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The raft-associated protein MAL is required for maintenance of proper axon--glia interactions in the central nervous system.

Schaeren-Wiemers N, Bonnet A, Erb M, Erne B, Bartsch U, Kern F, Mantei N, Sherman D, Suter U - J. Cell Biol. (2004)

Bottom Line: These structural changes were accompanied by a marked reduction of contactin-associated protein/paranodin, neurofascin 155 (NF155), and the potassium channel Kv1.2, whereas nodal clusters of sodium channels were unaltered.Biochemical analysis revealed reduced myelin-associated glycoprotein, myelin basic protein, and NF155 protein levels in myelin and myelin-derived rafts.Our results demonstrate a critical role for MAL in the maintenance of central nervous system paranodes, likely by controlling the trafficking and/or sorting of NF155 and other membrane components in oligodendrocytes.

View Article: PubMed Central - PubMed

Affiliation: Neurobiology, Department of Research, University Hospital Basel, 4056 Basel, Switzerland. Nicole.Schaeren-Wiemers@unibas.ch

ABSTRACT
The myelin and lymphocyte protein (MAL) is a tetraspan raft-associated proteolipid predominantly expressed by oligodendrocytes and Schwann cells. We show that genetic ablation of mal resulted in cytoplasmic inclusions within compact myelin, paranodal loops that are everted away from the axon, and disorganized transverse bands at the paranode--axon interface in the adult central nervous system. These structural changes were accompanied by a marked reduction of contactin-associated protein/paranodin, neurofascin 155 (NF155), and the potassium channel Kv1.2, whereas nodal clusters of sodium channels were unaltered. Initial formation of paranodal regions appeared normal, but abnormalities became detectable when MAL started to be expressed. Biochemical analysis revealed reduced myelin-associated glycoprotein, myelin basic protein, and NF155 protein levels in myelin and myelin-derived rafts. Our results demonstrate a critical role for MAL in the maintenance of central nervous system paranodes, likely by controlling the trafficking and/or sorting of NF155 and other membrane components in oligodendrocytes.

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Quantification of reduced protein clusters in the para- and juxtaparanodal compartments in adult and during development. (A) Confocal three-dimensional reconstruction analyses of sagittal sections from brains of a 3-mo-old WT and KO mouse for NaCh, Caspr, and Kv1.2. The mean number of particles larger than 1 μm3 in a total tissue volume of 73 × 73 × 7.5 μm from the longitudinally cut corpus callosum was quantified and graphically shown for NaCh and Caspr costaining (mouse monoclonal anti-pan NaCh [red], rabbit polyclonal anti-Caspr [green]). Note the strong reduction of Caspr cluster pairs, whereas the amount of NaCh was not altered in KO mice. Quantitative immunofluorescent intensity analysis for Caspr and Kv1.2 (rabbit polyclonal anti-Caspr, mouse monoclonal anti-Kv1.2) showed comparable reduction in KO mice. (B) Semiquantitative analysis of nodal, paranodal, and juxtaparanodal length of residual Caspr and Kv1.2 clusters in spinal cord visualized by a bivariate scattergram. The size of NaCh clusters, the distance between a pair of Caspr clusters, the distance between two Kv1.2 clusters, and the length of Kv1.2 clusters was measured. Median: horizontal bar; n = number of analyzed clusters.
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fig6: Quantification of reduced protein clusters in the para- and juxtaparanodal compartments in adult and during development. (A) Confocal three-dimensional reconstruction analyses of sagittal sections from brains of a 3-mo-old WT and KO mouse for NaCh, Caspr, and Kv1.2. The mean number of particles larger than 1 μm3 in a total tissue volume of 73 × 73 × 7.5 μm from the longitudinally cut corpus callosum was quantified and graphically shown for NaCh and Caspr costaining (mouse monoclonal anti-pan NaCh [red], rabbit polyclonal anti-Caspr [green]). Note the strong reduction of Caspr cluster pairs, whereas the amount of NaCh was not altered in KO mice. Quantitative immunofluorescent intensity analysis for Caspr and Kv1.2 (rabbit polyclonal anti-Caspr, mouse monoclonal anti-Kv1.2) showed comparable reduction in KO mice. (B) Semiquantitative analysis of nodal, paranodal, and juxtaparanodal length of residual Caspr and Kv1.2 clusters in spinal cord visualized by a bivariate scattergram. The size of NaCh clusters, the distance between a pair of Caspr clusters, the distance between two Kv1.2 clusters, and the length of Kv1.2 clusters was measured. Median: horizontal bar; n = number of analyzed clusters.

