atlanta, GA 30302-4010 USA
| | - Chun Jiang
- Department of Biology, Georgia State University, 100 Piedmont Avenue, Atlanta, GA 30302-4010 USA
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Loss and Gain of MeCP2 Cause Similar Hippocampal Circuit Dysfunction that Is Rescued by Deep Brain Stimulation in a Rett Syndrome Mouse Model. Neuron 2016; 91:739-747. [PMID: 27499081 DOI: 10.1016/j.neuron.2016.07.018] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2015] [Revised: 05/01/2016] [Accepted: 07/07/2016] [Indexed: 11/22/2022]
Abstract
Loss- and gain-of-function mutations in methyl-CpG-binding protein 2 (MECP2) underlie two distinct neurological syndromes with strikingly similar features, but the synaptic and circuit-level changes mediating these shared features are undefined. Here we report three novel signs of neural circuit dysfunction in three mouse models of MECP2 disorders (constitutive Mecp2 null, mosaic Mecp2(+/-), and MECP2 duplication): abnormally elevated synchrony in the firing activity of hippocampal CA1 pyramidal neurons, an impaired homeostatic response to perturbations of excitatory-inhibitory balance, and decreased excitatory synaptic response in inhibitory neurons. Conditional mutagenesis studies revealed that MeCP2 dysfunction in excitatory neurons mediated elevated synchrony at baseline, while MeCP2 dysfunction in inhibitory neurons increased susceptibility to hypersynchronization in response to perturbations. Chronic forniceal deep brain stimulation (DBS), recently shown to rescue hippocampus-dependent learning and memory in Mecp2(+/-) (Rett) mice, also rescued all three features of hippocampal circuit dysfunction in these mice.
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66
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Andoh M, Ikegaya Y, Koyama R. [Autism spectrum disorders and epilepsy]. Nihon Yakurigaku Zasshi 2016; 148:121-122. [PMID: 27478051 DOI: 10.1254/fpj.148.121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
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67
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Witteveen JS, Willemsen MH, Dombroski TCD, van Bakel NHM, Nillesen WM, van Hulten JA, Jansen EJR, Verkaik D, Veenstra-Knol HE, van Ravenswaaij-Arts CMA, Wassink-Ruiter JSK, Vincent M, David A, Le Caignec C, Schieving J, Gilissen C, Foulds N, Rump P, Strom T, Cremer K, Zink AM, Engels H, de Munnik SA, Visser JE, Brunner HG, Martens GJM, Pfundt R, Kleefstra T, Kolk SM. Haploinsufficiency of MeCP2-interacting transcriptional co-repressor SIN3A causes mild intellectual disability by affecting the development of cortical integrity. Nat Genet 2016; 48:877-87. [PMID: 27399968 DOI: 10.1038/ng.3619] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Accepted: 06/15/2016] [Indexed: 12/13/2022]
Abstract
Numerous genes are associated with neurodevelopmental disorders such as intellectual disability and autism spectrum disorder (ASD), but their dysfunction is often poorly characterized. Here we identified dominant mutations in the gene encoding the transcriptional repressor and MeCP2 interactor switch-insensitive 3 family member A (SIN3A; chromosome 15q24.2) in individuals who, in addition to mild intellectual disability and ASD, share striking features, including facial dysmorphisms, microcephaly and short stature. This phenotype is highly related to that of individuals with atypical 15q24 microdeletions, linking SIN3A to this microdeletion syndrome. Brain magnetic resonance imaging showed subtle abnormalities, including corpus callosum hypoplasia and ventriculomegaly. Intriguingly, in vivo functional knockdown of Sin3a led to reduced cortical neurogenesis, altered neuronal identity and aberrant corticocortical projections in the developing mouse brain. Together, our data establish that haploinsufficiency of SIN3A is associated with mild syndromic intellectual disability and that SIN3A can be considered to be a key transcriptional regulator of cortical brain development.
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Affiliation(s)
- Josefine S Witteveen
- Department of Molecular Animal Physiology, Donders Institute for Brain, Cognition and Behavior, Radboud University, Nijmegen, the Netherlands
| | - Marjolein H Willemsen
- Department of Human Genetics, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behavior, Nijmegen, the Netherlands
| | - Thaís C D Dombroski
- Department of Molecular Animal Physiology, Donders Institute for Brain, Cognition and Behavior, Radboud University, Nijmegen, the Netherlands
| | - Nick H M van Bakel
- Department of Molecular Animal Physiology, Donders Institute for Brain, Cognition and Behavior, Radboud University, Nijmegen, the Netherlands
| | - Willy M Nillesen
- Department of Human Genetics, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behavior, Nijmegen, the Netherlands
| | - Josephus A van Hulten
- Department of Molecular Animal Physiology, Donders Institute for Brain, Cognition and Behavior, Radboud University, Nijmegen, the Netherlands
| | - Eric J R Jansen
- Department of Molecular Animal Physiology, Donders Institute for Brain, Cognition and Behavior, Radboud University, Nijmegen, the Netherlands
| | - Dave Verkaik
- Department of Human Genetics, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behavior, Nijmegen, the Netherlands
| | - Hermine E Veenstra-Knol
- Department of Genetics, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands
| | | | | | - Marie Vincent
- Centre Hospitalier Universitaire de Nantes, Service de Génétique Médicale, Nantes, France
| | - Albert David
- Centre Hospitalier Universitaire de Nantes, Service de Génétique Médicale, Nantes, France
| | - Cedric Le Caignec
- Centre Hospitalier Universitaire de Nantes, Service de Génétique Médicale, Nantes, France.,Laboratoire de Physiopathologie de la Résorption Osseuse et Thérapie des Tumeurs Osseuses Primitives, Faculté de Médecine, INSERM UMRS 957, Nantes, France
| | - Jolanda Schieving
- Department of Neurology, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Christian Gilissen
- Department of Human Genetics, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behavior, Nijmegen, the Netherlands
| | - Nicola Foulds
- Wessex Clinical Genetics Services, University Hospital Southampton National Health Service Foundation Trust, Princess Anne Hospital, Southampton, UK.,Department of Human Genetics and Genomic Medicine, Faculty of Medicine, University of Southampton, Southampton, UK
| | - Patrick Rump
- Department of Genetics, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands
| | - Tim Strom
- Institute of Human Genetics, Helmholtz Zentrum München, Neuherberg, Germany.,Institute of Human Genetics, Technische Universität München, Munich, Germany
| | - Kirsten Cremer
- Institute of Human Genetics, University of Bonn, Bonn, Germany
| | | | - Hartmut Engels
- Institute of Human Genetics, University of Bonn, Bonn, Germany
| | - Sonja A de Munnik
- Department of Human Genetics, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behavior, Nijmegen, the Netherlands
| | - Jasper E Visser
- Department of Molecular Animal Physiology, Donders Institute for Brain, Cognition and Behavior, Radboud University, Nijmegen, the Netherlands.,Department of Neurology, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, Nijmegen, the Netherlands.,Department of Neurology, Amphia Hospital Breda, Berda, the Netherlands
| | - Han G Brunner
- Department of Human Genetics, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behavior, Nijmegen, the Netherlands
| | - Gerard J M Martens
- Department of Molecular Animal Physiology, Donders Institute for Brain, Cognition and Behavior, Radboud University, Nijmegen, the Netherlands
| | - Rolph Pfundt
- Department of Human Genetics, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behavior, Nijmegen, the Netherlands
| | - Tjitske Kleefstra
- Department of Human Genetics, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behavior, Nijmegen, the Netherlands
| | - Sharon M Kolk
