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D'Antoni S, Spatuzza M, Bonaccorso CM, Catania MV. Role of fragile X messenger ribonucleoprotein 1 in the pathophysiology of brain disorders: a glia perspective. Neurosci Biobehav Rev 2024; 162:105731. [PMID: 38763180 DOI: 10.1016/j.neubiorev.2024.105731] [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: 02/23/2024] [Revised: 05/14/2024] [Accepted: 05/15/2024] [Indexed: 05/21/2024]
Abstract
Fragile X messenger ribonucleoprotein 1 (FMRP) is a widely expressed RNA binding protein involved in several steps of mRNA metabolism. Mutations in the FMR1 gene encoding FMRP are responsible for fragile X syndrome (FXS), a leading genetic cause of intellectual disability and autism spectrum disorder, and fragile X-associated tremor-ataxia syndrome (FXTAS), a neurodegenerative disorder in aging men. Although FMRP is mainly expressed in neurons, it is also present in glial cells and its deficiency or altered expression can affect functions of glial cells with implications for the pathophysiology of brain disorders. The present review focuses on recent advances on the role of glial subtypes, astrocytes, oligodendrocytes and microglia, in the pathophysiology of FXS and FXTAS, and describes how the absence or reduced expression of FMRP in these cells can impact on glial and neuronal functions. We will also briefly address the role of FMRP in radial glial cells and its effects on neural development, and gliomas and will speculate on the role of glial FMRP in other brain disorders.
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Affiliation(s)
- S D'Antoni
- Institute for Biomedical Research and Innovation (IRIB), National Research Council (CNR), Via Paolo Gaifami 18, Catania 95126, Italy
| | - M Spatuzza
- Institute for Biomedical Research and Innovation (IRIB), National Research Council (CNR), Via Paolo Gaifami 18, Catania 95126, Italy
| | - C M Bonaccorso
- Oasi Research Institute - IRCCS, via Conte Ruggero 73, Troina 94018, Italy
| | - M V Catania
- Institute for Biomedical Research and Innovation (IRIB), National Research Council (CNR), Via Paolo Gaifami 18, Catania 95126, Italy.
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2
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Weisz ED, Fenton AR, Jongens TA. PGC-1α integrates insulin signaling with mitochondrial physiology and behavior in a Drosophila model of Fragile X Syndrome. NPJ METABOLIC HEALTH AND DISEASE 2024; 2:2. [PMID: 38741938 PMCID: PMC11090494 DOI: 10.1038/s44324-024-00004-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Accepted: 01/02/2024] [Indexed: 05/16/2024]
Abstract
Fragile X Syndrome (FXS) is the most prevalent monogenetic form of intellectual disability and autism. Recently, dysregulation of insulin signaling (IS) and aberrations in mitochondrial function have emerged as robust, evolutionarily conserved components of FXS pathophysiology. However, the mechanisms by which altered IS and mitochondrial dysfunction impact behavior in the context of FXS remain elusive. Here, we show that normalization of IS improves mitochondrial volume and function in flies that lack expression of dfmr1, the Drosophila homolog of the causal gene of FXS in humans. Further, we demonstrate that dysregulation of IS underlies diminished expression of the mitochondrial master regulator PGC-1α/Spargel in dfmr1 mutant flies. These results are behaviorally relevant, as we show that pan-neuronal augmentation of PGC-1α/Spargel improves circadian behavior in dfmr1 mutants. Notably, we also show that modulation of PGC-1α/Spargel expression in wild-type flies phenocopies the dfmr1 mutant circadian defect. Taken together, the results presented herein provide a mechanistic link between mitochondrial function and circadian behavior both in FXS pathogenesis as well as more broadly at the interface between metabolism and behavioral output.
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Affiliation(s)
- Eliana D. Weisz
- Department of Genetics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
- Autism Spectrum Program of Excellence, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Adam R. Fenton
- Department of Genetics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Thomas A. Jongens
- Department of Genetics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
- Autism Spectrum Program of Excellence, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
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3
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Song C, Broadie K. Dysregulation of BMP, Wnt, and Insulin Signaling in Fragile X Syndrome. Front Cell Dev Biol 2022; 10:934662. [PMID: 35880195 PMCID: PMC9307498 DOI: 10.3389/fcell.2022.934662] [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: 05/02/2022] [Accepted: 06/06/2022] [Indexed: 01/21/2023] Open
Abstract
Drosophila models of neurological disease contribute tremendously to research progress due to the high conservation of human disease genes, the powerful and sophisticated genetic toolkit, and the rapid generation time. Fragile X syndrome (FXS) is the most prevalent heritable cause of intellectual disability and autism spectrum disorders, and the Drosophila FXS disease model has been critical for the genetic screening discovery of new intercellular secretion mechanisms. Here, we focus on the roles of three major signaling pathways: BMP, Wnt, and insulin-like peptides. We present Drosophila FXS model defects compared to mouse models in stem cells/embryos, the glutamatergic neuromuscular junction (NMJ) synapse model, and the developing adult brain. All three of these secreted signaling pathways are strikingly altered in FXS disease models, giving new mechanistic insights into impaired cellular outcomes and neurological phenotypes. Drosophila provides a powerful genetic screening platform to expand understanding of these secretory mechanisms and to test cellular roles in both peripheral and central nervous systems. The studies demonstrate the importance of exploring broad genetic interactions and unexpected regulatory mechanisms. We discuss a number of research avenues to pursue BMP, Wnt, and insulin signaling in future FXS investigations and the development of potential therapeutics.
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Affiliation(s)
- Chunzhu Song
- Department of Biological Sciences, College of Arts and Science, Vanderbilt University, Nashville, TN, United States
| | - Kendal Broadie
- Department of Biological Sciences, College of Arts and Science, Vanderbilt University, Nashville, TN, United States
- Department of Cell and Developmental Biology, School of Medicine, Vanderbilt University, Nashville, TN, United States
- Kennedy Center for Research on Human Development, Nashville, TN, United States
- Vanderbilt Brain Institute, School of Medicine, Vanderbilt University and Medical Center, Nashville, TN, United States
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4
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Nguyen PK, Cheng LY. Non-autonomous regulation of neurogenesis by extrinsic cues: a Drosophila perspective. OXFORD OPEN NEUROSCIENCE 2022; 1:kvac004. [PMID: 38596708 PMCID: PMC10913833 DOI: 10.1093/oons/kvac004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Revised: 03/20/2022] [Accepted: 03/23/2022] [Indexed: 04/11/2024]
Abstract
The formation of a functional circuitry in the central nervous system (CNS) requires the correct number and subtypes of neural cells. In the developing brain, neural stem cells (NSCs) self-renew while giving rise to progenitors that in turn generate differentiated progeny. As such, the size and the diversity of cells that make up the functional CNS depend on the proliferative properties of NSCs. In the fruit fly Drosophila, where the process of neurogenesis has been extensively investigated, extrinsic factors such as the microenvironment of NSCs, nutrients, oxygen levels and systemic signals have been identified as regulators of NSC proliferation. Here, we review decades of work that explores how extrinsic signals non-autonomously regulate key NSC characteristics such as quiescence, proliferation and termination in the fly.
