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MYELIN & SCHWANN CELL COMPONENTS

Myelin
  Axon relations
  Diseases
  Domains
  Glycoproteins
  Other components
  Pathology
  Structure
    Cross-section
    Longitudinal
Node of Ranvier
Schwann cell
  Components: Non-myelinating
  Components: Other
  Development

Theodor Schwann



Myelinated axon + Schwann cell cytoplasm Schwann Cell Development2


Schwann cells & Myelin: Domains & Structure



Molecules in selective peripheral myelin & Schwann cell regions

Myelin Glycoproteins1

GlycoproteinProperties
P0 Location: Compact PNS myelin
Abundant: 50% of PNS myelin proteins
Molecular: Contains sulfated N-glycans; 30-kDa
Function: Stabilizes intraperiod line of compact PNS myelin by homophilic interactions
Diseases: CMT 1B; Dejerine-Sottas (CMT III);
    Congenital Hypomyelinating neuropathy
Myelin associated glycoprotein Locations
  CNS > PNS
  Cells: Myelin-forming oligodendrocytes & Schwann cells
  Membranes: Periaxonal Schwann cell; ? Abaxonal
Molecular: 100 kDa
  N-linked glycosylation: 30% by weight; Contain sialic acid, sulfate & GlcNAc
  Binds to α2,3-linked sialic acids
Function: Axon-Glia interactions; Schmidt-Lanterman clefts
Disease: Anti-MAG neuropathy
Peripheral myelin protein-22 (PMP-22) Location: Compact PNS myelin
Molecular: 22-kDa
  Similar to PLP/DM-20 & OTM in CNS
  4 hydrophobic transmembrane domains
Forms complexes with P0 in myelin membranes Disease: CMT 1A
170 kDa glycoprotein (SAG)PNS Schwann cells & myelin
Schwann cell myelin protein (SMP)Homology to MAG
? present in humans
Myelin/Oligodendrocyte glycoprotein (MOG) Location: External surface of oligodendrocytes & CNS myelin
Oligodendrocyte-myelin glycoprotein (OMgp) Location: CNS myelin
General properties
  • Many are members of immunoglobulin superfamily
  • Often express HNK-1 carbohydrate epitope
  • Carbohydrate epitope may be involved in homophilic cell-cell interactions
  • Glycosylation
    • PNS: Major myelin proteins glycosylated
    • CNS: Major myelin proteins not glycosylated


Nodes of Ranvier & Associated Structures6

Internode Juxtaparanode Compact myelin Compact myelin Paranode Node of Ranvier

Node of Ranvier

Myelinated axon near
Paranode & Node of Ranvier
Paranode Juxtaparanode Internodal region: Components

Other myelin-related components

Non-myelinating & Denervated Schwann cell components

Other Schwann cell components



Early growth response (EGR) genes



Myelin-Associated Glycoprotein (MAG; siglec-4) 1,4


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Return to Demyelinating neuropathies

References
1. J. Molec Neurosci 1997;7:1-12, Cell Mol Life Sci 2002;59:18511871, J Neurol Sci 2005;228:187-189
2. Trends Neurosci 1999;22:402-410, Journal of Peripheral Nervous System 2008;13:122135
3. Brain 2000;123:222-233
4. Glia 2000;29:154-165
5. Neuron 2001;30:677-687
6. J Periph Nerv Sys 2002;7:1-12, Glia 2008;56:1532-1540

8/28/2013