- Department of Molecular Animal Physiology, Donders Institute for Brain, Cognition and Behavior, Radboud University, Nijmegen, the Netherlands
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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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69
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Wu Y, Zhong W, Cui N, Johnson CM, Xing H, Zhang S, Jiang C. Characterization of Rett Syndrome-like phenotypes in Mecp2-knockout rats. J Neurodev Disord 2016; 8:23. [PMID: 27313794 PMCID: PMC4910223 DOI: 10.1186/s11689-016-9156-7] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Accepted: 06/02/2016] [Indexed: 12/04/2022] Open
Abstract
Background Rett Syndrome (RTT) is a neurodevelopmental disease caused by the disruption of the MECP2 gene. Several mouse models of RTT have been developed with Mecp2 disruptions. Although the mouse models are widely used in RTT research, results obtained need to be validated in other species. Therefore, we performed these studies to characterize phenotypes of a novel Mecp2−/Y rat model and compared them with the Mecp2tm1.1Bird mouse model of RTT. Methods RTT-like phenotypes were systematically studied and compared between Mecp2−/Y rats and Mecp2−/Y mice. In-cage conditions of the rats were monitored. Grip strength and spontaneous locomotion were used to evaluate the motor function. Three-chamber test was performed to show autism-type behaviors. Breathing activity was recorded with the plethysmograph. Individual neurons in the locus coeruleus (LC) were studied in the whole-cell current clamp. The lifespan of the rats was determined with their survival time. Results Mecp2−/Y rats displayed growth retardation, malocclusion, and lack of movements, while hindlimb clasping was not seen. They had weaker forelimb grip strength and a lower rate of locomotion than the WT littermates. Defects in social interaction with other rats were obvious. Breathing frequency variation and apnea in the null rats were significantly higher than in the WT. LC neurons in the null rats showed excessive firing activity. A half of the null rats died in 2 months. Most of the RTT-like symptoms were comparable to those seen in Mecp2−/Y mice, while some appeared more or less severe. The findings that most RTT-like symptoms exist in the rat model with moderate variations and differences from the mouse models support the usefulness of both Mecp2−/Y rodent models. Conclusions The novel Mecp2−/Y rat model recapitulated numerous RTT-like symptoms as Mecp2−/Y mouse models did, which makes it a valuable alternative model in the RTT studies when the body size matters.
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Affiliation(s)
- Yang Wu
- Department of Biology, Georgia State University, 50 Decatur Street, Atlanta, GA 30302 USA
| | - Weiwei Zhong
- Department of Biology, Georgia State University, 50 Decatur Street, Atlanta, GA 30302 USA
| | - Ningren Cui
- Department of Biology, Georgia State University, 50 Decatur Street, Atlanta, GA 30302 USA
| | - Christopher M Johnson
- Department of Biology, Georgia State University, 50 Decatur Street, Atlanta, GA 30302 USA
| | - Hao Xing
- Department of Biology, Georgia State University, 50 Decatur Street, Atlanta, GA 30302 USA
| | - Shuang Zhang
- Department of Biology, Georgia State University, 50 Decatur Street, Atlanta, GA 30302 USA
| | - Chun Jiang
- Department of Biology, Georgia State University, 50 Decatur Street, Atlanta, GA 30302 USA
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70
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Kyle SM, Saha PK, Brown HM, Chan LC, Justice MJ. MeCP2 co-ordinates liver lipid metabolism with the NCoR1/HDAC3 corepressor complex. Hum Mol Genet 2016; 25:3029-3041. [PMID: 27288453 PMCID: PMC5181597 DOI: 10.1093/hmg/ddw156] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Revised: 05/02/2016] [Accepted: 05/18/2016] [Indexed: 01/11/2023] Open
Abstract
Rett syndrome (RTT; OMIM 312750), a progressive neurological disorder, is caused by mutations in methyl-CpG-binding protein 2 (MECP2; OMIM 300005), a ubiquitously expressed factor. A genetic suppressor screen designed to identify therapeutic targets surprisingly revealed that downregulation of the cholesterol biosynthesis pathway improves neurological phenotypes in Mecp2 mutant mice. Here, we show that MeCP2 plays a direct role in regulating lipid metabolism. Mecp2 deletion in mice results in a host of severe metabolic defects caused by lipid accumulation, including insulin resistance, fatty liver, perturbed energy utilization, and adipose inflammation by macrophage infiltration. We show that MeCP2 regulates lipid homeostasis by anchoring the repressor complex containing NCoR1 and HDAC3 to its lipogenesis targets in hepatocytes. Consistently, we find that liver targeted deletion of Mecp2 causes fatty liver disease and dyslipidemia similar to HDAC3 liver-specific deletion. These findings position MeCP2 as a novel component in metabolic homeostasis. Rett syndrome patients also show signs of peripheral dyslipidemia; thus, together these data suggest that RTT should be classified as a neurological disorder with systemic metabolic components. We previously showed that treatment of Mecp2 mice with statin drugs alleviated motor symptoms and improved health and longevity. Lipid metabolism is a highly treatable target; therefore, our results shed light on new metabolic pathways for treatment of Rett syndrome.
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Affiliation(s)
- Stephanie M Kyle
- Genetics and Genome Biology Program, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, ON M5G 0A4, Canada.,Department of Molecular and Human Genetics
| | - Pradip K Saha
- Department of Medicine, Division of Diabetes, Endocrinology and Metabolism, Baylor College of Medicine, Houston, TX 77030, USA
| | | | - Lawrence C Chan
- Department of Medicine, Division of Diabetes, Endocrinology and Metabolism, Baylor College of Medicine, Houston, TX 77030, USA
| | - Monica J Justice
- Genetics and Genome Biology Program, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, ON M5G 0A4, Canada .,Department of Molecular and Human Genetics.,Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A1, Canada
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71
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Sajan SA, Jhangiani SN, Muzny DM, Gibbs RA, Lupski JR, Glaze DG, Kaufmann WE, Skinner SA, Annese F, Friez MJ, Lane J, Percy AK, Neul JL. Enrichment of mutations in chromatin regulators in people with Rett syndrome lacking mutations in MECP2. Genet Med 2016; 19:13-19. [PMID: 27171548 PMCID: PMC5107176 DOI: 10.1038/gim.2016.42] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Accepted: 02/24/2016] [Indexed: 02/08/2023] Open
Abstract
Purpose Rett Syndrome (RTT) is a neurodevelopmental disorder caused primarily by de novo mutations (DNMs) in MECP2 and sometimes in CDKL5 and FOXG1. However, some RTT cases lack mutations in these genes. Methods Twenty-two RTT cases without apparent MECP2, CDKL5, and FOXG1 mutations were subjected to both whole exome sequencing and single nucleotide polymorphism array-based copy number variant (CNV) analyses. Results Three cases had MECP2 mutations initially missed by clinical testing. Of the remaining 19 cases, 17 (89.5%) had 29 other likely pathogenic intragenic mutations and/or CNVs (10 cases had two or more). Interestingly, 13 cases had mutations in a gene/region previously reported in other NDDs, thereby providing a potential diagnostic yield of 68.4%. These mutations were significantly enriched in chromatin regulators (corrected p = 0.0068) and moderately in postsynaptic cell membrane molecules (corrected p = 0.076) implicating glutamate receptor signaling. Conclusion The genetic etiology of RTT without MECP2, CDKL5, and FOXG1 mutations is heterogeneous, overlaps with other NDDs, and complex due to high mutation burden. Dysregulation of chromatin structure and abnormal excitatory synaptic signaling may form two common pathological bases of RTT.
