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Rusu B, Kukreja B, Wu T, Dan SJ, Feng MY, Kalish BT. Single-Nucleus Profiling Identifies Accelerated Oligodendrocyte Precursor Cell Senescence in a Mouse Model of Down Syndrome. eNeuro 2023; 10:ENEURO.0147-23.2023. [PMID: 37491366 PMCID: PMC10449487 DOI: 10.1523/eneuro.0147-23.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Revised: 07/06/2023] [Accepted: 07/10/2023] [Indexed: 07/27/2023] Open
Abstract
Down syndrome (DS), the most common genetic cause of intellectual disability, is associated with lifelong cognitive deficits. However, the mechanisms by which triplication of chromosome 21 genes drive neuroinflammation and cognitive dysfunction are poorly understood. Here, using the Ts65Dn mouse model of DS, we performed an integrated single-nucleus ATAC and RNA-sequencing (snATAC-seq and snRNA-seq) analysis of the adult cortex. We identified cell type-specific transcriptional and chromatin-associated changes in the Ts65Dn cortex, including regulators of neuroinflammation, transcription and translation, myelination, and mitochondrial function. We discovered enrichment of a senescence-associated transcriptional signature in Ts65Dn oligodendrocyte (OL) precursor cells (OPCs) and epigenetic changes consistent with a loss of heterochromatin. We found that senescence is restricted to a subset of OPCs concentrated in deep cortical layers. Treatment of Ts65Dn mice with a senescence-reducing flavonoid rescued cortical OPC proliferation, restored microglial homeostasis, and improved contextual fear memory. Together, these findings suggest that cortical OPC senescence may be an important driver of neuropathology in DS.
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Affiliation(s)
- Bianca Rusu
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario M5G 1A8, Canada
- Program in Neuroscience and Mental Health, SickKids Research Institute, Toronto, Ontario M5G 1L7, Canada
| | - Bharti Kukreja
- Program in Neuroscience and Mental Health, SickKids Research Institute, Toronto, Ontario M5G 1L7, Canada
| | - Taiyi Wu
- Program in Neuroscience and Mental Health, SickKids Research Institute, Toronto, Ontario M5G 1L7, Canada
| | - Sophie J Dan
- Program in Neuroscience and Mental Health, SickKids Research Institute, Toronto, Ontario M5G 1L7, Canada
- Department of Physiology, University of Toronto, Toronto, Ontario M5G 1A8, Canada
- Department of Immunology, University of Toronto, Toronto, Ontario M5G 1A8, Canada
| | - Min Yi Feng
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario M5G 1A8, Canada
- Program in Neuroscience and Mental Health, SickKids Research Institute, Toronto, Ontario M5G 1L7, Canada
| | - Brian T Kalish
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario M5G 1A8, Canada
- Program in Neuroscience and Mental Health, SickKids Research Institute, Toronto, Ontario M5G 1L7, Canada
- Division of Neonatology, Department of Paediatrics, The Hospital for Sick Children, Toronto, Ontario M5G 1L7, Canada
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2
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Hernández K, Godoy L, Newquist G, Kellermeyer R, Alavi M, Mathew D, Kidd T. Dscam1 overexpression impairs the function of the gut nervous system in Drosophila. Dev Dyn 2023; 252:156-171. [PMID: 36454543 PMCID: PMC9812936 DOI: 10.1002/dvdy.554] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 11/04/2022] [Accepted: 11/22/2022] [Indexed: 12/05/2022] Open
Abstract
BACKGROUND Down syndrome (DS) patients have a 100-fold increase in the risk of Hirschsprung syndrome of the colon and rectum (HSCR), a lack of enteric neurons in the colon. The leading DS candidate gene is trisomy of the Down syndrome cell adhesion molecule (DSCAM). RESULTS We find that Dscam1 protein is expressed in the Drosophila enteric/stomatogastric nervous system (SNS). Axonal Dscam1 phenotypes can be rescued equally by diverse isoforms. Overexpression of Dscam1 resulted in frontal and hindgut nerve overgrowth. Expression of dominant negative Dscam1-ΔC led to a truncated frontal nerve and increased branching of the hindgut nerve. Larval locomotion is influenced by feeding state, and we found that the average speed of larvae with Dscam1 SNS expression was reduced, whereas overexpression of Dscam1-ΔC significantly increased the speed. Dscam1 overexpression reduced the efficiency of food clearance from the larval gut. CONCLUSION Our work demonstrates that overexpression of Dscam1 can perturb gut function in a model system.
