The Role of Connexin32 in the Pathogensis of CMTX

Summary

Principal Investigator: STEVEN SIMON SCHERER
Abstract: DESCRIPTION (provided by applicant): Recessive mutations in GJC2, the human gene that encodes Cx47, cause Pelizaeus-Merzbacher-like disease (PMLD) and hereditary spastic paraparesis (HSP), presumably related their lack of Cx47 function in oligodendrocytes. How the loss of Cx47 function results in the clinical picture of PMLD is unknown. MRI paints the picture of profound dysmyelination, but this has yet to be confirmed in an autopsy or biopsy. In cellular and animal models, the mutants associated with PMLD impair GJ communication, but we do not yet know why GJ communication is essential for the proper functioning of oligodendrocytes. In this competing renewal, we will determine whether novel Cx47 mutants affect GJ coupling, explore whether O: O coupling a general feature of oligodendrocytes, and the functional significance of O: O coupling. 1. Investigate the molecular defects of hCx47 mutants causing PMLD or familial lymphedema. In the last grant cycle of this grant, we showed that 3 recessive Cx47 mutants associated with PMLD have defective trafficking and do not form functional channels with either Cx47 or Cx43. We will build on this observation by investigating 2 additional missense mutations, 2 frameshift mutations that affect the C-terminus of Cx47, deletion of the PDZ-binding domain (del433-437;a relevant, but not a naturally-occurring mutation), and 6 dominant mutations that cause a completely different phenotype, Familial Lymphedema. The ability of each mutant to form functional GJ plaques will be investigated - by immunostaining, scrape loading, fluorescence recovery after photobleaching (FRAP), and electrophysiology. Whether the dominant mutants have dominant-negative effects on WT Cx47 will also be investigated (by co-staining, co-immunoprecipitation, and electrophysiology). We will also generate lines of transgenic mice that express the Cx47del433-437 or R257C, one of the dominant mutations causing Familial Lymphedema. We will assess the ability of these mutants to "rescue" the phenotype of Gjc2-null (Gjc2-/-) mice, and of the R257C mutant to worsen the phenotype of Gjc2-heterozygous (Gjc2+/-) mice. 2. Is O: O coupling a general feature of oligodendrocytes? In the last grant cycle of this grant, we showed that O: A coupling in lost in mice lacking both Cx32 and Cx47. We also showed, expectedly, O: O coupling was prominent in the corpus callosum, that O: O coupling was also lost in mice lacking both Cx32 and Cx47, that the GJs directly join intrafascicular oligodendrocytes. The goal of this aim is to determine whether O: O coupling is found in other white matter tracts, and hence is a general feature of intrafascicular oligodendrocytes. To that end, we will measure the diffusion of sulforhodamine-B (SR- B), examine the ultrastructure of O: O junctions, and examine the expression of glial connexins (Cx30, Cx32, Cx43, Cx47) in two tracts - the optic nerve and the ventral funiculus of the cervical spinal cord. 3. The functional significance of O: O coupling. The function of O: A and O: O coupling is uncertain. The experimental results to date support two, non-mutually exclusive, functions - spatial buffering of K+ and metabolic cooperation. K+ clearance is modestly decreased in acute brain slices from mice in which astrocytes lack both Cx43 and Cx30. These mice also provide the best evidence for metabolic coupling, demonstrating that Cx30 and Cx43 are required for the intracellular diffusion of a fluorescent glucose analogue (2-NDBG) to areas of neuropil with increased neuronal activity. We reasoned that O: O coupling might serve a similar purpose for myelinated axons, and propose an experimental analysis of this possibility in this Aim. We will determine whether (a) activity increases the extent of 2-NDBG diffusion, and (b) whether glucose infused into a single oligodendrocyte can "rescue" axonal conduction in glucose-deprived conditions.
Funding Period: 2006-04-01 - 2016-08-31
more information: NIH RePORT