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Affiliation(s)
- Samin A Sajan
- Section of Child Neurology and Developmental Neuroscience, Department of Pediatrics, Baylor College of Medicine, Houston, Texas, USA.,Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, Texas, USA.,Current address: Department of Neurosciences, University of California San Diego, San Diego, California, USA
| | - Shalini N Jhangiani
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas, USA
| | - Donna M Muzny
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas, USA
| | - Richard A Gibbs
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas, USA.,Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
| | - James R Lupski
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas, USA.,Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA.,Department of Pediatrics, Baylor College of Medicine and Texas Children's Hospital, Houston, Texas, USA
| | - Daniel G Glaze
- Section of Child Neurology and Developmental Neuroscience, Department of Pediatrics, Baylor College of Medicine, Houston, Texas, USA
| | - Walter E Kaufmann
- Department of Neurology, Boston Children's Hospital, Boston, Massachusetts, USA
| | | | - Fran Annese
- Greenwood Genetic Center, Greenwood, South Carolina, USA
| | | | - Jane Lane
- Department of Pediatrics, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Alan K Percy
- Department of Pediatrics, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Jeffrey L Neul
- Section of Child Neurology and Developmental Neuroscience, Department of Pediatrics, Baylor College of Medicine, Houston, Texas, USA.,Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, Texas, USA.,Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA.,Current address: Department of Neurosciences, University of California San Diego, San Diego, California, USA
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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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Zhang Y, Cao SX, Sun P, He HY, Yang CH, Chen XJ, Shen CJ, Wang XD, Chen Z, Berg DK, Duan S, Li XM. Loss of MeCP2 in cholinergic neurons causes part of RTT-like phenotypes via α7 receptor in hippocampus. Cell Res 2016; 26:728-42. [PMID: 27103432 DOI: 10.1038/cr.2016.48] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2015] [Revised: 02/03/2016] [Accepted: 02/17/2016] [Indexed: 01/08/2023] Open
Abstract
Mutations in the X-linked MECP2 gene cause Rett syndrome (RTT), an autism spectrum disorder characterized by impaired social interactions, motor abnormalities, cognitive defects and a high risk of epilepsy. Here, we showed that conditional deletion of Mecp2 in cholinergic neurons caused part of RTT-like phenotypes, which could be rescued by re-expressing Mecp2 in the basal forebrain (BF) cholinergic neurons rather than in the caudate putamen of conditional knockout (Chat-Mecp2(-/y)) mice. We found that choline acetyltransferase expression was decreased in the BF and that α7 nicotine acetylcholine receptor signaling was strongly impaired in the hippocampus of Chat-Mecp2(-/y) mice, which is sufficient to produce neuronal hyperexcitation and increase seizure susceptibility. Application of PNU282987 or nicotine in the hippocampus rescued these phenotypes in Chat-Mecp2(-/y) mice. Taken together, our findings suggest that MeCP2 is critical for normal function of cholinergic neurons and dysfunction of cholinergic neurons can contribute to numerous neuropsychiatric phenotypes.
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Affiliation(s)
- Ying Zhang
- Department of Neurobiology, Institute of Neuroscience, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Collaborative Innovation Center for Brain Science, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
| | - Shu-Xia Cao
- Department of Neurobiology, Institute of Neuroscience, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Collaborative Innovation Center for Brain Science, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
| | - Peng Sun
- Department of Neurobiology, Institute of Neuroscience, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Collaborative Innovation Center for Brain Science, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
| | - Hai-Yang He
- Department of Neurobiology, Institute of Neuroscience, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Collaborative Innovation Center for Brain Science, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
| | - Ci-Hang Yang
- Department of Neurobiology, Institute of Neuroscience, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Collaborative Innovation Center for Brain Science, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
| | - Xiao-Juan Chen
- Department of Neurobiology, Institute of Neuroscience, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Collaborative Innovation Center for Brain Science, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
| | - Chen-Jie Shen
- Department of Neurobiology, Institute of Neuroscience, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Collaborative Innovation Center for Brain Science, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
| | - Xiao-Dong Wang
- Department of Neurobiology, Institute of Neuroscience, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Collaborative Innovation Center for Brain Science, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
| | - Zhong Chen
- Department of Neurobiology, Institute of Neuroscience, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Collaborative Innovation Center for Brain Science, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
| | - Darwin K Berg
- Neurobiology Section, Division of Biological Sciences and Center for Neural Circuits and Behavior, University of California, San Diego, La Jolla, CA 92093-0357, USA
| | - Shumin Duan
- Department of Neurobiology, Institute of Neuroscience, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Collaborative Innovation Center for Brain Science, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China.,Soft Matter Research Center, Zhejiang University, Hangzhou, Zhejiang, China
| | - Xiao-Ming Li
- Department of Neurobiology, Institute of Neuroscience, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Collaborative Innovation Center for Brain Science, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China.,Soft Matter Research Center, Zhejiang University, Hangzhou, Zhejiang, China
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Loss of MeCP2 in Parvalbumin-and Somatostatin-Expressing Neurons in Mice Leads to Distinct Rett Syndrome-like Phenotypes. Neuron 2016; 88:651-8. [PMID: 26590342 DOI: 10.1016/j.neuron.2015.10.029] [Citation(s) in RCA: 116] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Revised: 07/16/2015] [Accepted: 09/16/2015] [Indexed: 01/02/2023]
Abstract
Inhibitory neurons are critical for proper brain function, and their dysfunction is implicated in several disorders, including autism, schizophrenia, and Rett syndrome. These neurons are heterogeneous, and it is unclear which subtypes contribute to specific neurological phenotypes. We deleted Mecp2, the mouse homolog of the gene that causes Rett syndrome, from the two most populous subtypes, parvalbumin-positive (PV+) and somatostatin-positive (SOM+) neurons. Loss of MeCP2 partially impairs the affected neuron, allowing us to assess the function of each subtype without profound disruption of neuronal circuitry. We found that mice lacking MeCP2 in either PV+ or SOM+ neurons have distinct, non-overlapping neurological features: mice lacking MeCP2 in PV+ neurons developed motor, sensory, memory, and social deficits, whereas those lacking MeCP2 in SOM+ neurons exhibited seizures and stereotypies. Our findings indicate that PV+ and SOM+ neurons contribute complementary aspects of the Rett phenotype and may have modular roles in regulating specific behaviors.
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75
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Hyperactive somatostatin interneurons contribute to excitotoxicity in neurodegenerative disorders. Nat Neurosci 2016; 19:557-559. [PMID: 26900927 PMCID: PMC4811704 DOI: 10.1038/nn.4257] [Citation(s) in RCA: 103] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 01/27/2016] [Indexed: 12/12/2022]
Abstract
Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are overlapping neurodegenerative disorders whose pathogenesis remains largely unknown. Here using TDP-43A315T mice, an ALS and FTD model with profound cortical pathology, we demonstrated that hyperactive somatostatin interneurons disinhibited layer 5 pyramidal neurons (L5-PN) and contributed to their excitotoxicity. Focal ablation of somatostatin interneurons efficiently restored normal excitability of L5-PN and alleviated neurodegeneration, suggesting a novel therapeutic target for ALS and FTD.