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Affiliation(s)
- Phuong-Khanh Nguyen
- Peter MacCallum Cancer Centre, Melbourne, Victoria 3000, Australia
- Department of Anatomy and Physiology, The University of Melbourne, Victoria 3010, Australia
| | - Louise Y Cheng
- Peter MacCallum Cancer Centre, Melbourne, Victoria 3000, Australia
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Victoria 3010, Australia
- Department of Anatomy and Physiology, The University of Melbourne, Victoria 3010, Australia
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5
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Manigandan S, Yun JW. Loss of cytoplasmic FMR1-interacting protein 2 (CYFIP2) induces browning in 3T3-L1 adipocytes via repression of GABA-BR and activation of mTORC1. J Cell Biochem 2022; 123:863-877. [PMID: 35233844 DOI: 10.1002/jcb.30231] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2021] [Revised: 02/05/2022] [Accepted: 02/13/2022] [Indexed: 11/11/2022]
Abstract
Obesity and related metabolic disorders are epidemic diseases. Promoting thermogenesis and a functional increase in the browning of white adipocytes may counteract obesity. On the other hand, the molecular mechanism that regulates brown and beige fat-mediated thermogenesis is unclear. This article reports a molecular network led by cytoplasmic FMR1-interacting protein 2 (CYFIP2) that negatively regulates adipocyte browning in white adipocytes. Although the function of CYFIP2 in Fragile X Syndrome (FXS) and autism have been reported, its physiological roles in adipocytes remain elusive. Therefore, this study examined the physiological consequences of its deprivation in cultured 3T3-L1 white adipocytes using loss-of-function studies. Combined real-time quantitative reverse-transcription polymerase chain reaction and immunoblot analysis showed that the loss of CYFIP2 induces fat browning, as evidenced by the gene and protein expression levels of the brown fat-associated markers. A deficiency of CYFIP2 promoted mitochondrial biogenesis and significantly enhanced the expression of the core set beige fat-specific genes (Cd137, Cidea, Cited1, Tbx1, and Tmem26) and proteins (PGC-1α, PRDM16, and UCP1). In addition, a CYFIP2 deficiency promoted lipid catabolism and suppressed adipogenesis, lipogenesis, and autophagy. A mechanistic study showed that the loss of CYFIP2 induces browning in white adipocytes, independently via the activation of mTORC1 and suppression of the GABA-BR signaling pathway. The present data revealed a previously unidentified mechanism of CYFIP2 in the browning of white adipocytes and emphasized the potential of CYFIP2 as a pharmacotherapeutic target for treating obesity and other metabolic disorders.
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Affiliation(s)
- Subramani Manigandan
- Department of Biotechnology, Daegu University, Gyeongsan, Gyeongbuk, Republic of Korea
| | - Jong Won Yun
- Department of Biotechnology, Daegu University, Gyeongsan, Gyeongbuk, Republic of Korea
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6
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The conserved alternative splicing factor caper regulates neuromuscular phenotypes during development and aging. Dev Biol 2021; 473:15-32. [PMID: 33508255 DOI: 10.1016/j.ydbio.2021.01.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 01/18/2021] [Accepted: 01/19/2021] [Indexed: 12/17/2022]
Abstract
RNA-binding proteins play an important role in the regulation of post-transcriptional gene expression throughout the nervous system. This is underscored by the prevalence of mutations in genes encoding RNA splicing factors and other RNA-binding proteins in a number of neurodegenerative and neurodevelopmental disorders. The highly conserved alternative splicing factor Caper is widely expressed throughout the developing embryo and functions in the development of various sensory neural subtypes in the Drosophila peripheral nervous system. Here we find that caper dysfunction leads to aberrant neuromuscular junction morphogenesis, as well as aberrant locomotor behavior during larval and adult stages. Despite its widespread expression, our results indicate that caper function is required to a greater extent within the nervous system, as opposed to muscle, for neuromuscular junction development and for the regulation of adult locomotor behavior. Moreover, we find that Caper interacts with the RNA-binding protein Fmrp to regulate adult locomotor behavior. Finally, we show that caper dysfunction leads to various phenotypes that have both a sex and age bias, both of which are commonly seen in neurodegenerative disorders in humans.
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Lago-Baldaia I, Fernandes VM, Ackerman SD. More Than Mortar: Glia as Architects of Nervous System Development and Disease. Front Cell Dev Biol 2020; 8:611269. [PMID: 33381506 PMCID: PMC7767919 DOI: 10.3389/fcell.2020.611269] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 11/17/2020] [Indexed: 12/12/2022] Open
Abstract
Glial cells are an essential component of the nervous system of vertebrates and invertebrates. In the human brain, glia are as numerous as neurons, yet the importance of glia to nearly every aspect of nervous system development has only been expounded over the last several decades. Glia are now known to regulate neural specification, synaptogenesis, synapse function, and even broad circuit function. Given their ubiquity, it is not surprising that the contribution of glia to neuronal disease pathogenesis is a growing area of research. In this review, we will summarize the accumulated evidence of glial participation in several distinct phases of nervous system development and organization-neural specification, circuit wiring, and circuit function. Finally, we will highlight how these early developmental roles of glia contribute to nervous system dysfunction in neurodevelopmental and neurodegenerative disorders.
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Affiliation(s)
- Inês Lago-Baldaia
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Vilaiwan M. Fernandes
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Sarah D. Ackerman
- Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, OR, United States
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Kennedy T, Rinker D, Broadie K. Genetic background mutations drive neural circuit hyperconnectivity in a fragile X syndrome model. BMC Biol 2020; 18:94. [PMID: 32731855 PMCID: PMC7392683 DOI: 10.1186/s12915-020-00817-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Accepted: 06/19/2020] [Indexed: 01/03/2023] Open
Abstract
BACKGROUND Neural circuits are initially assembled during development when neurons synapse with potential partners and later refined as appropriate connections stabilize into mature synapses while inappropriate contacts are eliminated. Disruptions to this synaptogenic process impair connectivity optimization and can cause neurodevelopmental disorders. Intellectual disability (ID) and autism spectrum disorder (ASD) are often characterized by synaptic overgrowth, with the maintenance of immature or inappropriate synapses. Such synaptogenic defects can occur through mutation of a single gene, such as fragile X mental retardation protein (FMRP) loss causing the neurodevelopmental disorder fragile X syndrome (FXS). FXS represents the leading heritable cause of ID and ASD, but many other genes that play roles in ID and ASD have yet to be identified. RESULTS In a Drosophila FXS disease model, one dfmr150M null mutant stock exhibits previously unreported axonal overgrowths at developmental and mature stages in the giant fiber (GF) escape circuit. These excess axon projections contain both chemical and electrical synapse markers, indicating mixed synaptic connections. Extensive analyses show these supernumerary synapses connect known GF circuit neurons, rather than new, inappropriate partners, indicating hyperconnectivity within the circuit. Despite the striking similarities to well-characterized FXS synaptic defects, this new GF circuit hyperconnectivity phenotype is driven by genetic background mutations in this dfmr150M stock. Similar GF circuit synaptic overgrowth is not observed in independent dfmr1 null alleles. Bulked segregant analysis (BSA) was combined with whole genome sequencing (WGS) to identify the quantitative trait loci (QTL) linked to neural circuit hyperconnectivity. The results reveal 8 QTL associated with inappropriate synapse formation and maintenance in the dfmr150M mutant background. CONCLUSIONS Synaptogenesis is a complex, precisely orchestrated neurodevelopmental process with a large cohort of gene products coordinating the connectivity, synaptic strength, and excitatory/inhibitory balance between neuronal partners. This work identifies a number of genetic regions that contain mutations disrupting proper synaptogenesis within a particularly well-mapped neural circuit. These QTL regions contain potential new genes involved in synapse formation and refinement. Given the similarity of the synaptic overgrowth phenotype to known ID and ASD inherited conditions, identifying these genes should increase our understanding of these devastating neurodevelopmental disease states.