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Affiliation(s)
| | - Luis Godoy
- Biology/MS 314, University of Nevada, Reno, NV 89557, USA
| | | | | | - Maryam Alavi
- Biology/MS 314, University of Nevada, Reno, NV 89557, USA
| | - Dennis Mathew
- Biology/MS 314, University of Nevada, Reno, NV 89557, USA
| | - Thomas Kidd
- Biology/MS 314, University of Nevada, Reno, NV 89557, USA
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3
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Molecular Organization and Patterning of the Medulla Oblongata in Health and Disease. Int J Mol Sci 2022; 23:ijms23169260. [PMID: 36012524 PMCID: PMC9409237 DOI: 10.3390/ijms23169260] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Revised: 08/15/2022] [Accepted: 08/16/2022] [Indexed: 11/17/2022] Open
Abstract
The medulla oblongata, located in the hindbrain between the pons and the spinal cord, is an important relay center for critical sensory, proprioceptive, and motoric information. It is an evolutionarily highly conserved brain region, both structural and functional, and consists of a multitude of nuclei all involved in different aspects of basic but vital functions. Understanding the functional anatomy and developmental program of this structure can help elucidate potential role(s) of the medulla in neurological disorders. Here, we have described the early molecular patterning of the medulla during murine development, from the fundamental units that structure the very early medullary region into 5 rhombomeres (r7–r11) and 13 different longitudinal progenitor domains, to the neuronal clusters derived from these progenitors that ultimately make-up the different medullary nuclei. By doing so, we developed a schematic overview that can be used to predict the cell-fate of a progenitor group, or pinpoint the progenitor domain of origin of medullary nuclei. This schematic overview can further be used to help in the explanation of medulla-related symptoms of neurodevelopmental disorders, e.g., congenital central hypoventilation syndrome, Wold–Hirschhorn syndrome, Rett syndrome, and Pitt–Hopkins syndrome. Based on the genetic defects seen in these syndromes, we can use our model to predict which medullary nuclei might be affected, which can be used to quickly direct the research into these diseases to the likely affected nuclei.
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Lemieux M, Thiry L, Laflamme OD, Bretzner F. Role of DSCAM in the Development of Neural Control of Movement and Locomotion. Int J Mol Sci 2021; 22:ijms22168511. [PMID: 34445216 PMCID: PMC8395195 DOI: 10.3390/ijms22168511] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Revised: 08/02/2021] [Accepted: 08/04/2021] [Indexed: 11/30/2022] Open
Abstract
Locomotion results in an alternance of flexor and extensor muscles between left and right limbs generated by motoneurons that are controlled by the spinal interneuronal circuit. This spinal locomotor circuit is modulated by sensory afferents, which relay proprioceptive and cutaneous inputs that inform the spatial position of limbs in space and potential contacts with our environment respectively, but also by supraspinal descending commands of the brain that allow us to navigate in complex environments, avoid obstacles, chase prey, or flee predators. Although signaling pathways are important in the establishment and maintenance of motor circuits, the role of DSCAM, a cell adherence molecule associated with Down syndrome, has only recently been investigated in the context of motor control and locomotion in the rodent. DSCAM is known to be involved in lamination and delamination, synaptic targeting, axonal guidance, dendritic and cell tiling, axonal fasciculation and branching, programmed cell death, and synaptogenesis, all of which can impact the establishment of motor circuits during development, but also their maintenance through adulthood. We discuss herein how DSCAM is important for proper motor coordination, especially for breathing and locomotion.