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76
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Du F, Nguyen MVC, Karten A, Felice CA, Mandel G, Ballas N. Acute and crucial requirement for MeCP2 function upon transition from early to late adult stages of brain maturation. Hum Mol Genet 2016; 25:1690-702. [PMID: 26908602 DOI: 10.1093/hmg/ddw038] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Accepted: 02/05/2016] [Indexed: 12/11/2022] Open
Abstract
Germline mutations in the X-linked gene, methyl-CpG-binding protein 2 (MECP2), underlie most cases of Rett syndrome (RTT), an autism spectrum disorder affecting approximately one in 10 000 female live births. The disease is characterized in affected girls by a latent appearance of symptoms between 12 and 18 months of age while boys usually die before the age of two. The nature of the latency is not known, but RTT-like phenotypes are recapitulated in mouse models, even when MeCP2 is removed at different postnatal stages, including juvenile and adolescent stages. Unexpectedly, here, we show that within a very brief developmental window, between 10 (adolescent) and 15 (adult) weeks after birth, symptom initiation and progression upon removal of MeCP2 in male mice transitions from 3 to 4 months to only several days, followed by lethality. We further show that this accelerated development of RTT phenotype and lethality occur at the transition to adult stage (15 weeks of age) and persists thereafter. Importantly, within this abbreviated time frame of days, the brain acquires dramatic anatomical, cellular and molecular abnormalities, typical of classical RTT. This study reveals a new postnatal developmental stage, which coincides with full-brain maturation, where the structure/function of the brain is extremely sensitive to levels of MeCP2 and loss of MeCP2 leads to precipitous collapse of the neuronal networks and incompatibility with life within days.
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Affiliation(s)
- Fang Du
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794, USA and
| | - Minh Vu Chuong Nguyen
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794, USA and
| | - Ariel Karten
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794, USA and
| | - Christy A Felice
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794, USA and
| | - Gail Mandel
- Vollum Institute, Howard Hughes Medical Institute, Oregon Health and Science University, Portland, OR 97239, USA
| | - Nurit Ballas
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794, USA and
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77
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Nelson SB, Valakh V. Excitatory/Inhibitory Balance and Circuit Homeostasis in Autism Spectrum Disorders. Neuron 2015; 87:684-98. [PMID: 26291155 DOI: 10.1016/j.neuron.2015.07.033] [Citation(s) in RCA: 680] [Impact Index Per Article: 75.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Autism spectrum disorders (ASDs) and related neurological disorders are associated with mutations in many genes affecting the ratio between neuronal excitation and inhibition. However, understanding the impact of these mutations on network activity is complicated by the plasticity of these networks, making it difficult in many cases to separate initial deficits from homeostatic compensation. Here we explore the contrasting evidence for primary defects in inhibition or excitation in ASDs and attempt to integrate the findings in terms of the brain's ability to maintain functional homeostasis.
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Affiliation(s)
- Sacha B Nelson
- Department of Biology and Center for Behavioral Genomics, Brandeis University, 415 South Street, Waltham, MA 02454, USA.
| | - Vera Valakh
- Department of Biology and Center for Behavioral Genomics, Brandeis University, 415 South Street, Waltham, MA 02454, USA
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78
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Abstract
Common somatic conditions are bound to occur by chance in individuals with neurological disorders as prevalent as epilepsy, but when biological links underlying the comorbidity can be uncovered, the relationship may provide clues into the origin and mechanisms of both. The expanding list of monogenic epilepsies and their associated clinical features offer a remarkable opportunity to mine the epilepsy genome for coordinate neurodevelopmental phenotypes and examine their pathogenic mechanisms. Defined single-gene-linked epilepsy syndromes identified to date include all of the most frequently cited comorbidities, such as cognitive disorders, autism, migraine, mood disorders, late-onset dementia, and even premature lethality. Gene-linked comorbidities may be aggravated by, or independent of, seizure history. Mutations in these genes establish clear biological links between abnormal neuronal synchronization and a variety of neurobehavioral disorders, and critically substantiate the definition of epilepsy as a complex spectrum disorder. Mapping the neural circuitry of epilepsy comorbidities and understanding their single-gene risk should substantially clarify this challenging aspect of clinical epilepsy management.
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Affiliation(s)
- Jeffrey L Noebels
- Developmental Neurogenetics Laboratory, Departments of Neurology, Neuroscience, and Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030
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79
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Abstract
Epigenetic processes in the brain involve the transfer of information arising from short-lived cellular signals and changes in neuronal activity into lasting effects on gene expression. Key molecular mediators of epigenetics include methylation of DNA, histone modifications, and noncoding RNAs. Emerging findings in animal models and human brain tissue reveal that epilepsy and epileptogenesis are associated with changes to each of these contributors to the epigenome. Understanding and influencing the molecular mechanisms controlling epigenetic change could open new avenues for treatment. DNA methylation, particularly hypermethylation, has been found to increase within gene body regions and interference with DNA methylation in epilepsy can change gene expression profiles and influence epileptogenesis. Posttranscriptional modification of histones, including transient as well as sustained changes to phosphorylation and acetylation, have been reported, which appear to influence gene expression. Finally, roles have emerged for noncoding RNAs in brain excitability and seizure thresholds, including microRNA and long noncoding RNA. Together, research supports strong effects of epigenetics influencing gene expression in epilepsy, suggesting future therapeutic approaches to manipulate epigenetic processes to treat or prevent epilepsy.
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Affiliation(s)
- David C Henshall
- Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, Dublin 2, Ireland
| | - Katja Kobow
- Department of Neuropathology, University Hospital Erlangen, 91054 Erlangen, Germany
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80
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Association of Tag SNPs and Rare CNVs of the MIR155HG/miR-155 Gene with Epilepsy in the Chinese Han Population. BIOMED RESEARCH INTERNATIONAL 2015; 2015:837213. [PMID: 26425555 PMCID: PMC4575730 DOI: 10.1155/2015/837213] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Revised: 06/28/2015] [Accepted: 07/09/2015] [Indexed: 01/12/2023]
Abstract
BACKGROUND miR-155 likely acts as an important modulator in the inflammatory mechanism of epilepsy, and this study investigated its association with epilepsy from the perspective of molecular genetics. METHODS This study enrolled 249 epileptic patients and 289 healthy individuals of the Chinese Han population; 4 tag single-nucleotide polymorphisms (SNPs: rs969885, rs12483428, rs987195, and rs4817027) of the MIR155HG/miR-155 gene were selected, and their association with epilepsy was investigated. Additionally, this study determined the copy numbers of the MIR155HG/miR-155 gene. RESULTS The TCA haplotype (rs12483428-rs987195-rs4817027) and the AA genotype at rs4817027 conferred higher vulnerability to epilepsy in males. Stratification by age of onset revealed that the CC haplotype (rs969885-rs987195) was a genetic susceptibility factor for early-onset epilepsy. Further stratification by drug-resistant status indicated the CC haplotype (rs969885-rs987195) and the AA genotype at rs4817027 were genetic susceptibility factors for drug-resistant epilepsy (DRE) but the CG haplotype (rs987195-rs969885) was a genetically protective factor against DRE. Besides, 3 epileptic patients with copy number variants of the MIR155HG/miR-155 gene were observed. CONCLUSIONS This study first demonstrates the association of MIR155HG/miR-155 tag SNPs with epilepsy and shows that rare CNVs were found exclusively in epileptic patients, clarifying the genetic role of miR-155 in epilepsy.
