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Zeitouny C, Korte M, Michaelsen-Preusse K. Prolonged and specific spatial training during adolescence reverses adult hippocampal network impairments in a mouse model of fragile X syndrome. Neurobiol Dis 2023; 185:106240. [PMID: 37516137 DOI: 10.1016/j.nbd.2023.106240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Revised: 07/19/2023] [Accepted: 07/26/2023] [Indexed: 07/31/2023] Open
Abstract
The fragile X syndrome (FXS) is the leading monogenetic cause of cognitive impairment and autism. A hallmark of FXS in patients and the FXS mouse model (Fmr1 KO) is an overabundance of immature appearing dendritic spines in the cortex and hippocampus which is associated with behavioral deficits. Spine analysis in the different hippocampal subregions and at different developmental stages revealed that in adult mice, hippocampal spine pathology occurs specifically in the CA3 subregion, which plays a pivotal role in pattern completion processes important for efficient memory recall from parts of the initial memory stimulus. In line with this synaptic defect we document an impairment in memory recall during partially cued reference memory test in the Morris water maze task. This is accompanied by impaired recruitment of engram cells as well as impaired spine structural plasticity in the CA3 region. In order to promote hippocampal network development adolescent mice were either raised in an enriched environment or subjected to specific hippocampus-dependent spatial training. Intriguingly, only specific spatial training alleviated the cognitive symptoms and the spine phenotype shown in adult Fmr1 KO mice suggesting that specific stimulation of hippocampal networks during development might be used in the future as a therapeutic strategy.
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Affiliation(s)
- Caroline Zeitouny
- Division of Cellular Neurobiology, Zoological Institute, TU Braunschweig, Germany
| | - Martin Korte
- Division of Cellular Neurobiology, Zoological Institute, TU Braunschweig, Germany; Helmholtz Center for Infection Research, Research group Neuroinflammation and Neurodegeneration, Braunschweig, Germany
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2
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Zhu SI, McCullough MH, Pujic Z, Sibberas J, Sun B, Darveniza T, Bucknall B, Avitan L, Goodhill GJ. fmr1 Mutation Alters the Early Development of Sensory Coding and Hunting and Social Behaviors in Larval Zebrafish. J Neurosci 2023; 43:1211-1224. [PMID: 36596699 PMCID: PMC9962781 DOI: 10.1523/jneurosci.1721-22.2022] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Revised: 12/16/2022] [Accepted: 12/20/2022] [Indexed: 01/05/2023] Open
Abstract
Autism spectrum disorders (ASDs) are developmental in origin; however, little is known about how they affect the early development of behavior and sensory coding. The most common inherited form of autism is Fragile X syndrome (FXS), caused by a mutation in FMR1 Mutation of fmr1 in zebrafish causes anxiety-like behavior, hyperactivity, and hypersensitivity in auditory and visual processing. Here, we show that zebrafish fmr1-/- mutant larvae of either sex also display changes in hunting behavior, tectal coding, and social interaction. During hunting, they were less successful at catching prey and displayed altered behavioral sequences. In the tectum, representations of prey-like stimuli were more diffuse and had higher dimensionality. In a social behavioral assay, they spent more time observing a conspecific but responded more slowly to social cues. However, when given a choice of rearing environment fmr1-/- larvae preferred one with reduced visual stimulation, and rearing them in this environment reduced genotype-specific effects on tectal excitability. Together, these results shed new light on how fmr1-/- changes the early development of neural systems and behavior in a vertebrate.SIGNIFICANCE STATEMENT Autism spectrum disorders (ASDs) are caused by changes in early neural development. Animal models of ASDs offer the opportunity to study these developmental processes in greater detail than in humans. Here, we found that a zebrafish mutant for a gene which in humans causes one type of ASD showed early alterations in hunting behavior, social behavior, and how visual stimuli are represented in the brain. However, we also found that mutant fish preferred reduced visual stimulation, and rearing them in this environment reduced alterations in neural activity patterns. These results suggest interesting new directions for using zebrafish as a model to study the development of brain and behavior in ASDs, and how the impact of ASDs could potentially be reduced.
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Affiliation(s)
- Shuyu I Zhu
- Queensland Brain Institute
- Departments of Developmental Biology and Neuroscience, Washington University in St. Louis, St. Louis, Missouri 63110
| | | | | | | | | | - Thomas Darveniza
- Departments of Developmental Biology and Neuroscience, Washington University in St. Louis, St. Louis, Missouri 63110
| | | | | | - Geoffrey J Goodhill
- Queensland Brain Institute
- School of Mathematics and Physics, The University of Queensland, Brisbane, Queensland 4072, Australia
- Departments of Developmental Biology and Neuroscience, Washington University in St. Louis, St. Louis, Missouri 63110
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3
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Kalyanasundar B, Blonde GD, Spector AC, Travers SP. A Novel Mechanism for T1R-Independent Taste Responses to Concentrated Sugars. J Neurosci 2023; 43:965-978. [PMID: 36623875 PMCID: PMC9908317 DOI: 10.1523/jneurosci.1760-22.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Revised: 12/22/2022] [Accepted: 01/03/2023] [Indexed: 01/11/2023] Open
Abstract
Recent findings from our laboratory demonstrated that the rostral nucleus of the solitary tract (rNST) retains some responsiveness to sugars in double-knock-out mice lacking either the T1R1+T1R3 (KO1+3) or T1R2+T1R3 (KO2+3) taste receptor heterodimers. Here, we extended these findings in the parabrachial nucleus (PBN) of male and female KO1+3 mice using warm stimuli to optimize sugar responses and employing additional concentrations and pharmacological agents to probe mechanisms. PBN T1R-independent sugar responses, including those to concentrated glucose, were more evident than in rNST. Similar to the NST, there were no "sugar-best" neurons in KO1+3 mice. Nevertheless, 1000 mm glucose activated nearly 55% of PBN neurons, with responses usually occurring in neurons that also displayed acid and amiloride-insensitive NaCl responses. In wild-type (WT) mice, concentrated sugars activated the same electrolyte-sensitive neurons but also "sugar-best" cells. Regardless of genotype, phlorizin, an inhibitor of the sodium-glucose co-transporter (SGLT), a component of a hypothesized alternate glucose-sensing mechanism, did not diminish responses to 1000 mm glucose. The efficacy of concentrated sugars for driving neurons broadly responsive to electrolytes implied an origin from Type III taste bud cells. To test this, we used the carbonic anhydrase (CA) inhibitor dorzolamide (DRZ), previously shown to inhibit amiloride-insensitive sodium responses arising from Type III taste bud cells. Dorzolamide had no effect on sugar-elicited responses in WT sugar-best PBN neurons but strongly suppressed them in WT and KO1+3 electrolyte-generalist neurons. These findings suggest a novel T1R-independent mechanism for hyperosmotic sugars, involving a CA-dependent mechanism in Type III taste bud cells.SIGNIFICANCE STATEMENT Since the discovery of Tas1r receptors for sugars and artificial sweeteners, evidence has accrued that mice lacking these receptors maintain some behavioral, physiological, and neural responsiveness to sugars. But the substrate(s) has remained elusive. Here, we recorded from parabrachial nucleus (PBN) taste neurons and identified T1R-independent responses to hyperosmotic sugars dependent on carbonic anhydrase (CA) and occurring primarily in neurons broadly responsive to NaCl and acid, implying an origin from Type III taste bud cells. The effectiveness of different sugars in driving these T1R-independent responses did not correlate with their efficacy in driving licking, suggesting they evoke a nonsweet sensation. Nevertheless, these salient responses are likely to comprise an adequate cue for learned preferences that occur in the absence of T1R receptors.
