1
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Vandael D, Jonas P. Structure, biophysics, and circuit function of a "giant" cortical presynaptic terminal. Science 2024; 383:eadg6757. [PMID: 38452088 DOI: 10.1126/science.adg6757] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Accepted: 01/19/2024] [Indexed: 03/09/2024]
Abstract
The hippocampal mossy fiber synapse, formed between axons of dentate gyrus granule cells and dendrites of CA3 pyramidal neurons, is a key synapse in the trisynaptic circuitry of the hippocampus. Because of its comparatively large size, this synapse is accessible to direct presynaptic recording, allowing a rigorous investigation of the biophysical mechanisms of synaptic transmission and plasticity. Furthermore, because of its placement in the very center of the hippocampal memory circuit, this synapse seems to be critically involved in several higher network functions, such as learning, memory, pattern separation, and pattern completion. Recent work based on new technologies in both nanoanatomy and nanophysiology, including presynaptic patch-clamp recording, paired recording, super-resolution light microscopy, and freeze-fracture and "flash-and-freeze" electron microscopy, has provided new insights into the structure, biophysics, and network function of this intriguing synapse. This brings us one step closer to answering a fundamental question in neuroscience: how basic synaptic properties shape higher network computations.
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Affiliation(s)
- David Vandael
- Institute of Science and Technology Austria (ISTA), A-3400 Klosterneuburg, Austria
| | - Peter Jonas
- Institute of Science and Technology Austria (ISTA), A-3400 Klosterneuburg, Austria
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2
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Napier M, Reynolds K, Scott AL. Glial-mediated dysregulation of neurodevelopment in Fragile X Syndrome. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2023; 173:187-215. [PMID: 37993178 DOI: 10.1016/bs.irn.2023.08.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2023]
Abstract
Astrocytes are highly involved in a multitude of developmental processes that are known to be dysregulated in Fragile X Syndrome. Here, we examine these processes individually and review the roles astrocytes play in contributing to the pathology of this syndrome. As a growing area of interest in the field, new and exciting insight is continually emerging. Understanding these glial-mediated roles is imperative for elucidating the underlying molecular mechanisms at play, not only in Fragile X Syndrome, but also other ASD-related disorders. Understanding these roles will be central to the future development of effective, clinically-relevant treatments of these disorders.
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Affiliation(s)
- M Napier
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Canada; Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Canada
| | - K Reynolds
- Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Canada; Department of Neuroscience, Tufts University School of Medicine, Boston, United States
| | - A L Scott
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Canada; Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Canada.
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3
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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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4
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Gredell M, Lu J, Zuo Y. The effect of single-cell knockout of Fragile X Messenger Ribonucleoprotein on synaptic structural plasticity. Front Synaptic Neurosci 2023; 15:1135479. [PMID: 37035256 PMCID: PMC10076639 DOI: 10.3389/fnsyn.2023.1135479] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Accepted: 03/07/2023] [Indexed: 04/11/2023] Open
Abstract
Fragile X Syndrome (FXS) is the best-known form of inherited intellectual disability caused by the loss-of-function mutation in a single gene. The FMR1 gene mutation abolishes the expression of Fragile X Messenger Ribonucleoprotein (FMRP), which regulates the expression of many synaptic proteins. Cortical pyramidal neurons in postmortem FXS patient brains show abnormally high density and immature morphology of dendritic spines; this phenotype is replicated in the Fmr1 knockout (KO) mouse. While FMRP is well-positioned in the dendrite to regulate synaptic plasticity, intriguing in vitro and in vivo data show that wild type neurons embedded in a network of Fmr1 KO neurons or glia exhibit spine abnormalities just as neurons in Fmr1 global KO mice. This raises the question: does FMRP regulate synaptic morphology and dynamics in a cell-autonomous manner, or do the synaptic phenotypes arise from abnormal pre-synaptic inputs? To address this question, we combined viral and mouse genetic approaches to delete FMRP from a very sparse subset of cortical layer 5 pyramidal neurons (L5 PyrNs) either during early postnatal development or in adulthood. We then followed the structural dynamics of dendritic spines on these Fmr1 KO neurons by in vivo two-photon microscopy. We found that, while L5 PyrNs in adult Fmr1 global KO mice have abnormally high density of thin spines, single-cell Fmr1 KO in adulthood does not affect spine density, morphology, or dynamics. On the contrary, neurons with neonatal FMRP deletion have normal spine density but elevated spine formation at 1 month of age, replicating the phenotype in Fmr1 global KO mice. Interestingly, these neurons exhibit elevated thin spine density, but normal total spine density, by adulthood. Together, our data reveal cell-autonomous FMRP regulation of cortical synaptic dynamics during adolescence, but spine defects in adulthood also implicate non-cell-autonomous factors.
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Affiliation(s)
| | | | - Yi Zuo
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA, United States
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5
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Speranza L, Filiz KD, Goebel S, Perrone-Capano C, Pulcrano S, Volpicelli F, Francesconi A. Combined DiI and Antibody Labeling Reveals Complex Dysgenesis of Hippocampal Dendritic Spines in a Mouse Model of Fragile X Syndrome. Biomedicines 2022; 10:2692. [PMID: 36359212 PMCID: PMC9687937 DOI: 10.3390/biomedicines10112692] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 10/18/2022] [Accepted: 10/19/2022] [Indexed: 11/30/2022] Open
Abstract
Structural, functional, and molecular alterations in excitatory spines are a common hallmark of many neurodevelopmental disorders including intellectual disability and autism. Here, we describe an optimized methodology, based on combined use of DiI and immunofluorescence, for rapid and sensitive characterization of the structure and composition of spines in native brain tissue. We successfully demonstrate the applicability of this approach by examining the properties of hippocampal spines in juvenile Fmr1 KO mice, a mouse model of Fragile X Syndrome. We find that mutant mice display pervasive dysgenesis of spines evidenced by an overabundance of both abnormally elongated thin spines and cup-shaped spines, in combination with reduced density of mushroom spines. We further find that mushroom spines expressing the actin-binding protein Synaptopodin-a marker for spine apparatus-are more prevalent in mutant mice. Previous work identified spines with Synaptopodin/spine apparatus as the locus of mGluR-LTD, which is abnormally elevated in Fmr1 KO mice. Altogether, our data suggest this enhancement may be linked to the preponderance of this subset of spines in the mutant. Overall, these findings demonstrate the sensitivity and versatility of the optimized methodology by uncovering a novel facet of spine dysgenesis in Fmr1 KO mice.
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Affiliation(s)
- Luisa Speranza
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, New York, NY 10461, USA
| | - Kardelen Dalım Filiz
- Department of Pharmacy, School of Medicine and Surgery, University of Naples Federico II, 80131 Naples, Italy
| | - Sarah Goebel
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, New York, NY 10461, USA
| | - Carla Perrone-Capano
- Department of Pharmacy, School of Medicine and Surgery, University of Naples Federico II, 80131 Naples, Italy
| | - Salvatore Pulcrano
- Institute of Genetics and Biophysics “A. Buzzati-Traverso”, C.N.R., 80131 Naples, Italy
| | - Floriana Volpicelli
- Department of Pharmacy, School of Medicine and Surgery, University of Naples Federico II, 80131 Naples, Italy
| | - Anna Francesconi
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, New York, NY 10461, USA
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6
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Monday HR, Kharod SC, Yoon YJ, Singer RH, Castillo PE. Presynaptic FMRP and local protein synthesis support structural and functional plasticity of glutamatergic axon terminals. Neuron 2022; 110:2588-2606.e6. [PMID: 35728596 PMCID: PMC9391299 DOI: 10.1016/j.neuron.2022.05.024] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 03/31/2022] [Accepted: 05/26/2022] [Indexed: 10/18/2022]
Abstract
Learning and memory rely on long-lasting, synapse-specific modifications. Although postsynaptic forms of plasticity typically require local protein synthesis, whether and how local protein synthesis contributes to presynaptic changes remain unclear. Here, we examined the mouse hippocampal mossy fiber (MF)-CA3 synapse, which expresses both structural and functional presynaptic plasticity and contains presynaptic fragile X messenger ribonucleoprotein (FMRP), an RNA-binding protein involved in postsynaptic protein-synthesis-dependent plasticity. We report that MF boutons contain ribosomes and synthesize protein locally. The long-term potentiation of MF-CA3 synaptic transmission (MF-LTP) was associated with the translation-dependent enlargement of MF boutons. Remarkably, increasing in vitro or in vivo MF activity enhanced the protein synthesis in MFs. Moreover, the deletion of presynaptic FMRP blocked structural and functional MF-LTP, suggesting that FMRP is a critical regulator of presynaptic MF plasticity. Thus, presynaptic FMRP and protein synthesis dynamically control presynaptic structure and function in the mature mammalian brain.
