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Foster MJ, Chu J, Shaia J, Singh RP, Talcott KE. Prevalence and diversity of retinal disease in adults with Down syndrome. Eye (Lond) 2024:10.1038/s41433-024-03508-0. [PMID: 39613904 DOI: 10.1038/s41433-024-03508-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 08/06/2024] [Accepted: 11/20/2024] [Indexed: 12/01/2024] Open
Abstract
While epidemiologic data exists for some ophthalmic diseases in people with Down Syndrome (DS), like strabismus and amblyopia, no studies explore the prevalence of retinal disease in people with DS on a large scale. This study utilized a literature review and exploratory epidemiology analysis to examine patterns of retinal disease in people with DS. To evaluate previous studies on physiology and/or anatomy in retinal models representing DS or in the retinas of people with DS, all relevant terms related to Down Syndrome, retina, and retinal diseases were searched in PubMed and Scopus. Data from the health platform TriNetX was then utilized to determine the prevalence and prevalence odds ratio (POR) of retinal disorders, including diabetic retinopathy and age-related macular degeneration (AMD), within the U.S. adult population with DS. The final literature review included 28 of 535 screened studies and found that a DS diagnosis was associated with atypical retinal vascularization, retinal thickening, and abnormal neuronal development. Of 55,198,979 individuals included in the population study, 97,795 (0.18%) had a recorded DS diagnosis. Compared to the population without DS, the population with DS had significantly increased PORs for any retinal diagnosis (3.78, 95% CI 3.63-3.93), for 16 of 18 recorded individual retinal diagnoses, and for 4 of 5 major diagnostic categories, including diabetic retinopathy (2.56, 95% CI 2.33-2.82) and macular degeneration (4.01, 95% CI 3.42-4.71). The conclusion is that retinal anomalies common to people with DS likely contribute to higher rates of recorded retinal disease. However, future studies should evaluate this relationship.
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Affiliation(s)
- Michael J Foster
- Case Western Reserve University School of Medicine, Cleveland, OH, USA
- Department of Ophthalmology, Eastern Virginia Medical School, Norfolk, VA, USA
| | - Jeffrey Chu
- Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Jacqueline Shaia
- Case Western Reserve University School of Medicine, Cleveland, OH, USA
- Center for Ophthalmic Bioinformatics, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
| | - Rishi P Singh
- Center for Ophthalmic Bioinformatics, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
- Cleveland Clinic Martin Hospitals, Cleveland Clinic Florida, Stuart, FL, USA
- Cleveland Clinic Cole Eye Institute, Cleveland, OH, USA
- Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH, USA
| | - Katherine E Talcott
- Center for Ophthalmic Bioinformatics, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA.
- Cleveland Clinic Cole Eye Institute, Cleveland, OH, USA.
- Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH, USA.
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2
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Baum ML, Wilton DK, Fox RG, Carey A, Hsu YHH, Hu R, Jäntti HJ, Fahey JB, Muthukumar AK, Salla N, Crotty W, Scott-Hewitt N, Bien E, Sabatini DA, Lanser TB, Frouin A, Gergits F, Håvik B, Gialeli C, Nacu E, Lage K, Blom AM, Eggan K, McCarroll SA, Johnson MB, Stevens B. CSMD1 regulates brain complement activity and circuit development. Brain Behav Immun 2024; 119:317-332. [PMID: 38552925 DOI: 10.1016/j.bbi.2024.03.041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Revised: 02/29/2024] [Accepted: 03/26/2024] [Indexed: 04/16/2024] Open
Abstract
Complement proteins facilitate synaptic elimination during neurodevelopmental pruning, but neural complement regulation is not well understood. CUB and Sushi Multiple Domains 1 (CSMD1) can regulate complement activity in vitro, is expressed in the brain, and is associated with increased schizophrenia risk. Beyond this, little is known about CSMD1 including whether it regulates complement activity in the brain or otherwise plays a role in neurodevelopment. We used biochemical, immunohistochemical, and proteomic techniques to examine the regional, cellular, and subcellular distribution as well as protein interactions of CSMD1 in the brain. To evaluate whether CSMD1 is involved in complement-mediated synapse elimination, we examined Csmd1-knockout mice and CSMD1-knockout human stem cell-derived neurons. We interrogated synapse and circuit development of the mouse visual thalamus, a process that involves complement pathway activity. We also quantified complement deposition on synapses in mouse visual thalamus and on cultured human neurons. Finally, we assessed uptake of synaptosomes by cultured microglia. We found that CSMD1 is present at synapses and interacts with complement proteins in the brain. Mice lacking Csmd1 displayed increased levels of complement component C3, an increased colocalization of C3 with presynaptic terminals, fewer retinogeniculate synapses, and aberrant segregation of eye-specific retinal inputs to the visual thalamus during the critical period of complement-dependent refinement of this circuit. Loss of CSMD1 in vivo enhanced synaptosome engulfment by microglia in vitro, and this effect was dependent on activity of the microglial complement receptor, CR3. Finally, human stem cell-derived neurons lacking CSMD1 were more vulnerable to complement deposition. These data suggest that CSMD1 can function as a regulator of complement-mediated synapse elimination in the brain during development.
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Affiliation(s)
- Matthew L Baum
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA; Department of Genetics, Harvard Medical School, Boston, MA 02115, USA; Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA; MD-PhD Program of Harvard & MIT, Harvard Medical School, Boston, MA 02115, USA
| | - Daniel K Wilton
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Rachel G Fox
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Alanna Carey
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Yu-Han H Hsu
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA; Novo Nordisk Foundation Center for Genomic Mechanisms of Disease, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Ruilong Hu
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA; Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Henna J Jäntti
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Jaclyn B Fahey
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Allie K Muthukumar
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Nikkita Salla
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA; Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - William Crotty
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA; Department of Stem Cell and Regenerative Biology and Harvard Stem Cell Institute, Harvard University, Cambridge, MA 02138, USA
| | - Nicole Scott-Hewitt
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Elizabeth Bien
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
| | - David A Sabatini
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Toby B Lanser
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Arnaud Frouin
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Frederick Gergits
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | | | - Chrysostomi Gialeli
- Division of Medical Protein Chemistry, Department of Translational Medicine, Lund University, S-214 28 Malmö, Sweden; Cardiovascular Research - Translational Studies Research Group, Department of Clinical Sciences, Lund University, S-214 28 Malmö, Sweden
| | - Eugene Nacu
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA; Novo Nordisk Foundation Center for Genomic Mechanisms of Disease, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Kasper Lage
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA; Novo Nordisk Foundation Center for Genomic Mechanisms of Disease, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Anna M Blom
- Division of Medical Protein Chemistry, Department of Translational Medicine, Lund University, S-214 28 Malmö, Sweden
| | - Kevin Eggan
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA; Department of Stem Cell and Regenerative Biology and Harvard Stem Cell Institute, Harvard University, Cambridge, MA 02138, USA
| | - Steven A McCarroll
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA; Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Matthew B Johnson
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA; Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA.
| | - Beth Stevens
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA; Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA; Howard Hughes Medical Institute, USA.
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3
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Hergenreder T, Yang T, Ye B. The role of Down syndrome cell adhesion molecule in Down syndrome. MEDICAL REVIEW (2021) 2024; 4:31-41. [PMID: 38515781 PMCID: PMC10954295 DOI: 10.1515/mr-2023-0056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/04/2023] [Accepted: 01/18/2024] [Indexed: 03/23/2024]
Abstract
Down syndrome (DS) is caused by the presence of an extra copy of the entire or a portion of human chromosome 21 (HSA21). This genomic alteration leads to elevated expression of numerous HSA21 genes, resulting in a variety of health issues in individuals with DS. Among the genes located in the DS "critical region" of HSA21, Down syndrome cell adhesion molecule (DSCAM) plays an important role in neuronal development. There is a growing body of evidence underscoring DSCAM's involvement in various DS-related disorders. This review aims to provide a concise overview of the established functions of DSCAM, with a particular focus on its implications in DS. We delve into the roles that DSCAM plays in DS-associated diseases. In the concluding section of this review, we explore prospective avenues for future research to further unravel DSCAM's role in DS and opportunities for therapeutic treatments.
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Affiliation(s)
- Ty Hergenreder
- Life Sciences Institute and Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
| | - Tao Yang
- Life Sciences Institute and Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
| | - Bing Ye
- Life Sciences Institute and Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
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Zhang C, Yadav S, Speer CM. The synaptic basis of activity-dependent eye-specific competition. Cell Rep 2023; 42:112085. [PMID: 36753422 PMCID: PMC10404640 DOI: 10.1016/j.celrep.2023.112085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 12/23/2022] [Accepted: 01/24/2023] [Indexed: 02/09/2023] Open
Abstract
Binocular vision requires proper developmental wiring of eye-specific inputs to the brain. In the thalamus, axons from the two eyes initially overlap in the dorsal lateral geniculate nucleus and undergo activity-dependent competition to segregate into target domains. Here, we combine eye-specific tract tracing with volumetric super-resolution imaging to measure the nanoscale molecular reorganization of developing retinogeniculate eye-specific synapses in the mouse brain. We show there are eye-specific differences in presynaptic vesicle pool size and vesicle association with the active zone at the earliest stages of retinogeniculate refinement but find no evidence of eye-specific differences in subsynaptic domain number, size, or transsynaptic alignment across development. Genetic disruption of spontaneous retinal activity decreases retinogeniculate synapse density, delays the emergence eye-specific differences in vesicle organization, and disrupts subsynaptic domain maturation. These results suggest that activity-dependent eye-specific presynaptic maturation underlies synaptic competition in the mammalian visual system.
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Affiliation(s)
- Chenghang Zhang
- Department of Biology, University of Maryland, College Park, MD 20742, USA
| | - Swapnil Yadav
- Department of Biology, University of Maryland, College Park, MD 20742, USA
| | - Colenso M Speer
- Department of Biology, University of Maryland, College Park, MD 20742, USA.