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Affiliation(s)
- B Kalyanasundar
- Division of Biosciences, College of Dentistry, Ohio State University, Columbus, Ohio, 43210-1267
| | - Ginger D Blonde
- Department of Psychology and Program in Neuroscience, Florida State University, Tallahassee, Florida, 32306-4301
| | - Alan C Spector
- Department of Psychology and Program in Neuroscience, Florida State University, Tallahassee, Florida, 32306-4301
| | - Susan P Travers
- Division of Biosciences, College of Dentistry, Ohio State University, Columbus, Ohio, 43210-1267
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Fmr1-KO mice failure to detect object novelty associates with a post-test decrease of structural and synaptic plasticity upstream of the hippocampus. Sci Rep 2023; 13:755. [PMID: 36641518 PMCID: PMC9840621 DOI: 10.1038/s41598-023-27991-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Accepted: 01/11/2023] [Indexed: 01/15/2023] Open
Abstract
Mice with deletion of the FMR1 gene show episodic memory impairments and exhibit dendritic spines and synaptic plasticity defects prevalently identified in non-training conditions. Based on evidence that synaptic changes associated with normal or abnormal memory emerge when mice are cognitively challenged, here we examine whether, and how, fragile entorhinal and hippocampal synapses are remodeled when mice succeed or fail to learn. We trained Fmr1 knockout (KO) and wild-type C57BL/6J (WT) mice in the novel object recognition (NOR) paradigm with 1 h or 24 h training-to-test intervals and then assessed whether varying the time between the presentation of similar and different objects modulates NOR performance and plasticity along the entorhinal cortex-hippocampus axis. At the 1 h-interval, KO mice failed to discriminate the novel object, showed a collapse of spines in the lateral entorhinal cortex (LEC), and of long-term potentiation (LTP) in the lateral perforant path (LPP), but a normal increase in hippocampal spines. At the 24 h, they exhibited intact NOR performance, typical LEC and hippocampal spines, and exaggerated LPP-LTP. Our findings reveal that the inability of mice to detect object novelty primarily stands in their impediment to elaborate, and convey to the hippocampus, sensory/perceptive object representations.
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Booker SA, Kind PC. Mechanisms regulating input-output function and plasticity of neurons in the absence of FMRP. Brain Res Bull 2021; 175:69-80. [PMID: 34245842 DOI: 10.1016/j.brainresbull.2021.06.025] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Revised: 06/13/2021] [Accepted: 06/29/2021] [Indexed: 12/12/2022]
Abstract
The function of brain circuits relies on high-fidelity information transfer within neurons. Synaptic inputs arrive primarily at dendrites, where they undergo integration and summation throughout the somatodendritic domain, ultimately leading to the generation of precise patterns of action potentials. Emerging evidence suggests that the ability of neurons to transfer synaptic information and modulate their output is impaired in a number of neurodevelopmental disorders including Fragile X Syndrome. In this review we summarise recent findings that have revealed the pathophysiological and plasticity mechanisms that alter the ability of neurons in sensory and limbic circuits to reliably code information in the absence of FMRP. We examine which aspects of this transform may result directly from the loss of FMRP and those that a result from compensatory or homeostatic alterations to neuronal function. Dissection of the mechanisms leading to altered input-output function of neurons in the absence of FMRP and their effects on regulating neuronal plasticity throughout development could have important implications for potential therapies for Fragile X Syndrome, including directing the timing and duration of different treatment options.
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Affiliation(s)
- Sam A Booker
- Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK; Patrick Wild Centre for Autism Research, University of Edinburgh, Edinburgh, UK; Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK.
| | - Peter C Kind
- Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK; Patrick Wild Centre for Autism Research, University of Edinburgh, Edinburgh, UK; Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK; National Centre for Biological Sciences (NCBS), Bangalore, India.
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6
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Morè L, Lauterborn JC, Papaleo F, Brambilla R. Enhancing cognition through pharmacological and environmental interventions: Examples from preclinical models of neurodevelopmental disorders. Neurosci Biobehav Rev 2020; 110:28-45. [PMID: 30981451 DOI: 10.1016/j.neubiorev.2019.02.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Revised: 02/04/2019] [Accepted: 02/05/2019] [Indexed: 12/29/2022]
Abstract
In this review we discuss the role of environmental and pharmacological treatments to enhance cognition with special regards to neurodevelopmental related disorders and aging. How the environment influences brain structure and function, and the interactions between rearing conditions and gene expression, are fundamental questions that are still poorly understood. We propose a model that can explain some of the discrepancies in findings for effects of environmental enrichment on outcome measures. Evidence of a direct causal correlation of nootropics and treatments that enhanced cognition also will be presented, and possible molecular mechanisms that include neurotrophin signaling and downstream pathways underlying these processes are discussed. Finally we review recent findings achieved with a wide set of behavioral and cognitive tasks that have translational validity to humans, and should be useful for future work on devising appropriate therapies. As will be discussed, the collective findings suggest that a combinational therapeutic approach of environmental enrichment and nootropics could be particularly successful for improving learning and memory in both developmental disorders and normal aging.