Mentions: Because axoglial contact controls local differentiation of myelinated axons, we performed confocal analyses to determine the localization of nodal (e.g., sodium channel [NaCh]), paranodal (e.g., Caspr and neurofascin 155 [NF155]), and juxtaparanodal (e.g., Kv1.2) proteins. Immunofluorescence analysis of optic nerve sections from adult KO showed a strong reduction in the number of Caspr-positive paranodes as well as in the intensity of the Caspr labeling (Fig. 5 B, overview) when compared with WT animals (Fig. 5 A, overview). Moreover, analysis of the few remaining Caspr-positive paranodes at higher magnification revealed a diffuse distribution of Caspr (Fig. 5 B inset, open arrow). Immunofluorescence analysis of Kv1.2 in the juxtaparanodal membrane also revealed a reduction in staining intensity and in the number of positive juxtaparanodes, as well as some lateral diffusion in KO mice (Fig. 5 D). The number of nodes, indicated by tight clusters of NaCh, was not altered in the mutant (Fig. 5 B). Quantification of the number of Caspr clusters in the paranode and of Kv1.2 clusters in the juxtaparanode revealed a reduction of 70–90% and ∼70%, respectively, in KO mice (Fig. 6 A). The number of NaCh clusters was similar in WT and KO mice. Immunofluorescence analysis of NF155, which colocalized with Caspr in WT animals (Fig. 5 E, arrowheads), revealed a similarly strong reduction in staining intensity as observed for Caspr, and was barely detectable in KO mice (Fig. 5 F, overview and inset).


The raft-associated protein MAL is required for maintenance of proper axon--glia interactions in the central nervous system.

Schaeren-Wiemers N, Bonnet A, Erb M, Erne B, Bartsch U, Kern F, Mantei N, Sherman D, Suter U - J. Cell Biol. (2004)