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Affiliation(s)
- Hannah R Monday
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York, NY 10461, USA.
| | - Shivani C Kharod
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York, NY 10461, USA
| | - Young J Yoon
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York, NY 10461, USA; Department of Cell Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York, NY 10461, USA
| | - Robert H Singer
- Department of Cell Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York, NY 10461, USA
| | - Pablo E Castillo
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York, NY 10461, USA; Department of Psychiatry and Behavioral Sciences, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York, NY 10461, USA.
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7
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Sungur AÖ, Zeitouny C, Gabele L, Metz I, Wöhr M, Michaelsen-Preusse K, Rust MB. Transient reduction in dendritic spine density in brain-specific profilin1 mutant mice is associated with behavioral deficits. Front Mol Neurosci 2022; 15:952782. [PMID: 35992199 PMCID: PMC9381693 DOI: 10.3389/fnmol.2022.952782] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Accepted: 07/13/2022] [Indexed: 01/16/2023] Open
Abstract
Actin filaments form the backbone of dendritic spines, the postsynaptic compartment of most excitatory synapses in the brain. Spine density changes affect brain function, and postsynaptic actin defects have been implicated in various neuropathies. It is mandatory to identify the actin regulators that control spine density. Based on previous studies, we hypothesized a role for the actin regulator profilin1 in spine formation. We report reduced hippocampal spine density in juvenile profilin1 mutant mice together with impairments in memory formation and reduced ultrasonic communication during active social behavior. Our results, therefore, underline a previously suggested function of profilin1 in controlling spine formation and behavior in juvenile mice.
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Affiliation(s)
- A. Özge Sungur
- Molecular Neurobiology Group, Institute of Physiological Chemistry, University of Marburg, Marburg, Germany
- Behavioral Neuroscience, Experimental and Biological Psychology, University of Marburg, Marburg, Germany
| | - Caroline Zeitouny
- Department of Cellular Neurobiology, Technical University (TU) Braunschweig, Braunschweig, Germany
| | - Lea Gabele
- Department of Cellular Neurobiology, Technical University (TU) Braunschweig, Braunschweig, Germany
| | - Isabell Metz
- Molecular Neurobiology Group, Institute of Physiological Chemistry, University of Marburg, Marburg, Germany
- Deutsche Forschungsgemeinschaft (German Research Foundation) (DFG) Research Training Group, Membrane Plasticity in Tissue Development and Remodeling, Graduiertenkolleg (Gradeschool) (GRK) 2213, University of Marburg, Marburg, Germany
| | - Markus Wöhr
- Behavioral Neuroscience, Experimental and Biological Psychology, University of Marburg, Marburg, Germany
- Social and Affective Neuroscience Research Group, Laboratory of Biological Psychology, Research Unit Brain and Cognition, Faculty of Psychology and Educational Sciences, Katholeike Universiteit (KU) Leuven, Leuven, Belgium
- Leuven Brain Institute, Katholeike Universiteit (KU) Leuven, Leuven, Belgium
| | - Kristin Michaelsen-Preusse
- Department of Cellular Neurobiology, Technical University (TU) Braunschweig, Braunschweig, Germany
- Kristin Michaelsen-Preusse,
| | - Marco B. Rust
- Molecular Neurobiology Group, Institute of Physiological Chemistry, University of Marburg, Marburg, Germany
- Deutsche Forschungsgemeinschaft (German Research Foundation) (DFG) Research Training Group, Membrane Plasticity in Tissue Development and Remodeling, Graduiertenkolleg (Gradeschool) (GRK) 2213, University of Marburg, Marburg, Germany
- Center for Mind, Brain and Behavior (CMBB), University of Marburg and Justus-Liebig-University Giessen, Marburg, Germany
- *Correspondence: Marco B. Rust,
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8
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Restrepo LJ, DePew AT, Moese ER, Tymanskyj SR, Parisi MJ, Aimino MA, Duhart JC, Fei H, Mosca TJ. γ-secretase promotes Drosophila postsynaptic development through the cleavage of a Wnt receptor. Dev Cell 2022; 57:1643-1660.e7. [PMID: 35654038 DOI: 10.1016/j.devcel.2022.05.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Revised: 04/06/2022] [Accepted: 05/10/2022] [Indexed: 12/27/2022]
Abstract
Developing synapses mature through the recruitment of specific proteins that stabilize presynaptic and postsynaptic structure and function. Wnt ligands signaling via Frizzled (Fz) receptors play many crucial roles in neuronal and synaptic development, but whether and how Wnt and Fz influence synaptic maturation is incompletely understood. Here, we show that Fz2 receptor cleavage via the γ-secretase complex is required for postsynaptic development and maturation. In the absence of γ-secretase, Drosophila neuromuscular synapses fail to recruit postsynaptic scaffolding and cytoskeletal proteins, leading to behavioral deficits. Introducing presenilin mutations linked to familial early-onset Alzheimer's disease into flies leads to synaptic maturation phenotypes that are identical to those seen in null alleles. This conserved role for γ-secretase in synaptic maturation and postsynaptic development highlights the importance of Fz2 cleavage and suggests that receptor processing by proteins linked to neurodegeneration may be a shared mechanism with aspects of synaptic development.
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Affiliation(s)
- Lucas J Restrepo
- Department of Neuroscience, Vickie and Jack Farber Institute of Neuroscience, Thomas Jefferson University, Bluemle Life Sciences Building, Philadelphia, PA 19107, USA
| | - Alison T DePew
- Department of Neuroscience, Vickie and Jack Farber Institute of Neuroscience, Thomas Jefferson University, Bluemle Life Sciences Building, Philadelphia, PA 19107, USA
| | - Elizabeth R Moese
- Department of Neuroscience, Vickie and Jack Farber Institute of Neuroscience, Thomas Jefferson University, Bluemle Life Sciences Building, Philadelphia, PA 19107, USA
| | - Stephen R Tymanskyj
- Department of Neuroscience, Vickie and Jack Farber Institute of Neuroscience, Thomas Jefferson University, Bluemle Life Sciences Building, Philadelphia, PA 19107, USA
| | - Michael J Parisi
- Department of Neuroscience, Vickie and Jack Farber Institute of Neuroscience, Thomas Jefferson University, Bluemle Life Sciences Building, Philadelphia, PA 19107, USA
| | - Michael A Aimino
- Department of Neuroscience, Vickie and Jack Farber Institute of Neuroscience, Thomas Jefferson University, Bluemle Life Sciences Building, Philadelphia, PA 19107, USA
| | - Juan Carlos Duhart
- Department of Neuroscience, Vickie and Jack Farber Institute of Neuroscience, Thomas Jefferson University, Bluemle Life Sciences Building, Philadelphia, PA 19107, USA
| | - Hong Fei
- Department of Neuroscience, Vickie and Jack Farber Institute of Neuroscience, Thomas Jefferson University, Bluemle Life Sciences Building, Philadelphia, PA 19107, USA
| | - Timothy J Mosca
- Department of Neuroscience, Vickie and Jack Farber Institute of Neuroscience, Thomas Jefferson University, Bluemle Life Sciences Building, Philadelphia, PA 19107, USA.