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Affiliation(s)
- Lorenzo Morè
- School of Pharmacy and Biomedical Sciences, University of Central Lancashire, PR1 2XT, Preston, UK.
| | - Julie C Lauterborn
- Department of Anatomy & Neurobiology, School of Medicine, University of California, Irvine, CA, 92617, USA.
| | - Francesco Papaleo
- Genetics of Cognition Laboratory, Istituto Italiano di Tecnologia, Via Morego, 30, 16163, Genova, Italy.
| | - Riccardo Brambilla
- Neuroscience and Mental Health Research Institute (NMHRI), Division of Neuroscience, School of Biosciences, Cardiff University, CF24 4HQ, Cardiff, UK.
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Lauterborn JC, Schultz MN, Le AA, Amani M, Friedman AE, Leach PT, Gall CM, Lynch GS, Crawley JN. Spaced training improves learning in Ts65Dn and Ube3a mouse models of intellectual disabilities. Transl Psychiatry 2019; 9:166. [PMID: 31182707 PMCID: PMC6557858 DOI: 10.1038/s41398-019-0495-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Revised: 03/14/2019] [Accepted: 03/23/2019] [Indexed: 12/29/2022] Open
Abstract
Benefits of distributed learning strategies have been extensively described in the human literature, but minimally investigated in intellectual disability syndromes. We tested the hypothesis that training trials spaced apart in time could improve learning in two distinct genetic mouse models of neurodevelopmental disorders characterized by intellectual impairments. As compared to training with massed trials, spaced training significantly improved learning in both the Ts65Dn trisomy mouse model of Down syndrome and the maternally inherited Ube3a mutant mouse model of Angelman syndrome. Spacing the training trials at 1 h intervals accelerated acquisition of three cognitive tasks by Ts65Dn mice: (1) object location memory, (2) novel object recognition, (3) water maze spatial learning. Further, (4) spaced training improved water maze spatial learning by Ube3a mice. In contrast, (5) cerebellar-mediated rotarod motor learning was not improved by spaced training. Corroborations in three assays, conducted in two model systems, replicated within and across two laboratories, confirm the strength of the findings. Our results indicate strong translational relevance of a behavioral intervention strategy for improving the standard of care in treating the learning difficulties that are characteristic and clinically intractable features of many neurodevelopmental disorders.
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Affiliation(s)
- J C Lauterborn
- Department of Anatomy & Neurobiology, School of Medicine, University of California Irvine, Irvine, CA, 92697, USA
| | - M N Schultz
- MIND Institute, Department of Psychiatry and Behavioral Sciences, University of California Davis School of Medicine, Sacramento, CA 95817, USA
| | - A A Le
- Department of Anatomy & Neurobiology, School of Medicine, University of California Irvine, Irvine, CA, 92697, USA
| | - M Amani
- Department of Psychiatry and Human Behavior, School of Medicine, University of California Irvine, Irvine, CA, 92697, USA
- Department of Physiology, School of Medicine, Ardabil University of Medical Sciences, Ardabil, Iran
| | - A E Friedman
- MIND Institute, Department of Psychiatry and Behavioral Sciences, University of California Davis School of Medicine, Sacramento, CA 95817, USA
- Harvard University, Cambridge, MA, USA
| | - P T Leach
- MIND Institute, Department of Psychiatry and Behavioral Sciences, University of California Davis School of Medicine, Sacramento, CA 95817, USA
- Biogen Inc., Cambridge, MA, USA
| | - C M Gall
- Department of Anatomy & Neurobiology, School of Medicine, University of California Irvine, Irvine, CA, 92697, USA
| | - G S Lynch
- Department of Anatomy & Neurobiology, School of Medicine, University of California Irvine, Irvine, CA, 92697, USA
- Department of Psychiatry and Human Behavior, School of Medicine, University of California Irvine, Irvine, CA, 92697, USA
| | - J N Crawley
- MIND Institute, Department of Psychiatry and Behavioral Sciences, University of California Davis School of Medicine, Sacramento, CA 95817, USA.
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8
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Whyte AJ, Kietzman HW, Swanson AM, Butkovich LM, Barbee BR, Bassell GJ, Gross C, Gourley SL. Reward-Related Expectations Trigger Dendritic Spine Plasticity in the Mouse Ventrolateral Orbitofrontal Cortex. J Neurosci 2019; 39:4595-4605. [PMID: 30940719 PMCID: PMC6554633 DOI: 10.1523/jneurosci.2031-18.2019] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2018] [Revised: 03/07/2019] [Accepted: 03/26/2019] [Indexed: 02/06/2023] Open
Abstract
An essential aspect of goal-directed decision-making is selecting actions based on anticipated consequences, a process that involves the orbitofrontal cortex (OFC) and potentially, the plasticity of dendritic spines in this region. To investigate this possibility, we trained male and female mice to nose poke for food reinforcers, or we delivered the same number of food reinforcers non-contingently to separate mice. We then decreased the likelihood of reinforcement for trained mice, requiring them to modify action-outcome expectations. In a separate experiment, we blocked action-outcome updating via chemogenetic inactivation of the OFC. In both cases, successfully selecting actions based on their likely consequences was associated with fewer immature, thin-shaped dendritic spines and a greater proportion of mature, mushroom-shaped spines in the ventrolateral OFC. This pattern was distinct from spine loss associated with aging, and we identified no effects on hippocampal CA1 neurons. Given that the OFC is involved in prospective calculations of likely outcomes, even when they are not observable, constraining spinogenesis while preserving mature spines may be important for solidifying durable expectations. To investigate causal relationships, we inhibited the RNA-binding protein fragile X mental retardation protein (encoded by Fmr1), which constrains dendritic spine turnover. Ventrolateral OFC-selective Fmr1 knockdown recapitulated the behavioral effects of inducible OFC inactivation (and lesions; also shown here), impairing action-outcome conditioning, and caused dendritic spine excess. Our findings suggest that a proper balance of dendritic spine plasticity within the OFC is necessary for one's ability to select actions based on anticipated consequences.SIGNIFICANCE STATEMENT Navigating a changing environment requires associating actions with their likely outcomes and updating these associations when they change. Dendritic spine plasticity is likely involved, yet relationships are unconfirmed. Using behavioral, chemogenetic, and viral-mediated gene silencing strategies and high-resolution microscopy, we find that modifying action-outcome expectations is associated with fewer immature spines and a greater proportion of mature spines in the ventrolateral orbitofrontal cortex (OFC). Given that the OFC is involved in prospectively calculating the likely outcomes of one's behavior, even when they are not observable, constraining spinogenesis while preserving mature spines may be important for maintaining durable expectations.
