Limits...
Functional gap junctions in the schwann cell myelin sheath.

Balice-Gordon RJ, Bone LJ, Scherer SS - J. Cell Biol. (1998)

Bottom Line: Gap junctions are localized to periodic interruptions in the compact myelin called Schmidt-Lanterman incisures and to paranodes; these regions contain at least one gap junction protein, connexin32 (Cx32).The radial diffusion of low molecular weight dyes across the myelin sheath was not interrupted in myelinating Schwann cells from cx32- mice, indicating that other connexins participate in forming gap junctions in these cells.Owing to the unique geometry of myelinating Schwann cells, a gap junction-mediated radial pathway may be essential for rapid diffusion between the adaxonal and perinuclear cytoplasm, since this radial pathway is approximately one million times faster than the circumferential pathway.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroscience, The University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6074, USA. rbaliceg@mail.med.upenn.edu

ABSTRACT
The Schwann cell myelin sheath is a multilamellar structure with distinct structural domains in which different proteins are localized. Intracellular dye injection and video microscopy were used to show that functional gap junctions are present within the myelin sheath that allow small molecules to diffuse between the adaxonal and perinuclear Schwann cell cytoplasm. Gap junctions are localized to periodic interruptions in the compact myelin called Schmidt-Lanterman incisures and to paranodes; these regions contain at least one gap junction protein, connexin32 (Cx32). The radial diffusion of low molecular weight dyes across the myelin sheath was not interrupted in myelinating Schwann cells from cx32- mice, indicating that other connexins participate in forming gap junctions in these cells. Owing to the unique geometry of myelinating Schwann cells, a gap junction-mediated radial pathway may be essential for rapid diffusion between the adaxonal and perinuclear cytoplasm, since this radial pathway is approximately one million times faster than the circumferential pathway.

Show MeSH
Schematic view of dye diffusion in myelinating Schwann cells following perinuclear dye injection. The left Schwann cell has  been injected with a low molecular mass compound (e.g., 5,6-carboxyfluorescein); the right Schwann cell has been injected with a high  molecular mass compound (e.g., 3,000-Da rhodamine dextran) or a low molecular mass compound in the presence of gap junction  blockers. The middle Schwann cell has been unrolled to visualize regions of compact myelin, incisures and paranodes. Not to scale.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2132877&req=5

Figure 9: Schematic view of dye diffusion in myelinating Schwann cells following perinuclear dye injection. The left Schwann cell has been injected with a low molecular mass compound (e.g., 5,6-carboxyfluorescein); the right Schwann cell has been injected with a high molecular mass compound (e.g., 3,000-Da rhodamine dextran) or a low molecular mass compound in the presence of gap junction blockers. The middle Schwann cell has been unrolled to visualize regions of compact myelin, incisures and paranodes. Not to scale.

Mentions: These results are summarized in Fig. 9, which is a schematic view of dye diffusion in myelinating Schwann cells after perinuclear dye injection. One myelinating Schwann cell has been unrolled to reveal the regions of compact myelin, incisures, and paranodes. The continuous lines represent rows of tight junctions; two or more rows form a circumferential belt around the perimeter of the cell and are also found in incisures (Tetzlaff, 1978; Shinowara et al., 1980; Sandri et al., 1982; Stolinski and Breathnach, 1982). These tight junctions are probably leaky, since they are not well developed as in tight epithelia (Friend and Gilula, 1972; Claude and Goodenough, 1973). Gap junctions are depicted as ovals and are found between the rows of tight junctions. The left Schwann cell has been injected with a low molecular mass compound, which we demonstrated diffused across incisures to fill the inner collars of Schwann cell cytoplasm. This resulted in a double train track pattern whose width closely matched the width of the myelin sheath. The right Schwann cell has been injected either with a high molecular mass compound or with a low molecular mass compound in the presence of a pharmacological blocker of gap junctions. In both cases, the dye diffused within the outer collar of Schwann cell cytoplasm, but did not reach the inner collar of cytoplasm.