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9
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Keeping Excitation-Inhibition Ratio in Balance. Int J Mol Sci 2022; 23:ijms23105746. [PMID: 35628556 PMCID: PMC9145842 DOI: 10.3390/ijms23105746] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 05/17/2022] [Accepted: 05/20/2022] [Indexed: 11/17/2022] Open
Abstract
Unrelated genetic mutations can lead to convergent manifestations of neurological disorders with similar behavioral phenotypes. Experimental data frequently show a lack of dramatic changes in neuroanatomy, indicating that the key cause of symptoms might arise from impairment in the communication between neurons. A transient imbalance between excitatory (glutamatergic) and inhibitory (GABAergic) synaptic transmission (the E/I balance) during early development is generally considered to underlie the development of several neurological disorders in adults. However, the E/I ratio is a multidimensional variable. Synaptic contacts are highly dynamic and the actual strength of synaptic projections is determined from the balance between synaptogenesis and synaptic elimination. During development, relatively slow postsynaptic receptors are replaced by fast ones that allow for fast stimulus-locked excitation/inhibition. Using the binomial model of synaptic transmission allows for the reassessing of experimental data from different mouse models, showing that a transient E/I shift is frequently counterbalanced by additional pre- and/or postsynaptic changes. Such changes—for instance, the slowing down of postsynaptic currents by means of immature postsynaptic receptors—stabilize the average synaptic strength, but impair the timing of information flow. Compensatory processes and/or astrocytic signaling may represent possible targets for medical treatments of different disorders directed to rescue the proper information processing.
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10
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Hirsch D, Kohl A, Wang Y, Sela-Donenfeld D. Axonal Projection Patterns of the Dorsal Interneuron Populations in the Embryonic Hindbrain. Front Neuroanat 2022; 15:793161. [PMID: 35002640 PMCID: PMC8738170 DOI: 10.3389/fnana.2021.793161] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Accepted: 11/29/2021] [Indexed: 12/12/2022] Open
Abstract
Unraveling the inner workings of neural circuits entails understanding the cellular origin and axonal pathfinding of various neuronal groups during development. In the embryonic hindbrain, different subtypes of dorsal interneurons (dINs) evolve along the dorsal-ventral (DV) axis of rhombomeres and are imperative for the assembly of central brainstem circuits. dINs are divided into two classes, class A and class B, each containing four neuronal subgroups (dA1-4 and dB1-4) that are born in well-defined DV positions. While all interneurons belonging to class A express the transcription factor Olig3 and become excitatory, all class B interneurons express the transcription factor Lbx1 but are diverse in their excitatory or inhibitory fate. Moreover, within every class, each interneuron subtype displays its own specification genes and axonal projection patterns which are required to govern the stage-by-stage assembly of their connectivity toward their target sites. Remarkably, despite the similar genetic landmark of each dINs subgroup along the anterior-posterior (AP) axis of the hindbrain, genetic fate maps of some dA/dB neuronal subtypes uncovered their contribution to different nuclei centers in relation to their rhombomeric origin. Thus, DV and AP positional information has to be orchestrated in each dA/dB subpopulation to form distinct neuronal circuits in the hindbrain. Over the span of several decades, different axonal routes have been well-documented to dynamically emerge and grow throughout the hindbrain DV and AP positions. Yet, the genetic link between these distinct axonal bundles and their neuronal origin is not fully clear. In this study, we reviewed the available data regarding the association between the specification of early-born dorsal interneuron subpopulations in the hindbrain and their axonal circuitry development and fate, as well as the present existing knowledge on molecular effectors underlying the process of axonal growth.
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Affiliation(s)
- Dana Hirsch
- Koret School of Veterinary Medicine, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel.,Department of Veterinary Resources, Weizmann Institute of Science, Rehovot, Israel
| | - Ayelet Kohl
- Koret School of Veterinary Medicine, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Yuan Wang
- Department of Biomedical Sciences, Program in Neuroscience, College of Medicine, Florida State University, Tallahassee, FL, United States
| | - Dalit Sela-Donenfeld
- Koret School of Veterinary Medicine, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
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11
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Murk K, Ornaghi M, Schiweck J. Profilin Isoforms in Health and Disease - All the Same but Different. Front Cell Dev Biol 2021; 9:681122. [PMID: 34458253 PMCID: PMC8387879 DOI: 10.3389/fcell.2021.681122] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 07/12/2021] [Indexed: 12/11/2022] Open
Abstract
Profilins are small actin binding proteins, which are structurally conserved throughout evolution. They are probably best known to promote and direct actin polymerization. However, they also participate in numerous cell biological processes beyond the roles typically ascribed to the actin cytoskeleton. Moreover, most complex organisms express several profilin isoforms. Their cellular functions are far from being understood, whereas a growing number of publications indicate that profilin isoforms are involved in the pathogenesis of various diseases. In this review, we will provide an overview of the profilin family and "typical" profilin properties including the control of actin dynamics. We will then discuss the profilin isoforms of higher animals in detail. In terms of cellular functions, we will focus on the role of Profilin 1 (PFN1) and Profilin 2a (PFN2a), which are co-expressed in the central nervous system. Finally, we will discuss recent findings that link PFN1 and PFN2a to neurological diseases, such as amyotrophic lateral sclerosis (ALS), Fragile X syndrome (FXS), Huntington's disease and spinal muscular atrophy (SMA).
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Affiliation(s)
- Kai Murk
- Institute of Biochemistry, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Marta Ornaghi
- Institute of Biochemistry, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Juliane Schiweck
- Institute of Biochemistry, Charité Universitätsmedizin Berlin, Berlin, Germany
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12
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Moskalyuk A, Van De Vijver S, Verstraelen P, De Vos WH, Kooy RF, Giugliano M. Single-Cell and Neuronal Network Alterations in an In Vitro Model of Fragile X Syndrome. Cereb Cortex 2021; 30:31-46. [PMID: 30958540 DOI: 10.1093/cercor/bhz068] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The Fragile X mental retardation protein (FMRP) is involved in many cellular processes and it regulates synaptic and network development in neurons. Its absence is known to lead to intellectual disability, with a wide range of comorbidities including autism. Over the past decades, FMRP research focused on abnormalities both in glutamatergic and GABAergic signaling, and an altered balance between excitation and inhibition has been hypothesized to underlie the clinical consequences of absence of the protein. Using Fmrp knockout mice, we studied an in vitro model of cortical microcircuitry and observed that the loss of FMRP largely affected the electrophysiological correlates of network development and maturation but caused less alterations in single-cell phenotypes. The loss of FMRP also caused a structural increase in the number of excitatory synaptic terminals. Using a mathematical model, we demonstrated that the combination of an increased excitation and reduced inhibition describes best our experimental observations during the ex vivo formation of the network connections.