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Santos RA, Del Rio R, Alvarez AD, Romero G, Vo BZ, Cohen-Cory S. DSCAM is differentially patterned along the optic axon pathway in the developing Xenopus visual system and guides axon termination at the target. Neural Dev 2022; 17:5. [PMID: 35422013 PMCID: PMC9011933 DOI: 10.1186/s13064-022-00161-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Accepted: 03/17/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The Xenopus retinotectal circuit is organized topographically, where the dorsal-ventral axis of the retina maps respectively on to the ventral-dorsal axis of the tectum; axons from the nasal-temporal axis of the retina project respectively to the caudal-rostral axis of the tectum. Studies throughout the last two decades have shown that mechanisms involving molecular recognition of proper termination domains are at work guiding topographic organization. Such studies have shown that graded distribution of molecular cues is important for topographic mapping. However, the complement of molecular cues organizing topography along the developing optic nerve, and as retinal axons cross the chiasm and navigate towards and innervate their target in the tectum, remains unknown. Down syndrome cell adhesion molecule (DSCAM) has been characterized as a key molecule in axon guidance, making it a strong candidate involved in the topographic organization of retinal fibers along the optic path and at their target. METHODS Using a combination of whole-brain clearing and immunohistochemistry staining techniques we characterized DSCAM expression and the projection of ventral and dorsal retinal fibers starting from the eye, following to the optic nerve and chiasm, and into the terminal target in the optic tectum in Xenopus laevis tadpoles. We then assessed the effects of DSCAM on the establishment of retinotopic maps through spatially and temporally targeted DSCAM knockdown on retinal ganglion cells (RGCs) with axons innervating the optic tectum. RESULTS Highest expression of DSCAM was localized to the ventral posterior region of the optic nerve and chiasm; this expression pattern coincides with ventral fibers derived from ventral RGCs. Targeted downregulation of DSCAM expression on ventral RGCs affected the segregation of medial axon fibers from their dorsal counterparts within the tectal neuropil, indicating that DSCAM plays a role in retinotopic organization. CONCLUSION These findings together with previous studies demonstrating cell-autonomous roles for DSCAM during the development of pre- and postsynaptic arbors in the Xenopus retinotectal circuit indicates that DSCAM exerts multiple roles in coordinating axon targeting and structural connectivity in the developing vertebrate visual system.
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Affiliation(s)
- Rommel Andrew Santos
- Department of Neurobiology and Behavior, University of California Irvine, 2205 McGaugh Hall, Irvine, CA 92697-4550 USA
| | - Rodrigo Del Rio
- Department of Neurobiology and Behavior, University of California Irvine, 2205 McGaugh Hall, Irvine, CA 92697-4550 USA
| | - Alexander Delfin Alvarez
- Department of Neurobiology and Behavior, University of California Irvine, 2205 McGaugh Hall, Irvine, CA 92697-4550 USA
| | - Gabriela Romero
- Department of Neurobiology and Behavior, University of California Irvine, 2205 McGaugh Hall, Irvine, CA 92697-4550 USA
| | - Brandon Zarate Vo
- Department of Neurobiology and Behavior, University of California Irvine, 2205 McGaugh Hall, Irvine, CA 92697-4550 USA
| | - Susana Cohen-Cory
- Department of Neurobiology and Behavior, University of California Irvine, 2205 McGaugh Hall, Irvine, CA 92697-4550 USA
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Moyer AJ, Gardiner K, Reeves RH. All Creatures Great and Small: New Approaches for Understanding Down Syndrome Genetics. Trends Genet 2020; 37:444-459. [PMID: 33097276 DOI: 10.1016/j.tig.2020.09.017] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Revised: 09/17/2020] [Accepted: 09/22/2020] [Indexed: 12/26/2022]
Abstract
Human chromosome 21 (Hsa21) contains more than 500 genes, making trisomy 21 one of the most complex genetic perturbations compatible with life. The ultimate goal of Down syndrome (DS) research is to design therapies that improve quality of life for individuals with DS by understanding which subsets of Hsa21 genes contribute to DS-associated phenotypes throughout the lifetime. However, the complexity of DS pathogenesis has made developing appropriate animal models an ongoing challenge. Here, we examine lessons learned from a variety of model systems, including yeast, nematode, fruit fly, and zebrafish, and discuss emerging methods for creating murine models that better reflect the genetic basis of trisomy 21.
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Affiliation(s)
- Anna J Moyer
- Department of Genetic Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD, USA; Department of Physiology, School of Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Katheleen Gardiner
- Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO, USA (retired)
| | - Roger H Reeves
- Department of Genetic Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD, USA; Department of Physiology, School of Medicine, Johns Hopkins University, Baltimore, MD, USA.
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Laflamme OD, Lemieux M, Thiry L, Bretzner F. DSCAM Mutation Impairs Motor Cortex Network Dynamic and Voluntary Motor Functions. Cereb Cortex 2020; 29:2313-2330. [PMID: 29718256 DOI: 10.1093/cercor/bhy097] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Revised: 04/04/2018] [Accepted: 04/11/2018] [Indexed: 01/25/2023] Open
Abstract
While it is well known that netrin-1 and its receptors UNC5 and UNC40 family members are involved in the normal establishment of the motor cortex and its corticospinal tract, less is known about its other receptor Down syndrome cell adherence molecule (DSCAM). DSCAM is expressed in the developing motor cortex, regulates axonal outgrowth of cortical neurons, and its mutation impairs the dendritic arborization of cortical neurons, thus suggesting that it might be involved in the normal development and functioning of the motor cortex. In comparison to WT littermates, DSCAM2J mutant mice slipped and misplaced their paw while walking on the rungs of a horizontal ladder, and exhibited more difficulties in stepping over an obstacle while walking at slow speed. Anterograde tracing showed a normal pyramidal decussation and corticospinal projection, but a more dorsal distribution of their axonal terminals in the spinal gray matter. Intracortical microstimulations showed a reduced corticospinal and intracortical efficacy, whereas stimulations of the pyramidal tract revealed a normal spinal efficacy and excitability of corticospinal tract axons, thus arguing for a dysfunctional cortical development. Our study reveals impairment of the network dynamics within the motor cortex, reducing corticospinal drive and impairing voluntary locomotor functions upon DSCAM2J mutation.
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Affiliation(s)
- Olivier D Laflamme
- Centre de recherche du Centre Hospitalier Universitaire (CHU) de Québec, CHUL, 2705 Boul. Laurier, Québec, Canada
| | - Maxime Lemieux
- Centre de recherche du Centre Hospitalier Universitaire (CHU) de Québec, CHUL, 2705 Boul. Laurier, Québec, Canada
| | - Louise Thiry
- Centre de recherche du Centre Hospitalier Universitaire (CHU) de Québec, CHUL, 2705 Boul. Laurier, Québec, Canada
| | - Frédéric Bretzner
- Centre de recherche du Centre Hospitalier Universitaire (CHU) de Québec, CHUL, 2705 Boul. Laurier, Québec, Canada.,Faculty of Medicine, Department of Psychiatry and Neurosciences, Université Laval, Québec, Canada
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Chuluun B, Pittaras E, Hong H, Fisher N, Colas D, Ruby NF, Heller HC. Suprachiasmatic lesions restore object recognition in down syndrome model mice. Neurobiol Sleep Circadian Rhythms 2020; 8:100049. [PMID: 32195448 PMCID: PMC7075983 DOI: 10.1016/j.nbscr.2020.100049] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Revised: 02/04/2020] [Accepted: 02/12/2020] [Indexed: 01/03/2023] Open
Abstract
The Ts65Dn mouse is a well-studied model of trisomy 21, Down syndrome. This mouse strain has severe learning disability as measured by several rodent learning tests that depend on hippocampal spatial memory function. Hippocampal long-term potentiation (LTP) is deficient in these mice. Short-term daily treatment with low-dose GABA receptor antagonists rescue spatial learning and LTP in Ts65Dn mice leading to the hypothesis that the learning disability is due to GABAergic over-inhibition of hippocampal circuits. The fact that the GABA receptor antagonists were only effective if delivered during the daily light phase suggested that the source of the excess GABA was controlled directly or indirectly by the circadian system. The central circadian pacemaker of mammals is the suprachiasmatic nucleus (SCN), which is largely a GABAergic nucleus. In this study we investigated whether elimination of the SCN in Ts65Dn mice would restore their ability to form recognition memories as tested by the novel object recognition (NOR) task. Full, but not partial lesions of the SCN of Ts65Dn mice normalized their ability to perform on the NOR test. These results suggest that the circadian system modulates neuroplasticity over the time frame involved in the process of consolidation of recognition memories.
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Zebrafish dscaml1 Deficiency Impairs Retinal Patterning and Oculomotor Function. J Neurosci 2019; 40:143-158. [PMID: 31685652 DOI: 10.1523/jneurosci.1783-19.2019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Revised: 10/15/2019] [Accepted: 10/22/2019] [Indexed: 11/21/2022] Open
Abstract
Down syndrome cell adhesion molecules (dscam and dscaml1) are essential regulators of neural circuit assembly, but their roles in vertebrate neural circuit function are still mostly unexplored. We investigated the functional consequences of dscaml1 deficiency in the larval zebrafish (sexually undifferentiated) oculomotor system, where behavior, circuit function, and neuronal activity can be precisely quantified. Genetic perturbation of dscaml1 resulted in deficits in retinal patterning and light adaptation, consistent with its known roles in mammals. Oculomotor analyses revealed specific deficits related to the dscaml1 mutation, including severe fatigue during gaze stabilization, reduced saccade amplitude and velocity in the light, greater disconjugacy, and impaired fixation. Two-photon calcium imaging of abducens neurons in control and dscaml1 mutant animals confirmed deficits in saccade-command signals (indicative of an impairment in the saccadic premotor pathway), whereas abducens activation by the pretectum-vestibular pathway was not affected. Together, we show that loss of dscaml1 resulted in impairments in specific oculomotor circuits, providing a new animal model to investigate the development of oculomotor premotor pathways and their associated human ocular disorders.SIGNIFICANCE STATEMENT Dscaml1 is a neural developmental gene with unknown behavioral significance. Using the zebrafish model, this study shows that dscaml1 mutants have a host of oculomotor (eye movement) deficits. Notably, the oculomotor phenotypes in dscaml1 mutants are reminiscent of human ocular motor apraxia, a neurodevelopmental disorder characterized by reduced saccade amplitude and gaze stabilization deficits. Population-level recording of neuronal activity further revealed potential subcircuit-specific requirements for dscaml1 during oculomotor behavior. These findings underscore the importance of dscaml1 in the development of visuomotor function and characterize a new model to investigate potential circuit deficits underlying human oculomotor disorders.
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TAFAZOLI A, BEHJATI F, FARHUD DD, ABBASZADEGAN MR. Combination of Genetics and Nanotechnology for Down Syndrome Modification: A Potential Hypothesis and Review of the Literature. IRANIAN JOURNAL OF PUBLIC HEALTH 2019; 48:371-378. [PMID: 31223563 PMCID: PMC6570805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Down syndrome (DS) is one of the most prevalent genetic disorders in humans. The use of new approaches in genetic engineering and nanotechnology methods in combination with natural cellular phenomenon can modify the disease in affected people. We consider two CRISPR/Cas9 systems to cut a specific region from short arm of the chromosome 21 (Chr21) and replace it with a novel designed DNA construct, containing the essential genes in chromatin remodeling for inactivating of an extra Chr21. This requires mimicking of the natural cellular pattern for inactivation of the extra X chromosome in females. By means of controlled dosage of an appropriate Nano-carrier (a surface engineered Poly D, L-lactide-co-glycolide (PLGA) for integrating the relevant construct in Trisomy21 brain cell culture media and then in DS mouse model, we would be able to evaluate the modification and the reduction of the active extra Chr21 and in turn reduce substantial adverse effects of the disease, like intellectual disabilities. The hypothesis and study seek new insights in Down syndrome modification.