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81
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Hainer C, Mosienko V, Koutsikou S, Crook JJ, Gloss B, Kasparov S, Lumb BM, Alenina N. Beyond Gene Inactivation: Evolution of Tools for Analysis of Serotonergic Circuitry. ACS Chem Neurosci 2015; 6:1116-29. [PMID: 26132472 DOI: 10.1021/acschemneuro.5b00045] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
In the brain, serotonin (5-hydroxytryptamine, 5-HT) controls a multitude of physiological and behavioral functions. Serotonergic neurons in the raphe nuclei give rise to a complex and extensive network of axonal projections throughout the whole brain. A major challenge in the analysis of these circuits is to understand how the serotonergic networks are linked to the numerous functions of this neurotransmitter. In the past, many studies employed approaches to inactivate different genes involved in serotonergic neuron formation, 5-HT transmission, or 5-HT metabolism. Although these approaches have contributed significantly to our understanding of serotonergic circuits, they usually result in life-long gene inactivation. As a consequence, compensatory changes in serotonergic and other neurotransmitter systems may occur and complicate the interpretation of the observed phenotypes. To dissect the complexity of the serotonergic system with greater precision, approaches to reversibly manipulate subpopulations of serotonergic neurons are required. In this review, we summarize findings on genetic animal models that enable control of 5-HT neuronal activity or mapping of the serotonergic system. This includes a comparative analysis of several mouse and rat lines expressing Cre or Flp recombinases under Tph2, Sert, or Pet1 promoters with a focus on specificity and recombination efficiency. We further introduce applications for Cre-mediated cell-type specific gene expression to optimize spatial and temporal precision for the manipulation of serotonergic neurons. Finally, we discuss other temporally regulated systems, such as optogenetics and designer receptors exclusively activated by designer drugs (DREADD) approaches to control 5-HT neuron activity.
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Affiliation(s)
- Cornelia Hainer
- Max-Delbrück-Center for Molecular Medicine (MDC), Berlin 13125, Germany
| | | | | | | | - Bernd Gloss
- National Institute of Environmental Health Science, Durham, North Carolina 27709, United States
| | | | | | - Natalia Alenina
- Max-Delbrück-Center for Molecular Medicine (MDC), Berlin 13125, Germany
- Institute
of Translational Biomedicine, St. Petersburg State University, St. Petersburg 199034, Russia
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82
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Molecular underpinnings of prefrontal cortex development in rodents provide insights into the etiology of neurodevelopmental disorders. Mol Psychiatry 2015; 20:795-809. [PMID: 25450230 PMCID: PMC4486649 DOI: 10.1038/mp.2014.147] [Citation(s) in RCA: 108] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Revised: 09/12/2014] [Accepted: 09/17/2014] [Indexed: 12/20/2022]
Abstract
The prefrontal cortex (PFC), seat of the highest-order cognitive functions, constitutes a conglomerate of highly specialized brain areas and has been implicated to have a role in the onset and installation of various neurodevelopmental disorders. The development of a properly functioning PFC is directed by transcription factors, guidance cues and other regulatory molecules and requires the intricate and temporal orchestration of a number of developmental processes. Disturbance or failure of any of these processes causing neurodevelopmental abnormalities within the PFC may contribute to several of the cognitive deficits seen in patients with neurodevelopmental disorders. In this review, we elaborate on the specific processes underlying prefrontal development, such as induction and patterning of the prefrontal area, proliferation, migration and axonal guidance of medial prefrontal progenitors, and their eventual efferent and afferent connections. We furthermore integrate for the first time the available knowledge from genome-wide studies that have revealed genes linked to neurodevelopmental disorders with experimental molecular evidence in rodents. The integrated data suggest that the pathogenic variants in the neurodevelopmental disorder-associated genes induce prefrontal cytoarchitectonical impairments. This enhances our understanding of the molecular mechanisms of prefrontal (mis)development underlying the four major neurodevelopmental disorders in humans, that is, intellectual disability, autism spectrum disorders, attention deficit hyperactivity disorder and schizophrenia, and may thus provide clues for the development of novel therapies.
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83
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Pohodich AE, Zoghbi HY. Rett syndrome: disruption of epigenetic control of postnatal neurological functions. Hum Mol Genet 2015; 24:R10-6. [PMID: 26060191 DOI: 10.1093/hmg/ddv217] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Accepted: 06/05/2015] [Indexed: 12/11/2022] Open
Abstract
Loss-of-function mutations in the X-linked gene Methyl-CpG-binding protein 2 (MECP2) cause a devastating pediatric neurological disorder called Rett syndrome. In males, these mutations typically result in severe neonatal encephalopathy and early lethality. On the other hand, owing to expression of the normal allele in ∼50% of cells, females do not suffer encephalopathy but instead develop Rett syndrome. Typically females with Rett syndrome exhibit a delayed onset of neurologic dysfunction that manifests around the child's first birthday and progresses over the next few years. Features of this disorder include loss of acquired language and motor skills, intellectual impairment and hand stereotypies. The developmental regression observed in patients with Rett syndrome arises from altered neuronal function and is not the result of neurodegeneration. Maintenance of an appropriate level of MeCP2 appears integral to the function of healthy neurons as patients with increased levels of MeCP2, owing to duplication of the Xq28 region encompassing the MECP2 locus, also present with intellectual disability and progressive neurologic symptoms. Despite major efforts over the past two decades to elucidate the molecular functions of MeCP2, the mechanisms underlying the delayed appearance of symptoms remain unclear. In this review, we will highlight recent findings that have expanded our knowledge of MeCP2's functions, and we will discuss how epigenetic regulation, chromatin organization and circuit dynamics may contribute to the postnatal onset of Rett syndrome.
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Affiliation(s)
- Amy E Pohodich
- Department of Neuroscience, Baylor College of Medicine, Houston 77030, USA Jan and Dan Duncan Neurological Research Institute at Texas Children's Hospital, Houston 77030, USA
| | - Huda Y Zoghbi
- Department of Neuroscience, Baylor College of Medicine, Houston 77030, USA Department of Molecular and Human Genetics, Baylor College of Medicine, Houston 77030, USA Howard Hughes Medical Institute, Baylor College of Medicine, Houston 77030, USA and Jan and Dan Duncan Neurological Research Institute at Texas Children's Hospital, Houston 77030, USA
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84
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Lee BH, Smith T, Paciorkowski AR. Autism spectrum disorder and epilepsy: Disorders with a shared biology. Epilepsy Behav 2015; 47:191-201. [PMID: 25900226 PMCID: PMC4475437 DOI: 10.1016/j.yebeh.2015.03.017] [Citation(s) in RCA: 103] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Revised: 03/06/2015] [Accepted: 03/13/2015] [Indexed: 12/17/2022]
Abstract
There is an increasing recognition of clinical overlap in patients presenting with epilepsy and autism spectrum disorder (ASD), and a great deal of new information regarding the genetic causes of both disorders is available. Several biological pathways appear to be involved in both disease processes, including gene transcription regulation, cellular growth, synaptic channel function, and maintenance of synaptic structure. We review several genetic disorders where ASD and epilepsy frequently co-occur, and we discuss the screening tools available for practicing neurologists and epileptologists to help determine which patients should be referred for formal ASD diagnostic evaluation. Finally, we make recommendations regarding the workflow of genetic diagnostic testing available for children with both ASD and epilepsy. This article is part of a Special Issue entitled "Autism and Epilepsy".
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Affiliation(s)
- Bo Hoon Lee
- Department of Pediatrics, University of Rochester Medical Center, Rochester, NY, USA
| | - Tristram Smith
- Division of Neurodevelopmental and Behavioral Pediatrics, Department of Pediatrics, University of Rochester Medical Center, Rochester, NY, USA
| | - Alex R Paciorkowski
- Department of Pediatrics, University of Rochester Medical Center, Rochester, NY, USA; Department of Neurology, University of Rochester Medical Center, Rochester, NY, USA; Department of Biomedical Genetics, University of Rochester Medical Center, Rochester, NY, USA; Center for Neural Development and Disease, University of Rochester Medical Center, Rochester, NY, USA.