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Affiliation(s)
- Tyler Kennedy
- Department of Biological Sciences, Vanderbilt University and Medical Center, Nashville, TN, 37235, USA
| | - David Rinker
- Department of Biological Sciences, Vanderbilt University and Medical Center, Nashville, TN, 37235, USA
| | - Kendal Broadie
- Department of Biological Sciences, Vanderbilt University and Medical Center, Nashville, TN, 37235, USA.
- Department of Cell and Developmental Biology, Vanderbilt University and Medical Center, Nashville, TN, 37235, USA.
- Vanderbilt Brain Institute, Vanderbilt University and Medical Center, Nashville, TN, 37235, USA.
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Kim T, Song B, Lee IS. Drosophila Glia: Models for Human Neurodevelopmental and Neurodegenerative Disorders. Int J Mol Sci 2020; 21:E4859. [PMID: 32660023 PMCID: PMC7402321 DOI: 10.3390/ijms21144859] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Revised: 06/27/2020] [Accepted: 07/07/2020] [Indexed: 12/12/2022] Open
Abstract
Glial cells are key players in the proper formation and maintenance of the nervous system, thus contributing to neuronal health and disease in humans. However, little is known about the molecular pathways that govern glia-neuron communications in the diseased brain. Drosophila provides a useful in vivo model to explore the conserved molecular details of glial cell biology and their contributions to brain function and disease susceptibility. Herein, we review recent studies that explore glial functions in normal neuronal development, along with Drosophila models that seek to identify the pathological implications of glial defects in the context of various central nervous system disorders.
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Affiliation(s)
| | | | - Im-Soon Lee
- Department of Biological Sciences, Center for CHANS, Konkuk University, Seoul 05029, Korea; (T.K.); (B.S.)
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10
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Waking up quiescent neural stem cells: Molecular mechanisms and implications in neurodevelopmental disorders. PLoS Genet 2020; 16:e1008653. [PMID: 32324743 PMCID: PMC7179833 DOI: 10.1371/journal.pgen.1008653] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Neural stem cells (NSCs) are crucial for development, regeneration, and repair of the nervous system. Most NSCs in mammalian adult brains are quiescent, but in response to extrinsic stimuli, they can exit from quiescence and become reactivated to give rise to new neurons. The delicate balance between NSC quiescence and activation is important for adult neurogenesis and NSC maintenance. However, how NSCs transit between quiescence and activation remains largely elusive. Here, we discuss our current understanding of the molecular mechanisms underlying the reactivation of quiescent NSCs. We review recent advances on signaling pathways originated from the NSC niche and their crosstalk in regulating NSC reactivation. We also highlight new intrinsic paradigms that control NSC reactivation in Drosophila and mammalian systems. We also discuss emerging evidence on modeling human neurodevelopmental disorders using NSCs.
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11
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Leboucher A, Pisani DF, Martinez-Gili L, Chilloux J, Bermudez-Martin P, Van Dijck A, Ganief T, Macek B, Becker JAJ, Le Merrer J, Kooy RF, Amri EZ, Khandjian EW, Dumas ME, Davidovic L. The translational regulator FMRP controls lipid and glucose metabolism in mice and humans. Mol Metab 2019; 21:22-35. [PMID: 30686771 PMCID: PMC6407369 DOI: 10.1016/j.molmet.2019.01.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2018] [Revised: 01/02/2019] [Accepted: 01/08/2019] [Indexed: 01/09/2023] Open
Abstract
Objectives The Fragile X Mental Retardation Protein (FMRP) is a widely expressed RNA-binding protein involved in translation regulation. Since the absence of FMRP leads to Fragile X Syndrome (FXS) and autism, FMRP has been extensively studied in brain. The functions of FMRP in peripheral organs and on metabolic homeostasis remain elusive; therefore, we sought to investigate the systemic consequences of its absence. Methods Using metabolomics, in vivo metabolic phenotyping of the Fmr1-KO FXS mouse model and in vitro approaches, we show that the absence of FMRP induced a metabolic shift towards enhanced glucose tolerance and insulin sensitivity, reduced adiposity, and increased β-adrenergic-driven lipolysis and lipid utilization. Results Combining proteomics and cellular assays, we highlight that FMRP loss increased hepatic protein synthesis and impacted pathways notably linked to lipid metabolism. Mapping metabolomic and proteomic phenotypes onto a signaling and metabolic network, we predicted that the coordinated metabolic response to FMRP loss was mediated by dysregulation in the abundances of specific hepatic proteins. We experimentally validated these predictions, demonstrating that the translational regulator FMRP associates with a subset of mRNAs involved in lipid metabolism. Finally, we highlight that FXS patients mirror metabolic variations observed in Fmr1-KO mice with reduced circulating glucose and insulin and increased free fatty acids. Conclusions Loss of FMRP results in a widespread coordinated systemic response that notably involves upregulation of protein translation in the liver, increased utilization of lipids, and significant changes in metabolic homeostasis. Our study unravels metabolic phenotypes in FXS and further supports the importance of translational regulation in the homeostatic control of systemic metabolism. Loss of the translational regulator FMRP impacts glucose and lipid homeostasis in mouse and human. FMR1-deficiency modifies blood metabolic markers. Loss of FMRP enhances the insulin response and lipolysis. Loss of FMRP exaggerates hepatic protein synthesis. FMRP controls the translation of key hepatic proteins involved in lipid metabolism.
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Affiliation(s)
- Antoine Leboucher
- Université Côte d'Azur, CNRS, Institut de Pharmacologie Moléculaire et Cellulaire, Valbonne, France
| | - Didier F Pisani
- Université Côte d'Azur, CNRS, Inserm, Institut de Biologie Valrose, Nice, France
| | - Laura Martinez-Gili
- Division of Integrative Systems Medicine and Digestive Diseases, Department of Surgery and Cancer, Imperial College London, Exhibition Road, South Kensington, London SW7 2AZ, United Kingdom
| | - Julien Chilloux
- Division of Integrative Systems Medicine and Digestive Diseases, Department of Surgery and Cancer, Imperial College London, Exhibition Road, South Kensington, London SW7 2AZ, United Kingdom
| | - Patricia Bermudez-Martin
- Université Côte d'Azur, CNRS, Institut de Pharmacologie Moléculaire et Cellulaire, Valbonne, France
| | - Anke Van Dijck
- Department of Medical Genetics, University and University Hospital of Antwerp, Prins Boudewijnlaan 43/6, 2650 Edegem, Belgium
| | | | | | - Jérôme A J Becker
- Physiologie de la Reproduction et des Comportements, INRA UMR-0085, CNRS UMR-7247, Inserm, Université François Rabelais, IFCE, 37380, Nouzilly, France
| | - Julie Le Merrer
- Physiologie de la Reproduction et des Comportements, INRA UMR-0085, CNRS UMR-7247, Inserm, Université François Rabelais, IFCE, 37380, Nouzilly, France
| | - R Frank Kooy
- Department of Medical Genetics, University and University Hospital of Antwerp, Prins Boudewijnlaan 43/6, 2650 Edegem, Belgium
| | - Ez-Zoubir Amri
- Université Côte d'Azur, CNRS, Inserm, Institut de Biologie Valrose, Nice, France
| | - Edouard W Khandjian
- Centre de Recherche CERVO, Institut en Santé Mentale de Québec, PQ, Canada; Département de Psychiatrie et des Neurosciences, Faculté de Médecine, Université Laval, Québec, PQ, Canada
| | - Marc-Emmanuel Dumas
- Division of Integrative Systems Medicine and Digestive Diseases, Department of Surgery and Cancer, Imperial College London, Exhibition Road, South Kensington, London SW7 2AZ, United Kingdom
| | - Laetitia Davidovic
- Université Côte d'Azur, CNRS, Institut de Pharmacologie Moléculaire et Cellulaire, Valbonne, France.