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Affiliation(s)
- Alireza TAFAZOLI
- Department of Analysis and Bioanalysis of Medicine, Faculty of Pharmacy with the Division of Laboratory Medicine, Medical University of Bialystok, Bialystok, Poland, Department of Endocrinology, Diabetology and Internal Medicine, Clinical Research Center, Medical University of Bialystok, Bialystok, Poland
| | - Farkhondeh BEHJATI
- Genetics Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
| | - Dariush D. FARHUD
- School of Public Health, Tehran University of Medical Sciences, Tehran, Iran, Department of Basic Sciences, Iranian Academy of Medical Sciences, Tehran, Iran
| | - Mohammad Reza ABBASZADEGAN
- Medical Genetics Research Center, Mashhad University of Medical Sciences, Mashhad, Iran,Corresponding Author:
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Sachse SM, Lievens S, Ribeiro LF, Dascenco D, Masschaele D, Horré K, Misbaer A, Vanderroost N, De Smet AS, Salta E, Erfurth ML, Kise Y, Nebel S, Van Delm W, Plaisance S, Tavernier J, De Strooper B, De Wit J, Schmucker D. Nuclear import of the DSCAM-cytoplasmic domain drives signaling capable of inhibiting synapse formation. EMBO J 2019; 38:embj.201899669. [PMID: 30745319 DOI: 10.15252/embj.201899669] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Revised: 01/04/2019] [Accepted: 01/09/2019] [Indexed: 11/09/2022] Open
Abstract
DSCAM and DSCAML1 are immunoglobulin and cell adhesion-type receptors serving important neurodevelopmental functions including control of axon growth, branching, neurite self-avoidance, and neuronal cell death. The signal transduction mechanisms or effectors of DSCAM receptors, however, remain poorly characterized. We used a human ORFeome library to perform a high-throughput screen in mammalian cells and identified novel cytoplasmic signaling effector candidates including the Down syndrome kinase Dyrk1a, STAT3, USP21, and SH2D2A. Unexpectedly, we also found that the intracellular domains (ICDs) of DSCAM and DSCAML1 specifically and directly interact with IPO5, a nuclear import protein of the importin beta family, via a conserved nuclear localization signal. The DSCAM ICD is released by γ-secretase-dependent cleavage, and both the DSCAM and DSCAML1 ICDs efficiently translocate to the nucleus. Furthermore, RNA sequencing confirms that expression of the DSCAM as well as the DSCAML1 ICDs alone can profoundly alter the expression of genes associated with neuronal differentiation and apoptosis, as well as synapse formation and function. Gain-of-function experiments using primary cortical neurons show that increasing the levels of either the DSCAM or the DSCAML1 ICD leads to an impairment of neurite growth. Strikingly, increased expression of either full-length DSCAM or the DSCAM ICD, but not the DSCAML1 ICD, significantly decreases synapse numbers in primary hippocampal neurons. Taken together, we identified a novel membrane-to-nucleus signaling mechanism by which DSCAM receptors can alter the expression of regulators of neuronal differentiation and synapse formation and function. Considering that chromosomal duplications lead to increased DSCAM expression in trisomy 21, our findings may help uncover novel mechanisms contributing to intellectual disability in Down syndrome.
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Affiliation(s)
- Sonja M Sachse
- VIB Center for Brain & Disease Research, Leuven, Belgium.,Department of Neurosciences, KU Leuven, Leuven, Belgium
| | - Sam Lievens
- VIB Center for Medical Biotechnology, Ghent, Belgium.,Department of Biomolecular Medicine, Ghent University, Ghent, Belgium
| | - Luís F Ribeiro
- VIB Center for Brain & Disease Research, Leuven, Belgium.,Department of Neurosciences, KU Leuven, Leuven, Belgium
| | - Dan Dascenco
- VIB Center for Brain & Disease Research, Leuven, Belgium.,Department of Neurosciences, KU Leuven, Leuven, Belgium
| | - Delphine Masschaele
- VIB Center for Medical Biotechnology, Ghent, Belgium.,Department of Biomolecular Medicine, Ghent University, Ghent, Belgium
| | - Katrien Horré
- VIB Center for Brain & Disease Research, Leuven, Belgium.,Department of Neurosciences, KU Leuven, Leuven, Belgium
| | - Anke Misbaer
- VIB Center for Brain & Disease Research, Leuven, Belgium.,Department of Neurosciences, KU Leuven, Leuven, Belgium
| | - Nele Vanderroost
- VIB Center for Medical Biotechnology, Ghent, Belgium.,Department of Biomolecular Medicine, Ghent University, Ghent, Belgium
| | - Anne Sophie De Smet
- VIB Center for Medical Biotechnology, Ghent, Belgium.,Department of Biomolecular Medicine, Ghent University, Ghent, Belgium
| | - Evgenia Salta
- VIB Center for Brain & Disease Research, Leuven, Belgium.,Department of Neurosciences, KU Leuven, Leuven, Belgium
| | | | - Yoshiaki Kise
- VIB Center for Brain & Disease Research, Leuven, Belgium
| | - Siegfried Nebel
- VIB Center for Brain & Disease Research, Leuven, Belgium.,Department of Neurosciences, KU Leuven, Leuven, Belgium
| | | | | | - Jan Tavernier
- VIB Center for Medical Biotechnology, Ghent, Belgium.,Department of Biomolecular Medicine, Ghent University, Ghent, Belgium
| | - Bart De Strooper
- VIB Center for Brain & Disease Research, Leuven, Belgium.,Department of Neurosciences, KU Leuven, Leuven, Belgium.,Dementia Research Institute, University College London, London, UK
| | - Joris De Wit
- VIB Center for Brain & Disease Research, Leuven, Belgium.,Department of Neurosciences, KU Leuven, Leuven, Belgium
| | - Dietmar Schmucker
- VIB Center for Brain & Disease Research, Leuven, Belgium .,Department of Neurosciences, KU Leuven, Leuven, Belgium
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12
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Moore SW. Advances in understanding the association between Down syndrome and Hirschsprung disease (DS-HSCR). Pediatr Surg Int 2018; 34:1127-1137. [PMID: 30218169 DOI: 10.1007/s00383-018-4344-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 09/10/2018] [Indexed: 02/07/2023]
Abstract
The clinical association between Trisomy 21 (Down syndrome) and aganglionosis (Hirschsprung disease; DS-HSCR) is well-established, being of the order of 5% and remains the most common congenital association with Hirschsprung disease. However, little consensus exists as to the possible etiologic and genetic factors influencing this association. Recent research has identified a number of levels at which development of the enteric nervous system is potentially affected in Trisomy 21. These include a decreased central pool of available neuroblasts for migration into the enteric nervous system, abnormal neuroblast type, poor synaptic nerve function and early germline gene-related influences on the migrating neuroblasts due to genetic mutations of a number of important developmental genes, and possible somatic mutations resulting from alterations in the local tissue microenvironment. In this paper, we review available evidence for this association. In addition, we provide evidence of both germline and somatic gene mutations suggesting causation. Although the picture is complex, recent associations between specific RET proto-oncogene variations have been shown to be significant in Down syndrome patients with Hirschsprung disease, as they probably interfere with vital RET functions in the development of the autonomic and enteric nervous systems, increasing the risk of disturbed normal function. In addition, we explore potential role of other facilitatory influence of other susceptibility genes as well as potential other chromosome 21 gene actions and the microenvironment on the Down syndrome gastro-intestinal tract. The various ways in which trisomy of chromosome influences the enteric nervous system are becoming clearer. The sum of these effects influences the outcome of surgery in Down syndrome patients with Hirschsprung Disease.
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Affiliation(s)
- S W Moore
- Division of Paediatric Surgery, Faculty of Medicine and Health Sciences, University of Stellenbosch, PO Box 241, Cape Town, South Africa.
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13
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DSCAM differentially modulates pre- and postsynaptic structural and functional central connectivity during visual system wiring. Neural Dev 2018; 13:22. [PMID: 30219101 PMCID: PMC6138929 DOI: 10.1186/s13064-018-0118-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Accepted: 08/26/2018] [Indexed: 01/20/2023] Open
Abstract
BACKGROUND Proper patterning of dendritic and axonal arbors is a critical step in the formation of functional neuronal circuits. Developing circuits rely on an array of molecular cues to shape arbor morphology, but the underlying mechanisms guiding the structural formation and interconnectivity of pre- and postsynaptic arbors in real time remain unclear. Here we explore how Down syndrome cell adhesion molecule (DSCAM) differentially shapes the dendritic morphology of central neurons and their presynaptic retinal ganglion cell (RGC) axons in the developing vertebrate visual system. METHODS The cell-autonomous role of DSCAM, in tectal neurons and in RGCs, was examined using targeted single-cell knockdown and overexpression approaches in developing Xenopus laevis tadpoles. Axonal arbors of RGCs and dendritic arbors of tectal neurons were visualized using real-time in vivo confocal microscopy imaging over the course of 3 days. RESULTS In the Xenopus visual system, DSCAM immunoreactivity is present in RGCs, cells in the optic tectum and the tectal neuropil at the time retinotectal synaptic connections are made. Downregulating DSCAM in tectal neurons significantly increased dendritic growth and branching rates while inducing dendrites to take on tortuous paths. Overexpression of DSCAM, in contrast, reduced dendritic branching and growth rate. Functional deficits mediated by tectal DSCAM knockdown were examined using visually guided behavioral assays in swimming tadpoles, revealing irregular behavioral responses to visual stimulus. Functional deficits in visual behavior also corresponded with changes in VGLUT/VGAT expression, markers of excitatory and inhibitory transmission, in the tectum. Conversely, single-cell DSCAM knockdown in the retina revealed that RGC axon arborization at the target is influenced by DSCAM, where axons grew at a slower rate and remained relatively simple. In the retina, dendritic arbors of RGCs were not affected by the reduction of DSCAM expression. CONCLUSIONS Together, our observations implicate DSCAM in the control of both pre- and postsynaptic structural and functional connectivity in the developing retinotectal circuit, where it primarily acts as a neuronal brake to limit and guide postsynaptic dendrite growth of tectal neurons while it also facilitates arborization of presynaptic RGC axons cell autonomously.