Top Publications

  1. pmc Loss-of-function GJA12/Connexin47 mutations cause Pelizaeus-Merzbacher-like disease
    Jennifer L Orthmann-Murphy
    Department of Neurology, University of Pennsylvania School of Medicine, Room 464 Stemmler Hall, 3450 Hamilton Walk, Philadelphia, PA 19104 6077, USA
    Mol Cell Neurosci 34:629-41. 2007
  2. pmc Axonal pathology precedes demyelination in a mouse model of X-linked demyelinating/type I Charcot-Marie Tooth neuropathy
    Natalie Vavlitou
    Neuroscience Laboratory and Neurology Clinics, The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus
    J Neuropathol Exp Neurol 69:945-58. 2010
  3. pmc Dominant Cx26 mutants associated with hearing loss have dominant-negative effects on wild type Cx26
    Junxian Zhang
    Department of Pediatrics, Division of Neurology, The Children s Hospital of Philadelphia, USA
    Mol Cell Neurosci 47:71-8. 2011
  4. pmc A dominant connexin43 mutant does not have dominant effects on gap junction coupling in astrocytes
    Sameh Wasseff
    Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104 6077, USA
    Neuron Glia Biol 6:213-23. 2010
  5. pmc Cx32 and Cx47 mediate oligodendrocyte:astrocyte and oligodendrocyte:oligodendrocyte gap junction coupling
    Sameh K Wasseff
    Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104 6077, USA
    Neurobiol Dis 42:506-13. 2011
  6. pmc Gap junctions in inherited human disorders of the central nervous system
    Charles K Abrams
    Department of Neurology and Physiology and Pharmacology, SUNY Downstate Medical Center, Brooklyn, NY 11203, USA
    Biochim Biophys Acta 1818:2030-47. 2012
  7. pmc Microtubules, axonal transport, and neuropathy
    Erika L F Holzbaur
    From the Departments of Physiology E L F H and Neurology S S S, Perelman School of Medicine at the University of Pennsylvania, Philadelphia
    N Engl J Med 365:2330-2. 2011
  8. pmc Neuronal cadherin (NCAD) increases sensory neurite formation and outgrowth on astrocytes
    Toby A Ferguson
    Department of Neurology, Temple University and Shriners Pediatric Research Center, Philadelphia, PA 19140, USA
    Neurosci Lett 522:108-12. 2012
  9. pmc How do mutations in GJB1 cause X-linked Charcot-Marie-Tooth disease?
    Kleopas A Kleopa
    Neurology Clinics and Neuroscience Laboratory, The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus
    Brain Res 1487:198-205. 2012
  10. pmc X-linked Charcot-Marie-Tooth disease
    Steven S Scherer
    Department of Neurology, The Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
    J Peripher Nerv Syst 17:9-13. 2012