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12
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Drozd M, Bardoni B, Capovilla M. Modeling Fragile X Syndrome in Drosophila. Front Mol Neurosci 2018; 11:124. [PMID: 29713264 PMCID: PMC5911982 DOI: 10.3389/fnmol.2018.00124] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Accepted: 03/29/2018] [Indexed: 01/18/2023] Open
Abstract
Intellectual disability (ID) and autism are hallmarks of Fragile X Syndrome (FXS), a hereditary neurodevelopmental disorder. The gene responsible for FXS is Fragile X Mental Retardation gene 1 (FMR1) encoding the Fragile X Mental Retardation Protein (FMRP), an RNA-binding protein involved in RNA metabolism and modulating the expression level of many targets. Most cases of FXS are caused by silencing of FMR1 due to CGG expansions in the 5'-UTR of the gene. Humans also carry the FXR1 and FXR2 paralogs of FMR1 while flies have only one FMR1 gene, here called dFMR1, sharing the same level of sequence homology with all three human genes, but functionally most similar to FMR1. This enables a much easier approach for FMR1 genetic studies. Drosophila has been widely used to investigate FMR1 functions at genetic, cellular, and molecular levels since dFMR1 mutants have many phenotypes in common with the wide spectrum of FMR1 functions that underlay the disease. In this review, we present very recent Drosophila studies investigating FMRP functions at genetic, cellular, molecular, and electrophysiological levels in addition to research on pharmacological treatments in the fly model. These studies have the potential to aid the discovery of pharmacological therapies for FXS.
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Affiliation(s)
- Małgorzata Drozd
- Université Côte d'Azur, CNRS, IPMC, Valbonne, France.,CNRS LIA (Neogenex), Valbonne, France
| | - Barbara Bardoni
- CNRS LIA (Neogenex), Valbonne, France.,Université Côte d'Azur, INSERM, CNRS, IPMC, Valbonne, France
| | - Maria Capovilla
- Université Côte d'Azur, CNRS, IPMC, Valbonne, France.,CNRS LIA (Neogenex), Valbonne, France
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13
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Li Y, Stockton ME, Bhuiyan I, Eisinger BE, Gao Y, Miller JL, Bhattacharyya A, Zhao X. MDM2 inhibition rescues neurogenic and cognitive deficits in a mouse model of fragile X syndrome. Sci Transl Med 2017; 8:336ra61. [PMID: 27122614 DOI: 10.1126/scitranslmed.aad9370] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2015] [Accepted: 04/08/2016] [Indexed: 12/15/2022]
Abstract
Fragile X syndrome, the most common form of inherited intellectual disability, is caused by loss of the fragile X mental retardation protein (FMRP). However, the mechanism remains unclear, and effective treatment is lacking. We show that loss of FMRP leads to activation of adult mouse neural stem cells (NSCs) and a subsequent reduction in the production of neurons. We identified the ubiquitin ligase mouse double minute 2 homolog (MDM2) as a target of FMRP. FMRP regulates Mdm2 mRNA stability, and loss of FMRP resulted in elevated MDM2 mRNA and protein. Further, we found that increased MDM2 expression led to reduced P53 expression in adult mouse NSCs, leading to alterations in NSC proliferation and differentiation. Treatment with Nutlin-3, a small molecule undergoing clinical trials for treating cancer, specifically inhibited the interaction of MDM2 with P53, and rescued neurogenic and cognitive deficits in FMRP-deficient mice. Our data reveal a potential regulatory role for FMRP in the balance between adult NSC activation and quiescence, and identify a potential new treatment for fragile X syndrome.
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Affiliation(s)
- Yue Li
- Waisman Center, University of Wisconsin-Madison, Madison, WI 53705, USA. Department of Neuroscience, University of Wisconsin-Madison, Madison, WI 53705, USA
| | | | - Ismat Bhuiyan
- Waisman Center, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Brian E Eisinger
- Waisman Center, University of Wisconsin-Madison, Madison, WI 53705, USA. Department of Neuroscience, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Yu Gao
- Waisman Center, University of Wisconsin-Madison, Madison, WI 53705, USA. Department of Neuroscience, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Jessica L Miller
- Waisman Center, University of Wisconsin-Madison, Madison, WI 53705, USA
| | | | - Xinyu Zhao
- Waisman Center, University of Wisconsin-Madison, Madison, WI 53705, USA. Department of Neuroscience, University of Wisconsin-Madison, Madison, WI 53705, USA.
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Monyak RE, Emerson D, Schoenfeld BP, Zheng X, Chambers DB, Rosenfelt C, Langer S, Hinchey P, Choi CH, McDonald TV, Bolduc FV, Sehgal A, McBride SM, Jongens TA. Insulin signaling misregulation underlies circadian and cognitive deficits in a Drosophila fragile X model. Mol Psychiatry 2017; 22:1140-1148. [PMID: 27090306 PMCID: PMC5071102 DOI: 10.1038/mp.2016.51] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/20/2016] [Accepted: 03/01/2016] [Indexed: 12/22/2022]
Abstract
Fragile X syndrome (FXS) is an undertreated neurodevelopmental disorder characterized by low intelligence quotent and a wide range of other symptoms including disordered sleep and autism. Although FXS is the most prevalent inherited cause of intellectual disability, its mechanistic underpinnings are not well understood. Using Drosophila as a model of FXS, we showed that select expression of dfmr1 in the insulin-producing cells (IPCs) of the brain was sufficient to restore normal circadian behavior and to rescue the memory deficits in the fragile X mutant fly. Examination of the insulin signaling (IS) pathway revealed elevated levels of Drosophila insulin-like peptide 2 (Dilp2) in the IPCs and elevated IS in the dfmr1 mutant brain. Consistent with a causal role for elevated IS in dfmr1 mutant phenotypes, the expression of dfmr1 specifically in the IPCs reduced IS, and genetic reduction of the insulin pathway also led to amelioration of circadian and memory defects. Furthermore, we showed that treatment with the FDA-approved drug metformin also rescued memory. Finally, we showed that reduction of IS is required at different time points to rescue circadian behavior and memory. Our results indicate that insulin misregulation underlies the circadian and cognitive phenotypes displayed by the Drosophila fragile X model, and thus reveal a metabolic pathway that can be targeted by new and already approved drugs to treat fragile X patients.