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Affiliation(s)
- Maxime Lemieux
- Centre de Recherche du Centre Hospitalier Universitaire de Québec, CHUL-Neurosciences P09800, 2705 boul. Laurier, Québec, QC G1V 4G2, Canada; (M.L.); (L.T.); (O.D.L.)
| | - Louise Thiry
- Centre de Recherche du Centre Hospitalier Universitaire de Québec, CHUL-Neurosciences P09800, 2705 boul. Laurier, Québec, QC G1V 4G2, Canada; (M.L.); (L.T.); (O.D.L.)
| | - Olivier D. Laflamme
- Centre de Recherche du Centre Hospitalier Universitaire de Québec, CHUL-Neurosciences P09800, 2705 boul. Laurier, Québec, QC G1V 4G2, Canada; (M.L.); (L.T.); (O.D.L.)
| | - Frédéric Bretzner
- Centre de Recherche du Centre Hospitalier Universitaire de Québec, CHUL-Neurosciences P09800, 2705 boul. Laurier, Québec, QC G1V 4G2, Canada; (M.L.); (L.T.); (O.D.L.)
- Department of Psychiatry and Neurosciences, Faculty of Medicine, Université Laval, Québec, QC G1V 4G2, Canada
- Correspondence:
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5
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LaMantia AS. Why Does the Face Predict the Brain? Neural Crest Induction, Craniofacial Morphogenesis, and Neural Circuit Development. Front Physiol 2020; 11:610970. [PMID: 33362582 PMCID: PMC7759552 DOI: 10.3389/fphys.2020.610970] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 11/24/2020] [Indexed: 12/14/2022] Open
Abstract
Mesenchephalic and rhombencephalic neural crest cells generate the craniofacial skeleton, special sensory organs, and subsets of cranial sensory receptor neurons. They do so while preserving the anterior-posterior (A-P) identity of their neural tube origins. This organizational principle is paralleled by central nervous system circuits that receive and process information from facial structures whose A-P identity is in register with that in the brain. Prior to morphogenesis of the face and its circuits, however, neural crest cells act as "inductive ambassadors" from distinct regions of the neural tube to induce differentiation of target craniofacial domains and establish an initial interface between the brain and face. At every site of bilateral, non-axial secondary induction, neural crest constitutes all or some of the mesenchymal compartment for non-axial mesenchymal/epithelial (M/E) interactions. Thus, for epithelial domains in the craniofacial primordia, aortic arches, limbs, the spinal cord, and the forebrain (Fb), neural crest-derived mesenchymal cells establish local sources of inductive signaling molecules that drive morphogenesis and cellular differentiation. This common mechanism for building brains, faces, limbs, and hearts, A-P axis specified, neural crest-mediated M/E induction, coordinates differentiation of distal structures, peripheral neurons that provide their sensory or autonomic innervation in some cases, and central neural circuits that regulate their behavioral functions. The essential role of this neural crest-mediated mechanism identifies it as a prime target for pathogenesis in a broad range of neurodevelopmental disorders. Thus, the face and the brain "predict" one another, and this mutual developmental relationship provides a key target for disruption by developmental pathology.