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Affiliation(s)
- Anastasiya Moskalyuk
- Molecular, Cellular, and Network Excitability Lab, University of Antwerp, Wilrijk, Flanders, Belgium
| | - Sebastiaan Van De Vijver
- Molecular, Cellular, and Network Excitability Lab, University of Antwerp, Wilrijk, Flanders, Belgium
| | - Peter Verstraelen
- Laboratory of Cell Biology and Histology, University of Antwerp, Wilrijk, Flanders, Belgium
| | - Winnok H De Vos
- Laboratory of Cell Biology and Histology, University of Antwerp, Wilrijk, Flanders, Belgium
| | - R Frank Kooy
- Department of Medical Genetics, University of Antwerp, Edegem, Flanders, Belgium
| | - Michele Giugliano
- Molecular, Cellular, and Network Excitability Lab, University of Antwerp, Wilrijk, Flanders, Belgium.,International School for Advanced Studies (SISSA), Trieste, Italy
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13
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Reynolds KE, Wong CR, Scott AL. Astrocyte-mediated purinergic signaling is upregulated in a mouse model of Fragile X syndrome. Glia 2021; 69:1816-1832. [PMID: 33754385 DOI: 10.1002/glia.23997] [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: 07/09/2020] [Revised: 03/10/2021] [Accepted: 03/11/2021] [Indexed: 12/12/2022]
Abstract
Fragile X syndrome (FXS) is the leading monogenic cause of intellectual disability and autism spectrum disorders. With increasing investigation into the molecular mechanisms underlying FXS, there is growing evidence that perturbations in glial signaling are widely associated with neurological pathology. Purinergic signaling, which utilizes nucleoside triphosphates as signaling molecules, provides one of the most ubiquitous signaling systems for glial-neuronal and glial-glial crosstalk. Here, we sought to identify whether purinergic signaling is dysregulated within the FXS mouse cortex, and whether this dysregulation contributes to aberrant intercellular communication. In primary astrocyte cultures derived from the Fmr1 knockout (KO) mouse model of FXS, we found that application of exogenous ATP and UTP evoked elevated intracellular calcium responses compared to wildtype levels. Accordingly, purinergic P2Y2 and P2Y6 receptor expression was increased in Fmr1 KO astrocytes both in vitro and in acutely dissociated tissue, while P2Y antagonism via suramin prevented intracellular calcium elevations, suggesting a role for these receptors in aberrant FXS astrocyte activation. To investigate the impact of elevated purinergic signaling on astrocyte-mediated synaptogenesis, we quantified synaptogenic protein TSP-1, known to be regulated by P2Y activation. TSP-1 secretion and expression were both heightened in Fmr1 KO vs wildtype astrocytes following UTP application, while naïve TSP-1 cortical expression was also transiently elevated in vivo, indicating increased potential for excitatory TSP-1-mediated synaptogenesis in the FXS cortex. Together, our results demonstrate novel and significant purinergic signaling elevations in Fmr1 KO astrocytes, which may serve as a potential therapeutic target to mitigate the signaling aberrations observed in FXS.
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Affiliation(s)
- Kathryn E Reynolds
- Neuroscience Graduate Program, McMaster University, Hamilton, Ontario, Canada
| | - Chloe R Wong
- Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada
| | - Angela L Scott
- Neuroscience Graduate Program, McMaster University, Hamilton, Ontario, Canada.,Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada
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14
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Cheffer A, Flitsch LJ, Krutenko T, Röderer P, Sokhranyaeva L, Iefremova V, Hajo M, Peitz M, Schwarz MK, Brüstle O. Human stem cell-based models for studying autism spectrum disorder-related neuronal dysfunction. Mol Autism 2020; 11:99. [PMID: 33308283 PMCID: PMC7733257 DOI: 10.1186/s13229-020-00383-w] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Accepted: 09/22/2020] [Indexed: 12/13/2022] Open
Abstract
The controlled differentiation of pluripotent stem cells (PSCs) into neurons and glia offers a unique opportunity to study early stages of human central nervous system development under controlled conditions in vitro. With the advent of cell reprogramming and the possibility to generate induced pluripotent stem cells (iPSCs) from any individual in a scalable manner, these studies can be extended to a disease- and patient-specific level. Autism spectrum disorder (ASD) is considered a neurodevelopmental disorder, with substantial evidence pointing to early alterations in neurogenesis and network formation as key pathogenic drivers. For that reason, ASD represents an ideal candidate for stem cell-based disease modeling. Here, we provide a concise review on recent advances in the field of human iPSC-based modeling of syndromic and non-syndromic forms of ASD, with a particular focus on studies addressing neuronal dysfunction and altered connectivity. We further discuss recent efforts to translate stem cell-based disease modeling to 3D via brain organoid and cell transplantation approaches, which enable the investigation of disease mechanisms in a tissue-like context. Finally, we describe advanced tools facilitating the assessment of altered neuronal function, comment on the relevance of iPSC-based models for the assessment of pharmaceutical therapies and outline potential future routes in stem cell-based ASD research.
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Affiliation(s)
- Arquimedes Cheffer
- Institute of Reconstructive Neurobiology, University of Bonn Medical Faculty & University Hospital Bonn, Venusberg-Campus 1, Building 76, 53127, Bonn, Germany
| | - Lea Jessica Flitsch
- Institute of Reconstructive Neurobiology, University of Bonn Medical Faculty & University Hospital Bonn, Venusberg-Campus 1, Building 76, 53127, Bonn, Germany
| | - Tamara Krutenko
- Institute of Reconstructive Neurobiology, University of Bonn Medical Faculty & University Hospital Bonn, Venusberg-Campus 1, Building 76, 53127, Bonn, Germany
| | - Pascal Röderer
- Life & Brain GmbH, Platform Cellomics, Venusberg-Campus 1, Building 76, 53127, Bonn, Germany
| | - Liubov Sokhranyaeva
- Institute of Experimental Epileptology and Cognition Research, University of Bonn Medical Faculty & University Hospital Bonn, Venusberg-Campus 1, Building 76, 53127, Bonn, Germany
| | - Vira Iefremova
- Institute of Reconstructive Neurobiology, University of Bonn Medical Faculty & University Hospital Bonn, Venusberg-Campus 1, Building 76, 53127, Bonn, Germany
| | - Mohamad Hajo
- Institute of Reconstructive Neurobiology, University of Bonn Medical Faculty & University Hospital Bonn, Venusberg-Campus 1, Building 76, 53127, Bonn, Germany
| | - Michael Peitz
- Institute of Reconstructive Neurobiology, University of Bonn Medical Faculty & University Hospital Bonn, Venusberg-Campus 1, Building 76, 53127, Bonn, Germany
- Life & Brain GmbH, Platform Cellomics, Venusberg-Campus 1, Building 76, 53127, Bonn, Germany
- Cell Programming Core Facility, University of Bonn Medical Faculty, Bonn, Germany
| | - Martin Karl Schwarz
- Life & Brain GmbH, Platform Cellomics, Venusberg-Campus 1, Building 76, 53127, Bonn, Germany
- Institute of Experimental Epileptology and Cognition Research, University of Bonn Medical Faculty & University Hospital Bonn, Venusberg-Campus 1, Building 76, 53127, Bonn, Germany
| | - Oliver Brüstle
- Institute of Reconstructive Neurobiology, University of Bonn Medical Faculty & University Hospital Bonn, Venusberg-Campus 1, Building 76, 53127, Bonn, Germany.
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15
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Nguyen U, Tinsley B, Sen Y, Stein J, Palacios Y, Ceballos A, Welch C, Nzenkue K, Penn A, Murphy L, Leodones K, Casiquin J, Ivory I, Ghenta K, Danziger K, Widman E, Newman J, Triplehorn M, Hindi Z, Mulligan K. Exposure to bisphenol A differentially impacts neurodevelopment and behavior in Drosophila melanogaster from distinct genetic backgrounds. Neurotoxicology 2020; 82:146-157. [PMID: 33309840 DOI: 10.1016/j.neuro.2020.12.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Revised: 11/30/2020] [Accepted: 12/06/2020] [Indexed: 12/13/2022]
Abstract
Bisphenol A (BPA) is a ubiquitous environmental chemical that has been linked to behavioral differences in children and shown to impact critical neurodevelopmental processes in animal models. Though data is emerging, we still have an incomplete picture of how BPA disrupts neurodevelopment; in particular, how its impacts may vary across different genetic backgrounds. Given the genetic tractability of Drosophila melanogaster, they present a valuable model to address this question. Fruit flies are increasingly being used for assessment of neurotoxicants because of their relatively simple brain structure and variety of measurable behaviors. Here we investigated the neurodevelopmental impacts of BPA across two genetic strains of Drosophila-w1118 (control) and the Fragile X Syndrome (FXS) model-by examining both behavioral and neuronal phenotypes. We show that BPA induces hyperactivity in larvae, increases repetitive grooming behavior in adults, reduces courtship behavior, impairs axon guidance in the mushroom body, and disrupts neural stem cell development in the w1118 genetic strain. Remarkably, for every behavioral and neuronal phenotype examined, the impact of BPA in FXS flies was either insignificant or contrasted with the phenotypes observed in the w1118 strain. This data indicates that the neurodevelopmental impacts of BPA can vary widely depending on genetic background and suggests BPA may elicit a gene-environment interaction with Drosophila fragile X mental retardation 1 (dFmr1)-the ortholog of human FMR1, which causes Fragile X Syndrome and is associated with autism spectrum disorder.