Detail Information

Publications22

  1. pmc Loss-of-function GJA12/Connexin47 mutations cause Pelizaeus-Merzbacher-like disease
    Jennifer L Orthmann-Murphy
    Department of Neurology, University of Pennsylvania School of Medicine, Room 464 Stemmler Hall, 3450 Hamilton Walk, Philadelphia, PA 19104 6077, USA
    Mol Cell Neurosci 34:629-41. 2007
    ..Thus, the Cx47 mutants associated with PMLD likely disrupt the gap junction coupling between astrocytes and oligodendrocytes...
  2. pmc Axonal pathology precedes demyelination in a mouse model of X-linked demyelinating/type I Charcot-Marie Tooth neuropathy
    Natalie Vavlitou
    Neuroscience Laboratory and Neurology Clinics, The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus
    J Neuropathol Exp Neurol 69:945-58. 2010
    ..These findings demonstrate that axonal abnormalities including impaired cytoskeletal organization and defects in axonal transport precede demyelination in this mouse model of CMT1X...
  3. pmc Dominant Cx26 mutants associated with hearing loss have dominant-negative effects on wild type Cx26
    Junxian Zhang
    Department of Pediatrics, Division of Neurology, The Children s Hospital of Philadelphia, USA
    Mol Cell Neurosci 47:71-8. 2011
    ..Taken together, these results show that dominant-negative effects of these Cx26 mutants likely contribute to the pathogenesis of hearing loss...
  4. pmc A dominant connexin43 mutant does not have dominant effects on gap junction coupling in astrocytes
    Sameh Wasseff
    Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104 6077, USA
    Neuron Glia Biol 6:213-23. 2010
    ..In co-transfected cells, the G60S mutant co-immunoprecipitated with WT Cx43, but did not diminish GJ coupling as measured by dual patch clamp. Thus, whereas G60S has dominant effects, it did not appreciably reduce GJ coupling...
  5. pmc Cx32 and Cx47 mediate oligodendrocyte:astrocyte and oligodendrocyte:oligodendrocyte gap junction coupling
    Sameh K Wasseff
    Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104 6077, USA
    Neurobiol Dis 42:506-13. 2011
    ..O:O coupling was more affected in mice lacking Cx32 than in mice lacking Cx47. In the neocortex, oligodendrocytes appeared to be directly and exclusively coupled to astrocytes; Cx47, but not Cx32, was required for O:A coupling...
  6. pmc Gap junctions in inherited human disorders of the central nervous system
    Charles K Abrams
    Department of Neurology and Physiology and Pharmacology, SUNY Downstate Medical Center, Brooklyn, NY 11203, USA
    Biochim Biophys Acta 1818:2030-47. 2012
    ..Recessive GJA1 mutations cause Hallermann-Streiff syndrome, a disorder showing substantial overlap with ODDD. This article is part of a Special Issue entitled: The Communicating junctions, composition, structure and functions...
  7. pmc Microtubules, axonal transport, and neuropathy
    Erika L F Holzbaur
    From the Departments of Physiology E L F H and Neurology S S S, Perelman School of Medicine at the University of Pennsylvania, Philadelphia
    N Engl J Med 365:2330-2. 2011
    ..Understanding the function of proteins rendered mutant in disease provides insight into the mechanism of disease. Recent studies implicate the axonal cytoskeleton in neuropathies...
  8. pmc Neuronal cadherin (NCAD) increases sensory neurite formation and outgrowth on astrocytes
    Toby A Ferguson
    Department of Neurology, Temple University and Shriners Pediatric Research Center, Philadelphia, PA 19140, USA
    Neurosci Lett 522:108-12. 2012
    ..Thus, the loss of NCAD greatly impairs the formation and extension neurites on astrocytes...
  9. pmc How do mutations in GJB1 cause X-linked Charcot-Marie-Tooth disease?
    Kleopas A Kleopa
    Neurology Clinics and Neuroscience Laboratory, The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus
    Brain Res 1487:198-205. 2012
    ..Animal models of CMT1X demonstrate that loss of Cx32 in myelinating Schwann cells causes a demyelinating neuropathy. Effective therapies remain to be developed. This article is part of a Special Issue entitled Electrical Synapses...
  10. pmc X-linked Charcot-Marie-Tooth disease
    Steven S Scherer
    Department of Neurology, The Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
    J Peripher Nerv Syst 17:9-13. 2012
    ..Animal models of CMT1X demonstrate that loss of Cx32 in myelinating Schwann cells causes a demyelinating neuropathy. An effective therapy remains to be developed...
  11. pmc Dominant connexin26 mutants associated with human hearing loss have trans-dominant effects on connexin30
    Sabrina W Yum
    Division of Neurology, The Children s Hospital of Philadelphia, Department of Neurology, University of Pennsylvania, Philadelphia, PA 19104, USA
    Neurobiol Dis 38:226-36. 2010