Quantification of reduced protein clusters in the para- and juxtaparanodal compartments in adult and during development. (A) Confocal three-dimensional reconstruction analyses of sagittal sections from brains of a 3-mo-old WT and KO mouse for NaCh, Caspr, and Kv1.2. The mean number of particles larger than 1 μm3 in a total tissue volume of 73 × 73 × 7.5 μm from the longitudinally cut corpus callosum was quantified and graphically shown for NaCh and Caspr costaining (mouse monoclonal anti-pan NaCh [red], rabbit polyclonal anti-Caspr [green]). Note the strong reduction of Caspr cluster pairs, whereas the amount of NaCh was not altered in KO mice. Quantitative immunofluorescent intensity analysis for Caspr and Kv1.2 (rabbit polyclonal anti-Caspr, mouse monoclonal anti-Kv1.2) showed comparable reduction in KO mice. (B) Semiquantitative analysis of nodal, paranodal, and juxtaparanodal length of residual Caspr and Kv1.2 clusters in spinal cord visualized by a bivariate scattergram. The size of NaCh clusters, the distance between a pair of Caspr clusters, the distance between two Kv1.2 clusters, and the length of Kv1.2 clusters was measured. Median: horizontal bar; n = number of analyzed clusters.
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fig6: Quantification of reduced protein clusters in the para- and juxtaparanodal compartments in adult and during development. (A) Confocal three-dimensional reconstruction analyses of sagittal sections from brains of a 3-mo-old WT and KO mouse for NaCh, Caspr, and Kv1.2. The mean number of particles larger than 1 μm3 in a total tissue volume of 73 × 73 × 7.5 μm from the longitudinally cut corpus callosum was quantified and graphically shown for NaCh and Caspr costaining (mouse monoclonal anti-pan NaCh [red], rabbit polyclonal anti-Caspr [green]). Note the strong reduction of Caspr cluster pairs, whereas the amount of NaCh was not altered in KO mice. Quantitative immunofluorescent intensity analysis for Caspr and Kv1.2 (rabbit polyclonal anti-Caspr, mouse monoclonal anti-Kv1.2) showed comparable reduction in KO mice. (B) Semiquantitative analysis of nodal, paranodal, and juxtaparanodal length of residual Caspr and Kv1.2 clusters in spinal cord visualized by a bivariate scattergram. The size of NaCh clusters, the distance between a pair of Caspr clusters, the distance between two Kv1.2 clusters, and the length of Kv1.2 clusters was measured. Median: horizontal bar; n = number of analyzed clusters.
Mentions: Because axoglial contact controls local differentiation of myelinated axons, we performed confocal analyses to determine the localization of nodal (e.g., sodium channel [NaCh]), paranodal (e.g., Caspr and neurofascin 155 [NF155]), and juxtaparanodal (e.g., Kv1.2) proteins. Immunofluorescence analysis of optic nerve sections from adult KO showed a strong reduction in the number of Caspr-positive paranodes as well as in the intensity of the Caspr labeling (Fig. 5 B, overview) when compared with WT animals (Fig. 5 A, overview). Moreover, analysis of the few remaining Caspr-positive paranodes at higher magnification revealed a diffuse distribution of Caspr (Fig. 5 B inset, open arrow). Immunofluorescence analysis of Kv1.2 in the juxtaparanodal membrane also revealed a reduction in staining intensity and in the number of positive juxtaparanodes, as well as some lateral diffusion in KO mice (Fig. 5 D). The number of nodes, indicated by tight clusters of NaCh, was not altered in the mutant (Fig. 5 B). Quantification of the number of Caspr clusters in the paranode and of Kv1.2 clusters in the juxtaparanode revealed a reduction of 70–90% and ∼70%, respectively, in KO mice (Fig. 6 A). The number of NaCh clusters was similar in WT and KO mice. Immunofluorescence analysis of NF155, which colocalized with Caspr in WT animals (Fig. 5 E, arrowheads), revealed a similarly strong reduction in staining intensity as observed for Caspr, and was barely detectable in KO mice (Fig. 5 F, overview and inset).

Bottom Line: These structural changes were accompanied by a marked reduction of contactin-associated protein/paranodin, neurofascin 155 (NF155), and the potassium channel Kv1.2, whereas nodal clusters of sodium channels were unaltered.Biochemical analysis revealed reduced myelin-associated glycoprotein, myelin basic protein, and NF155 protein levels in myelin and myelin-derived rafts.Our results demonstrate a critical role for MAL in the maintenance of central nervous system paranodes, likely by controlling the trafficking and/or sorting of NF155 and other membrane components in oligodendrocytes.

View Article: PubMed Central - PubMed

Affiliation: Neurobiology, Department of Research, University Hospital Basel, 4056 Basel, Switzerland. Nicole.Schaeren-Wiemers@unibas.ch

ABSTRACT
The myelin and lymphocyte protein (MAL) is a tetraspan raft-associated proteolipid predominantly expressed by oligodendrocytes and Schwann cells. We show that genetic ablation of mal resulted in cytoplasmic inclusions within compact myelin, paranodal loops that are everted away from the axon, and disorganized transverse bands at the paranode--axon interface in the adult central nervous system. These structural changes were accompanied by a marked reduction of contactin-associated protein/paranodin, neurofascin 155 (NF155), and the potassium channel Kv1.2, whereas nodal clusters of sodium channels were unaltered. Initial formation of paranodal regions appeared normal, but abnormalities became detectable when MAL started to be expressed. Biochemical analysis revealed reduced myelin-associated glycoprotein, myelin basic protein, and NF155 protein levels in myelin and myelin-derived rafts. Our results demonstrate a critical role for MAL in the maintenance of central nervous system paranodes, likely by controlling the trafficking and/or sorting of NF155 and other membrane components in oligodendrocytes.

Show MeSH
Related in: MedlinePlus