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85
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Tang L, Wang Y, Leng T, Sun H, Zhou Y, Zhu W, Qiu P, Zhang J, Lu B, Yan M, Chen W, Su X, Yin W, Huang Y, Hu H, Yan G. Cholesterol metabolite cholestane-3β,5α,6β-triol suppresses epileptic seizures by negative modulation of voltage-gated sodium channels. Steroids 2015; 98:166-72. [PMID: 25578735 DOI: 10.1016/j.steroids.2014.12.025] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Revised: 12/27/2014] [Accepted: 12/29/2014] [Indexed: 11/24/2022]
Abstract
Imbalance of excitation and inhibition in neurons is implicated in the pathogenesis of epilepsy. Voltage-gated sodium channels, which play a vital role in regulating neuronal excitability, are one of the major targets for developing anti-epileptic drugs. Here we provide evidence that cholestane-3β,5α,6β-triol (triol), a major metabolic oxysterol of cholesterol, is an effective state-dependent negative sodium channels modulator. Triol reduced Na(+) current density in a concentration-dependent manner. 10 μM triol shifted steady-state/fast/slow inactivation curves of sodium channels toward the hyperpolarizing direction. Additionally, triol reduced voltage-gated sodium currents in a voltage- and frequency-dependent manner. In a kainic acid-induced seizures mouse model, triol (25 mg/kg) significantly increased the latency of seizure onset and attenuated seizure severity. Our findings provide novel insights for understanding the modulatory role of a small molecular oxysterol on voltage-gated sodium channels and suggest triol may represent a novel and promising candidate for epilepsy intervention.
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Affiliation(s)
- Lipeng Tang
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, GD 510080, China
| | - Youqiong Wang
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, GD 510080, China
| | - Tiandong Leng
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, GD 510080, China
| | - Huanhuan Sun
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, GD 510080, China
| | - Yuehan Zhou
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, GD 510080, China; Department of Pharmacology, Guilin Medical University, Guilin, GX 541004, China
| | - Wenbo Zhu
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, GD 510080, China
| | - Pengxin Qiu
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, GD 510080, China
| | - Jingxia Zhang
- School of Pharmaceutical Sciences, Sun Yat-Sen University, Guangzhou, GD 510006, China
| | - Bingzheng Lu
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, GD 510080, China
| | - Min Yan
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, GD 510080, China
| | - Wenli Chen
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, GD 510080, China
| | - Xinwen Su
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, GD 510080, China
| | - Wei Yin
- Department of Biochemistry, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, GD 510080, China
| | - Yijun Huang
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, GD 510080, China
| | - Haiyan Hu
- School of Pharmaceutical Sciences, Sun Yat-Sen University, Guangzhou, GD 510006, China.
| | - Guangmei Yan
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, GD 510080, China.
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86
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Zhong W, Cui N, Jin X, Oginsky MF, Wu Y, Zhang S, Bondy B, Johnson CM, Jiang C. Methyl CpG Binding Protein 2 Gene Disruption Augments Tonic Currents of γ-Aminobutyric Acid Receptors in Locus Coeruleus Neurons: IMPACT ON NEURONAL EXCITABILITY AND BREATHING. J Biol Chem 2015; 290:18400-11. [PMID: 25979331 DOI: 10.1074/jbc.m115.650465] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Indexed: 12/20/2022] Open
Abstract
People with Rett syndrome and mouse models show autonomic dysfunction involving the brain stem locus coeruleus (LC). Neurons in the LC of Mecp2-null mice are overly excited, likely resulting from a defect in neuronal intrinsic membrane properties and a deficiency in GABA synaptic inhibition. In addition to the synaptic GABA receptors, there is a group of GABAA receptors (GABAARs) that is located extrasynaptically and mediates tonic inhibition. Here we show evidence for augmentation of the extrasynaptic GABAARs in Mecp2-null mice. In brain slices, exposure of LC neurons to GABAAR agonists increased tonic currents that were blocked by GABAAR antagonists. With 10 μm GABA, the bicuculline-sensitive tonic currents were ∼4-fold larger in Mecp2-null LC neurons than in the WT. Single-cell PCR analysis showed that the δ subunit, the principal subunit of extrasynaptic GABAARs, was present in LC neurons. Expression levels of the δ subunit were ∼50% higher in Mecp2-null neurons than in the WT. Also increased in expression in Mecp2-null mice was another extrasynaptic GABAAR subunit, α6, by ∼4-fold. The δ subunit-selective agonists 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol hydrochloride and 4-chloro-N-[2-(2-thienyl)imidazo[1,2-a]pyridin-3-yl]]benzamide activated the tonic GABAA currents in LC neurons and reduced neuronal excitability to a greater degree in Mecp2-null mice than in the WT. Consistent with these findings, in vivo application of 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol hydrochloride alleviated breathing abnormalities of conscious Mecp2-null mice. These results suggest that extrasynaptic GABAARs seem to be augmented with Mecp2 disruption, which may be a compensatory response to the deficiency in GABAergic synaptic inhibition and allows control of neuronal excitability and breathing abnormalities.
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Affiliation(s)
- Weiwei Zhong
- From the Department of Biology, Georgia State University, Atlanta, Georgia 30303
| | - Ningren Cui
- From the Department of Biology, Georgia State University, Atlanta, Georgia 30303
| | - Xin Jin
- From the Department of Biology, Georgia State University, Atlanta, Georgia 30303
| | - Max F Oginsky
- From the Department of Biology, Georgia State University, Atlanta, Georgia 30303
| | - Yang Wu
- From the Department of Biology, Georgia State University, Atlanta, Georgia 30303
| | - Shuang Zhang
- From the Department of Biology, Georgia State University, Atlanta, Georgia 30303
| | - Brian Bondy
- From the Department of Biology, Georgia State University, Atlanta, Georgia 30303
| | | | - Chun Jiang
- From the Department of Biology, Georgia State University, Atlanta, Georgia 30303
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87
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Bedogni F, Cobolli Gigli C, Pozzi D, Rossi RL, Scaramuzza L, Rossetti G, Pagani M, Kilstrup-Nielsen C, Matteoli M, Landsberger N. Defects During Mecp2 Null Embryonic Cortex Development Precede the Onset of Overt Neurological Symptoms. Cereb Cortex 2015; 26:2517-2529. [PMID: 25979088 DOI: 10.1093/cercor/bhv078] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
MeCP2 is associated with several neurological disorders; of which, Rett syndrome undoubtedly represents the most frequent. Its molecular roles, however, are still unclear, and data from animal models often describe adult, symptomatic stages, while MeCP2 functions during embryonic development remain elusive. We describe the pattern and timing of Mecp2 expression in the embryonic neocortex highlighting its low but consistent expression in virtually all cells and show the unexpected occurrence of transcriptional defects in the Mecp2 null samples at a stage largely preceding the onset of overt symptoms. Through the deregulated expression of ionic channels and glutamatergic receptors, the lack of Mecp2 during early neuronal maturation leads to the reduction in the neuronal responsiveness to stimuli. We suggest that such features concur to morphological alterations that begin affecting Mecp2 null neurons around the perinatal age and become evident later in adulthood. We indicate MeCP2 as a key modulator of the transcriptional mechanisms regulating cerebral cortex development. Neurological phenotypes of MECP2 patients could thus be the cumulative result of different adverse events that are already present at stages when no obvious signs of the pathology are evident and are worsened by later impairments affecting the central nervous system during maturation and maintenance of its functionality.