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Affiliation(s)
- U Nguyen
- Department of Biological Sciences, California State University, Sacramento, 6000 J Street, Sacramento, CA, 95819, United States
| | - B Tinsley
- Department of Biological Sciences, California State University, Sacramento, 6000 J Street, Sacramento, CA, 95819, United States
| | - Y Sen
- Department of Biological Sciences, California State University, Sacramento, 6000 J Street, Sacramento, CA, 95819, United States
| | - J Stein
- Department of Biological Sciences, California State University, Sacramento, 6000 J Street, Sacramento, CA, 95819, United States
| | - Y Palacios
- Department of Biological Sciences, California State University, Sacramento, 6000 J Street, Sacramento, CA, 95819, United States
| | - A Ceballos
- Department of Biological Sciences, California State University, Sacramento, 6000 J Street, Sacramento, CA, 95819, United States
| | - C Welch
- Department of Biological Sciences, California State University, Sacramento, 6000 J Street, Sacramento, CA, 95819, United States
| | - K Nzenkue
- Department of Biological Sciences, California State University, Sacramento, 6000 J Street, Sacramento, CA, 95819, United States
| | - A Penn
- Department of Biological Sciences, California State University, Sacramento, 6000 J Street, Sacramento, CA, 95819, United States
| | - L Murphy
- Department of Biological Sciences, California State University, Sacramento, 6000 J Street, Sacramento, CA, 95819, United States
| | - K Leodones
- Department of Biological Sciences, California State University, Sacramento, 6000 J Street, Sacramento, CA, 95819, United States
| | - J Casiquin
- Department of Biological Sciences, California State University, Sacramento, 6000 J Street, Sacramento, CA, 95819, United States
| | - I Ivory
- Department of Biological Sciences, California State University, Sacramento, 6000 J Street, Sacramento, CA, 95819, United States
| | - K Ghenta
- Department of Biological Sciences, California State University, Sacramento, 6000 J Street, Sacramento, CA, 95819, United States
| | - K Danziger
- Department of Biological Sciences, California State University, Sacramento, 6000 J Street, Sacramento, CA, 95819, United States
| | - E Widman
- Department of Biological Sciences, California State University, Sacramento, 6000 J Street, Sacramento, CA, 95819, United States
| | - J Newman
- Department of Biological Sciences, California State University, Sacramento, 6000 J Street, Sacramento, CA, 95819, United States
| | - M Triplehorn
- Department of Biological Sciences, California State University, Sacramento, 6000 J Street, Sacramento, CA, 95819, United States
| | - Z Hindi
- Department of Biological Sciences, California State University, Sacramento, 6000 J Street, Sacramento, CA, 95819, United States
| | - K Mulligan
- Department of Biological Sciences, California State University, Sacramento, 6000 J Street, Sacramento, CA, 95819, United States.
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16
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Wang X, Kohl A, Yu X, Zorio DAR, Klar A, Sela-Donenfeld D, Wang Y. Temporal-specific roles of fragile X mental retardation protein in the development of the hindbrain auditory circuit. Development 2020; 147:dev.188797. [PMID: 32747436 DOI: 10.1242/dev.188797] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Accepted: 06/29/2020] [Indexed: 01/01/2023]
Abstract
Fragile X mental retardation protein (FMRP) is an RNA-binding protein abundant in the nervous system. Functional loss of FMRP leads to sensory dysfunction and severe intellectual disabilities. In the auditory system, FMRP deficiency alters neuronal function and synaptic connectivity and results in perturbed processing of sound information. Nevertheless, roles of FMRP in embryonic development of the auditory hindbrain have not been identified. Here, we developed high-specificity approaches to genetically track and manipulate throughout development of the Atoh1+ neuronal cell type, which is highly conserved in vertebrates, in the cochlear nucleus of chicken embryos. We identified distinct FMRP-containing granules in the growing axons of Atoh1+ neurons and post-migrating NM cells. FMRP downregulation induced by CRISPR/Cas9 and shRNA techniques resulted in perturbed axonal pathfinding, delay in midline crossing, excess branching of neurites, and axonal targeting errors during the period of circuit development. Together, these results provide the first in vivo identification of FMRP localization and actions in developing axons of auditory neurons, and demonstrate the importance of investigating early embryonic alterations toward understanding the pathogenesis of neurodevelopmental disorders.
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Affiliation(s)
- Xiaoyu Wang
- Department of Biomedical Sciences, Program in Neuroscience, Florida State University College of Medicine, Tallahassee, FL 32306, USA.,Division of Histology & Embryology, Key Laboratory for Regenerative Medicine of the Ministry of Education, Medical College, Jinan University, Guangzhou 510632, China
| | - Ayelet Kohl
- Koret School of Veterinary Medicine, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel
| | - Xiaoyan Yu
- Department of Biomedical Sciences, Program in Neuroscience, Florida State University College of Medicine, Tallahassee, FL 32306, USA
| | - Diego A R Zorio
- Department of Biomedical Sciences, Program in Neuroscience, Florida State University College of Medicine, Tallahassee, FL 32306, USA
| | - Avihu Klar
- Department of Medical Neurobiology IMRIC, Hebrew University Medical School, Jerusalem 91120, Israel
| | - Dalit Sela-Donenfeld
- Koret School of Veterinary Medicine, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel
| | - Yuan Wang
- Department of Biomedical Sciences, Program in Neuroscience, Florida State University College of Medicine, Tallahassee, FL 32306, USA
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17
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Telias M. Pharmacological Treatments for Fragile X Syndrome Based on Synaptic Dysfunction. Curr Pharm Des 2020; 25:4394-4404. [PMID: 31682210 DOI: 10.2174/1381612825666191102165206] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2019] [Accepted: 10/31/2019] [Indexed: 12/29/2022]
Abstract
BACKGROUND Fragile X syndrome (FXS) is the most common form of monogenic hereditary cognitive impairment, including intellectual disability, autism, hyperactivity, and epilepsy. METHODS This article reviews the literature pertaining to the role of synaptic dysfunction in FXS. RESULTS In FXS, synaptic dysfunction alters the excitation-inhibition ratio, dysregulating molecular and cellular processes underlying cognition, learning, memory, and social behavior. Decades of research have yielded important hypotheses that could explain, at least in part, the development of these neurological disorders in FXS patients. However, the main goal of translating lab research in animal models to pharmacological treatments in the clinic has been so far largely unsuccessful, leaving FXS a still incurable disease. CONCLUSION In this concise review, we summarize and analyze the main hypotheses proposed to explain synaptic dysregulation in FXS, by reviewing the scientific evidence that led to pharmaceutical clinical trials and their outcome.