    ..Furthermore, 8/9 Cx26 mutants inhibited the transfer of neurobiotin or calcein, indicating that these Cx26 mutants have trans-dominant effects on Cx30, an effect that may contribute to the pathogenesis of hearing loss...
  12. pmc A patient with neurofibromatosis type 1 and Charcot-Marie-Tooth disease type 1B
    Eric Lancaster
    Department of Neurology, University of Pennsylvania Medical Center, 3400 Spruce Street, 3W Gates Neurology, Philadelphia, Pennsylvania 19104, USA
    Muscle Nerve 41:555-8. 2010
    ..Although one might expect an overwhelming tumor burden due to the combination of these two disorders, the two mutations did not appear to interact...
  13. pmc Cx29 and Cx32, two connexins expressed by myelinating glia, do not interact and are functionally distinct
    Meejin Ahn
    Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104 6077, USA
    J Neurosci Res 86:992-1006. 2008
    ..Substituting the intracellular loop and/or tail of Cx32 with those of Cx29 appears to prevent Cx32 from forming functional gap junctions...
  14. pmc Cell expression of GDAP1 in the nervous system and pathogenesis of Charcot-Marie-Tooth type 4A disease
    Laia Pedrola
    Department of Genomics and Proteomics, Instituto de Biomedicina, CSIC, Valencia, Spain
    J Cell Mol Med 12:679-89. 2008
    ....
  15. ncbi Two distinct heterotypic channels mediate gap junction coupling between astrocyte and oligodendrocyte connexins
    Jennifer L Orthmann-Murphy
    Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104 6077, USA
    J Neurosci 27:13949-57. 2007
    ..Finally, Cx47 mutants that cause Pelizaeus-Merzbacher-like disease do not efficiently form functional channels with Cx43, indicating that disrupted Cx47/Cx43 channels cause this disease...
  16. pmc Gap junctions couple astrocytes and oligodendrocytes
    Jennifer L Orthmann-Murphy
    Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
    J Mol Neurosci 35:101-16. 2008
    ..Mutations of these connexin genes demonstrate that the proper functioning of myelin and oligodendrocytes requires the expression of these connexins. The physiological function of O/A and A/A junctions, however, remains to be illuminated...
  17. pmc National Institute of Neurological Disorders and Stroke (NINDS): advances in understanding and treating neuropathy, 24-25 October 2006; Bethesda, Maryland
    Eva L Feldman
    Department of Neurology, University of Michigan, Ann Arbor, MI 48109 2200, USA
    J Peripher Nerv Syst 13:1-6. 2008
    ..Short-term goals of the workshop were to form a working group for neuropathy, the Peripheral Neuropathy Study Group, and to translate new scientific findings into therapies and complete clinical trials...
  18. pmc Human oligodendrocytes express Cx31.3: function and interactions with Cx32 mutants
    Irene Sargiannidou
    Clinical Neurosciences Section, Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus
    Neurobiol Dis 30:221-33. 2008
    ..3. Thus, Cx31.3 shares many characteristics with its ortholog Cx29. Cx32 mutants with CNS phenotypes do not affect the trafficking or function of Cx31.3, and may have other toxic effects in oligodendrocytes...
  19. pmc Molecular mechanisms of inherited demyelinating neuropathies
    Steven S Scherer
    The University of Pennsylvania Medical School, Philadelphia, Pennsylvania
    Glia 56:1578-89. 2008
    ..Here, we review selected recent developments from work on the molecular mechanisms of these disorders and their implications for treatment strategies...
  20. pmc Hereditary spastic paraplegia is a novel phenotype for GJA12/GJC2 mutations
    Jennifer L Orthmann-Murphy
    Department of Neurology, University of Pennsylvania School of Medicine, Room 464 Stemmler Hall, Philadelphia, PA 19104 6077, USA
    Brain 132:426-38. 2009
    ..Thus, GJA12/GJC2 mutations can result in a milder phenotype than previously appreciated, but whether I33M retains a function of Cx47 not directly related to forming functional gap junction channels is not known...
  21. pmc Connexin32 mutations cause loss of function in Schwann cells and oligodendrocytes leading to PNS and CNS myelination defects
    Irene Sargiannidou
    Neuroscience Laboratory, The Cyprus Institute of Neurology and Genetics, 1683 Nicosia, Cyprus
    J Neurosci 29:4736-49. 2009
    ..These findings suggest that Cx32 mutations result in loss of function in myelinated cells without trans-dominant effects on other GJ proteins. Loss of Cx32 function alone in the CNS causes myelination defects...
  22. pmc Activated microglia do not form functional gap junctions in vivo
    Sameh K Wasseff
    Department of Neurology, The Perelman School of Medicine at the University of Pennsylvania, United States Electronic address
    J Neuroimmunol 269:90-3. 2014
    ..Although microglia are in close physical proximity to glia and neurons, they do not form functional gap junctions under these pathological conditions. ..