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Affiliation(s)
- Anthony-Samuel LaMantia
- Laboratory of Developmental Disorders and Genetics and Center for Neurobiology Research, Fralin Biomedical Research Institute, Department of Pediatrics, Virginia Tech-Carilion School of Medicine, Virginia Tech, Roanoke, VA, United States.,Department of Biological Sciences, Virginia Tech, Blacksburg, VA, United States
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6
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Hildebrandt C, Fulton A, Rodan LH. Homozygous deletion of 21q22.2 in a patient with hypotonia, developmental delay, cortical visual impairment, and retinopathy. Am J Med Genet A 2020; 185:555-560. [PMID: 33170561 DOI: 10.1002/ajmg.a.61969] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 10/22/2020] [Accepted: 10/27/2020] [Indexed: 11/09/2022]
Abstract
21q22 contains several dosage sensitive genes that are important in neurocognitive development. Determining impacts of gene dosage alterations in this region can be useful in establishing contributions of these genes to human development and disease. We describe a 15-month-old girl with a 1,140 kb homozygous deletion in the Down Syndrome Critical Region at 21q22.2 including 4 genes; B3GALT5, IGSF5, PCP4, DSCAM, and a microRNA (MIR4760). Clinical singleton genome sequencing did not report any candidate gene variants for the patient's phenotype. She presented with hypotonia, global developmental delay, cortical visual impairment, and mild facial dysmorphism. Ophthalmological exam was suggestive of retinopathy. We propose that the absence of DSCAM and PCP4 may contribute to the patient's neurological and retinal phenotype, while the role of absent B3GALT5 and IGSF5 in her presentation remain unclear at this time.
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Affiliation(s)
- Clara Hildebrandt
- Medical Biochemical Fellowship at Boston Children's Hospital, Boston, Massachusetts, USA
| | - Anne Fulton
- Department of Ophthalmology, Boston Children's Hospital, Boston, Massachusetts, USA
| | - Lance H Rodan
- Department of Genetics and Genomics, Boston Children's Hospital, Boston, Massachusetts, USA
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7
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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: 35] [Impact Index Per Article: 7.0] [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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8
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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: 3.1] [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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9
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A small pons as a characteristic finding in Down syndrome: A quantitative MRI study. Brain Dev 2017; 39:298-305. [PMID: 27865668 DOI: 10.1016/j.braindev.2016.10.016] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Revised: 10/24/2016] [Accepted: 10/29/2016] [Indexed: 12/29/2022]
Abstract
BACKGROUND Down syndrome (DS) is the most common chromosomal aberration, but the characteristics of the brainstem component in this condition during childhood (from newborn to preteen stages) have not been clarified. OBJECTIVE To evaluate the morphological features of the brainstem in DS on magnetic resonance imaging (MRI). MATERIALS AND METHODS MRIs for 32 children with DS (16 boys and girls each; age range, 0-11years) without major brain insults, and 32 age-matched controls (16 boys and girls each) were retrospectively analyzed. Height, width, and area of the midbrain, pons, and medulla oblongata were measured on sagittal T1-weighted images; these were compared in children with DS and age-matched controls. The ratios of the brainstem to the size of the posterior fossa (BS/PF index) were calculated; these were also compared in the children with DS and the control group. RESULTS The width and area of the midbrain; height, width, area of the pons; and area of the medulla oblongata were significantly smaller in children with DS than in control children (P<0.05); the area of the pons, particularly for the ventral part, showed the largest differences in the mean relative differences. The BS/PF indices of the height, width, and area of the pons were significantly smaller in children with DS than in the control group (P<0.01). However, the BS/PF indices for the midbrain and the medulla oblongata did not differ between these two groups. CONCLUSIONS Children with DS may have small brainstems, particularly in the pons; this may be a characteristic morphological feature of the brainstem on MRI in childhood including neonates.