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Affiliation(s)
- Alonzo J Whyte
- Departments of Cell Biology
- Pediatrics, Emory School of Medicine
- Yerkes National Primate Research Center
| | - Henry W Kietzman
- Pediatrics, Emory School of Medicine
- Yerkes National Primate Research Center
- Graduate Program in Neuroscience
| | - Andrew M Swanson
- Pediatrics, Emory School of Medicine
- Yerkes National Primate Research Center
- Graduate Program in Neuroscience
| | - Laura M Butkovich
- Pediatrics, Emory School of Medicine
- Yerkes National Primate Research Center
- Graduate Program in Neuroscience
| | - Britton R Barbee
- Pediatrics, Emory School of Medicine
- Yerkes National Primate Research Center
- Graduate Program in Molecular and Systems Pharmacology, Emory University, Atlanta, Georgia 30329
| | - Gary J Bassell
- Departments of Cell Biology
- Graduate Program in Neuroscience
| | - Christina Gross
- Division of Neurology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio 45229, and
- Department of Pediatrics, University of Cincinnati, College of Medicine, Cincinnati, Ohio 45267
| | - Shannon L Gourley
- Pediatrics, Emory School of Medicine,
- Yerkes National Primate Research Center
- Graduate Program in Neuroscience
- Graduate Program in Molecular and Systems Pharmacology, Emory University, Atlanta, Georgia 30329
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9
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Llorens-Martín M. Exercising New Neurons to Vanquish Alzheimer Disease. Brain Plast 2018; 4:111-126. [PMID: 30564550 PMCID: PMC6296267 DOI: 10.3233/bpl-180065] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/21/2018] [Indexed: 02/07/2023] Open
Abstract
Alzheimer disease (AD) is the most common type of dementia in individuals over 65 years of age. The neuropathological hallmarks of the condition are Tau neurofibrillary tangles and Amyloid-β senile plaques. Moreover, certain susceptible regions of the brain experience a generalized lack of neural plasticity and marked synaptic alterations during the progression of this as yet incurable disease. One of these regions, the hippocampus, is characterized by the continuous addition of new neurons throughout life. This phenomenon, named adult hippocampal neurogenesis (AHN), provides a potentially endless source of new synaptic elements that increase the complexity and plasticity of the hippocampal circuitry. Numerous lines of evidence show that physical activity and environmental enrichment (EE) are among the most potent positive regulators of AHN. Given that neural plasticity is markedly decreased in many neurodegenerative diseases, the therapeutic potential of making certain lifestyle changes, such as increasing physical activity, is being recognised in several non-pharmacologic strategies seeking to slow down or prevent the progression of these diseases. This review article summarizes current evidence supporting the putative therapeutic potential of EE and physical exercise to increase AHN and hippocampal plasticity both under physiological and pathological circumstances, with a special emphasis on neurodegenerative diseases and AD.
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Affiliation(s)
- María Llorens-Martín
- Department of Molecular Neuropathology, Centro de Biología Molecular “Severo Ochoa”, CBMSO, CSIC-UAM, Madrid, Spain
- Center for Networked Biomedical Research on Neurodegenerative Diseases CIBERNED, Madrid, Spain
- Department of Molecular Biology, Faculty of Sciences, Universidad Autónoma de Madrid, Madrid, Spain
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10
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In Vivo Volume Dynamics of Dendritic Spines in the Neocortex of Wild-Type and Fmr1 KO Mice. eNeuro 2018; 5:eN-NWR-0282-18. [PMID: 30417082 PMCID: PMC6223115 DOI: 10.1523/eneuro.0282-18.2018] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Revised: 09/30/2018] [Accepted: 10/03/2018] [Indexed: 02/06/2023] Open
Abstract
Excitatory synapses are often formed at small protrusions of dendrite, called dendritic spines, in most projection neurons, and the spine-head volumes show strong correlations with synaptic connectivity. We examined the dynamics of spine volume in the adult mouse visual cortex using time-lapse in vivo two-photon imaging with a resonant Galvano scanner. Contrary to expectations, we found that the spines in the adult neocortex showed fluctuations to a similar degree as that observed in young hippocampal preparations, but there were systematic differences in how the dynamics were dependent on spine volumes, thus allowing for fewer fluctuations in small spines, which could account for the relatively low turnover rates of neocortical spines in vivo. We found that spine volumes fluctuated to a greater extent in a mouse model (Fmr1 knockout) of fragile X mental retardation than in wild-type mice, and the spine turnover rates were also higher in Fmr1 knock-out mice. Such features of spine dynamics in Fmr1 knock-out mice could be represented by a single slope factor in our model. Our data and model indicate a small but significant change in the average spine volume and more eminent differences in the statistical distribution in Fmr1 knock-out mice even in adulthood, which reflects the abnormal in vivo dynamics of spine volumes.
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11
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Michaelsen‐Preusse K, Feuge J, Korte M. Imbalance of synaptic actin dynamics as a key to fragile X syndrome? J Physiol 2018; 596:2773-2782. [PMID: 29380377 PMCID: PMC6046079 DOI: 10.1113/jp275571] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Accepted: 01/09/2018] [Indexed: 11/08/2022] Open
Abstract
Our experiences and memories define who we are, and evidence has accumulated that memory formation is dependent on functional and structural adaptations of synaptic structures in our brain. Especially dendritic spines, the postsynaptic compartments of synapses show a strong structure-to-function relationship and a high degree of structural plasticity. Although the molecular mechanisms are not completely understood, it is known that these modifications are highly dependent on the actin cytoskeleton, the major cytoskeletal component of the spine. Given the crucial involvement of actin in these mechanisms, dysregulations of spine actin dynamics (reflected by alterations in dendritic spine morphology) can be found in a variety of neurological disorders ranging from schizophrenia to several forms of autism spectrum disorders such as fragile X syndrome (FXS). FXS is caused by a single mutation leading to an inactivation of the X-linked fragile X mental retardation 1 gene and loss of its gene product, the RNA-binding protein fragile X mental retardation protein 1 (FMRP), which normally can be found both pre- and postsynaptically. FMRP is involved in mRNA transport as well as regulation of local translation at the synapse, and although hundreds of FMRP-target mRNAs could be identified only a very few interactions between FMRP and actin-regulating proteins have been reported and validated. In this review we give an overview of recent work by our lab and others providing evidence that dysregulated actin dynamics might indeed be at the very base of a deeper understanding of neurological disorders ranging from cognitive impairment to the autism spectrum.