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14
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Lowe SA, Hodge JJL, Usowicz MM. A third copy of the Down syndrome cell adhesion molecule (Dscam) causes synaptic and locomotor dysfunction in Drosophila. Neurobiol Dis 2017; 110:93-101. [PMID: 29196216 PMCID: PMC5773243 DOI: 10.1016/j.nbd.2017.11.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Revised: 10/13/2017] [Accepted: 11/27/2017] [Indexed: 02/06/2023] Open
Abstract
Down syndrome (DS) is caused by triplication of chromosome 21 (HSA21). It is characterised by intellectual disability and impaired motor coordination that arise from changes in brain volume, structure and function. However, the contribution of each HSA21 gene to these various phenotypes and to the causal alterations in neuronal and synaptic structure and function are largely unknown. Here we have investigated the effect of overexpression of the HSA21 gene DSCAM (Down syndrome cell adhesion molecule), on glutamatergic synaptic transmission and motor coordination, using Drosophila expressing three copies of Dscam1. Electrophysiological recordings of miniature and evoked excitatory junction potentials at the glutamatergic neuromuscular junction of Drosophila larvae showed that the extra copy of Dscam1 changed the properties of spontaneous and electrically-evoked transmitter release and strengthened short-term synaptic depression during high-frequency firing of the motor nerve. Behavioural analyses uncovered impaired locomotor coordination despite preserved gross motor function. This work identifies DSCAM as a candidate causative gene in DS that is sufficient to modify synaptic transmission and synaptic plasticity and cause a DS behavioural phenotype. Drosophila expressing a third copy of Dscam have altered neuromuscular transmission. Drosophila expressing a third copy of Dscam have deficits in locomotor coordination. Drosophila are a powerful system for studying single-gene effects in Down syndrome.
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Affiliation(s)
- Simon A Lowe
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - James J L Hodge
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, University Walk, Bristol BS8 1TD, UK.
| | - Maria M Usowicz
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, University Walk, Bristol BS8 1TD, UK.
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15
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Guidance of retinal axons in mammals. Semin Cell Dev Biol 2017; 85:48-59. [PMID: 29174916 DOI: 10.1016/j.semcdb.2017.11.027] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2017] [Revised: 11/17/2017] [Accepted: 11/20/2017] [Indexed: 11/21/2022]
Abstract
In order to navigate through the surrounding environment many mammals, including humans, primarily rely on vision. The eye, composed of the choroid, sclera, retinal pigmented epithelium, cornea, lens, iris and retina, is the structure that receives the light and converts it into electrical impulses. The retina contains six major types of neurons involving in receiving and modifying visual information and passing it onto higher visual processing centres in the brain. Visual information is relayed to the brain via the axons of retinal ganglion cells (RGCs), a projection known as the optic pathway. The proper formation of this pathway during development is essential for normal vision in the adult individual. Along this pathway there are several points where visual axons face 'choices' in their direction of growth. Understanding how these choices are made has advanced significantly our knowledge of axon guidance mechanisms. Thus, the development of the visual pathway has served as an extremely useful model to reveal general principles of axon pathfinding throughout the nervous system. However, due to its particularities, some cellular and molecular mechanisms are specific for the visual circuit. Here we review both general and specific mechanisms involved in the guidance of mammalian RGC axons when they are traveling from the retina to the brain to establish precise and stereotyped connections that will sustain vision.
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16
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Simmons AB, Bloomsburg SJ, Sukeena JM, Miller CJ, Ortega-Burgos Y, Borghuis BG, Fuerst PG. DSCAM-mediated control of dendritic and axonal arbor outgrowth enforces tiling and inhibits synaptic plasticity. Proc Natl Acad Sci U S A 2017; 114:E10224-E10233. [PMID: 29114051 PMCID: PMC5703318 DOI: 10.1073/pnas.1713548114] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Mature mammalian neurons have a limited ability to extend neurites and make new synaptic connections, but the mechanisms that inhibit such plasticity remain poorly understood. Here, we report that OFF-type retinal bipolar cells in mice are an exception to this rule, as they form new anatomical connections within their tiled dendritic fields well after retinal maturity. The Down syndrome cell-adhesion molecule (Dscam) confines these anatomical rearrangements within the normal tiled fields, as conditional deletion of the gene permits extension of dendrite and axon arbors beyond these borders. Dscam deletion in the mature retina results in expanded dendritic fields and increased cone photoreceptor contacts, demonstrating that DSCAM actively inhibits circuit-level plasticity. Electrophysiological recordings from Dscam-/- OFF bipolar cells showed enlarged visual receptive fields, demonstrating that expanded dendritic territories comprise functional synapses. Our results identify cell-adhesion molecule-mediated inhibition as a regulator of circuit-level neuronal plasticity in the adult retina.
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Affiliation(s)
- Aaron B Simmons
- Department of Biological Sciences, University of Idaho, Moscow, ID 83844
| | | | - Joshua M Sukeena
- Department of Biological Sciences, University of Idaho, Moscow, ID 83844
| | - Calvin J Miller
- Department of Biological Sciences, University of Idaho, Moscow, ID 83844
| | - Yohaniz Ortega-Burgos
- Department of Chemistry, University of Puerto Rico-Humacao, Humacao Puerto Rico, 00792
| | - Bart G Borghuis
- Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, KY 40202;
| | - Peter G Fuerst
- Department of Biological Sciences, University of Idaho, Moscow, ID 83844;
- Washington-Wyoming-Alaska-Montana-Idaho Medical Education Program, University of Washington School of Medicine, Moscow, ID 83844
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17
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Thiry L, Lemieux M, Bretzner F. Age- and speed-dependent modulation of gaits in DSCAM 2J mutant mice. J Neurophysiol 2017; 119:723-737. [PMID: 29093169 DOI: 10.1152/jn.00471.2017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Gaits depend on the interplay between distributed spinal neural networks, termed central pattern generators, generating rhythmic and coordinated movements, primary afferents, and descending supraspinal inputs. Recent studies demonstrated that the mouse displays a rich repertoire of gaits. Changes in gaits occur in mutant mice lacking particular neurons or molecular signaling pathways implicated in the normal establishment of these neural networks. Given the role of the Down syndrome cell adherence molecule (DSCAM) to the formation and maintenance of spinal interneuronal circuits and sensorimotor integration, we have investigated its functional contribution to gaits over a wide range of locomotor speeds using freely walking mice. We show in this study that the DSCAM2J mutation, while not precluding any gait, impairs the age- and speed-dependent modulation of gaits. It impairs the ability of mice to maintain their locomotion at high treadmill speeds. DSCAM2J mutation induces the dominance of lateral walk over trot and the emergence of aberrant gaits for mice, such as pace and diagonal walk. Gaits were also more labile in DSCAM2J mutant mice, i.e., less stable, less attractive, and less predictable than in their wild-type littermates. Our results suggest that the DSCAM mutation affects the behavioral repertoire of gaits in an age- and speed-dependent manner. NEW & NOTEWORTHY Gaits evolve throughout development, up to adulthood, and according to the genetic background. Using mutant mice lacking DSCAM (a cell adherence molecule associated with Down syndrome), we show that the DSCAM2J mutation alters the repertoire of gaits according to the mouse's age and speed, and prevents fast gaits. Such an incapacity suggests a reorganization of spinal, propriospinal, and supraspinal neuronal circuits underlying locomotor control in DSCAM2J mutant mice.
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Affiliation(s)
- Louise Thiry
- Centre de Recherche du Centre Hospitalier Universitaire de Québec, CHUL-Neurosciences, Quebec City, Quebec , Canada
| | - Maxime Lemieux
- Centre de Recherche du Centre Hospitalier Universitaire de Québec, CHUL-Neurosciences, Quebec City, Quebec , Canada
| | - Frédéric Bretzner
- Centre de Recherche du Centre Hospitalier Universitaire de Québec, CHUL-Neurosciences, Quebec City, Quebec , Canada.,Faculty of Medicine, Department of Psychiatry and Neurosciences, Université Laval , Quebec City, Quebec , Canada
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18
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Activity-Dependent Dysfunction in Visual and Olfactory Sensory Systems in Mouse Models of Down Syndrome. J Neurosci 2017; 37:9880-9888. [PMID: 28899917 DOI: 10.1523/jneurosci.1045-17.2017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Revised: 08/08/2017] [Accepted: 09/05/2017] [Indexed: 02/06/2023] Open
Abstract
Activity-dependent synaptic plasticity plays a critical role in the refinement of circuitry during postnatal development and may be disrupted in conditions that cause intellectual disability, such as Down syndrome (DS). To test this hypothesis, visual cortical plasticity was assessed in Ts65Dn mice that harbor a chromosomal duplication syntenic to human chromosome 21q. We find that Ts65Dn mice demonstrate a defect in ocular dominance plasticity (ODP) following monocular deprivation. This phenotype is similar to that of transgenic mice that express amyloid precursor protein (APP), which is duplicated in DS and in Ts65DN mice; however, normalizing APP gene copy number in Ts65Dn mice fails to rescue plasticity. Ts1Rhr mice harbor a duplication of the telomeric third of the Ts65Dn-duplicated sequence and demonstrate the same ODP defect, suggesting a gene or genes sufficient to drive the phenotype are located in that smaller duplication. In addition, we find that Ts65Dn mice demonstrate an abnormality in olfactory system connectivity, a defect in the refinement of connections to second-order neurons in the olfactory bulb. Ts1Rhr mice do not demonstrate a defect in glomerular refinement, suggesting that distinct genes or sets of genes underlie visual and olfactory system phenotypes. Importantly, these data suggest that developmental plasticity and connectivity are impaired in sensory systems in DS model mice, that such defects may contribute to functional impairment in DS, and that these phenotypes, present in male and female mice, provide novel means for examining the genetic and molecular bases for neurodevelopmental impairment in model mice in vivoSIGNIFICANCE STATEMENT Our understanding of the basis for intellectual impairment in Down syndrome is hindered by the large number of genes duplicated in Trisomy 21 and a lack of understanding of the effect of disease pathology on the function of neural circuits in vivo This work describes early postnatal developmental abnormalities in visual and olfactory sensory systems in Down syndrome model mice, which provide insight into defects in the function of neural circuits in vivo and provide an approach for exploring the genetic and molecular basis for impairment in the disease. In addition, these findings raise the possibility that basic dysfunction in primary sensory circuitry may illustrate mechanisms important for global learning and cognitive impairment in Down syndrome patients.