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Affiliation(s)
- Francesco Bedogni
- San Raffaele Rett Research Unit, Division of Neuroscience, San Raffaele Scientific Institute, 20132 Milan, Italy
| | - Clementina Cobolli Gigli
- San Raffaele Rett Research Unit, Division of Neuroscience, San Raffaele Scientific Institute, 20132 Milan, Italy.,Laboratory of Genetic and Epigenetic Control of Gene Expression, Division of Biomedical Research, Department of Theoretical and Applied Sciences, University of Insubria, Busto Arsizio, 21052 Varese, Italy
| | - Davide Pozzi
- Laboratory of Pharmacology and Brain Pathology, Humanitas Clinical and Research Center, Rozzano, 20089 Milan, Italy
| | - Riccardo Lorenzo Rossi
- Istituto Nazionale di Genetica Molecolare "Romeo ed Enrica Invernizzi", 20122 Milan, Italy
| | - Linda Scaramuzza
- San Raffaele Rett Research Unit, Division of Neuroscience, San Raffaele Scientific Institute, 20132 Milan, Italy
| | - Grazisa Rossetti
- Istituto Nazionale di Genetica Molecolare "Romeo ed Enrica Invernizzi", 20122 Milan, Italy
| | - Massimiliano Pagani
- Istituto Nazionale di Genetica Molecolare "Romeo ed Enrica Invernizzi", 20122 Milan, Italy
| | - Charlotte Kilstrup-Nielsen
- Laboratory of Genetic and Epigenetic Control of Gene Expression, Division of Biomedical Research, Department of Theoretical and Applied Sciences, University of Insubria, Busto Arsizio, 21052 Varese, Italy
| | - Michela Matteoli
- Laboratory of Pharmacology and Brain Pathology, Humanitas Clinical and Research Center, Rozzano, 20089 Milan, Italy.,Dip di Biotecnologie Mediche e Medicina Traslazionale, Università di Milano, Milan, Italy
| | - Nicoletta Landsberger
- San Raffaele Rett Research Unit, Division of Neuroscience, San Raffaele Scientific Institute, 20132 Milan, Italy.,Laboratory of Genetic and Epigenetic Control of Gene Expression, Division of Biomedical Research, Department of Theoretical and Applied Sciences, University of Insubria, Busto Arsizio, 21052 Varese, Italy
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88
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Abstract
Rett syndrome (RTT) is a severe neurological disorder caused by mutations in the X-linked gene MECP2 (methyl-CpG-binding protein 2). Two decades of research have fostered the view that MeCP2 is a multifunctional chromatin protein that integrates diverse aspects of neuronal biology. More recently, studies have focused on specific RTT-associated mutations within the protein. This work has yielded molecular insights into the critical functions of MeCP2 that promise to simplify our understanding of RTT pathology.
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Affiliation(s)
- Matthew J Lyst
- The Wellcome Trust Centre for Cell Biology, University of Edinburgh, Michael Swann Building, Max Born Crescent, The King's Buildings, Edinburgh EH9 3BF, UK
| | - Adrian Bird
- The Wellcome Trust Centre for Cell Biology, University of Edinburgh, Michael Swann Building, Max Born Crescent, The King's Buildings, Edinburgh EH9 3BF, UK
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89
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Wang H, Pati S, Pozzo-Miller L, Doering LC. Targeted pharmacological treatment of autism spectrum disorders: fragile X and Rett syndromes. Front Cell Neurosci 2015; 9:55. [PMID: 25767435 PMCID: PMC4341567 DOI: 10.3389/fncel.2015.00055] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2015] [Accepted: 02/05/2015] [Indexed: 12/27/2022] Open
Abstract
Autism spectrum disorders (ASDs) are genetically and clinically heterogeneous and lack effective medications to treat their core symptoms. Studies of syndromic ASDs caused by single gene mutations have provided insights into the pathophysiology of autism. Fragile X and Rett syndromes belong to the syndromic ASDs in which preclinical studies have identified rational targets for drug therapies focused on correcting underlying neural dysfunction. These preclinical discoveries are increasingly translating into exciting human clinical trials. Since there are significant molecular and neurobiological overlaps among ASDs, targeted treatments developed for fragile X and Rett syndromes may be helpful for autism of different etiologies. Here, we review the targeted pharmacological treatment of fragile X and Rett syndromes and discuss related issues in both preclinical studies and clinical trials of potential therapies for the diseases.
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Affiliation(s)
- Hansen Wang
- Faculty of Medicine, University of Toronto, 1 King's College Circle Toronto, ON, Canada
| | - Sandipan Pati
- Department of Neurology, Epilepsy Division, The University of Alabama at Birmingham Birmingham, AL, USA
| | - Lucas Pozzo-Miller
- Department of Neurobiology, Civitan International Research Center, The University of Alabama at Birmingham Birmingham, AL, USA
| | - Laurie C Doering
- Faculty of Health Sciences, Department of Pathology and Molecular Medicine, McMaster University Hamilton, ON, Canada
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90
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Noebels J. Pathway-driven discovery of epilepsy genes. Nat Neurosci 2015; 18:344-50. [PMID: 25710836 DOI: 10.1038/nn.3933] [Citation(s) in RCA: 127] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Accepted: 12/22/2014] [Indexed: 12/12/2022]
Abstract
Epilepsy genes deliver critical insights into the molecular control of brain synchronization and are revolutionizing our understanding and treatment of the disease. The epilepsy-associated genome is rapidly expanding, and two powerful complementary approaches, isolation of de novo exome variants in patients and targeted mutagenesis in model systems, account for the steep increase. In sheer number, the tally of genes linked to seizures will likely match that of cancer and exceed it in biological diversity. The proteins act within most intracellular compartments and span the molecular determinants of firing and wiring in the developing brain. Every facet of neurotransmission, from dendritic spine to exocytotic machinery, is in play, and defects of synaptic inhibition are over-represented. The contributions of somatic mutations and noncoding microRNAs are also being explored. The functional spectrum of established epilepsy genes and the arrival of rapid, precise technologies for genome editing now provide a robust scaffold to prioritize hypothesis-driven discovery and further populate this genetic proto-map. Although each gene identified offers translational potential to stratify patient care, the complexity of individual variation and covert actions of genetic modifiers may confound single-gene solutions for the clinical disorder. In vivo genetic deconstruction of epileptic networks, ex vivo validation of variant profiles in patient-derived induced pluripotent stem cells, in silico variant modeling and modifier gene discovery, now in their earliest stages, will help clarify individual patterns. Because seizures stand at the crossroads of all neuronal synchronization disorders in the developing and aging brain, the neurobiological analysis of epilepsy-associated genes provides an extraordinary gateway to new insights into higher cortical function.