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Affiliation(s)
- Kristin Michaelsen‐Preusse
- Zoological Institute, Division of Cellular NeurobiologyTU BraunschweigSpielmannstr. 7Braunschweig38106Germany
| | - Jonas Feuge
- Zoological Institute, Division of Cellular NeurobiologyTU BraunschweigSpielmannstr. 7Braunschweig38106Germany
| | - Martin Korte
- Zoological Institute, Division of Cellular NeurobiologyTU BraunschweigSpielmannstr. 7Braunschweig38106Germany
- Helmholtz Centre for Infection ResearchAG NINDInhoffenstr. 7Braunschweig38124Germany
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12
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Faw TD, Lerch JK, Thaxton TT, Deibert RJ, Fisher LC, Basso DM. Unique Sensory and Motor Behavior in Thy1-GFP-M Mice before and after Spinal Cord Injury. J Neurotrauma 2018; 35:2167-2182. [PMID: 29385890 DOI: 10.1089/neu.2017.5395] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Sensorimotor recovery after spinal cord injury (SCI) is of utmost importance to injured individuals and will rely on improved understanding of SCI pathology and recovery. Novel transgenic mouse lines facilitate discovery, but must be understood to be effective. The purpose of this study was to characterize the sensory and motor behavior of a common transgenic mouse line (Thy1-GFP-M) before and after SCI. Thy1-GFP-M positive (TG+) mice and their transgene negative littermates (TG-) were acquired from two sources (in-house colony, n = 32, Jackson Laboratories, n = 4). C57BL/6J wild-type (WT) mice (Jackson Laboratories, n = 10) were strain controls. Moderate-severe T9 contusion (SCI) or transection (TX) occurred in TG+ (SCI, n = 25, TX, n = 5), TG- (SCI, n = 5), and WT (SCI, n = 10) mice. To determine responsiveness to rehabilitation, a cohort of TG+ mice with SCI (n = 4) had flat treadmill (TM) training 42-49 days post-injury (dpi). To characterize recovery, we performed Basso Mouse Scale, Grid Walk, von Frey Hair, and Plantar Heat Testing before and out to day 42 post-SCI. Open field locomotion was significantly better in the Thy1 SCI groups (TG+ and TG-) compared with WT by 7 dpi (p < 0.01) and was maintained through 42 dpi (p < 0.01). These unexpected locomotor gains were not apparent during grid walking, indicating severe impairment of precise motor control. Thy1 derived mice were hypersensitive to mechanical stimuli at baseline (p < 0.05). After SCI, mechanical hyposensitivity emerged in Thy1 derived groups (p < 0.001), while thermal hyperalgesia occurred in all groups (p < 0.001). Importantly, consistent findings across TG+ and TG- groups suggest that the effects are mediated by the genetic background rather than transgene manipulation itself. Surprisingly, TM training restored mechanical and thermal sensation to baseline levels in TG+ mice with SCI. This behavioral profile and responsiveness to chronic training will be important to consider when choosing models to study the mechanisms underlying sensorimotor recovery after SCI.
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Affiliation(s)
- Timothy D Faw
- 1 Neuroscience Graduate Program, The Ohio State University , Columbus, Ohio.,2 School of Health and Rehabilitation Sciences, The Ohio State University , Columbus, Ohio.,3 Center for Brain and Spinal Cord Repair, The Ohio State University , Columbus, Ohio
| | - Jessica K Lerch
- 3 Center for Brain and Spinal Cord Repair, The Ohio State University , Columbus, Ohio.,4 Department of Neuroscience, The Ohio State University , Columbus, Ohio
| | - Tyler T Thaxton
- 2 School of Health and Rehabilitation Sciences, The Ohio State University , Columbus, Ohio.,3 Center for Brain and Spinal Cord Repair, The Ohio State University , Columbus, Ohio
| | - Rochelle J Deibert
- 2 School of Health and Rehabilitation Sciences, The Ohio State University , Columbus, Ohio.,3 Center for Brain and Spinal Cord Repair, The Ohio State University , Columbus, Ohio
| | - Lesley C Fisher
- 2 School of Health and Rehabilitation Sciences, The Ohio State University , Columbus, Ohio.,3 Center for Brain and Spinal Cord Repair, The Ohio State University , Columbus, Ohio
| | - D Michele Basso
- 2 School of Health and Rehabilitation Sciences, The Ohio State University , Columbus, Ohio.,3 Center for Brain and Spinal Cord Repair, The Ohio State University , Columbus, Ohio
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13
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Chen YW, Akad A, Aderogba R, Chowdhury TG, Aoki C. Dendrites of the dorsal and ventral hippocampal CA1 pyramidal neurons of singly housed female rats exhibit lamina-specific growths and retractions during adolescence that are responsive to pair housing. Synapse 2018; 72:e22034. [PMID: 29631321 DOI: 10.1002/syn.22034] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Revised: 03/27/2018] [Accepted: 04/01/2018] [Indexed: 01/07/2023]
Abstract
Adolescence is accompanied by increased vulnerability to psychiatric illnesses, including anxiety, depression, schizophrenia, and eating disorders. The hippocampus is important for regulating emotional state through its ventral compartment and spatial cognition through its dorsal compartment. Previous animal studies have examined hippocampal development at stages before, after or at single time points during adolescence. However, only one study has investigated morphological changes at multiple time points during adolescence, and no study has yet compared developmental changes of dorsal versus ventral hippocampi. We analyzed the dorsal and ventral hippocampi of rats to determine the developmental trajectory of Golgi-stained hippocampal CA1 neurons by sampling at five time points, ranging from postnatal day (P) 35 (puberty) to 55 (end of adolescence). We show that the dorsal hippocampus undergoes transient dendritic retractions in stratum radiatum (SR), while the ventral hippocampus undergoes transient dendritic growths in SR. During adulthood, stress and hormonal fluctuations have been shown to alter the physiology and morphology of hippocampal neurons, but studies of the impact of these factors upon adolescent hippocampi are scarce. In addition, we show that female-female pair housing from P 36-44 significantly increases branching in the dorsal SR and reduces branching in the ventral SR. Taken together with data on spine density, these results indicate that pyramidal cells in the dorsal and ventral CA1 of female adolescents are remodeled differently following single housing. Social housing during adolescence elicits pathway-specific changes in the hippocampus that may underlie behavioral benefits, including stability of emotion regulation and superior cognition.