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19
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Colas D, Chuluun B, Garner CC, Heller HC. Short-term treatment with flumazenil restores long-term object memory in a mouse model of Down syndrome. Neurobiol Learn Mem 2017; 140:11-16. [DOI: 10.1016/j.nlm.2017.02.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2016] [Accepted: 02/10/2017] [Indexed: 01/06/2023]
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20
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DSCAM promotes axon fasciculation and growth in the developing optic pathway. Proc Natl Acad Sci U S A 2017; 114:1702-1707. [PMID: 28137836 DOI: 10.1073/pnas.1618606114] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Although many aspects of optic pathway development are beginning to be understood, the mechanisms promoting the growth of retinal ganglion cell (RGC) axons toward visual targets remain largely unknown. Down syndrome cell adhesion molecule (Dscam) is expressed by mouse RGCs shortly after they differentiate at embryonic day 12 and is essential for multiple aspects of postnatal visual system development. Here we show that Dscam is also required during embryonic development for the fasciculation and growth of RGC axons. Dscam is expressed along the developing optic pathway in a pattern consistent with a role in regulating RGC axon outgrowth. In mice carrying spontaneous mutations in Dscam (Dscamdel17 ; Dscam2J), RGC axons pathfind normally, but growth from the chiasm toward their targets is impaired, resulting in a delay in RGC axons reaching the dorsal thalamus compared with that seen in wild-type littermates. Conversely, Dscam gain of function results in exuberant growth into the dorsal thalamus. The growth of ipsilaterally projecting axons is particularly affected. Axon organization in the optic chiasm and tract and RGC growth cone morphologies are also altered in Dscam mutants. In vitro DSCAM promotes RGC axon growth and fasciculation, and can act independently of cell contact. In vitro and in situ DSCAM is required both in the RGC axons and in their environment for the promotion of axon outgrowth, consistent with a homotypic mode of action. These findings identify DSCAM as a permissive signal that promotes the growth and fasciculation of RGC axons, controlling the timing of when RGC axons reach their targets.
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21
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Lepeta K, Lourenco MV, Schweitzer BC, Martino Adami PV, Banerjee P, Catuara-Solarz S, de La Fuente Revenga M, Guillem AM, Haidar M, Ijomone OM, Nadorp B, Qi L, Perera ND, Refsgaard LK, Reid KM, Sabbar M, Sahoo A, Schaefer N, Sheean RK, Suska A, Verma R, Vicidomini C, Wright D, Zhang XD, Seidenbecher C. Synaptopathies: synaptic dysfunction in neurological disorders - A review from students to students. J Neurochem 2016; 138:785-805. [PMID: 27333343 PMCID: PMC5095804 DOI: 10.1111/jnc.13713] [Citation(s) in RCA: 220] [Impact Index Per Article: 24.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Revised: 06/03/2016] [Accepted: 06/06/2016] [Indexed: 12/12/2022]
Abstract
Synapses are essential components of neurons and allow information to travel coordinately throughout the nervous system to adjust behavior to environmental stimuli and to control body functions, memories, and emotions. Thus, optimal synaptic communication is required for proper brain physiology, and slight perturbations of synapse function can lead to brain disorders. In fact, increasing evidence has demonstrated the relevance of synapse dysfunction as a major determinant of many neurological diseases. This notion has led to the concept of synaptopathies as brain diseases with synapse defects as shared pathogenic features. In this review, which was initiated at the 13th International Society for Neurochemistry Advanced School, we discuss basic concepts of synapse structure and function, and provide a critical view of how aberrant synapse physiology may contribute to neurodevelopmental disorders (autism, Down syndrome, startle disease, and epilepsy) as well as neurodegenerative disorders (Alzheimer and Parkinson disease). We finally discuss the appropriateness and potential implications of gathering synapse diseases under a single term. Understanding common causes and intrinsic differences in disease-associated synaptic dysfunction could offer novel clues toward synapse-based therapeutic intervention for neurological and neuropsychiatric disorders. In this Review, which was initiated at the 13th International Society for Neurochemistry (ISN) Advanced School, we discuss basic concepts of synapse structure and function, and provide a critical view of how aberrant synapse physiology may contribute to neurodevelopmental (autism, Down syndrome, startle disease, and epilepsy) as well as neurodegenerative disorders (Alzheimer's and Parkinson's diseases), gathered together under the term of synaptopathies. Read the Editorial Highlight for this article on page 783.
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Affiliation(s)
- Katarzyna Lepeta
- Department of Molecular and Cellular Neurobiology, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland
| | - Mychael V Lourenco
- Institute of Medical Biochemistry Leopoldo de Meis, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Barbara C Schweitzer
- Department for Neurochemistry and Molecular Biology, Leibniz Institute for Neurobiology Magdeburg, Magdeburg, Germany
| | - Pamela V Martino Adami
- Laboratory of Amyloidosis and Neurodegeneration, Fundación Instituto Leloir-IIBBA-CONICET, Buenos Aires, Argentina
| | - Priyanjalee Banerjee
- Department of Biochemistry, Institute of Post Graduate Medical Education & Research, Kolkata, West Bengal, India
| | - Silvina Catuara-Solarz
- Systems Biology Program, Cellular and Systems Neurobiology, Centre for Genomic Regulation, The Barcelona Institute of Science and Technology, Barcelona, Spain.,Universitat Pompeu Fabra, Barcelona, Spain
| | - Mario de La Fuente Revenga
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, VA, United States of America
| | - Alain Marc Guillem
- Laboratorio de Neurotoxicología, Departamento de Toxicología, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, México D.F. 07000, Mexico
| | - Mouna Haidar
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Victoria, Australia
| | - Omamuyovwi M Ijomone
- Department of Human Anatomy, Cross River University of Technology, Okuku Campus, Cross River, Nigeria
| | - Bettina Nadorp
- The Department of Biological Chemistry, The Edmond and Lily Safra Center for Brain Sciences, The Alexander Grass Center for Bioengineering, The Hebrew University of Jerusalem, Israel
| | - Lin Qi
- Laboratory of Molecular Neuro-Oncology, Texas Children's Hospital, Baylor College of Medicine, Houston, TX, United States of America
| | - Nirma D Perera
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Victoria, Australia
| | - Louise K Refsgaard
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
| | - Kimberley M Reid
- Department of Pharmacology, UCL School of Pharmacy, 29-39 Brunswick Square, London, WC1N 1AX, UK
| | - Mariam Sabbar
- Brain Function Research Group, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Arghyadip Sahoo
- Department of Biochemistry, Midnapore Medical College, West Bengal University of Health Sciences, West Bengal, India
| | - Natascha Schaefer
- Institute for Clinical Neurobiology, Julius-Maximilians-University of Wuerzburg, Wuerzburg, Germany
| | - Rebecca K Sheean
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Victoria, Australia
| | - Anna Suska
- Department of Molecular and Cellular Neurobiology, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland
| | - Rajkumar Verma
- Department of Neurosciences Uconn Health Center, Farmington, CT, United States of America
| | | | - Dean Wright
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Victoria, Australia
| | - Xing-Ding Zhang
- Department of Lymphoma/Myeloma, The University of Texas MD Anderson Cancer Center, Houston, TX, United States of America
| | - Constanze Seidenbecher
- Department for Neurochemistry and Molecular Biology, Leibniz Institute for Neurobiology Magdeburg, Magdeburg, Germany. .,Center for Behavioral Brain Sciences (CBBS) Magdeburg, Magdeburg, Germany.
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22
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Fernandes KA, Bloomsburg SJ, Miller CJ, Billingslea SA, Merrill MM, Burgess RW, Libby RT, Fuerst PG. Novel axon projection after stress and degeneration in the Dscam mutant retina. Mol Cell Neurosci 2015; 71:1-12. [PMID: 26691152 DOI: 10.1016/j.mcn.2015.12.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Revised: 11/30/2015] [Accepted: 12/07/2015] [Indexed: 11/17/2022] Open
Abstract
The Down syndrome cell adhesion molecule gene (Dscam) is required for normal dendrite patterning and promotes developmental cell death in the mouse retina. Loss-of-function studies indicate that Dscam is required for refinement of retinal ganglion cell (RGC) axons in the lateral geniculate nucleus, and in this study we report and describe a requirement for Dscam in the maintenance of RGC axon projections within the retina. Mouse Dscam loss of function phenotypes related to retinal ganglion cell axon outgrowth and targeting have not been previously reported, despite the abundance of axon phenotypes reported in Drosophila Dscam1 loss and gain of function models. Analysis of the Dscam deficient retina was performed by immunohistochemistry and Western blot analysis during postnatal development of the retina. Conditional targeting of Dscam and Jun was performed to identify factors underlying axon-remodeling phenotypes. A subset of RGC axons were observed to project and branch extensively within the Dscam mutant retina after eye opening. Axon remodeling was preceded by histological signs of RGC stress. These included neurofilament accumulation, axon swelling, axon blebbing and activation of JUN, JNK and AKT. Novel and extensive projection of RGC axons within the retina was observed after upregulation of these markers, and novel axon projections were maintained to at least one year of age. Further analysis of retinas in which Dscam was conditionally targeted with Brn3b or Pax6α Cre indicated that axon stress and remodeling could occur in the absence of hydrocephalus, which frequently occurs in Dscam mutant mice. Analysis of mice mutant for the cell death gene Bax, which executes much of Dscam dependent cell death, identified a similar axon misprojection phenotype. Deleting Jun and Dscam resulted in increased axon remodeling compared to Dscam or Bax mutants. Retinal ganglion cells have a very limited capacity to regenerate after damage in the adult retina, compared to the extensive projections made in the embryo. In this study we find that DSCAM and JUN limit ectopic growth of RGC axons, thereby identifying these proteins as targets for promoting axon regeneration and reconnection.
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Affiliation(s)
- K A Fernandes
- Flaum Eye Institute, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - S J Bloomsburg
- University of Idaho, Department of Biological Sciences, Moscow, ID 83844, USA
| | - C J Miller
- University of Idaho, Department of Biological Sciences, Moscow, ID 83844, USA
| | - S A Billingslea
- University of Idaho, Department of Biological Sciences, Moscow, ID 83844, USA
| | - M M Merrill
- University of Idaho, Department of Biological Sciences, Moscow, ID 83844, USA
| | - R W Burgess
- The Jackson Laboratory, Bar Harbor, ME 04609, USA
| | - R T Libby
- Flaum Eye Institute, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - P G Fuerst
- University of Idaho, Department of Biological Sciences, Moscow, ID 83844, USA; WWAMI Medical Education Program, Moscow, ID 83844, USA.