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Affiliation(s)
- Jeffrey Noebels
- Developmental Neurogenetics Laboratory, Departments of Neurology, Neuroscience, and Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
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91
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What you seize is what you get: do we yet understand epilepsy in rett syndrome? Epilepsy Curr 2014; 14:283-5. [PMID: 25346641 DOI: 10.5698/1535-7597-14.5.283] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
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92
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Calfa G, Li W, Rutherford JM, Pozzo-Miller L. Excitation/inhibition imbalance and impaired synaptic inhibition in hippocampal area CA3 of Mecp2 knockout mice. Hippocampus 2014; 25:159-68. [PMID: 25209930 DOI: 10.1002/hipo.22360] [Citation(s) in RCA: 98] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/05/2014] [Indexed: 01/01/2023]
Abstract
Rett syndrome (RTT) is a neurodevelopment disorder associated with intellectual disabilities and caused by loss-of-function mutations in the gene encoding the transcriptional regulator Methyl-CpG-binding Protein-2 (MeCP2). Neuronal dysfunction and changes in cortical excitability occur in RTT individuals and Mecp2-deficient mice, including hippocampal network hyperactivity and higher frequency of spontaneous multiunit spikes in the CA3 cell body layer. Here, we describe impaired synaptic inhibition and an excitation/inhibition (E/I) imbalance in area CA3 of acute slices from symptomatic Mecp2 knockout male mice (referred to as Mecp2(-/y) ). The amplitude of TTX-resistant miniature inhibitory postsynaptic currents (mIPSC) was smaller in CA3 pyramidal neurons of Mecp2(-/y) slices than in wildtype controls, while the amplitude of miniature excitatory postsynaptic currents (mEPSC) was significantly larger in Mecp2(-/y) neurons. Consistently, quantitative confocal immunohistochemistry revealed significantly lower intensity of the alpha-1 subunit of GABAA Rs in the CA3 cell body layer of Mecp2(-/y) mice, while GluA1 puncta intensities were significantly higher in the CA3 dendritic layers of Mecp2(-/y) mice. In addition, the input/output (I/O) relationship of evoked IPSCs had a shallower slope in CA3 pyramidal neurons Mecp2(-/y) neurons. Consistent with the absence of neuronal degeneration in RTT and MeCP2-based mouse models, the density of parvalbumin- and somatostatin-expressing interneurons in area CA3 was not affected in Mecp2(-/y) mice. Furthermore, the intrinsic membrane properties of several interneuron subtypes in area CA3 were not affected by Mecp2 loss. However, mEPSCs are smaller and less frequent in CA3 fast-spiking basket cells of Mecp2(-/y) mice, suggesting an impaired glutamatergic drive in this interneuron population. These results demonstrate that a loss-of-function mutation in Mecp2 causes impaired E/I balance onto CA3 pyramidal neurons, leading to a hyperactive hippocampal network, likely contributing to limbic seizures in Mecp2(-/y) mice and RTT individuals.
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Affiliation(s)
- Gaston Calfa
- Department of Neurobiology, Civitan International Research Center, The University of Alabama at Birmingham, Birmingham, Alabama
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93
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Deidda G, Bozarth IF, Cancedda L. Modulation of GABAergic transmission in development and neurodevelopmental disorders: investigating physiology and pathology to gain therapeutic perspectives. Front Cell Neurosci 2014; 8:119. [PMID: 24904277 PMCID: PMC4033255 DOI: 10.3389/fncel.2014.00119] [Citation(s) in RCA: 125] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Accepted: 04/14/2014] [Indexed: 01/30/2023] Open
Abstract
During mammalian ontogenesis, the neurotransmitter GABA is a fundamental regulator of neuronal networks. In neuronal development, GABAergic signaling regulates neural proliferation, migration, differentiation, and neuronal-network wiring. In the adult, GABA orchestrates the activity of different neuronal cell-types largely interconnected, by powerfully modulating synaptic activity. GABA exerts these functions by binding to chloride-permeable ionotropic GABAA receptors and metabotropic GABAB receptors. According to its functional importance during development, GABA is implicated in a number of neurodevelopmental disorders such as autism, Fragile X, Rett syndrome, Down syndrome, schizophrenia, Tourette's syndrome and neurofibromatosis. The strength and polarity of GABAergic transmission is continuously modulated during physiological, but also pathological conditions. For GABAergic transmission through GABAA receptors, strength regulation is achieved by different mechanisms such as modulation of GABAA receptors themselves, variation of intracellular chloride concentration, and alteration in GABA metabolism. In the never-ending effort to find possible treatments for GABA-related neurological diseases, of great importance would be modulating GABAergic transmission in a safe and possibly physiological way, without the dangers of either silencing network activity or causing epileptic seizures. In this review, we will discuss the different ways to modulate GABAergic transmission normally at work both during physiological and pathological conditions. Our aim is to highlight new research perspectives for therapeutic treatments that reinstate natural and physiological brain functions in neuro-pathological conditions.
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Affiliation(s)
- Gabriele Deidda
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia Genova, Italy
| | - Ignacio F Bozarth
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia Genova, Italy
| | - Laura Cancedda
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia Genova, Italy
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94
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Seltzer LE, Paciorkowski AR. Genetic disorders associated with postnatal microcephaly. AMERICAN JOURNAL OF MEDICAL GENETICS PART C-SEMINARS IN MEDICAL GENETICS 2014; 166C:140-55. [PMID: 24839169 DOI: 10.1002/ajmg.c.31400] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Several genetic disorders are characterized by normal head size at birth, followed by deceleration in head growth resulting in postnatal microcephaly. Among these are classic disorders such as Angelman syndrome and MECP2-related disorder (formerly Rett syndrome), as well as more recently described clinical entities associated with mutations in CASK, CDKL5, CREBBP, and EP300 (Rubinstein-Taybi syndrome), FOXG1, SLC9A6 (Christianson syndrome), and TCF4 (Pitt-Hopkins syndrome). These disorders can be identified clinically by phenotyping across multiple neurodevelopmental and neurobehavioral realms, and enough data are available to recognize these postnatal microcephaly disorders as separate diagnostic entities in their own right. A second diagnostic grouping, comprised of Warburg MICRO syndrome, Cockayne syndrome, and Cerebral-oculo-facial skeletal syndrome, share similar features of somatic growth failure, ophthalmologic, and dysmorphologic features. Many postnatal microcephaly syndromes are caused by mutations in genes important in the regulation of gene expression in the developing forebrain and hindbrain, although important synaptic structural genes also play a role. This is an emerging group of disorders with a fascinating combination of brain malformations, specific epilepsies, movement disorders, and other complex neurobehavioral abnormalities.
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95
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Maheshwari A, Noebels JL. Monogenic models of absence epilepsy: windows into the complex balance between inhibition and excitation in thalamocortical microcircuits. PROGRESS IN BRAIN RESEARCH 2014; 213:223-52. [PMID: 25194492 DOI: 10.1016/b978-0-444-63326-2.00012-0] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Absence epilepsy is a common disorder that arises in childhood and can be refractory to medical treatment. Single genetic mutations in mice, at times found in patients with absence epilepsy, provide the unique opportunity to bridge the gap between dysfunction at the genetic level and pathological oscillations within the thalamocortical circuit. Interestingly, unlike other forms of epilepsy, only genes related to ion channels have so far been linked to absence phenotypes. Here, we delineate a paradigm which attempts to unify the various monogenic models based on decades of research. While reviewing the particular impact of these individual mutations, we posit a framework involving fast feedforward disinhibition as one common mechanism that can lead to increased tonic inhibition in the cortex and/or thalamus. Enhanced tonic inhibition hyperpolarizes principal cells, deinactivates T-type calcium channels, and leads to reciprocal burst firing within the thalamocortical loop. We also review data from pharmacologic and polygenic models in light of this paradigm. Ultimately, many questions remain unanswered regarding the pathogenesis of absence epilepsy.
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Affiliation(s)
- Atul Maheshwari
- Department of Neurology, Developmental Neurogenetics Laboratory, Baylor College of Medicine Houston, TX, USA.
| | - Jeffrey L Noebels
- Department of Neurology, Developmental Neurogenetics Laboratory, Baylor College of Medicine Houston, TX, USA; Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA; Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.
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