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Affiliation(s)
- Michael Telias
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA, United States
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18
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Telias M. Molecular Mechanisms of Synaptic Dysregulation in Fragile X Syndrome and Autism Spectrum Disorders. Front Mol Neurosci 2019; 12:51. [PMID: 30899214 PMCID: PMC6417395 DOI: 10.3389/fnmol.2019.00051] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Accepted: 02/12/2019] [Indexed: 12/21/2022] Open
Abstract
Fragile X syndrome (FXS) is the most common form of monogenic hereditary cognitive impairment. FXS patient exhibit a high comorbidity rate with autism spectrum disorders (ASDs). This makes FXS a model disease for understanding how synaptic dysregulation alters neuronal excitability, learning and memory, social behavior, and more. Since 1991, with the discovery of fragile X mental retardation 1 (FMR1) as the sole gene that is mutated in FXS, thousands of studies into the function of the gene and its encoded protein FMR1 protein (FMRP), have been conducted, yielding important information regarding the pathophysiology of the disease, as well as insight into basic synaptic mechanisms that control neuronal networking and circuitry. Among the most important, are molecular mechanisms directly involved in plasticity, including glutamate and γ-aminobutyric acid (GABA) receptors, which can control synaptic transmission and signal transduction, including short- and long-term plasticity. More recently, several novel mechanisms involving growth factors, enzymatic cascades and transcription factors (TFs), have been proposed to have the potential of explaining some of the synaptic dysregulation in FXS. In this review article, I summarize the main mechanisms proposed to underlie synaptic disruption in FXS and ASDs. I focus on studies conducted on the Fmr1 knock-out (KO) mouse model and on FXS-human pluripotent stem cells (hPSCs), emphasizing the differences and even contradictions between mouse and human, whenever possible. As FXS and ASDs are both neurodevelopmental disorders that follow a specific time-course of disease progression, I highlight those studies focusing on the differential developmental regulation of synaptic abnormalities in these diseases.
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Affiliation(s)
- Michael Telias
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, United States
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19
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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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20
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Shinoda Y, Sadakata T, Akagi T, Sakamaki Y, Hashikawa T, Sano Y, Furuichi T. Calcium-dependent activator protein for secretion 2 (CADPS2) deficiency causes abnormal synapse development in hippocampal mossy fiber terminals. Neurosci Lett 2018; 677:65-71. [PMID: 29689341 DOI: 10.1016/j.neulet.2018.04.036] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Revised: 04/06/2018] [Accepted: 04/18/2018] [Indexed: 12/27/2022]
Abstract
Hippocampal mossy fibers (MFs) project from dentate gyrus granule cells onto the CA2-CA3 region. MF-mediated synaptic transmission plays an important role in hippocampal learning and memory. However, the molecular mechanisms underlying MF synaptic development and subsequent functional organization are not fully understood. We previously reported that calcium-dependent activator protein for secretion 2 (CADPS2, also known as CAPS2) regulates the secretion of dense-core vesicles (DCVs). Because CADPS2 is strongly expressed in MF terminals, we hypothesized that CADPS2 regulates the development and functional organization of MF synapses by controlling the secretion of DCVs and their contents. To test this, we compared the synaptic microstructures of hippocampal MF terminals in Cadps2 knockout (KO) mice and wild-type (WT) mice by electron microscopy (EM). On postnatal day 15 (P15), KO mice exhibited morphological abnormalities in MF boutons, including smaller bouton size, a larger number of DCVs and a smaller number of post-synaptic densities (PSDs), compared with WT mice. In adults (P56), MF boutons were larger in KO mice. Synaptic vesicles (SVs) were increased but with a lower density compared with the WT. Furthermore, the number of SVs was decreased near the active zone. Moreover, MF-innervated CA3 postsynapses in KO mice displayed aberrant structures at the postsynaptic density (PSD), with an increased number of PSDs (likely because of a larger number of perforated PSDs), compared with WT mice. Taken together, our findings suggest that CADPS2 plays a critical role in MF synaptic development and functional organization.
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Affiliation(s)
- Yo Shinoda
- Department of Environmental Health, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo 192-0392, Japan; Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, Noda, Chiba 278-8510, Japan; Laboratory for Molecular Neurogenesis, RIKEN Brain Science Institute, Wako, Saitama 351-0198, Japan.
| | - Tetsushi Sadakata
- Laboratory for Molecular Neurogenesis, RIKEN Brain Science Institute, Wako, Saitama 351-0198, Japan; Education and Research Support Center, Gunma University Graduate School of Medicine, Maebashi, Gunma 371-8511, Japan
| | - Takumi Akagi
- Research Resource Center, RIKEN Brain Science Institute, Wako, Saitama 351-0106, Japan; Department of Physiology, Nippon Medical School, Bunkyo-ku, Tokyo 113-8602, Japan
| | - Yuriko Sakamaki
- Research Resource Center, RIKEN Brain Science Institute, Wako, Saitama 351-0106, Japan; Research Core, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Tsutomu Hashikawa
- Research Resource Center, RIKEN Brain Science Institute, Wako, Saitama 351-0106, Japan; Laboratory for Molecular Mechanisms of Thalamus Development, RIKEN Brain Science Institute, Wako, Saitama 351-0198, Japan
| | - Yoshitake Sano
- Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, Noda, Chiba 278-8510, Japan
| | - Teiichi Furuichi
- Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, Noda, Chiba 278-8510, Japan; Laboratory for Molecular Neurogenesis, RIKEN Brain Science Institute, Wako, Saitama 351-0198, Japan.
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21
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De Bruyckere E, Simon R, Nestel S, Heimrich B, Kätzel D, Egorov AV, Liu P, Jenkins NA, Copeland NG, Schwegler H, Draguhn A, Britsch S. Stability and Function of Hippocampal Mossy Fiber Synapses Depend on Bcl11b/Ctip2. Front Mol Neurosci 2018; 11:103. [PMID: 29674952 PMCID: PMC5895709 DOI: 10.3389/fnmol.2018.00103] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Accepted: 03/15/2018] [Indexed: 01/04/2023] Open
Abstract
Structural and functional plasticity of synapses are critical neuronal mechanisms underlying learning and memory. While activity-dependent regulation of synaptic strength has been extensively studied, much less is known about the transcriptional control of synapse maintenance and plasticity. Hippocampal mossy fiber (MF) synapses connect dentate granule cells to CA3 pyramidal neurons and are important for spatial memory formation and consolidation. The transcription factor Bcl11b/Ctip2 is expressed in dentate granule cells and required for postnatal hippocampal development. Ablation of Bcl11b/Ctip2 in the adult hippocampus results in impaired adult neurogenesis and spatial memory. The molecular mechanisms underlying the behavioral impairment remained unclear. Here we show that selective deletion of Bcl11b/Ctip2 in the adult mouse hippocampus leads to a rapid loss of excitatory synapses in CA3 as well as reduced ultrastructural complexity of remaining mossy fiber boutons (MFBs). Moreover, a dramatic decline of long-term potentiation (LTP) of the dentate gyrus-CA3 (DG-CA3) projection is caused by adult loss of Bcl11b/Ctip2. Differential transcriptomics revealed the deregulation of genes associated with synaptic transmission in mutants. Together, our data suggest Bcl11b/Ctip2 to regulate maintenance and function of MF synapses in the adult hippocampus.