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Thiry L, Lemieux M, D Laflamme O, Bretzner F. Role of DSCAM in the development of the spinal locomotor and sensorimotor circuits. J Neurophysiol 2015; 115:1338-54. [PMID: 26655819 DOI: 10.1152/jn.00557.2015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Accepted: 12/06/2015] [Indexed: 11/22/2022] Open
Abstract
Locomotion is controlled by spinal circuits that generate rhythm and coordinate left-right and flexor-extensor motoneuronal activities. The outputs of motoneurons and spinal interneuronal circuits are shaped by sensory feedback, relaying peripheral signals that are critical to the locomotor and postural control. Several studies in invertebrates and vertebrates have argued that the Down syndrome cell adhesion molecule (DSCAM) would play an important role in the normal development of neural circuits through cell spacing and targeting, axonal and dendritic branching, and synapse establishment and maintenance. Although there is evidence that DSCAM is important for the normal development of neural circuits, little is known about its functional contribution to spinal motor circuits. We show here that adult DSCAM(2J) mutant mice, lacking DSCAM, exhibit a higher variability in their locomotor pattern and rhythm during treadmill locomotion. Retrograde tracing studies in neonatal isolated spinal cords show an increased number of spinal commissural interneurons, which likely contributes to reducing the left-right alternation and to increasing the flexor/swing duration during neonatal and adult locomotion. Moreover, our results argue that, by reducing the peripheral excitatory drive onto spinal motoneurons, the DSCAM mutation reduces or abolishes spinal reflexes in both neonatal isolated spinal cords and adult mice, thus likely impairing sensorimotor control. Collectively, our functional, electrophysiological, and anatomical studies suggest that the mammalian DSCAM protein is involved in the normal development of spinal locomotor and sensorimotor circuits.
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Affiliation(s)
- Louise Thiry
- Centre de Recherche du Centre Hospitalier, (CHU) de Québec-CHUL and Département de Psychiatrie et Neurosciences de l'Université Laval, Québec, Québec, Canada
| | - Maxime Lemieux
- Centre de Recherche du Centre Hospitalier, (CHU) de Québec-CHUL and Département de Psychiatrie et Neurosciences de l'Université Laval, Québec, Québec, Canada
| | - Olivier D Laflamme
- Centre de Recherche du Centre Hospitalier, (CHU) de Québec-CHUL and Département de Psychiatrie et Neurosciences de l'Université Laval, Québec, Québec, Canada
| | - Frédéric Bretzner
- Centre de Recherche du Centre Hospitalier, (CHU) de Québec-CHUL and Département de Psychiatrie et Neurosciences de l'Université Laval, Québec, Québec, Canada
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24
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DSCAM promotes refinement in the mouse retina through cell death and restriction of exploring dendrites. J Neurosci 2015; 35:5640-54. [PMID: 25855178 DOI: 10.1523/jneurosci.2202-14.2015] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
In this study we develop and use a gain-of-function mouse allele of the Down syndrome cell adhesion molecule (Dscam) to complement loss-of-function models. We assay the role of Dscam in promoting cell death, spacing, and laminar targeting of neurons in the developing mouse retina. We find that ectopic or overexpression of Dscam is sufficient to drive cell death. Gain-of-function studies indicate that Dscam is not sufficient to increase spatial organization, prevent cell-to-cell pairing, or promote active avoidance in the mouse retina, despite the similarity of the Dscam loss-of-function phenotype in the mouse retina to phenotypes observed in Drosophila Dscam1 mutants. Both gain- and loss-of-function studies support a role for Dscam in targeting neurites; DSCAM is necessary for precise dendrite lamination, and is sufficient to retarget neurites of outer retinal cells after ectopic expression. We further demonstrate that DSCAM guides dendrite targeting in type 2 dopaminergic amacrine cells, by restricting the stratum in which exploring retinal dendrites stabilize, in a Dscam dosage-dependent manner. Based on these results we propose a single model to account for the numerous Dscam gain- and loss-of-function phenotypes reported in the mouse retina whereby DSCAM eliminates inappropriately placed cells and connections.
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25
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Colas D, Chuluun B, Warrier D, Blank M, Wetmore DZ, Buckmaster P, Garner CC, Heller HC. Short-term treatment with the GABAA receptor antagonist pentylenetetrazole produces a sustained pro-cognitive benefit in a mouse model of Down's syndrome. Br J Pharmacol 2015; 169:963-73. [PMID: 23489250 DOI: 10.1111/bph.12169] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2012] [Revised: 01/25/2013] [Accepted: 02/16/2013] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND AND PURPOSE Down's syndrome is a common genetic cause of intellectual disability, for which there are no drug therapies. Mechanistic studies in a model of Down's syndrome [Ts65Dn (TS) mice] demonstrated that impaired cognitive function was due to excessive neuronal inhibitory tone. These deficits were normalized by low doses of GABAA receptor antagonists in adult animals. In this study, we explore the therapeutic potential of pentylenetetrazole, a GABAA receptor antagonist with a history of safe use in humans. EXPERIMENTAL APPROACH Long-term memory was assessed by the novel object recognition test in different cohorts of TS mice after a delay following a short-term chronic treatment with pentylenetetrazole. Seizure susceptibility, an index of treatment safety, was studied by means of EEG, behaviour and hippocampus morphology. EEG spectral analysis was used as a bio-marker of the treatment. KEY RESULTS PTZ has a wide therapeutic window (0.03-3 mg·kg(-1)) that is >10-1000-fold below its seizure threshold and chronic pentylenetetrazole treatment did not lower the seizure threshold. Short-term, low, chronic dose regimens of pentylenetetrazole elicited long-lasting (>1 week) normalization of cognitive function in young and aged mice. Pentylenetetrazole effectiveness was dependent on the time of treatment; cognitive performance improved after treatment during the light (inactive) phase, but not during the dark (active) phase. Chronic pentylenetetrazole treatment normalized EEG power spectra in TS mice. CONCLUSIONS AND IMPLICATIONS Low doses of pentylenetetrazole were safe, produced long-lasting cognitive improvements and have the potential of fulfilling an unmet therapeutic need in Down's syndrome.
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Affiliation(s)
- D Colas
- Department of Biology, Stanford University, Stanford, CA 94305-5020, USA
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26
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de Andrade GB, Long SS, Fleming H, Li W, Fuerst PG. DSCAM localization and function at the mouse cone synapse. J Comp Neurol 2015; 522:2609-33. [PMID: 24477985 DOI: 10.1002/cne.23552] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2013] [Revised: 01/14/2014] [Accepted: 01/21/2014] [Indexed: 01/14/2023]
Abstract
The Down syndrome cell adhesion molecule (DSCAM) is required for regulation of cell number, soma spacing, and cell type-specific dendrite avoidance in many types of retinal ganglion and amacrine cells. In this study we assay the organization of cells making up the outer plexiform layer of the retina in the absence of Dscam. Some types of OFF bipolar cells, type 3b and type 4 bipolar cells, had defects in dendrite arborization in the Dscam mutant retina, whereas other cell types appeared similar to wild type. The cone synapses that these cells project their dendrites to were intact, as visualized by electron microscopy, and had a distribution and density that was not significantly different from that of wild type. The spacing of type 3b bipolar cell dendrites was further analyzed by Voronoi domain analysis, density recovery profiling (DRP) analysis, and nearest neighbor analysis. Spacing was found to be significantly different when wild-type and mutant type 3b bipolar cell dendrites were compared. Defects in arborization of these bipolar cells could not be attributed to the disorganization of inner plexiform layer cells that occurs in the Dscam mutant retina or an increase in cell number, as they arborized when Dscam was targeted in retinal ganglion cells only or in the bax null retina. Localization of DSCAM was assayed and the protein was localized near to cone synapses in mouse, macaque, and ground squirrel retinas. DSCAM protein was detected in several types of bipolar cells, including type 3b and type 4 bipolar cells.
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Affiliation(s)
- Gabriel Belem de Andrade
- Department of Biological Sciences, University of Idaho, Moscow, Idaho, 83844; Ministry of Education of Brazil, CAPES Foundation, Brasília-DF 70.040-020, Brazil
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27
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Nest building is impaired in the Ts65Dn mouse model of Down syndrome and rescued by blocking 5HT2a receptors. Neurobiol Learn Mem 2014; 116:162-71. [PMID: 25463650 DOI: 10.1016/j.nlm.2014.10.002] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Revised: 10/14/2014] [Accepted: 10/15/2014] [Indexed: 12/14/2022]
Abstract
Down syndrome (DS) has an incidence of about 1/700 births, and is therefore the most common cause of cognitive and behavioral impairments in children. Recent studies on mouse models of DS indicate that a number of pharmacotherapies could be beneficial for restoring cognitive abilities in individuals with DS. Attention deficits that are present in DS account in part for learning and memory deficiencies yet have been scarcely studied in corresponding models. Investigations of this relevant group of behaviors is more difficult in mouse models because of the difficulty in homologizing mouse and human behaviors and because standard laboratory environments do not always elicit behaviors of interest. Here we characterize nest building as a goal-directed behavior that is seriously impaired in young Ts65Dn mice, a genetic model of DS. We believe this impairment may reflect in part attention deficits, and we investigate the physiological, genetic, and pharmacological factors influencing its expression. Nesting behavior in young Ts65Dn mice was severely impaired when the animals were placed in a novel environment. But this context-dependent impairment was transient and reversible. The genetic determinants of this deficiency are restricted to a ∼100 gene segment on the murine chromosome 16. Nest building behavior is a highly integrated phenotypic trait that relies in part on limbic circuitry and on the frontal cortex in relation to cognitive and attention processes. We show that both serotonin content and 5HT2a receptors are increased in the frontal cortex of Ts65Dn mice and that pharmacological blockage of 5HT2a receptors in Ts65Dn mice rescues their context dependent nest building impairment. We propose that the nest-building trait could represent a marker of attention related deficits in DS models and could be of value in designing pharmacotherapies for this specific aspect of DS. 5HT2a modulation may improve goal-directed behavior in DS.
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28
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Roles for DSCAM and DSCAML1 in central nervous system development and disease. ADVANCES IN NEUROBIOLOGY 2014; 8:249-70. [PMID: 25300140 DOI: 10.1007/978-1-4614-8090-7_11] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
DSCAMs (Down syndrome cell adhesion molecules) are a group of immunoglobulin-like transmembrane proteins that contain fibronectin III domains. The founding member of the family was isolated in a positional cloning study that sought to identify genes located on chromosome 21 at the locus 21q22.2-q22.3 that is implicated in the neurological and cardiac phenotypes associated with Down's syndrome. In Drosophila, Dscam proteins are involved in neuronal wiring, while in vertebrates, the role of these cell adhesion molecules in neurogenesis, dendritogenesis, axonal outgrowth, synaptogenesis, and synaptic plasticity is only just beginning to be understood. In this chapter, we will review the functions ascribed to the two paralogous proteins found in humans, DSCAM and DSCAML1 (DSCAM-like 1), based on findings in knockout mice. The signaling pathways downstream of DSCAM activation and the role of DSCAM miss-expression in disease will be also discussed, particularly with regard to the intellectual disability in Down's syndrome.
