Paranodal permeability in "myelin mutants"
Seema Shroff1, Amanda Mierzwa, Steven S Scherer
1Department Physiology & Neuroscience, NYU School of Medicine, New York, New York, USA.
Glia
|May 28, 2011
Summary
Paranodal permeability in myelinated nerve fibers is not affected by transverse bands (TBs) but depends on paranode length. This study used fluorescent dextran tracers in control and mutant mice to assess nerve fiber permeability.
Area of Science:
- Neuroscience
- Cell Biology
- Biochemistry
Background:
- The paranode is a specialized structure in myelinated nerve fibers crucial for saltatory conduction.
- Transverse bands (TBs) are key components of the paranodal junction, but their role in permeability is not fully understood.
Purpose of the Study:
- To investigate the role of transverse bands (TBs) and paranode length in regulating paranodal permeability.
- To assess the impact of myelin mutations on paranodal barrier function using fluorescent dextran tracers.
Main Methods:
- Utilized fluorescent dextran tracers of varying molecular weights (3-70 kDa) to evaluate paranodal permeability in sciatic nerve fibers.
- Examined control mice and three myelin mutant mouse models: Caspr-null, cst-null, and shaking mice.
Main Results:
- Paranodes are permeable to small dextran tracers (3 and 10 kDa) in all tested mice.
- Larger dextran tracers (40 and 70 kDa) showed limited penetration and shorter distances in all groups.
- Caspr-null and cst-null mice, despite lacking TBs, exhibited normal paranodal permeability.
- Shaking mice, with thinner myelin and shorter paranodes, displayed increased tracer permeability.
Conclusions:
- Paranodal permeability is independent of the presence or absence of transverse bands (TBs).
- Paranode length is a critical determinant of tracer penetration through the paranodal pathway.
- The helical extracellular pathway (pathway 3) through the paranode is influenced by paranode length, affecting tracer movement.
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