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Affiliation(s)
- Yi-Wen Chen
- Center for Neural Science, New York University, New York, New York 10003
| | - Ada Akad
- Center for Neural Science, New York University, New York, New York 10003
| | - Ruka Aderogba
- Center for Neural Science, New York University, New York, New York 10003
| | - Tara G Chowdhury
- Center for Neural Science, New York University, New York, New York 10003
| | - Chiye Aoki
- Center for Neural Science, New York University, New York, New York 10003.,Neuroscience Institute, Langone Medical Center, New York University, New York, New York 10016
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14
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Ashokan A, Hegde A, Balasingham A, Mitra R. Housing environment influences stress-related hippocampal substrates and depression-like behavior. Brain Res 2018; 1683:78-85. [DOI: 10.1016/j.brainres.2018.01.021] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Revised: 01/15/2018] [Accepted: 01/17/2018] [Indexed: 01/14/2023]
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15
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Cox CD, Palmer LC, Pham DT, Trieu BH, Gall CM, Lynch G. Experiential learning in rodents: past experience enables rapid learning and localized encoding in hippocampus. Learn Mem 2017; 24:569-579. [PMID: 29038218 PMCID: PMC5647927 DOI: 10.1101/lm.045559.117] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Accepted: 07/28/2017] [Indexed: 01/08/2023]
Abstract
Humans routinely use past experience with complexity to deal with novel, challenging circumstances. This fundamental aspect of real-world behavior has received surprisingly little attention in animal studies, and the underlying brain mechanisms are unknown. The present experiments tested for transfer from past experience in rats and then used quantitative imaging to localize synaptic modifications in hippocampus. Six daily exposures to an enriched environment (EE) caused a marked enhancement of short- and long-term memory encoded during a 30-min session in a different and complex environment relative to rats given extensive handling or access to running wheels. Relatedly, the EE animals investigated the novel environment in a different manner than the other groups, suggesting transfer of exploration strategies acquired in earlier interactions with complexity. This effect was not associated with changes in the number or size of excitatory synapses in hippocampus. Maps of synapses expressing a marker for long-term potentiation indicated that encoding in the EE group, relative to control animals, was concentrated in hippocampal field CA1. Importantly, <1% of the total population of synapses was involved in production of the regional map. These results constitute the first evidence that the transfer of experience profoundly affects the manner in which hippocampus encodes complex information.
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Affiliation(s)
- Conor D Cox
- Department of Anatomy and Neurobiology, University of California, Irvine, California 92697, USA
| | - Linda C Palmer
- Department of Anatomy and Neurobiology, University of California, Irvine, California 92697, USA
| | - Danielle T Pham
- Department of Anatomy and Neurobiology, University of California, Irvine, California 92697, USA
| | - Brian H Trieu
- Department of Anatomy and Neurobiology, University of California, Irvine, California 92697, USA
| | - Christine M Gall
- Department of Anatomy and Neurobiology, University of California, Irvine, California 92697, USA
- Department of Neurobiology and Behavior, University of California, Irvine, California 92697, USA
| | - Gary Lynch
- Department of Anatomy and Neurobiology, University of California, Irvine, California 92697, USA
- Department of Psychiatry, University of California, Irvine, California 92697, USA
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16
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Mustroph ML, Pinardo H, Merritt JR, Rhodes JS. Parameters for abolishing conditioned place preference for cocaine from running and environmental enrichment in male C57BL/6J mice. Behav Brain Res 2016; 312:366-73. [PMID: 27363922 DOI: 10.1016/j.bbr.2016.06.049] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Revised: 06/21/2016] [Accepted: 06/26/2016] [Indexed: 12/21/2022]
Abstract
RATIONALE Evidence suggests that 4 weeks of voluntary wheel running abolishes conditioned place preference (CPP) for cocaine in male C57BL/6J mice. OBJECTIVES To determine the duration and timing of exposure to running wheels necessary to reduce CPP, and the extent to which the running per se influences CPP as compared to environmental enrichment without running. METHODS A total of 239 males were conditioned for 4days twice daily with cocaine (10mg/kg) and then split into 7 intervention groups prior to 4days of CPP testing. Experiment 1 consisted of two groups housed as follows: short sedentary group (SS; n=20) in normal cages for 1 week; the short running group (SR; n=20) with running wheels for 1 week. Experiment 2 consisted of five groups housed as follows; short 1 week of running followed by a 3 week sedentary period (SRS; n=20); a 3 week sedentary period followed by 1 week of running (SSR; n=20); long sedentary group (LS; n=66) in normal cages for 4 weeks; long running group (LR; n=66) with running wheels for 4 weeks; and long environmental enrichment group (EE; n=27) with toys for 4 weeks. RESULTS Levels of running were similar in all running groups. Both running and environmental enrichment reduced CPP relative to sedentary groups. CONCLUSIONS Results suggest that the abolishment of cocaine CPP from running is robust and occurs with as low as 1 week of intervention but may be related to enrichment component of running rather than physical activity.