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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: 1.2] [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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11
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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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12
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Huang J, Wang Y, Raghavan S, Feng S, Kiesewetter K, Wang J. Human down syndrome cell adhesion molecules (DSCAMs) are functionally conserved with Drosophila Dscam[TM1] isoforms in controlling neurodevelopment. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2011; 41:778-787. [PMID: 21645617 DOI: 10.1016/j.ibmb.2011.05.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2011] [Revised: 05/19/2011] [Accepted: 05/20/2011] [Indexed: 05/30/2023]
Abstract
Drosophila Down syndrome cell adhesion molecule (Dscam) potentially produces more than 150,000 cell adhesion molecules that share two alternative transmembrane/juxtamembrane (TM) domains, which dictate the dendrite versus axon subcellular distribution and function of different Dscam isoforms. Vertebrate genomes contain two closely related genes, DSCAM and DSCAM-Like1 (DSCAML1), which do not have extensive alternative splicing. We investigated the functional conservation between invertebrate Dscams and vertebrate DSCAMs by cross-species rescue assays and found that human DSCAM and DSCAML1 partially, but substantially, rescued the larval lethality of Drosophila Dscam mutants. Interestingly, both human DSCAM and DSCAML1 were targeted to the dendrites in Drosophila neurons, had synergistic rescue effects with Drosophila Dscam[TM2], and preferentially rescued the dendrite defects of Drosophila Dscam mutant neurons. Therefore, human DSCAM and DSCAML1 are functionally conserved with Drosophila Dscam[TM1] isoforms.
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Affiliation(s)
- Jianhua Huang
- Department of Entomology, University of Maryland, College Park, MD 20742, USA
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Xu Y, Ye H, Shen Y, Xu Q, Zhu L, Liu J, Wu JY. Dscam mutation leads to hydrocephalus and decreased motor function. Protein Cell 2011; 2:647-55. [PMID: 21904980 DOI: 10.1007/s13238-011-1072-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2011] [Accepted: 05/30/2011] [Indexed: 11/28/2022] Open
Abstract
The nervous system is one of the most complicated organ systems in invertebrates and vertebrates. Down syndrome cell adhesion molecule (DSCAM) of the immunoglobulin (Ig) superfamily is expressed widely in the nervous system during embryonic development. Previous studies in Drosophila suggest that Dscam plays important roles in neural development including axon branching, dendritic tiling and cell spacing. However, the function of the mammalian DSCAM gene in the formation of the nervous system remains unclear. Here, we show that Dscam ( del17 ) mutant mice exhibit severe hydrocephalus, decreased motor function and impaired motor learning ability. Our data indicate that the mammalian DSCAM gene is critical for the formation of the central nervous system.
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Affiliation(s)
- Yiliang Xu
- National Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Science and Peking Union Medical College, Tsinghua University, Beijing 100084, China
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14
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Satgé D, Bénard J. Carcinogenesis in Down syndrome: What can be learned from trisomy 21? Semin Cancer Biol 2008; 18:365-71. [DOI: 10.1016/j.semcancer.2008.03.020] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2008] [Accepted: 03/25/2008] [Indexed: 11/26/2022]
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15
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Abstract
Down syndrome (DS) is the most common chromosomal abnormality occurring in humans. Up to 77% of DS children have associated gastrointestinal (GI) abnormalities, which may be structural or functional in nature. Functional disturbances may, in turn, affect the outcome of corrective surgical procedures, prompting to caution. It is becoming clear that the processes affecting the enteric nervous system (ENS) in DS not only affect the micro-anatomy but also nerve function, and there is some histological evidence of ENS variations in both human and DS animal models. This suggests that developmental disorders of the ENS are probably fundamental to the functional GI disturbances encountered in patients with DS. The anomalous brain development, function and resulting intellectual impairment associated with DS appears to result from the genetic imbalance created by the trisomy of chromosome 21. The possible links between the brain, GI and ENS involvement are not as yet entirely clear. Neurotropic factors affecting brain development during embryogenesis are probably interlinked with ENS development, but the precise mechanism of how this occurs has yet to be established. This study explores what is known about the ENS dysfunction in DS and reviews the possible importance of chromosome 21 located and other genes in its etiology. Functional motor disturbances of the esophagus and colon are not uncommon and may be congenital or acquired in nature. The most prominent of these include esophageal dysmotility syndromes (e.g. achalasia, gastroesophageal reflux, dysphagia) as well as a higher incidence of chronic constipation and Hirschsprung's disease (HSCR) (2-15%) occurring in association with DS. Chromosome 21 itself is thought to be the site of a modifier gene for HSCR. Recently identified candidate genetic mechanisms provide unique insights into the genetic background of the neurological and cognitive disorders associated with DS. Although the role of the triplicated chromosome 21 and genetic dosage remain important, the additional role of other chromosome 21 genes in the etiology of ENS developmental anomalies remains undetermined and requires ongoing research.