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Affiliation(s)
| | - Ruth Simon
- Institute of Molecular and Cellular Anatomy, Ulm University, Ulm, Germany
| | - Sigrun Nestel
- Institute of Anatomy and Cell Biology, Faculty of Medicine, Albert-Ludwigs-University, Freiburg, Germany
| | - Bernd Heimrich
- Institute of Anatomy and Cell Biology, Faculty of Medicine, Albert-Ludwigs-University, Freiburg, Germany
| | - Dennis Kätzel
- Institute of Applied Physiology, Ulm University, Ulm, Germany
| | - Alexei V Egorov
- Institute of Physiology and Pathophysiology, Heidelberg University, Heidelberg, Germany
| | - Pentao Liu
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong
| | - Nancy A Jenkins
- Genetics Department, University of Texas, MD Anderson Cancer Center, Houston, TX, United States
| | - Neal G Copeland
- Genetics Department, University of Texas, MD Anderson Cancer Center, Houston, TX, United States
| | - Herbert Schwegler
- Institute of Anatomy, Otto-von-Guericke-University, Magdeburg, Germany
| | - Andreas Draguhn
- Institute of Physiology and Pathophysiology, Heidelberg University, Heidelberg, Germany
| | - Stefan Britsch
- Institute of Molecular and Cellular Anatomy, Ulm University, Ulm, Germany
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22
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Khayachi A, Gwizdek C, Poupon G, Alcor D, Chafai M, Cassé F, Maurin T, Prieto M, Folci A, De Graeve F, Castagnola S, Gautier R, Schorova L, Loriol C, Pronot M, Besse F, Brau F, Deval E, Bardoni B, Martin S. Sumoylation regulates FMRP-mediated dendritic spine elimination and maturation. Nat Commun 2018; 9:757. [PMID: 29472612 PMCID: PMC5823917 DOI: 10.1038/s41467-018-03222-y] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Accepted: 01/28/2018] [Indexed: 12/02/2022] Open
Abstract
Fragile X syndrome (FXS) is the most frequent inherited cause of intellectual disability and the best-studied monogenic cause of autism. FXS results from the functional absence of the fragile X mental retardation protein (FMRP) leading to abnormal pruning and consequently to synaptic communication defects. Here we show that FMRP is a substrate of the small ubiquitin-like modifier (SUMO) pathway in the brain and identify its active SUMO sites. We unravel the functional consequences of FMRP sumoylation in neurons by combining molecular replacement strategy, biochemical reconstitution assays with advanced live-cell imaging. We first demonstrate that FMRP sumoylation is promoted by activation of metabotropic glutamate receptors. We then show that this increase in sumoylation controls the homomerization of FMRP within dendritic mRNA granules which, in turn, regulates spine elimination and maturation. Altogether, our findings reveal the sumoylation of FMRP as a critical activity-dependent regulatory mechanism of FMRP-mediated neuronal function. Fragile X syndrome patients display intellectual disability and autism, caused by mutations in the RNA-binding protein fragile X mental retardation protein (FMRP). Here, the authors show that FMRP sumoylation is required for regulating spine density and maturation.
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Affiliation(s)
| | - Carole Gwizdek
- Université Côte d'Azur, CNRS, IPMC, 06560, Valbonne, France
| | - Gwénola Poupon
- Université Côte d'Azur, CNRS, IPMC, 06560, Valbonne, France
| | - Damien Alcor
- Université Côte d'Azur, INSERM, C3M, 06200, Nice, France
| | - Magda Chafai
- Université Côte d'Azur, CNRS, IPMC, 06560, Valbonne, France
| | - Frédéric Cassé
- Université Côte d'Azur, CNRS, IPMC, 06560, Valbonne, France
| | - Thomas Maurin
- Université Côte d'Azur, CNRS, IPMC, 06560, Valbonne, France
| | - Marta Prieto
- Université Côte d'Azur, CNRS, IPMC, 06560, Valbonne, France
| | | | | | | | - Romain Gautier
- Université Côte d'Azur, CNRS, IPMC, 06560, Valbonne, France
| | - Lenka Schorova
- Université Côte d'Azur, CNRS, IPMC, 06560, Valbonne, France
| | - Céline Loriol
- Université Côte d'Azur, CNRS, IPMC, 06560, Valbonne, France
| | - Marie Pronot
- Université Côte d'Azur, CNRS, IPMC, 06560, Valbonne, France
| | - Florence Besse
- Université Côte d'Azur, CNRS, INSERM, iBV, 06108, Nice, France
| | - Frédéric Brau
- Université Côte d'Azur, CNRS, IPMC, 06560, Valbonne, France
| | - Emmanuel Deval
- Université Côte d'Azur, CNRS, IPMC, 06560, Valbonne, France
| | - Barbara Bardoni
- Université Côte d'Azur, INSERM, CNRS, IPMC, 06560, Valbonne, France
| | - Stéphane Martin
- Université Côte d'Azur, INSERM, CNRS, IPMC, 06560, Valbonne, France.
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23
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Mulholland PJ, Teppen TL, Miller KM, Sexton HG, Pandey SC, Swartzwelder HS. Donepezil Reverses Dendritic Spine Morphology Adaptations and Fmr1 Epigenetic Modifications in Hippocampus of Adult Rats After Adolescent Alcohol Exposure. Alcohol Clin Exp Res 2018; 42:706-717. [PMID: 29336496 DOI: 10.1111/acer.13599] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Accepted: 01/08/2018] [Indexed: 12/12/2022]
Abstract
BACKGROUND Adolescent intermittent ethanol (AIE) exposure produces persistent impairments in cholinergic and epigenetic signaling and alters markers of synapses in the hippocampal formation, effects that are thought to drive hippocampal dysfunction in adult rodents. Donepezil (Aricept), a cholinesterase inhibitor, is used clinically to ameliorate memory-related cognitive deficits. Given that donepezil also prevents morphological impairment in preclinical models of neuropsychiatric disorders, we investigated the ability of donepezil to reverse morphological and epigenetic adaptations in the hippocampus of adult rats exposed to AIE. Because of the known relationship between dendritic spine density and morphology with the fragile X mental retardation 1 (Fmr1) gene, we also assessed Fmr1 expression and its epigenetic regulation in hippocampus after AIE and donepezil pretreatment. METHODS Adolescent rats were administered intermittent ethanol for 16 days starting on postnatal day 30. Rats were treated with donepezil (2.5 mg/kg) once a day for 4 days starting 20 days after the completion of AIE exposure. Brains were dissected out after the fourth donepezil dose, and spine analysis was completed in dentate gyrus granule neurons. A separate cohort of rats, treated identically, was used for molecular studies. RESULTS AIE exposure significantly reduced dendritic spine density and altered morphological characteristics of subclasses of dendritic spines. AIE exposure also increased mRNA levels and H3-K27 acetylation occupancy of the Fmr1 gene in hippocampus. Treatment of AIE-exposed adult rats with donepezil reversed both the dendritic spine adaptations and epigenetic modifications and expression of Fmr1. CONCLUSIONS These findings indicate that AIE produces long-lasting decreases in dendritic spine density and changes in Fmr1 gene expression in the hippocampal formation, suggesting morphological and epigenetic mechanisms underlying previously reported behavioral deficits after AIE. The reversal of these effects by subchronic, post-AIE donepezil treatment indicates that these AIE effects can be reversed by up-regulating cholinergic function.
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Affiliation(s)
- Patrick J Mulholland
- Departments of Neuroscience and Psychiatry & Behavioral Sciences, Charleston Alcohol Research Center, Charleston, South Carolina
| | - Tara L Teppen
- Center for Alcohol Research in Epigenetics, Department of Psychiatry, University of Illinois at Chicago and Jesse Brown VA Medical Center, Chicago, Illinois
| | - Kelsey M Miller
- Department of Psychiatry and Behavioral Sciences, Duke University Medical Center and Durham VA Medical Center, Durham, North Carolina
| | - Hannah G Sexton
- Department of Psychiatry and Behavioral Sciences, Duke University Medical Center and Durham VA Medical Center, Durham, North Carolina
| | - Subhash C Pandey
- Center for Alcohol Research in Epigenetics, Department of Psychiatry, University of Illinois at Chicago and Jesse Brown VA Medical Center, Chicago, Illinois
| | - H Scott Swartzwelder
- Department of Psychiatry and Behavioral Sciences, Duke University Medical Center and Durham VA Medical Center, Durham, North Carolina
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24
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Smidak R, Sialana FJ, Kristofova M, Stojanovic T, Rajcic D, Malikovic J, Feyissa DD, Korz V, Hoeger H, Wackerlig J, Mechtcheriakova D, Lubec G. Reduced Levels of the Synaptic Functional Regulator FMRP in Dentate Gyrus of the Aging Sprague-Dawley Rat. Front Aging Neurosci 2017; 9:384. [PMID: 29218006 PMCID: PMC5703695 DOI: 10.3389/fnagi.2017.00384] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Accepted: 11/09/2017] [Indexed: 11/15/2022] Open
Abstract
Fragile X mental retardation protein (FMRP) encoded by Fragile X mental retardation 1 (FMR1) gene is a RNA-binding regulator of mRNA translation, transport and stability with multiple targets responsible for proper synaptic function. Epigenetic silencing of FMR1 gene expression leads to the development of Fragile X syndrome (FXS) that is characterized by intellectual disability and other behavioral problems including autism. In the rat FXS model, the lack of FMRP caused a deficit in hippocampal-dependent memory. However, the hippocampal changes of FMRP in aging rats are not fully elucidated. The current study addresses the changes in FMRP levels in dentate gyrus (DG) from young (17 weeks) and aging (22 months) Sprague – Dawley rats. The aging animal group showed significant decline in spatial reference memory. Protein samples from five rats per each group were analyzed by quantitative proteomic analysis resulting in 153 significantly changed proteins. FMRP showed significant reduction in aging animals which was confirmed by immunoblotting and immunofluorescence microscopy. Furthermore, bioinformatic analysis of the differential protein dataset revealed several functionally related protein groups with individual interactions with FMRP. These include high representation of the RNA translation and processing machinery connected to FMRP and other RNA-binding regulators including CAPRIN1, the members of Pumilio (PUM) and CUG-BP, Elav-like (CELF) family, and YTH N(6)-methyladenosine RNA-binding proteins (YTHDF). The results of the current study point to the important role of FMRP and regulation of RNA processing in the rat DG and memory decline during the aging process.