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Affiliation(s)
- M L Mustroph
- University of Illinois at Urbana-Champaign, Beckman Institute of Advanced Science and Technology, 405 N. Mathews Avenue, Urbana, IL 61801, USA.
| | - H Pinardo
- University of Illinois at Urbana-Champaign, Beckman Institute of Advanced Science and Technology, 405 N. Mathews Avenue, Urbana, IL 61801, USA
| | - J R Merritt
- University of Illinois at Urbana-Champaign, Beckman Institute of Advanced Science and Technology, 405 N. Mathews Avenue, Urbana, IL 61801, USA
| | - J S Rhodes
- University of Illinois at Urbana-Champaign, Beckman Institute of Advanced Science and Technology, 405 N. Mathews Avenue, Urbana, IL 61801, USA
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17
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Chronic Ampakine Treatments Stimulate Dendritic Growth and Promote Learning in Middle-Aged Rats. J Neurosci 2016; 36:1636-46. [PMID: 26843645 DOI: 10.1523/jneurosci.3157-15.2016] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
UNLABELLED Positive allosteric modulators of AMPA-type glutamate receptors (ampakines) have been shown to rescue synaptic plasticity and reduce neuropathology in rodent models of cognitive disorders. Here we tested whether chronic ampakine treatment offsets age-related dendritic retraction in middle-aged (MA) rats. Starting at 10 months of age, rats were housed in an enriched environment and given daily treatment with a short half-life ampakine or vehicle for 3 months. Dendritic branching and spine measures were collected from 3D reconstructions of Lucifer yellow-filled CA1 pyramidal cells. There was a substantial loss of secondary branches, relative to enriched 2.5-month-old rats, in apical and basal dendritic fields of vehicle-treated, but not ampakine-treated, 13-month-old rats. Baseline synaptic responses in CA1 were only subtly different between the two MA groups, but long-term potentiation was greater in ampakine-treated rats. Unsupervised learning of a complex environment was used to assess treatment effects on behavior. Vehicle- and drug-treated rats behaved similarly during a first 30 min session in the novel environment but differed markedly on subsequent measures of long-term memory. Markov sequence analysis uncovered a clear increase in the predictability of serial movements between behavioral sessions 2 and 3 in the ampakine, but not vehicle, group. These results show that a surprising degree of dendritic retraction occurs by middle age and that this can be mostly offset by pharmacological treatments without evidence for unwanted side effects. The functional consequences of rescue were prominent with regard to memory but also extended to self-organization of behavior. SIGNIFICANCE STATEMENT Brain aging is characterized by a progressive loss of dendritic arbors and the emergence of impairments to learning-related synaptic plasticity. The present studies show that dendritic losses are evident by middle age despite housing in an enriched environment and can be mostly reversed by long-term, oral administration of a positive allosteric modulator of AMPA-type glutamate receptors. Dendritic recovery was accompanied by improvements to both synaptic plasticity and the encoding of long-term memory of a novel, complex environment. Because the short half-life compound had no evident negative effects, the results suggest a plausible strategy for treating age-related neuronal deterioration.
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18
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Green T, Barnea-Goraly N, Raman M, Hall SS, Lightbody AA, Bruno JL, Quintin EM, Reiss AL. Specific effect of the fragile-X mental retardation-1 gene (FMR1) on white matter microstructure. Br J Psychiatry 2015; 207:143-8. [PMID: 25792692 PMCID: PMC4523928 DOI: 10.1192/bjp.bp.114.151654] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Accepted: 10/13/2014] [Indexed: 11/23/2022]
Abstract
BACKGROUND Fragile-X syndrome (FXS) is a neurodevelopmental disorder associated with intellectual disability and neurobiological abnormalities including white matter microstructural differences. White matter differences have been found relative to neurotypical individuals. AIMS To examine whether FXS white matter differences are related specifically to FXS or more generally to the presence of intellectual disability. METHOD We used voxel-based and tract-based analytic approaches to compare individuals with FXS (n = 40) with gender- and IQ-matched controls (n = 30). RESULTS Individuals with FXS had increased fractional anisotropy and decreased radial diffusivity values compared with IQ-matched controls in the inferior longitudinal, inferior fronto-occipital and uncinate fasciculi. CONCLUSIONS The genetic variation associated with FXS affects white matter microstructure independently of overall IQ. White matter differences, found in FXS relative to IQ-matched controls, are distinct from reported differences relative to neurotypical controls. This underscores the need to consider cognitive ability differences when investigating white matter microstructure in neurodevelopmental disorders.
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Affiliation(s)
| | | | | | | | | | | | | | - Allan L. Reiss
- Correspondence: Allan L. Reiss, Center for Interdisciplinary Brain Sciences Research, 401 Quarry Road, MC 5795, Stanford, CA 94305, USA.
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19
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Wang GX, Smith SJ, Mourrain P. Fmr1 KO and fenobam treatment differentially impact distinct synapse populations of mouse neocortex. Neuron 2015; 84:1273-86. [PMID: 25521380 DOI: 10.1016/j.neuron.2014.11.016] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/18/2014] [Indexed: 02/07/2023]
Abstract
Cognitive deficits in fragile X syndrome (FXS) are attributed to molecular abnormalities of the brain's vast and heterogeneous synapse populations. Unfortunately, the density of synapses coupled with their molecular heterogeneity presents formidable challenges in understanding the specific contribution of synapse changes in FXS. We demonstrate powerful new methods for the large-scale molecular analysis of individual synapses that allow quantification of numerous specific changes in synapse populations present in the cortex of a mouse model of FXS. Analysis of nearly a million individual synapses reveals distinct, quantitative changes in synaptic proteins distributed across over 6,000 pairwise metrics. Some, but not all, of these synaptic alterations are reversed by treatment with the candidate therapeutic fenobam, an mGluR5 antagonist. These patterns of widespread, but diverse synaptic protein changes in response to global perturbation suggest that FXS and its treatment must be understood as a networked system at the synapse level.
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Affiliation(s)
- Gordon X Wang
- Center for Sleep Sciences and Medicine, Department of Psychiatry and Behavioral Sciences, Stanford University, Stanford, CA 94305, USA; Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94305, USA.