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Affiliation(s)
- S W Moore
- Division of Paediatric Surgery, Department of Surgical Sciences, Faculty of Health Sciences, University of Stellenbosch, P.O. Box 19063, Tygerberg, 7505, South Africa.
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16
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Association study between the Down syndrome cell adhesion molecule (DSCAM) gene and bipolar disorder. Psychiatr Genet 2008; 18:1-10. [DOI: 10.1097/ypg.0b013e3281ac238e] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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17
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18
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Millard SS, Flanagan JJ, Pappu KS, Wu W, Zipursky SL. Dscam2 mediates axonal tiling in the Drosophila visual system. Nature 2007; 447:720-4. [PMID: 17554308 PMCID: PMC2691714 DOI: 10.1038/nature05855] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2007] [Accepted: 04/17/2007] [Indexed: 01/25/2023]
Abstract
Sensory processing centres in both the vertebrate and the invertebrate brain are often organized into reiterated columns, thus facilitating an internal topographic representation of the external world. Cells within each column are arranged in a stereotyped fashion and form precise patterns of synaptic connections within discrete layers. These connections are largely confined to a single column, thereby preserving the spatial information from the periphery. Other neurons integrate this information by connecting to multiple columns. Restricting axons to columns is conceptually similar to tiling. Axons and dendrites of neighbouring neurons of the same class use tiling to form complete, yet non-overlapping, receptive fields. It is thought that, at the molecular level, cell-surface proteins mediate tiling through contact-dependent repulsive interactions, but proteins serving this function have not yet been identified. Here we show that the immunoglobulin superfamily member Dscam2 restricts the connections formed by L1 lamina neurons to columns in the Drosophila visual system. Our data support a model in which Dscam2 homophilic interactions mediate repulsion between neurites of L1 cells in neighbouring columns. We propose that Dscam2 is a tiling receptor for L1 neurons.
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Affiliation(s)
- S Sean Millard
- Howard Hughes Medical Institute, Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California 90095, USA
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Li W, Guan KL. The Down syndrome cell adhesion molecule (DSCAM) interacts with and activates Pak. J Biol Chem 2004; 279:32824-31. [PMID: 15169762 DOI: 10.1074/jbc.m401878200] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Down syndrome cell adhesion molecule (DSCAM) is a member of the immunoglobulin superfamily that maps to a Down syndrome region of chromosome 21q22.2-22.3. In Drosophila, Dscam functions as an axon guidance receptor regulating targeting and branching. Genetic and biochemical studies have shown that in Drosophila, Dscam activates Pak1 via the Dock adaptor molecule. The extracellular domain of human DSCAM is highly homologous to the Drosophila protein; however, the intracellular domains of both human and Drosophila DSCAM share no obvious sequence identity. To study the signaling mechanisms of human DSCAM, we investigated the interaction between DSCAM and potential downstream molecules. We found that DSCAM directly binds to Pak1 and stimulates Pak1 phosphorylation and activity, unlike Drosophila where an adaptor protein Dock mediates the interaction between Dscam and Pak1. We also observed that DSCAM activates both JNK and p38 MAP kinases. Furthermore, expression of the cytoplasmic domain of DSCAM induces a morphological change in cultured cells that is JNK-dependent. These observations suggest that human DSCAM also signals through Pak1 and may function in axon guidance similar to the Drosophila Dscam.
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Affiliation(s)
- Weiquan Li
- Life Sciences Institute, Department of Biological Chemistry, Institute of Gerontology, University of Michigan, Ann Arbor, 48109, USA
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