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29
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Developmentally dynamic colocalization patterns of DSCAM with adhesion and synaptic proteins in the mouse retina. Mol Vis 2014; 20:1422-33. [PMID: 25352748 PMCID: PMC4191645] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2014] [Accepted: 10/08/2014] [Indexed: 10/27/2022] Open
Abstract
PURPOSE The Down syndrome cell adhesion molecule (Dscam) gene is required for normal dendrite arborization and lamination in the mouse retina. In this study, we characterized the developmental localization of the DSCAM protein to better understand the postnatal stages of retinal development during which laminar disorganization occur in the absence of the protein. METHODS Immunohistochemistry and colocalization analysis software were used to assay the localization of the DSCAM protein during development of the retina. RESULTS We found that DSCAM was initially localized diffusely throughout mouse retinal neurites but then adopted a punctate distribution. DSCAM colocalized with catenins in the adult retina but was not detected at the active zone of chemical synapses, electrical synapses, and tight junctions. Further analysis identified a wave of colocalization between DSCAM and numerous synaptic and junction proteins coinciding with synaptogenesis between bipolar and retinal ganglion cells. CONCLUSIONS Research presented in this study expands our understanding of DSCAM function by characterizing its location during the development of the retina and identifies temporally regulated localization patterns as an important consideration in understanding the function of adhesion molecules in neural development.
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30
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Morales Diaz HD. Down syndrome cell adhesion molecule is important for early development in Xenopus tropicalis. Genesis 2014; 52:849-57. [PMID: 25088188 DOI: 10.1002/dvg.22804] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2014] [Revised: 07/25/2014] [Accepted: 07/28/2014] [Indexed: 11/10/2022]
Abstract
The Down syndrome cell adhesion molecule (DSCAM) is an Ig containing cell adhesion molecule with remarkable structural conservation throughout metazoans. In insects, DSCAM has 38,000 potential isoforms that convey axon guidance, fasciculation, and dendrite morphogenesis during neurodevelopment. In vertebrates, DSCAM is expressed throughout the nervous system and seems to also mediate proper axonal guidance and synaptogenesis without the isoform diversity found in insects. Differences in DSCAM function among several vertebrate species complicate the understanding of an evolutionarily conserved role during embryogenesis. We take advantage of the frog developmental model Xenopus tropicalis to study DSCAM function in early development by expression analysis and morpholino-mediated knockdown. Our results indicate that DSCAM is expressed early in development and restricted to the head and nervous system. Knockdown of protein expression results in early morphogenetic phenotypes characterized by failed gastrulation and improper posterior neural tube closure. Our results reveal a specific, fundamental role of DSCAM in early morphogenetic movements, presumably through its well-known role in homophilic cell adhesion.
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Affiliation(s)
- Heidi D Morales Diaz
- Department of Molecular, Cellular and Developmental Biology, University of California Santa Barbara, California USA
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31
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Kirkby LA, Sack GS, Firl A, Feller MB. A role for correlated spontaneous activity in the assembly of neural circuits. Neuron 2014; 80:1129-44. [PMID: 24314725 DOI: 10.1016/j.neuron.2013.10.030] [Citation(s) in RCA: 217] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/01/2013] [Indexed: 11/28/2022]
Abstract
Before the onset of sensory transduction, developing neural circuits spontaneously generate correlated activity in distinct spatial and temporal patterns. During this period of patterned activity, sensory maps develop and initial coarse connections are refined, which are critical steps in the establishment of adult neural circuits. Over the last decade, there has been substantial evidence that altering the pattern of spontaneous activity disrupts refinement, but the mechanistic understanding of this process remains incomplete. In this review, we discuss recent experimental and theoretical progress toward the process of activity-dependent refinement, focusing on circuits in the visual, auditory, and motor systems. Although many outstanding questions remain, the combination of several novel approaches has brought us closer to a comprehensive understanding of how complex neural circuits are established by patterned spontaneous activity during development.
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Affiliation(s)
- Lowry A Kirkby
- Biophysics Graduate Group, UC Berkeley, Berkeley, CA 94720, USA
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32
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Towards a 'systems'-level understanding of the nervous system and its disorders. Trends Neurosci 2013; 36:674-84. [PMID: 23988221 DOI: 10.1016/j.tins.2013.07.003] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Revised: 07/17/2013] [Accepted: 07/24/2013] [Indexed: 12/26/2022]
Abstract
It is becoming clear that nervous system development and adult functioning are highly coupled with other physiological systems. Accordingly, neurological and psychiatric disorders are increasingly being associated with a range of systemic comorbidities including, most prominently, impairments in immunological and bioenergetic parameters as well as in the gut microbiome. Here, we discuss various aspects of the dynamic crosstalk between these systems that underlies nervous system development, homeostasis, and plasticity. We believe a better definition of this underappreciated systems physiology will yield important insights into how nervous system diseases with systemic comorbidities arise and potentially identify novel diagnostic and therapeutic strategies.
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33
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Kim JH, Wang X, Coolon R, Ye B. Dscam expression levels determine presynaptic arbor sizes in Drosophila sensory neurons. Neuron 2013; 78:827-38. [PMID: 23764288 DOI: 10.1016/j.neuron.2013.05.020] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/15/2013] [Indexed: 11/19/2022]
Abstract
Expression of the Down syndrome cell-adhesion molecule (Dscam) is increased in the brains of patients with several neurological disorders. Although Dscam is critically involved in many aspects of neuronal development, little is known about either the mechanism that regulates its expression or the functional consequences of dysregulated Dscam expression. Here, we show that Dscam expression levels serve as an instructive code for the size control of presynaptic arbor. Two convergent pathways, involving dual leucine zipper kinase (DLK) and fragile X mental retardation protein (FMRP), control Dscam expression through protein translation. Defects in this regulation of Dscam translation lead to exuberant presynaptic arbor growth in Drosophila somatosensory neurons. Our findings uncover a function of Dscam in presynaptic size control and provide insights into how dysregulated Dscam may contribute to the pathogenesis of neurological disorders.
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Affiliation(s)
- Jung Hwan Kim
- Life Sciences Institute and Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
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34
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Laguna A, Barallobre MJ, Marchena MÁ, Mateus C, Ramírez E, Martínez-Cue C, Delabar JM, Castelo-Branco M, de la Villa P, Arbonés ML. Triplication of DYRK1A causes retinal structural and functional alterations in Down syndrome. Hum Mol Genet 2013; 22:2775-84. [PMID: 23512985 DOI: 10.1093/hmg/ddt125] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2023] Open
Abstract
Down syndrome (DS) results from the triplication of approximately 300 human chromosome 21 (Hsa21) genes and affects almost all body organs. Children with DS have defects in visual processing that may have a negative impact on their daily life and cognitive development. However, there is little known about the genes and pathogenesis underlying these defects. Here, we show morphometric in vivo data indicating that the neural retina is thicker in DS individuals than in the normal population. A similar thickening specifically affecting the inner part of the retina was also observed in a trisomic model of DS, the Ts65Dn mouse. Increased retinal size and cellularity in this model correlated with abnormal retinal function and resulted from an impaired caspase-9-mediated apoptosis during development. Moreover, we show that mice bearing only one additional copy of Dyrk1a have the same retinal phenotype as Ts65Dn mice and normalization of Dyrk1a gene copy number in Ts65Dn mice completely rescues both, morphological and functional phenotypes. Thus, triplication of Dyrk1a is necessary and sufficient to cause the retinal phenotype described in the trisomic model. Our data demonstrate for the first time the implication of DYRK1A overexpression in a developmental alteration of the central nervous system associated with DS, thereby providing insights into the aetiology of neurosensorial dysfunction in a complex disease.
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Affiliation(s)
- Ariadna Laguna
- Department of Developmental Biology, Institut de Biologia Molecular de Barcelona IBMB-CSIC, Barcelona 08028, Spain
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35
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Cvetkovska V, Hibbert AD, Emran F, Chen BE. Overexpression of Down syndrome cell adhesion molecule impairs precise synaptic targeting. Nat Neurosci 2013; 16:677-82. [PMID: 23666178 PMCID: PMC3954815 DOI: 10.1038/nn.3396] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2012] [Accepted: 04/10/2013] [Indexed: 12/17/2022]
Abstract
Fragile X syndrome is caused by loss of Fragile X Mental Retardation Protein (FMRP), an RNA binding protein that suppresses protein translation. Here, we identified Down Syndrome Cell Adhesion Molecule (Dscam) RNA, a molecule involved in neural development and implicated in Down syndrome, bound to FMRP. Elevated Dscam protein levels in Drosophila FMRP null animals and in animals with three copies of the Dscam gene both produced specific and similar synaptic targeting errors in a hard-wired neural circuit which impaired the animal’s sensory perception. Reducing Dscam levels in FMRP null animals reduced synaptic targeting errors and rescued behavioral responses. Our results demonstrate that excess Dscam protein may be a common molecular mechanism underlying altered neural wiring in major causes of intellectual disability.
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Affiliation(s)
- Vedrana Cvetkovska
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre, Montréal, Québec, Canada
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36
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DSCAM contributes to dendrite arborization and spine formation in the developing cerebral cortex. J Neurosci 2013; 32:16637-50. [PMID: 23175819 DOI: 10.1523/jneurosci.2811-12.2012] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Down syndrome cell adhesion molecule, or DSCAM, has been implicated in many neurodevelopmental processes including axon guidance, dendrite arborization, and synapse formation. Here we show that DSCAM plays an important role in regulating the morphogenesis of cortical pyramidal neurons in the mouse. We report that DSCAM expression is developmentally regulated and localizes to synaptic plasma membranes during a time of robust cortical dendrite arborization and spine formation. Analysis of mice that carry a spontaneous mutation in DSCAM (DSCAM(del17)) revealed gross morphological changes in brain size and shape in addition to subtle changes in cortical organization, volume, and lamination. Early postnatal mutant mice displayed a transient decrease in cortical thickness, but these reductions could not be attributed to changes in neuron production or cell death. DSCAM(del17) mutants showed temporary impairments in the branching of layer V pyramidal neuron dendrites at P10 and P17 that recovered to normal by adulthood. Defects in DSCAM(del17) dendrite branching correlated with a temporal increase in apical branch spine density and lasting changes in spine morphology. At P15 and P42, mutant mice displayed a decrease in the percentage of large, stable spines and an increase in the percentage of small, immature spines. Together, our findings suggest that DSCAM contributes to pyramidal neuron morphogenesis by regulating dendrite arborization and spine formation during cortical circuit development.