Research Grants32

  1. Connexin Distribution in Physiological Versus Pathological Cardiac Hypertrophy
    Michael R Zile; Fiscal Year: 2013
    ..pathological hypertrophy, with ex- tensively characterized cytoskeletal properties in each setting. ..
  2. INBRE III: Hawaii Statewide Research and Education Partnership (HISREP)
    ROBERT ALAN NICHOLS; Fiscal Year: 2013
    ..Overall, HISREP has matured into a well-developed alliance of partners participating in a broad range of research opportunities to expand research capacity in the state of Hawaii. ..
  3. Hippocampal Electrophysiology and Myelinogenesis in Healthy Cognitive Aging
    Philip W Landfield; Fiscal Year: 2013
    ..Therefore, the proposed studies should have both predictive and therapeutic value in determining the course of human cognitive aging. ..
  4. The Role of Intrathecal Plasma Cell Clones in MS Pathogenesis
    GREGORY PARKS OWENS; Fiscal Year: 2013
    ..Identification of pathogenic MS-specific antigen(s) will have wide application, not only for early definitive diagnosis, but also for developing strategies to modulate and possibly prevent disease. ..
  5. Structural determinants of DTI observations in developing cortex and white matter
    Christopher D Kroenke; Fiscal Year: 2013
    ..We will also use this experimental strategy to expand the capabilities of MRI to studies of earlier stages of brain development. ..
  6. Signaling in Inflammation, Stress, and Tumorigenesis
    GEORGE ROBERT STARK; Fiscal Year: 2013
    ..abstract_text> ..
  7. Molecular Mechanisms in Vanishing White Matter Disease
    ADELINE LUCIE VANDERVER; Fiscal Year: 2013
    ..This research goal is consistent with the career goal of the applicant to improve understanding and treatment of patients with leukodystrophy. ..
  8. INITIATION OF HUMAN LABOR: PREVENTION OF PREMATURITY
    Carole R Mendelson; Fiscal Year: 2013
    ..We propose that these interrelated projects, carried out by a highly interactive research team, will achieve the long-range goals of this Program and contribute to a reduction in the incidence of preterm birth. ..
  9. Pathophysiology of Alveolar Epithelial Lung Injury
    Jacob I Sznajder; Fiscal Year: 2013
    ..The insights gained from the data generated from these studies will provide novel molecular targets for the development of new therapeutic strategies to treat patients with lung injury. ..
  10. Alerations of Sleep and Circadian Timing in Aging
    Eve Van Cauter; Fiscal Year: 2013
    ..Core B (Methods and Analysis) will standard operating procedures for data collection, archival and analysis. Core C will assay peripheral levels of hormones, cytokines and other blood constituents. ..
  11. Alzheimer's Disease Research Center
    Oscar L Lopez; Fiscal Year: 2013
    ..Alzheimer's centers such as the one in Pittsburgh play a critical role in the nation's struggle to: 1) care for those currently afflicted;2) improve diagnosis and treatment;and 3) find a means of prevention. ..
  12. Increased Therapeutic Potential of Migrating Neural Stem Cells &ASC101 Treatment
    LEONARD P MILLER; Fiscal Year: 2013
    ..EAE is a widely accepted and utilized animal model of MS. If successful, this project will provide the basis for further testing ASC-101 technology in additional animal models of MS using NSCs. ..
  13. TBI-Induced Cerebral Metabolic Depression and Recovery
    David A Hovda; Fiscal Year: 2013
    ..This program project will be housed within the UCLA Brain Injury Research Center (Dr. David A. Hovda, Director) so as to assure appropriate imaging, administrative and laboratory support. ..
  14. Injury and Recovery in Developing Brain
    Flora M Vaccarino; Fiscal Year: 2013
    ..The long-term goal of these studies is to identify new means of therapeutic intervention to decrease the developmental disability and neurobehavioral sequelae of preterm birth. ..
  15. Synaptic Function: Effects of the Nerve Injury, Repair, and Altered Activity
    Timothy C Cope; Fiscal Year: 2013
    ..The Resume and Summary of Discussion above summarizes the final outcome of the group discussion. OVERALL PROGRAM EVALUATION ..
  16. Oligo-Vascular Signaling in Stroke
    Ken Arai; Fiscal Year: 2013
    ..These experiments should provide evidence to show that trophic coupling between endothelium and OL/OPC maintains and protects white matter. ..
  17. Structure-function based development of JC virion specific antagonists for PML
    Walter Atwood; Fiscal Year: 2013
    ..The three major investigators on the team have built a strong working collaboration that is evidenced by the solid preliminary data supporting this application. ..
  18. The Gateway Hypothesis: A new framework for unraveling diverse leukodystrophies
    John E Rash; Fiscal Year: 2013
    ....