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Affiliation(s)
- Rachel E. Monyak
- Department of Genetics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104-5158
| | - Danielle Emerson
- Department of Genetics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104-5158
| | - Brian P. Schoenfeld
- Department of Genetics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104-5158,Section of Molecular Cardiology, Departments of Medicine and Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Xiangzhong Zheng
- Department of Neuroscience and Howard Hughes Medical Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104-5158
| | - Daniel B. Chambers
- Department of Pediatric Neurology, Center for Neuroscience, University of Alberta, Edmonton, Canada AB T6G 2H7
| | - Cory Rosenfelt
- Department of Pediatric Neurology, Center for Neuroscience, University of Alberta, Edmonton, Canada AB T6G 2H7
| | - Steven Langer
- Department of Pediatric Neurology, Center for Neuroscience, University of Alberta, Edmonton, Canada AB T6G 2H7
| | - Paul Hinchey
- Section of Molecular Cardiology, Departments of Medicine and Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Catherine H. Choi
- Section of Molecular Cardiology, Departments of Medicine and Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461,Department of Dermatology, Drexel University College of Medicine, 219 N. Broad Street, Philadelphia, PA, 19107
| | - Thomas V. McDonald
- Section of Molecular Cardiology, Departments of Medicine and Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Francois V. Bolduc
- Department of Pediatric Neurology, Center for Neuroscience, University of Alberta, Edmonton, Canada AB T6G 2H7
| | - Amita Sehgal
- Department of Neuroscience and Howard Hughes Medical Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104-5158
| | - Sean M.J. McBride
- Department of Psychiatry, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104-5158,To whom correspondence should be addressed: and , phone: 215-573-9332, fax: 215-573-9411
| | - Thomas A. Jongens
- Department of Genetics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104-5158,To whom correspondence should be addressed: and , phone: 215-573-9332, fax: 215-573-9411
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15
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McCoy M, Poliquin-Duchesneau D, Corbin F. Molecular dynamics of FMRP and other RNA-binding proteins in MEG-01 differentiation: the role of mRNP complexes in non-neuronal development. Biochem Cell Biol 2016; 94:597-608. [DOI: 10.1139/bcb-2015-0131] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Asymmetrically differentiating cells are formed with the aid of RNA-binding proteins (RBPs), which can bind, stabilize, regulate, and transport target mRNAs. The loss of RBPs in neurons may lead to severe neurodevelopmental diseases such as the Fragile X Syndrome with the absence of the Fragile X Mental Retardation Protein (FMRP). Because the latter is ubiquitous and shares many similarities with other RBPs involved in the development of peripheral cells, we suggest that FMRP would have a role in the differentiation of all tissues where it is expressed. A MEG-01 differentiation model was, therefore, established to study the global developmental functions of FMRP. PMA induction of MEG-01 cells causes important morphological changes driven by cytoskeletal dynamics. Cytoskeleton change and colocalization analyses were performed by confocal microscopy and sucrose gradient fractionation. Total cellular protein content and de novo synthesis were also analyzed. Microtubular transport mediates the displacement of FMRP and other RBP-containing mRNP complexes towards regions of the cell in development. De novo protein synthesis decreases significantly upon differentiation and total protein content composition is altered. Because those results are comparable with those obtained in neurons, the absence of FMRP would have significant consequences in cells everywhere in the body. The latter should be further investigated to give a better understanding of the systemic implications of imbalances of FMRP and other functionally similar RBPs.
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Affiliation(s)
- M. McCoy
- Department of Biochemistry, Université de Sherbrooke, Sherbrooke, QC, Canada
- Department of Biochemistry, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - D. Poliquin-Duchesneau
- Department of Biochemistry, Université de Sherbrooke, Sherbrooke, QC, Canada
- Department of Biochemistry, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - F. Corbin
- Department of Biochemistry, Université de Sherbrooke, Sherbrooke, QC, Canada
- Department of Biochemistry, Université de Sherbrooke, Sherbrooke, QC, Canada
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16
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Novak SM, Joardar A, Gregorio CC, Zarnescu DC. Regulation of Heart Rate in Drosophila via Fragile X Mental Retardation Protein. PLoS One 2015; 10:e0142836. [PMID: 26571124 PMCID: PMC4646288 DOI: 10.1371/journal.pone.0142836] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 10/27/2015] [Indexed: 01/07/2023] Open
Abstract
RNA binding proteins play a pivotal role in post-transcriptional gene expression regulation, however little is understood about their role in cardiac function. The Fragile X (FraX) family of RNA binding proteins is most commonly studied in the context of neurological disorders, as mutations in Fragile X Mental Retardation 1 (FMR1) are the leading cause of inherited mental retardation. More recently, alterations in the levels of Fragile X Related 1 protein, FXR1, the predominant FraX member expressed in vertebrate striated muscle, have been linked to structural and functional defects in mice and zebrafish models. FraX proteins are established regulators of translation and are known to regulate specific targets in different tissues. To decipher the direct role of FraX proteins in the heart in vivo, we turned to Drosophila, which harbors a sole, functionally conserved and ubiquitously expressed FraX protein, dFmr1. Using classical loss of function alleles as well as muscle specific RNAi knockdown, we show that Drosophila FMRP, dFmr1, is required for proper heart rate during development. Functional analyses in the context of cardiac-specific dFmr1 knockdown by RNAi demonstrate that dFmr1 is required cell autonomously in cardiac cells for regulating heart rate. Interestingly, these functional defects are not accompanied by any obvious structural abnormalities, suggesting that dFmr1 may regulate a different repertoire of targets in Drosophila than in vertebrates. Taken together, our findings support the hypothesis that dFmr1 protein is essential for proper cardiac function and establish the fly as a new model for studying the role(s) of FraX proteins in the heart.
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Affiliation(s)
- Stefanie Mares Novak
- Department of Cellular and Molecular Medicine and Sarver Molecular Cardiovascular Research Program, The University of Arizona, Tucson, Arizona, 85724, United States of America
| | - Archi Joardar
- Department of Molecular and Cellular Biology The University of Arizona, Tucson, Arizona, 85721, United States of America
| | - Carol C. Gregorio
- Department of Cellular and Molecular Medicine and Sarver Molecular Cardiovascular Research Program, The University of Arizona, Tucson, Arizona, 85724, United States of America
| | - Daniela C. Zarnescu
- Department of Molecular and Cellular Biology The University of Arizona, Tucson, Arizona, 85721, United States of America
- * E-mail:
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17
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Pacey LKK, Guan S, Tharmalingam S, Thomsen C, Hampson DR. Persistent astrocyte activation in the fragile X mouse cerebellum. Brain Behav 2015; 5:e00400. [PMID: 26516618 PMCID: PMC4614053 DOI: 10.1002/brb3.400] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Revised: 07/31/2015] [Accepted: 08/21/2015] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Fragile X Syndrome, the most common single gene cause of autism, results from loss of the RNA-binding protein FMRP. Although FMRP is highly expressed in neurons, it has also recently been identified in glia. It has been postulated that in the absence of FMRP, abnormal function of non-neuronal cells may contribute to the pathogenesis of the disorder. We previously demonstrated reduced numbers of oligodendrocyte precursor cells and delayed myelination in the cerebellum of fragile X (Fmr1) knockout mice. METHODS We used quantitative western blotting and immunocytochemistry to examine the status of astrocytes and microglia in the cerebellum of Fmr1 mice during development and in adulthood. RESULTS We report increased expression of the astrocyte marker GFAP in the cerebellum of Fmr1 mice starting in the second postnatal week and persisting in to adulthood. At 2 weeks postnatal, expression of Tumor Necrosis Factor Receptor 2 (TNFR2) and Leukemia Inhibitory Factor (LIF) were elevated in the Fmr1 KO cerebellum. In adults, expression of TNFR2 and the glial marker S100β were also elevated in Fmr1 knockouts, but LIF expression was not different from wild-type mice. We found no evidence of microglial activation or neuroinflammation at any age examined. CONCLUSIONS These findings demonstrate an atypical pattern of astrogliosis in the absence of microglial activation in Fmr1 knockout mouse cerebellum. Enhanced TNFR2 and LIF expression in young mice suggests that changes in the expression of astrocytic proteins may be an attempt to compensate for delayed myelination in the developing cerebellum of Fmr1 mice.