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37
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A novel mouse Dscam mutation inhibits localization and shedding of DSCAM. PLoS One 2012; 7:e52652. [PMID: 23300735 PMCID: PMC3530462 DOI: 10.1371/journal.pone.0052652] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2012] [Accepted: 11/19/2012] [Indexed: 11/25/2022] Open
Abstract
The differential adhesion hypothesis of development states that patterning of organisms, organs and tissues is mediated in large part by expression of cell adhesion molecules. The cues provided by cell adhesion molecules are also hypothesized to facilitate specific connectivity within the nervous system. In this study we characterize a novel mouse mutation in the gene Dscam (Down Syndrome Cell Adhesion Molecule). Vertebrate DSCAM is required for normal development of the central nervous system and has been best characterized in the visual system. In the visual system DSCAM is required for regulation of cell number, mosaic formation, laminar specificity, and refinement of retinal-tectal projections. We have identified a novel mutation in Dscam that results in a single amino acid substitution, R1018P, in the extracellular domain of the DSCAM protein. Mice homozygous for the R1018P mutation develop a subset of defects observed in Dscam null mice. In vitro analysis identified defects in DSCAMR1018P localization to filopodia. We also find that wild type DSCAM protein is constitutively cleaved and shed from transfected cells. This secretion is inhibited by the R1018P mutation. We also characterized a novel splice isoform of Dscam and identified defects in lamination of type 2 and type 6 cone bipolar cells in Dscam mutant mice. The identification and characterization of partial loss of function mutations in genes such as Dscam will be helpful in predicting signs and symptoms that may be observed in human patients with partial loss of DSCAM function.
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38
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Lee AR, Lamb RR, Chang JH, Erdmann-Gilmore P, Lichti CF, Rohrs HW, Malone JP, Wairkar YP, DiAntonio A, Townsend RR, Culican SM. Identification of potential mediators of retinotopic mapping: a comparative proteomic analysis of optic nerve from WT and Phr1 retinal knockout mice. J Proteome Res 2012; 11:5515-26. [PMID: 22985349 DOI: 10.1021/pr300767a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Retinal ganglion cells (RGCs) transmit visual information topographically from the eye to the brain, creating a map of visual space in retino-recipient nuclei (retinotopy). This process is affected by retinal activity and by activity-independent molecular cues. Phr1, which encodes a presumed E3 ubiquitin ligase (PHR1), is required presynaptically for proper placement of RGC axons in the lateral geniculate nucleus and the superior colliculus, suggesting that increased levels of PHR1 target proteins may be instructive for retinotopic mapping of retinofugal projections. To identify potential target proteins, we conducted a proteomic analysis of optic nerve to identify differentially abundant proteins in the presence or absence of Phr1 in RGCs. 1D gel electrophoresis identified a specific band in controls that was absent in mutants. Targeted proteomic analysis of this band demonstrated the presence of PHR1. Additionally, we conducted an unbiased proteomic analysis that identified 30 proteins as being significantly different between the two genotypes. One of these, heterogeneous nuclear ribonucleoprotein M (hnRNP-M), regulates antero-posterior patterning in invertebrates and can function as a cell surface adhesion receptor in vertebrates. Thus, we have demonstrated that network analysis of quantitative proteomic data is a useful approach for hypothesis generation and for identifying biologically relevant targets in genetically altered biological models.
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Affiliation(s)
- Andrew R Lee
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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39
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Garrett AM, Tadenev ALD, Burgess RW. DSCAMs: restoring balance to developmental forces. Front Mol Neurosci 2012; 5:86. [PMID: 22912601 PMCID: PMC3421437 DOI: 10.3389/fnmol.2012.00086] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2012] [Accepted: 07/30/2012] [Indexed: 12/31/2022] Open
Abstract
Many of the models of neurodevelopmental processes such as cell migration, axon outgrowth, and dendrite arborization involve cell adhesion and chemoattraction as critical physical or mechanical aspects of the mechanism. However, the prevention of adhesion or attraction is under-appreciated as a necessary, active process that balances these forces, insuring that the correct cells are present and adhering in the correct place at the correct time. The phenomenon of not adhering is often viewed as the passive alternative to adhesion, and in some cases this may be true. However, it is becoming increasingly clear that active signaling pathways are involved in preventing adhesion. These provide a balancing force during development that prevents overly exuberant adhesion, which would otherwise disrupt normal cellular and tissue morphogenesis. The strength of chemoattractive signals may be similarly modulated. Recent studies, described here, suggest that Down Syndrome Cell Adhesion Molecule (DSCAM), and closely related proteins such as DSCAML1, may play an important developmental role as such balancers in multiple systems.
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40
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Keeley PW, Sliff BJ, Lee SCS, Fuerst PG, Burgess RW, Eglen SJ, Reese BE. Neuronal clustering and fasciculation phenotype in Dscam- and Bax-deficient mouse retinas. J Comp Neurol 2012; 520:1349-64. [PMID: 22396220 DOI: 10.1002/cne.23033] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Individual types of retinal neurons are distributed to minimize proximity to neighboring cells. Many of these same cell types extend dendrites to provide coverage of the retinal surface. These two cardinal features of retinal mosaics are disrupted, for certain cell types, in mice deficient for the Down syndrome cell adhesion molecule, Dscam, exhibiting an aberrant clustering of somata and fasciculation of dendrites. The Dscam mutant mouse retina also exhibits excess numbers of these same cell types. The present study compared these two features in Dscam mutant retinas with the Bax knockout retina, in which excess numbers of two of these cell types, the melanopsin-positive retinal ganglion cells (MRGCs) and the dopaminergic amacrine cells (DACs), are also present. Whole retinas were immunolabeled for both populations, and every labeled soma was plotted. For the MRGCs, we found a gene dosage effect for Dscam, with the Dscam+/- retinas showing smaller increases in cell number, clustering, and fasciculation. Curiously, Bax-/- retinas, showing numbers of MRGCs intermediate to those found in the Dscam-/- and Dscam+/- retinas, also had clustering and fasciculation phenotypes that were intermediate to retinas with those genotypes. DACs, by comparison, showed changes in both the Dscam-/- and the Bax-/- retinas that did not correlate with their increases in DAC number. The fasciculation phenotype in the Dscam-/- retina was particularly prominent despite only modest clustering. These results demonstrate that the somal clustering and fasciculation observed in the Dscam mutant retina are not unique to Dscam deficiency and are manifested distinctively by different retinal cell types.
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Affiliation(s)
- Patrick W Keeley
- Neuroscience Research Institute, Department of Molecular, Cellular and Developmental Biology, University of California at Santa Barbara, Santa Barbara, California 93106, USA
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Deregulated mTOR-mediated translation in intellectual disability. Prog Neurobiol 2012; 96:268-82. [DOI: 10.1016/j.pneurobio.2012.01.005] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2011] [Revised: 01/02/2012] [Accepted: 01/12/2012] [Indexed: 02/04/2023]
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Fuerst PG, Bruce F, Rounds RP, Erskine L, Burgess RW. Cell autonomy of DSCAM function in retinal development. Dev Biol 2012; 361:326-37. [PMID: 22063212 PMCID: PMC3246579 DOI: 10.1016/j.ydbio.2011.10.028] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2011] [Revised: 10/19/2011] [Accepted: 10/21/2011] [Indexed: 01/19/2023]
Abstract
Cell adhesion molecules (CAMs) provide identifying cues by which neural architecture is sculpted. The Down Syndrome Cell Adhesion Molecule (DSCAM) is required for many neurodevelopmental processes in different species and also has several potential mechanisms of activity, including homophilic adhesion, homophilic repulsion and heterophilic interactions. In the mouse retina, Dscam is expressed in many, but not all neuronal subtypes. Mutations in Dscam cause the fasciculation of dendrites of neighboring homotypic neurons, indicating a role in self-avoidance among cells of a given type, a disruption of the non-random patterning of their cell bodies, and a decrease in developmental cell death in affected cell populations. In order to address how DSCAM facilitates retinal pattering, we developed a conditional allele of Dscam to use alongside existing Dscam mutant mouse strains. Conditional deletion of Dscam reproduces cell spacing, cell number and dendrite arborization defects. Inducible deletion of Dscam and retinal ganglion cell depletion in Brn3b mutant retinas both indicate that these DSCAM-mediated phenotypes can occur independently. In chimeric retinas, in which wild type and Dscam mutant cells are comingled, Dscam mutant cells entangle adjacent wild type cells of the same type, as if both cells were lacking Dscam, consistent with DSCAM-dependent cell spacing and neurite arborization being mediated through homophilic binding cell-to-cell. Deletion of Dscam in specific cell types causes cell-type-autonomous cell body spacing defects, indicating that DSCAM mediates arborization and spacing by acting within given cell types. We also examine the cell autonomy of DSCAM in laminar stratification and find that laminar disorganization can be caused in a non-cell autonomous fashion. Finally, we find Dscam dosage-dependent defects in developmental cell death and amacrine cell spacing, relevant to the increased cell death and other disorders observed in Down syndrome mouse models and human patients, in which Dscam is present in three copies.
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Affiliation(s)
- Peter G Fuerst
- Department of Biological Sciences and WWAMI Medical Education Program, University of Idaho, Moscow, ID 83844, USA.
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Begenisic T, Spolidoro M, Braschi C, Baroncelli L, Milanese M, Pietra G, Fabbri ME, Bonanno G, Cioni G, Maffei L, Sale A. Environmental enrichment decreases GABAergic inhibition and improves cognitive abilities, synaptic plasticity, and visual functions in a mouse model of Down syndrome. Front Cell Neurosci 2011; 5:29. [PMID: 22207837 PMCID: PMC3245647 DOI: 10.3389/fncel.2011.00029] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Accepted: 12/12/2011] [Indexed: 01/20/2023] Open
Abstract
Down syndrome (DS) is the most common genetic disorder associated with mental retardation. It has been repeatedly shown that Ts65Dn mice, the prime animal model for DS, have severe cognitive and neural plasticity defects due to excessive inhibition. We report that increasing sensory-motor stimulation in adulthood through environmental enrichment (EE) reduces brain inhibition levels and promotes recovery of spatial memory abilities, hippocampal synaptic plasticity, and visual functions in adult Ts65Dn mice.
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