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Affiliation(s)
- Roman Smidak
- Department of Pharmaceutical Chemistry, Faculty of Life Sciences, University of Vienna, Vienna, Austria
| | - Fernando J Sialana
- Department of Pharmaceutical Chemistry, Faculty of Life Sciences, University of Vienna, Vienna, Austria
| | - Martina Kristofova
- Department of Pharmaceutical Chemistry, Faculty of Life Sciences, University of Vienna, Vienna, Austria
| | - Tamara Stojanovic
- Department of Pharmaceutical Chemistry, Faculty of Life Sciences, University of Vienna, Vienna, Austria
| | - Dragana Rajcic
- Department of Pharmaceutical Chemistry, Faculty of Life Sciences, University of Vienna, Vienna, Austria
| | - Jovana Malikovic
- Department of Pharmaceutical Chemistry, Faculty of Life Sciences, University of Vienna, Vienna, Austria
| | - Daniel D Feyissa
- Department of Pharmaceutical Chemistry, Faculty of Life Sciences, University of Vienna, Vienna, Austria
| | - Volker Korz
- Core Unit of Biomedical Research, Division of Laboratory Animal Science and Genetics, Medical University of Vienna, Vienna, Austria
| | - Harald Hoeger
- Core Unit of Biomedical Research, Division of Laboratory Animal Science and Genetics, Medical University of Vienna, Vienna, Austria
| | - Judit Wackerlig
- Department of Pharmaceutical Chemistry, Faculty of Life Sciences, University of Vienna, Vienna, Austria
| | - Diana Mechtcheriakova
- Department of Pathophysiology and Allergy Research, Medical University of Vienna, Vienna, Austria
| | - Gert Lubec
- Department of Pharmaceutical Chemistry, Faculty of Life Sciences, University of Vienna, Vienna, Austria.,Neuroproteomics, Paracelsus Private Medical University, Salzburg, Austria
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25
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Davis JK, Broadie K. Multifarious Functions of the Fragile X Mental Retardation Protein. Trends Genet 2017; 33:703-714. [PMID: 28826631 PMCID: PMC5610095 DOI: 10.1016/j.tig.2017.07.008] [Citation(s) in RCA: 81] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Revised: 07/20/2017] [Accepted: 07/24/2017] [Indexed: 01/01/2023]
Abstract
Fragile X syndrome (FXS), a heritable intellectual and autism spectrum disorder (ASD), results from the loss of Fragile X mental retardation protein (FMRP). This neurodevelopmental disease state exhibits neural circuit hyperconnectivity and hyperexcitability. Canonically, FMRP functions as an mRNA-binding translation suppressor, but recent findings have enormously expanded its proposed roles. Although connections between burgeoning FMRP functions remain unknown, recent advances have extended understanding of its involvement in RNA, channel, and protein binding that modulate calcium signaling, activity-dependent critical period development, and the excitation-inhibition (E/I) neural circuitry balance. In this review, we contextualize 3 years of FXS model research. Future directions extrapolated from recent advances focus on discovering links between FMRP roles to determine whether FMRP has a multitude of unrelated functions or whether combinatorial mechanisms can explain its multifaceted existence.
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Affiliation(s)
- Jenna K Davis
- Department of Biological Sciences, Kennedy Center for Research on Human Development, Vanderbilt University, Nashville, TN 37235, USA
| | - Kendal Broadie
- Department of Biological Sciences, Kennedy Center for Research on Human Development, Vanderbilt University, Nashville, TN 37235, USA.
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26
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ESCRT-III Membrane Trafficking Misregulation Contributes To Fragile X Syndrome Synaptic Defects. Sci Rep 2017; 7:8683. [PMID: 28819289 PMCID: PMC5561180 DOI: 10.1038/s41598-017-09103-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Accepted: 07/19/2017] [Indexed: 12/12/2022] Open
Abstract
The leading cause of heritable intellectual disability (ID) and autism spectrum disorders (ASD), Fragile X syndrome (FXS), is caused by loss of the mRNA-binding translational suppressor Fragile X Mental Retardation Protein (FMRP). In the Drosophila FXS disease model, we found FMRP binds shrub mRNA (human Chmp4) to repress Shrub expression, causing overexpression during the disease state early-use critical period. The FXS hallmark is synaptic overelaboration causing circuit hyperconnectivity. Testing innervation of a central brain learning/memory center, we found FMRP loss and Shrub overexpression similarly increase connectivity. The ESCRT-III core protein Shrub has a central role in endosome-to-multivesicular body membrane trafficking, with synaptic requirements resembling FMRP. Consistently, we found FMRP loss and Shrub overexpression similarly elevate endosomes and result in the arrested accumulation of enlarged intraluminal vesicles within synaptic boutons. Importantly, genetic correction of Shrub levels in the FXS model prevents synaptic membrane trafficking defects and strongly restores innervation. These results reveal a new molecular mechanism underpinning the FXS disease state.
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27
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Doll CA, Vita DJ, Broadie K. Fragile X Mental Retardation Protein Requirements in Activity-Dependent Critical Period Neural Circuit Refinement. Curr Biol 2017; 27:2318-2330.e3. [PMID: 28756946 PMCID: PMC5572839 DOI: 10.1016/j.cub.2017.06.046] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Revised: 04/30/2017] [Accepted: 06/19/2017] [Indexed: 12/22/2022]
Abstract
Activity-dependent synaptic remodeling occurs during early-use critical periods, when naive juveniles experience sensory input. Fragile X mental retardation protein (FMRP) sculpts synaptic refinement in an activity sensor mechanism based on sensory cues, with FMRP loss causing the most common heritable autism spectrum disorder (ASD), fragile X syndrome (FXS). In the well-mapped Drosophila olfactory circuitry, projection neurons (PNs) relay peripheral sensory information to the central brain mushroom body (MB) learning/memory center. FMRP-null PNs reduce synaptic branching and enlarge boutons, with ultrastructural and synaptic reconstitution MB connectivity defects. Critical period activity modulation via odorant stimuli, optogenetics, and transgenic tetanus toxin neurotransmission block show that elevated PN activity phenocopies FMRP-null defects, whereas PN silencing causes opposing changes. FMRP-null PNs lose activity-dependent synaptic modulation, with impairments restricted to the critical period. We conclude that FMRP is absolutely required for experience-dependent changes in synaptic connectivity during the developmental critical period of neural circuit optimization for sensory input.
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Affiliation(s)
- Caleb A Doll
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37203, USA
| | - Dominic J Vita
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37203, USA
| | - Kendal Broadie
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37203, USA; Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37203, USA; Department of Pharmacology, Vanderbilt University, Nashville, TN 37203, USA; Vanderbilt Kennedy Center for Research on Human Development, Vanderbilt University, Nashville, TN 37203, USA.
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