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Affiliation(s)
- Laura K K Pacey
- Department of Pharmaceutical Sciences Leslie Dan Faculty of Pharmacy University of Toronto 144 College Street Toronto Ontario Canada M5S 3M2
| | - Sihui Guan
- Department of Pharmaceutical Sciences Leslie Dan Faculty of Pharmacy University of Toronto 144 College Street Toronto Ontario Canada M5S 3M2
| | - Sujeenthar Tharmalingam
- Department of Pharmaceutical Sciences Leslie Dan Faculty of Pharmacy University of Toronto 144 College Street Toronto Ontario Canada M5S 3M2
| | - Christian Thomsen
- Department of Neuroinflammation Lundbeck Research USA 215 College Road Paramus New Jersey 07652
| | - David R Hampson
- Department of Pharmaceutical Sciences Leslie Dan Faculty of Pharmacy University of Toronto 144 College Street Toronto Ontario Canada M5S 3M2 ; Department of Pharmacology Faculty of Medicine University of Toronto 144 College Street Toronto Ontario Canada M5S 3M2
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18
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Coyne AN, Yamada SB, Siddegowda BB, Estes PS, Zaepfel BL, Johannesmeyer JS, Lockwood DB, Pham LT, Hart MP, Cassel JA, Freibaum B, Boehringer AV, Taylor JP, Reitz AB, Gitler AD, Zarnescu DC. Fragile X protein mitigates TDP-43 toxicity by remodeling RNA granules and restoring translation. Hum Mol Genet 2015; 24:6886-98. [PMID: 26385636 DOI: 10.1093/hmg/ddv389] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Accepted: 09/14/2015] [Indexed: 12/12/2022] Open
Abstract
RNA dysregulation is a newly recognized disease mechanism in amyotrophic lateral sclerosis (ALS). Here we identify Drosophila fragile X mental retardation protein (dFMRP) as a robust genetic modifier of TDP-43-dependent toxicity in a Drosophila model of ALS. We find that dFMRP overexpression (dFMRP OE) mitigates TDP-43 dependent locomotor defects and reduced lifespan in Drosophila. TDP-43 and FMRP form a complex in flies and human cells. In motor neurons, TDP-43 expression increases the association of dFMRP with stress granules and colocalizes with polyA binding protein in a variant-dependent manner. Furthermore, dFMRP dosage modulates TDP-43 solubility and molecular mobility with overexpression of dFMRP resulting in a significant reduction of TDP-43 in the aggregate fraction. Polysome fractionation experiments indicate that dFMRP OE also relieves the translation inhibition of futsch mRNA, a TDP-43 target mRNA, which regulates neuromuscular synapse architecture. Restoration of futsch translation by dFMRP OE mitigates Futsch-dependent morphological phenotypes at the neuromuscular junction including synaptic size and presence of satellite boutons. Our data suggest a model whereby dFMRP is neuroprotective by remodeling TDP-43 containing RNA granules, reducing aggregation and restoring the translation of specific mRNAs in motor neurons.
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Affiliation(s)
- Alyssa N Coyne
- Department of Molecular and Cellular Biology, Department of Neuroscience
| | | | | | | | | | | | - Donovan B Lockwood
- Department of Molecular and Cellular Biology, Department of Neuroscience
| | - Linh T Pham
- Department of Molecular and Cellular Biology
| | - Michael P Hart
- Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA
| | | | - Brian Freibaum
- Department of Neurobiology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Ashley V Boehringer
- Department of Molecular and Cellular Biology, Department of Neuroscience, Department of Neurology, University of Arizona, Tucson, AZ, USA
| | - J Paul Taylor
- Department of Neurobiology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | | | - Aaron D Gitler
- Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA
| | - Daniela C Zarnescu
- Department of Molecular and Cellular Biology, Department of Neuroscience, Department of Neurology, University of Arizona, Tucson, AZ, USA,
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19
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Androschuk A, Al-Jabri B, Bolduc FV. From Learning to Memory: What Flies Can Tell Us about Intellectual Disability Treatment. Front Psychiatry 2015; 6:85. [PMID: 26089803 PMCID: PMC4453272 DOI: 10.3389/fpsyt.2015.00085] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/07/2015] [Accepted: 05/19/2015] [Indexed: 01/13/2023] Open
Abstract
Intellectual disability (ID), previously known as mental retardation, affects 3% of the population and remains without pharmacological treatment. ID is characterized by impaired general mental abilities associated with defects in adaptive function in which onset occurs before 18 years of age. Genetic factors are increasing and being recognized as the causes of severe ID due to increased use of genome-wide screening tools. Unfortunately drug discovery for treatment of ID has not followed the same pace as gene discovery, leaving clinicians, patients, and families without the ability to ameliorate symptoms. Despite this, several model organisms have proven valuable in developing and screening candidate drugs. One such model organism is the fruit fly Drosophila. First, we review the current understanding of memory in human and its model in Drosophila. Second, we describe key signaling pathways involved in ID and memory such as the cyclic adenosine 3',5'-monophosphate (cAMP)-cAMP response element binding protein (CREB) pathway, the regulation of protein synthesis, the role of receptors and anchoring proteins, the role of neuronal proliferation, and finally the role of neurotransmitters. Third, we characterize the types of memory defects found in patients with ID. Finally, we discuss how important insights gained from Drosophila learning and memory could be translated in clinical research to lead to better treatment development.
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Affiliation(s)
- Alaura Androschuk
- Department of Pediatrics, University of Alberta, Edmonton, AB, Canada
| | - Basma Al-Jabri
- Department of Pediatrics, University of Alberta, Edmonton, AB, Canada
| | - Francois V. Bolduc
- Department of Pediatrics, University of Alberta, Edmonton, AB, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
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20
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Weisz ED, Monyak RE, Jongens TA. Deciphering discord: How Drosophila research has enhanced our understanding of the importance of FMRP in different spatial and temporal contexts. Exp Neurol 2015; 274:14-24. [PMID: 26026973 DOI: 10.1016/j.expneurol.2015.05.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Revised: 05/18/2015] [Accepted: 05/23/2015] [Indexed: 01/06/2023]
Abstract
Fragile X Syndrome (FXS) is the most common heritable form of intellectual impairment as well as the leading monogenetic cause of autism. In addition to its canonical definition as a neurodevelopmental disease, recent findings in the clinic suggest that FXS is a systemic disorder that is characterized by a variety of heterogeneous phenotypes. Efforts to study FXS pathogenesis have been aided by the development and characterization of animal models of the disease. Research efforts in Drosophila melanogaster have revealed key insights into the mechanistic underpinnings of FXS. While much remains unknown, it is increasingly apparent that FXS involves a myriad of spatially and temporally specific alterations in cellular function. Consequently, the literature is filled with numerous discordant findings. Researchers and clinicians alike must be cognizant of this dissonance, as it will likely be important for the design of preclinical studies to assess the efficacy of therapeutic strategies to improve the lives of FXS patients.