| | - Stephen J Smith
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94305, USA; Allen Institute for Brain Science, Seattle, WA 98103, USA
| | - Philippe Mourrain
- Center for Sleep Sciences and Medicine, Department of Psychiatry and Behavioral Sciences, Stanford University, Stanford, CA 94305, USA; INSERM 1024, Ecole Normale Supérieure Paris, 75005, France
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20
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Early social enrichment rescues adult behavioral and brain abnormalities in a mouse model of fragile X syndrome. Neuropsychopharmacology 2015; 40:1113-22. [PMID: 25348604 PMCID: PMC4367453 DOI: 10.1038/npp.2014.291] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Revised: 09/16/2014] [Accepted: 09/23/2014] [Indexed: 01/10/2023]
Abstract
Converging lines of evidence support the use of environmental stimulation to ameliorate the symptoms of a variety of neurodevelopmental disorders. Applying these interventions at very early ages is critical to achieve a marked reduction of the pathological phenotypes. Here we evaluated the impact of early social enrichment in Fmr1-KO mice, a genetic mouse model of fragile X syndrome (FXS), a major developmental disorder and the most frequent monogenic cause of autism. Enrichment was achieved by providing male KO pups and their WT littermates with enhanced social stimulation, housing them from birth until weaning with the mother and an additional nonlactating female. At adulthood they were tested for locomotor, social, and cognitive abilities; furthermore, dendritic alterations were assessed in the hippocampus and amygdala, two brain regions known to be involved in the control of the examined behaviors and affected by spine pathology in Fmr1-KOs. Enrichment rescued the behavioral FXS-like deficits displayed in adulthood by Fmr1-KO mice, that is, hyperactivity, reduced social interactions, and cognitive deficits. Early social enrichment also eliminated the abnormalities shown by adult KO mice in the morphology of hippocampal and amygdala dendritic spines, namely an enhanced density of immature vs mature types. Importantly, enrichment did not induce neurobehavioral changes in WT mice, thus supporting specific effects on FXS-like pathology. These findings show that early environmental stimulation has profound and long-term beneficial effects on the pathological FXS phenotype, thereby encouraging the use of nonpharmacological interventions for the treatment of this and perhaps other neurodevelopmental diseases.
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21
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Genetic removal of matrix metalloproteinase 9 rescues the symptoms of fragile X syndrome in a mouse model. J Neurosci 2014; 34:9867-79. [PMID: 25057190 DOI: 10.1523/jneurosci.1162-14.2014] [Citation(s) in RCA: 122] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Fmr1 knock-out (ko) mice display key features of fragile X syndrome (FXS), including delayed dendritic spine maturation and FXS-associated behaviors, such as poor socialization, obsessive-compulsive behavior, and hyperactivity. Here we provide conclusive evidence that matrix metalloproteinase-9 (MMP-9) is necessary to the development of FXS-associated defects in Fmr1 ko mice. Genetic disruption of Mmp-9 rescued key aspects of Fmr1 deficiency, including dendritic spine abnormalities, abnormal mGluR5-dependent LTD, as well as aberrant behaviors in open field and social novelty tests. Remarkably, MMP-9 deficiency also corrected non-neural features of Fmr1 deficiency-specifically macroorchidism-indicating that MMP-9 dysregulation contributes to FXS-associated abnormalities outside the CNS. Further, MMP-9 deficiency suppressed elevations of Akt, mammalian target of rapamycin, and eukaryotic translation initiation factor 4E phosphorylation seen in Fmr1 ko mice, which are also associated with other autistic spectrum disorders. These findings establish that MMP-9 is critical to the mechanisms responsible for neural and non-neural aspects of the FXS phenotype.
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22
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Cea-Del Rio CA, Huntsman MM. The contribution of inhibitory interneurons to circuit dysfunction in Fragile X Syndrome. Front Cell Neurosci 2014; 8:245. [PMID: 25202236 PMCID: PMC4142705 DOI: 10.3389/fncel.2014.00245] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Accepted: 08/04/2014] [Indexed: 12/24/2022] Open
Abstract
Many neurological disorders, including neurodevelopmental disorders, report hypersynchrony of neuronal networks. These alterations in neuronal synchronization suggest a link to the function of inhibitory interneurons. In Fragile X Syndrome (FXS), it has been reported that altered synchronization may underlie hyperexcitability, cognitive dysfunction and provide a link to the increased incidence of epileptic seizures. Therefore, understanding the roles of inhibitory interneurons and how they control neuronal networks is of great importance in studying neurodevelopmental disorders such as FXS. Here, we present a review of how interneuron populations and inhibition are important contributors to the loss of excitatory/inhibitory balance seen in hypersynchronous and hyperexcitable networks from neurodevelopmental disorders, and specifically in FXS.
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Affiliation(s)
- Christian A Cea-Del Rio
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado, Anschutz Medical Campus Aurora, CO, USA
| | - Molly M Huntsman
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado, Anschutz Medical Campus Aurora, CO, USA ; Department of Pediatrics, School of Medicine, University of Colorado, Anschutz Medical Campus Aurora, CO, USA
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23
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Doll CA, Broadie K. Impaired activity-dependent neural circuit assembly and refinement in autism spectrum disorder genetic models. Front Cell Neurosci 2014; 8:30. [PMID: 24570656 PMCID: PMC3916725 DOI: 10.3389/fncel.2014.00030] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Accepted: 01/21/2014] [Indexed: 01/23/2023] Open
Abstract
Early-use activity during circuit-specific critical periods refines brain circuitry by the coupled processes of eliminating inappropriate synapses and strengthening maintained synapses. We theorize these activity-dependent (A-D) developmental processes are specifically impaired in autism spectrum disorders (ASDs). ASD genetic models in both mouse and Drosophila have pioneered our insights into normal A-D neural circuit assembly and consolidation, and how these developmental mechanisms go awry in specific genetic conditions. The monogenic fragile X syndrome (FXS), a common cause of heritable ASD and intellectual disability, has been particularly well linked to defects in A-D critical period processes. The fragile X mental retardation protein (FMRP) is positively activity-regulated in expression and function, in turn regulates excitability and activity in a negative feedback loop, and appears to be required for the A-D remodeling of synaptic connectivity during early-use critical periods. The Drosophila FXS model has been shown to functionally conserve the roles of human FMRP in synaptogenesis, and has been centrally important in generating our current mechanistic understanding of the FXS disease state. Recent advances in Drosophila optogenetics, transgenic calcium reporters, highly-targeted transgenic drivers for individually-identified neurons, and a vastly improved connectome of the brain are now being combined to provide unparalleled opportunities to both manipulate and monitor A-D processes during critical period brain development in defined neural circuits. The field is now poised to exploit this new Drosophila transgenic toolbox for the systematic dissection of A-D mechanisms in normal versus ASD brain development, particularly utilizing the well-established Drosophila FXS disease model.
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Affiliation(s)
- Caleb A Doll
- Department of Biological Sciences, Vanderbilt University Nashville, TN, USA
| | - Kendal Broadie
- Department of Biological Sciences, Vanderbilt University Nashville, TN, USA ; Kennedy Center for Research on Human Development, Vanderbilt University Nashville, TN, USA
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