The paranodal junction (PNJ) is a crucial component of myelinated nerve fibers responsible for attaching the myelin sheath to the axon, restricting short-circuiting of nodal action currents under the myelin sheath, segregating nodal Na channels from juxtaparanodal K+ channels and maintaining axonal domains over time. Long-term stability of this junction depends on the presence of a structural element, the transverse bands, without which the PNJ deteriorates gradually, resulting in progressive neurological impairment and shortened lifespan. PNJs in the PNS also display short-term structural plasticity in response to electrical stimulation that may modulate nodal behavior. In this renewal period, we propose to address three questions as a way of further probing the function of the PNJ and the transverse bands and their role in physiology and pathology: 1. How do PNJs in the CNS, where myelin is thinner and is formed by oligodendrocytes, differ with respect to structure and permeability from those in the PNS, where myelin is formed by Schwann cells? 2. How 'plastic'are PNJs in the CNS;i.e., how do their structure and permeability change with neural activity, and how do those changes affect function? 3. How do genetic defects that cause loss of transverse bands affect the structure and permeability of PNJs and their susceptibility to activity-mediated changes? The proposed studies will make use of new methods, specifically EM tomography and high-pressure freezing, for defining the structure and dimensions of the PNJ. Second, we will make use of fluorescent dextran tracers and electron opaque tracers for comparing the permeability of CNS PNJs with that of PNJs in the PNS. Third, we will examine the effects of different degrees of electrical stimulation in situ on the structure and permeability of PNJs in order to define their responses to normal and abnormal levels of activity. Finally we will carry out parallel structural, permeability and stimulation studies on mutant mice with genetically defective transverse bands in order to determine how these defects modify the structure and permeability of the PNJs and their susceptibility to activity-induced changes. These studies are relevant to genetic and acquired human diseases of myelin in which pathological processes affect transverse bands and the PNJ.

Public Health Relevance

The studies outlined are relevant to various diseases of myelin including multiple sclerosis (MS). The project proposed would focus on an important component of myelinated nerve fibers, the paranodal junction. Abnormalities of that junction in mutant mice may provide insight into the mechanisms underlying some of the neurological deficits seen in MS and other diseases of myelin and suggest strategies for correcting those deficits.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS037475-11
Application #
8287065
Study Section
Cellular and Molecular Biology of Glia Study Section (CMBG)
Program Officer
Utz, Ursula
Project Start
1998-04-01
Project End
2014-06-30
Budget Start
2012-07-01
Budget End
2013-06-30
Support Year
11
Fiscal Year
2012
Total Cost
$369,688
Indirect Cost
$150,938
Name
New York University
Department
Physiology
Type
Schools of Medicine
DUNS #
121911077
City
New York
State
NY
Country
United States
Zip Code
10016
Rosenbluth, Jack; Bobrowski-Khoury, Natasha (2014) Paranodal dysmyelination in peripheral nerves of Trembler mice. J Neurosci Res 92:476-85
Amor, Veronique; Feinberg, Konstantin; Eshed-Eisenbach, Yael et al. (2014) Long-term maintenance of Na+ channels at nodes of Ranvier depends on glial contact mediated by gliomedin and NrCAM. J Neurosci 34:5089-98
Gordon, Aaron; Adamsky, Konstantin; Vainshtein, Anya et al. (2014) Caspr and caspr2 are required for both radial and longitudinal organization of myelinated axons. J Neurosci 34:14820-6
Rosenbluth, J; Bobrowski-Khoury, N (2013) Structural bases for central nervous system malfunction in the quaking mouse: dysmyelination in a potential model of schizophrenia. J Neurosci Res 91:374-81
Rosenbluth, Jack; Mierzwa, Amanda; Shroff, Seema (2013) Molecular architecture of myelinated nerve fibers: leaky paranodal junctions and paranodal dysmyelination. Neuroscientist 19:629-41
Ivanovic, Aleksandra; Horresh, Ido; Golan, Neev et al. (2012) The cytoskeletal adapter protein 4.1G organizes the internodes in peripheral myelinated nerves. J Cell Biol 196:337-44
Rosenbluth, Jack; Petzold, Chris; Peles, Elior (2012) Dependence of paranodal junctional gap width on transverse bands. J Comp Neurol 520:2774-84
Shroff, Seema; Mierzwa, Amanda; Scherer, Steven S et al. (2011) Paranodal permeability in "myelin mutants". Glia 59:1447-57
Brown, Michael E; Martin, John R; Rosenbluth, Jack et al. (2011) A novel path for rapid transverse communication of vestibular signals in turtle cerebellum. J Neurophysiol 105:1071-88
Mierzwa, Amanda J; Arevalo, Juan-Carlos; Schiff, Rolf et al. (2010) Role of transverse bands in maintaining paranodal structure and axolemmal domain organization in myelinated nerve fibers: effect on longevity in dysmyelinated mutant mice. J Comp Neurol 518:2841-53

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