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Affiliation(s)
- Eliana D Weisz
- Department of Genetics, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, United States
| | - Rachel E Monyak
- Department of Genetics, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, United States
| | - Thomas A Jongens
- Department of Genetics, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, United States.
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21
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Glial cells in neuronal development: recent advances and insights from Drosophila melanogaster. Neurosci Bull 2015; 30:584-94. [PMID: 25015062 DOI: 10.1007/s12264-014-1448-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Accepted: 05/22/2014] [Indexed: 12/30/2022] Open
Abstract
Glia outnumber neurons and are the most abundant cell type in the nervous system. Whereas neurons are the major carriers, transducers, and processors of information, glial cells, once considered mainly to play a passive supporting role, are now recognized for their active contributions to almost every aspect of nervous system development. Recently, insights from the invertebrate organism Drosophila melanogaster have advanced our knowledge of glial cell biology. In particular, findings on neuron-glia interactions via intrinsic and extrinsic mechanisms have shed light on the importance of glia during different stages of neuronal development. Here, we summarize recent advances in understanding the functions of Drosophila glia, which resemble their mammalian counterparts in morphology and function, neural stem-cell conversion, synapse formation, and developmental axon pruning. These discoveries reinforce the idea that glia are substantial players in the developing nervous system and further advance the understanding of mechanisms leading to neurodegeneration.
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22
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Gholizadeh S, Halder SK, Hampson DR. Expression of fragile X mental retardation protein in neurons and glia of the developing and adult mouse brain. Brain Res 2015; 1596:22-30. [DOI: 10.1016/j.brainres.2014.11.023] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2014] [Accepted: 11/10/2014] [Indexed: 01/20/2023]
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23
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Lumaban JG, Nelson DL. The Fragile X proteins Fmrp and Fxr2p cooperate to regulate glucose metabolism in mice. Hum Mol Genet 2014; 24:2175-84. [PMID: 25552647 DOI: 10.1093/hmg/ddu737] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Fragile X syndrome results from loss of FMR1 expression. Individuals with the disorder exhibit not only intellectual disability, but also an array of physical and behavioral abnormalities, including sleep difficulties. Studies in mice demonstrated that Fmr1, along with its paralog Fxr2, regulate circadian behavior, and that their absence disrupts expression and cycling of essential clock mRNAs in the liver. Recent reports have identified circadian genes to be essential for normal metabolism. Here we describe the metabolic defects that arise in mice mutated for both Fmr1 and Fxr2. These mice have reduced fat deposits compared with age- and weight-matched controls. Several metabolic markers show either low levels in plasma or abnormal circadian cycling (or both). Insulin levels are consistently low regardless of light exposure and feeding conditions, and the animals are extremely sensitive to injected insulin. Glucose production from introduced pyruvate and glucagon is impaired and the mice quickly clear injected glucose. These mice also have higher food intake and higher VO2 and VCO2 levels. We analyzed liver expression of genes involved in glucose homeostasis and found several that are expressed differentially in the mutant mice. These results point to the involvement of Fmr1 and Fxr2 in maintaining the normal metabolic state in mice.
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Affiliation(s)
- Jeannette G Lumaban
- Department of Molecular and Human Genetics, Jan and Dan Duncan Neurological Research Institute, Baylor College of Medicine, 1250 Moursund Street, Houston, TX 77030, USA
| | - David L Nelson
- Department of Molecular and Human Genetics, Jan and Dan Duncan Neurological Research Institute, Baylor College of Medicine, 1250 Moursund Street, Houston, TX 77030, USA
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24
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Li Y, Zhao X. Concise review: Fragile X proteins in stem cell maintenance and differentiation. Stem Cells 2014; 32:1724-33. [PMID: 24648324 PMCID: PMC4255947 DOI: 10.1002/stem.1698] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2014] [Revised: 02/18/2014] [Accepted: 03/01/2014] [Indexed: 12/15/2022]
Abstract
Fragile X syndrome (FXS), the most common genetic form of autism spectrum disorder, is caused by deficiency of the fragile X mental retardation protein (FMRP). Despite extensive research and scientific progress, understanding how FMRP regulates brain development and function remains a major challenge. FMRP is a neuronal RNA-binding protein that binds about a third of messenger RNAs in the brain and controls their translation, stability, and cellular localization. The absence of FMRP results in increased protein synthesis, leading to enhanced signaling in a number of intracellular pathways, including the mTOR, mGLuR5, ERK, Gsk3β, PI3K, and insulin pathways. Until recently, FXS was largely considered a deficit of mature neurons; however, a number of new studies have shown that FMRP may also play important roles in stem cells, among them neural stem cells, germline stem cells, and pluripotent stem cells. In this review, we will cover these newly discovered functions of FMRP, as well as the other two fragile X-related proteins, in stem cells. We will also discuss the literature on the use of stem cells, particularly neural stem cells and induced pluripotent stem cells, as model systems for studying the functions of FMRP in neuronal development.
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Affiliation(s)
- Yue Li
- Waisman Center and Department of Neuroscience, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA
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25
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Corty MM, Freeman MR. Cell biology in neuroscience: Architects in neural circuit design: glia control neuron numbers and connectivity. ACTA ACUST UNITED AC 2014; 203:395-405. [PMID: 24217617 PMCID: PMC3824021 DOI: 10.1083/jcb.201306099] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Glia serve many important functions in the mature nervous system. In addition, these diverse cells have emerged as essential participants in nearly all aspects of neural development. Improved techniques to study neurons in the absence of glia, and to visualize and manipulate glia in vivo, have greatly expanded our knowledge of glial biology and neuron-glia interactions during development. Exciting studies in the last decade have begun to identify the cellular and molecular mechanisms by which glia exert control over neuronal circuit formation. Recent findings illustrate the importance of glial cells in shaping the nervous system by controlling the number and connectivity of neurons.
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Affiliation(s)
- Megan M Corty
- Department of Neurobiology, University of Massachusetts Medical School, Howard Hughes Medical Institute, Worcester, MA 01605
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26
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Coutinho-Budd J, Freeman MR. Probing the enigma: unraveling glial cell biology in invertebrates. Curr Opin Neurobiol 2013; 23:1073-9. [PMID: 23896311 DOI: 10.1016/j.conb.2013.07.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Revised: 07/02/2013] [Accepted: 07/02/2013] [Indexed: 12/11/2022]
Abstract
Despite their predominance in the nervous system, the precise ways in which glial cells develop and contribute to overall neural function remain poorly defined in any organism. Investigations in simple model organisms have identified remarkable morphological, molecular, and functional similarities between invertebrate and vertebrate glial subtypes. Invertebrates like Drosophila and Caenorhabditis elegans offer an abundance of tools for in vivo genetic manipulation of single cells or whole populations of glia, ease of access to neural tissues throughout development, and the opportunity for forward genetic analysis of fundamental aspects of glial cell biology. These features suggest that invertebrate model systems have high potential for vastly improving the understanding of glial biology. This review highlights recent work in Drosophila and other invertebrates that reveal new insights into basic mechanisms involved in glial development.