Functional gap junctions in the schwann cell myelin sheath.

Balice-Gordon RJ, Bone LJ, Scherer SS - J. Cell Biol. (1998)

Schematic view of dye diffusion in myelinating Schwann cells following perinuclear dye injection. The left Schwann cell has  been injected with a low molecular mass compound (e.g., 5,6-carboxyfluorescein); the right Schwann cell has been injected with a high  molecular mass compound (e.g., 3,000-Da rhodamine dextran) or a low molecular mass compound in the presence of gap junction  blockers. The middle Schwann cell has been unrolled to visualize regions of compact myelin, incisures and paranodes. Not to scale.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2132877&req=5

Figure 9: Schematic view of dye diffusion in myelinating Schwann cells following perinuclear dye injection. The left Schwann cell has been injected with a low molecular mass compound (e.g., 5,6-carboxyfluorescein); the right Schwann cell has been injected with a high molecular mass compound (e.g., 3,000-Da rhodamine dextran) or a low molecular mass compound in the presence of gap junction blockers. The middle Schwann cell has been unrolled to visualize regions of compact myelin, incisures and paranodes. Not to scale.
Mentions: These results are summarized in Fig. 9, which is a schematic view of dye diffusion in myelinating Schwann cells after perinuclear dye injection. One myelinating Schwann cell has been unrolled to reveal the regions of compact myelin, incisures, and paranodes. The continuous lines represent rows of tight junctions; two or more rows form a circumferential belt around the perimeter of the cell and are also found in incisures (Tetzlaff, 1978; Shinowara et al., 1980; Sandri et al., 1982; Stolinski and Breathnach, 1982). These tight junctions are probably leaky, since they are not well developed as in tight epithelia (Friend and Gilula, 1972; Claude and Goodenough, 1973). Gap junctions are depicted as ovals and are found between the rows of tight junctions. The left Schwann cell has been injected with a low molecular mass compound, which we demonstrated diffused across incisures to fill the inner collars of Schwann cell cytoplasm. This resulted in a double train track pattern whose width closely matched the width of the myelin sheath. The right Schwann cell has been injected either with a high molecular mass compound or with a low molecular mass compound in the presence of a pharmacological blocker of gap junctions. In both cases, the dye diffused within the outer collar of Schwann cell cytoplasm, but did not reach the inner collar of cytoplasm.

Bottom Line: Gap junctions are localized to periodic interruptions in the compact myelin called Schmidt-Lanterman incisures and to paranodes; these regions contain at least one gap junction protein, connexin32 (Cx32).The radial diffusion of low molecular weight dyes across the myelin sheath was not interrupted in myelinating Schwann cells from cx32- mice, indicating that other connexins participate in forming gap junctions in these cells.Owing to the unique geometry of myelinating Schwann cells, a gap junction-mediated radial pathway may be essential for rapid diffusion between the adaxonal and perinuclear cytoplasm, since this radial pathway is approximately one million times faster than the circumferential pathway.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroscience, The University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6074, USA. rbaliceg@mail.med.upenn.edu

ABSTRACT
The Schwann cell myelin sheath is a multilamellar structure with distinct structural domains in which different proteins are localized. Intracellular dye injection and video microscopy were used to show that functional gap junctions are present within the myelin sheath that allow small molecules to diffuse between the adaxonal and perinuclear Schwann cell cytoplasm. Gap junctions are localized to periodic interruptions in the compact myelin called Schmidt-Lanterman incisures and to paranodes; these regions contain at least one gap junction protein, connexin32 (Cx32). The radial diffusion of low molecular weight dyes across the myelin sheath was not interrupted in myelinating Schwann cells from cx32- mice, indicating that other connexins participate in forming gap junctions in these cells. Owing to the unique geometry of myelinating Schwann cells, a gap junction-mediated radial pathway may be essential for rapid diffusion between the adaxonal and perinuclear cytoplasm, since this radial pathway is approximately one million times faster than the circumferential pathway.

Show MeSH