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Affiliation(s)
- Jaeda Coutinho-Budd
- Neurobiology Department, University of Massachusetts Medical School, Worcester, MA 01605, United States
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27
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Baumgartner R, Stocker H, Hafen E. The RNA-binding proteins FMR1, rasputin and caprin act together with the UBA protein lingerer to restrict tissue growth in Drosophila melanogaster. PLoS Genet 2013; 9:e1003598. [PMID: 23874212 PMCID: PMC3708825 DOI: 10.1371/journal.pgen.1003598] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2013] [Accepted: 05/15/2013] [Indexed: 12/19/2022] Open
Abstract
Appropriate expression of growth-regulatory genes is essential to ensure normal animal development and to prevent diseases like cancer. Gene regulation at the levels of transcription and translational initiation mediated by the Hippo and Insulin signaling pathways and by the TORC1 complex, respectively, has been well documented. Whether translational control mediated by RNA-binding proteins contributes to the regulation of cellular growth is less clear. Here, we identify Lingerer (Lig), an UBA domain-containing protein, as growth suppressor that associates with the RNA-binding proteins Fragile X mental retardation protein 1 (FMR1) and Caprin (Capr) and directly interacts with and regulates the RNA-binding protein Rasputin (Rin) in Drosophila melanogaster. lig mutant organs overgrow due to increased proliferation, and a reporter for the JAK/STAT signaling pathway is upregulated in a lig mutant situation. rin, Capr or FMR1 in combination as double mutants, but not the respective single mutants, display lig like phenotypes, implicating a redundant function of Rin, Capr and FMR1 in growth control in epithelial tissues. Thus, Lig regulates cell proliferation during development in concert with Rin, Capr and FMR1. Animal growth is orchestrated by controlled expression of growth-regulatory factors. This regulation is achieved at different molecular levels like transcription, translation initiation, and translational regulation. Whereas transcriptional control and translation initiation of growth components have been well studied, the role of translational control in this process is less well understood. Here, we describe Lingerer (Lig), an UBA domain-containing protein, as a new growth suppressor that associates with the three RNA-binding proteins Fragile X mental retardation protein 1 (FMR1), Rasputin (Rin) and Caprin (Capr). Drosophila FMR1, Rin and Capr orthologs are known translational regulators. In lig mutants and in FMR1, Capr and rin in combination as double mutants, organ size is increased due to excess proliferation. These data unveil a growth-regulatory function of Lig, and a redundant function of the RNA-binding proteins FMR1, Capr and Rin. Our findings demonstrate the involvement of mRNA-binding proteins in epithelial growth control and may also contribute to a better molecular understanding of the Fragile X mental retardation syndrome.
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Affiliation(s)
- Roland Baumgartner
- Institute of Molecular Systems Biology, ETH Zürich, Wolfgang-Pauli-Strasse, Zürich, Switzerland
| | - Hugo Stocker
- Institute of Molecular Systems Biology, ETH Zürich, Wolfgang-Pauli-Strasse, Zürich, Switzerland
| | - Ernst Hafen
- Institute of Molecular Systems Biology, ETH Zürich, Wolfgang-Pauli-Strasse, Zürich, Switzerland
- * E-mail:
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Pacey LKK, Xuan ICY, Guan S, Sussman D, Henkelman RM, Chen Y, Thomsen C, Hampson DR. Delayed myelination in a mouse model of fragile X syndrome. Hum Mol Genet 2013; 22:3920-30. [PMID: 23740941 DOI: 10.1093/hmg/ddt246] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Fragile X Syndrome is the most common inherited cause of autism. Fragile X mental retardation protein (FMRP), which is absent in fragile X, is an mRNA binding protein that regulates the translation of hundreds of different mRNA transcripts. In the adult brain, FMRP is expressed primarily in the neurons; however, it is also expressed in developing glial cells, where its function is not well understood. Here, we show that fragile X (Fmr1) knockout mice display abnormalities in the myelination of cerebellar axons as early as the first postnatal week, corresponding roughly to the equivalent time in human brain development when symptoms of the syndrome first become apparent (1-3 years of age). At postnatal day (PND) 7, diffusion tensor magnetic resonance imaging showed reduced volume of the Fmr1 cerebellum compared with wild-type mice, concomitant with an 80-85% reduction in the expression of myelin basic protein, fewer myelinated axons and reduced thickness of myelin sheaths, as measured by electron microscopy. Both the expression of the proteoglycan NG2 and the number of PDGFRα+/NG2+ oligodendrocyte precursor cells were reduced in the Fmr1 cerebellum at PND 7. Although myelin proteins were still depressed at PND 15, they regained wild-type levels by PND 30. These findings suggest that impaired maturation or function of oligodendrocyte precursor cells induces delayed myelination in the Fmr1 mouse brain. Our results bolster an emerging recognition that white matter abnormalities in early postnatal brain development represent an underlying neurological deficit in Fragile X syndrome.
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Freitas BCG, Trujillo CA, Carromeu C, Yusupova M, Herai RH, Muotri AR. Stem cells and modeling of autism spectrum disorders. Exp Neurol 2012; 260:33-43. [PMID: 23036599 DOI: 10.1016/j.expneurol.2012.09.017] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Accepted: 09/24/2012] [Indexed: 01/21/2023]
Abstract
Human neurons, generated from reprogrammed somatic cells isolated from live patients, bring a new perspective on the understanding of Autism Spectrum Disorders (ASD). The new technology can nicely complement other models for basic research and the development of therapeutic compounds aiming to revert or ameliorate the condition. Here, we discuss recent advances on the use of stem cells and other models to study ASDs, as well as their limitations, implications and future perspectives.
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Affiliation(s)
- Beatriz C G Freitas
- University of California San Diego, School of Medicine, Department of Pediatrics/Rady Children's Hospital San Diego, Department of Cellular & Molecular Medicine, Stem Cell Program, La Jolla, CA 92093, MC 0695, USA
| | - Cleber A Trujillo
- University of California San Diego, School of Medicine, Department of Pediatrics/Rady Children's Hospital San Diego, Department of Cellular & Molecular Medicine, Stem Cell Program, La Jolla, CA 92093, MC 0695, USA
| | - Cassiano Carromeu
- University of California San Diego, School of Medicine, Department of Pediatrics/Rady Children's Hospital San Diego, Department of Cellular & Molecular Medicine, Stem Cell Program, La Jolla, CA 92093, MC 0695, USA
| | - Marianna Yusupova
- University of California San Diego, School of Medicine, Department of Pediatrics/Rady Children's Hospital San Diego, Department of Cellular & Molecular Medicine, Stem Cell Program, La Jolla, CA 92093, MC 0695, USA
| | - Roberto H Herai
- University of California San Diego, School of Medicine, Department of Pediatrics/Rady Children's Hospital San Diego, Department of Cellular & Molecular Medicine, Stem Cell Program, La Jolla, CA 92093, MC 0695, USA
| | - Alysson R Muotri
- University of California San Diego, School of Medicine, Department of Pediatrics/Rady Children's Hospital San Diego, Department of Cellular & Molecular Medicine, Stem Cell Program, La Jolla, CA 92093, MC 0695, USA.
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