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Neural cell adhesion molecule, NCAM, regulates thalamocortical axon pathfinding and the organization of the cortical somatosensory representation in mouse.

Enriquez-Barreto L, Palazzetti C, Brennaman LH, Maness PF, Fairén A - Front Mol Neurosci (2012)

Bottom Line: During the early postnatal period, rostrolateral TC axons within the internal capsule along the ventral telencephalon adopted distorted trajectories in the ventral telencephalon and failed to reach the neocortex in NCAM mutant animals.NCAM mutants showed abnormal segregation of layer IV barrels in a restricted portion of the somatosensory cortex.These results indicate a novel role for NCAM in axonal pathfinding and topographic sorting of TC axons, which may be important for the function of specific territories of sensory representation in the somatosensory cortex.

View Article: PubMed Central - PubMed

Affiliation: Instituto de Neurociencias, Consejo Superior de Investigaciones Científicas-Universidad Miguel Hernández San Juan de Alicante, Spain.

ABSTRACT
To study the potential role of neural cell adhesion molecule (NCAM) in the development of thalamocortical (TC) axon topography, wild type, and NCAM mutant mice were analyzed for NCAM expression, projection, and targeting of TC afferents within the somatosensory area of the neocortex. Here we report that NCAM and its α-2,8-linked polysialic acid (PSA) are expressed in developing TC axons during projection to the neocortex. Pathfinding of TC axons in wild type and mutant mice was mapped using anterograde DiI labeling. At embryonic day E16.5, mutant mice displayed misguided TC axons in the dorsal telencephalon, but not in the ventral telencephalon, an intermediate target that initially sorts TC axons toward correct neocortical areas. During the early postnatal period, rostrolateral TC axons within the internal capsule along the ventral telencephalon adopted distorted trajectories in the ventral telencephalon and failed to reach the neocortex in NCAM mutant animals. NCAM mutants showed abnormal segregation of layer IV barrels in a restricted portion of the somatosensory cortex. As shown by Nissl and cytochrome oxidase staining, barrels of the anterolateral barrel subfield (ALBSF) and the most distal barrels of the posteromedial barrel subfield (PMBSF) did not segregate properly in mutant mice. These results indicate a novel role for NCAM in axonal pathfinding and topographic sorting of TC axons, which may be important for the function of specific territories of sensory representation in the somatosensory cortex.

No MeSH data available.


Related in: MedlinePlus

Thalamocortical axons expressed NCAM and PSA at E14.5. Sections containing DiI-labeled TC axons were labeled with antibodies to the intracellular domains of large NCAM isoforms (A) and PSA (B). Insets show the regions analyzed. A', A” and B and B” show the detection channels separately. Note that the red signal of DiI labeled axons in the ventral telencephalon coincided in all cases with the green signal corresponding to NCAM (A–A”) or PSA (B–B”) immunoreactivities. Maximum projections of confocal microscope stacks. DT, dorsal thalamus; ctx, cortex. Bars in A, B, 200 μm; insets, 100 μm.
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Figure 1: Thalamocortical axons expressed NCAM and PSA at E14.5. Sections containing DiI-labeled TC axons were labeled with antibodies to the intracellular domains of large NCAM isoforms (A) and PSA (B). Insets show the regions analyzed. A', A” and B and B” show the detection channels separately. Note that the red signal of DiI labeled axons in the ventral telencephalon coincided in all cases with the green signal corresponding to NCAM (A–A”) or PSA (B–B”) immunoreactivities. Maximum projections of confocal microscope stacks. DT, dorsal thalamus; ctx, cortex. Bars in A, B, 200 μm; insets, 100 μm.

Mentions: We assessed the presence of PSA and NCAM in thalamocortical (TC) axons during prenatal development using axonal tract-tracing and immunohistochemistry. As a first step to verify that TCAs expressed NCAM and its polysialilated form PSA-NCAM, small crystals of DiI were inserted in the dorsal thalamus of E14.5 wild type mice. DiI is a lipophilic tracer that diffuses within the lipid bilayer of the plasma membrane and accurately labels axonal projections in brain tissues fixed with aldehydes (Godement et al., 1987). DiI-labeled TC axons were immunofluorescently labeled with antibodies to the cytoplasmic domain of transmembrane NCAM isoforms (140 and 180 kDa) and PSA. DiI labeled TC axons displayed both NCAM and PSA (Figures 1A,B). DiI was excited with a HeNe 543 nm laser, while an Ar/Kr 488 nm laser excited AlexaFluor 488 used to detect NCAM and PSA immunoreactivities. Comparison of Figures 1A',A”,B',B” shows that no bleeding occurred between the two detection channels in the confocal microscope, thus confirming the localization of NCAM or PSA detection signals in DiI-labeled TC axons.


Neural cell adhesion molecule, NCAM, regulates thalamocortical axon pathfinding and the organization of the cortical somatosensory representation in mouse.

Enriquez-Barreto L, Palazzetti C, Brennaman LH, Maness PF, Fairén A - Front Mol Neurosci (2012)

Thalamocortical axons expressed NCAM and PSA at E14.5. Sections containing DiI-labeled TC axons were labeled with antibodies to the intracellular domains of large NCAM isoforms (A) and PSA (B). Insets show the regions analyzed. A', A” and B and B” show the detection channels separately. Note that the red signal of DiI labeled axons in the ventral telencephalon coincided in all cases with the green signal corresponding to NCAM (A–A”) or PSA (B–B”) immunoreactivities. Maximum projections of confocal microscope stacks. DT, dorsal thalamus; ctx, cortex. Bars in A, B, 200 μm; insets, 100 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3378950&req=5

Figure 1: Thalamocortical axons expressed NCAM and PSA at E14.5. Sections containing DiI-labeled TC axons were labeled with antibodies to the intracellular domains of large NCAM isoforms (A) and PSA (B). Insets show the regions analyzed. A', A” and B and B” show the detection channels separately. Note that the red signal of DiI labeled axons in the ventral telencephalon coincided in all cases with the green signal corresponding to NCAM (A–A”) or PSA (B–B”) immunoreactivities. Maximum projections of confocal microscope stacks. DT, dorsal thalamus; ctx, cortex. Bars in A, B, 200 μm; insets, 100 μm.
Mentions: We assessed the presence of PSA and NCAM in thalamocortical (TC) axons during prenatal development using axonal tract-tracing and immunohistochemistry. As a first step to verify that TCAs expressed NCAM and its polysialilated form PSA-NCAM, small crystals of DiI were inserted in the dorsal thalamus of E14.5 wild type mice. DiI is a lipophilic tracer that diffuses within the lipid bilayer of the plasma membrane and accurately labels axonal projections in brain tissues fixed with aldehydes (Godement et al., 1987). DiI-labeled TC axons were immunofluorescently labeled with antibodies to the cytoplasmic domain of transmembrane NCAM isoforms (140 and 180 kDa) and PSA. DiI labeled TC axons displayed both NCAM and PSA (Figures 1A,B). DiI was excited with a HeNe 543 nm laser, while an Ar/Kr 488 nm laser excited AlexaFluor 488 used to detect NCAM and PSA immunoreactivities. Comparison of Figures 1A',A”,B',B” shows that no bleeding occurred between the two detection channels in the confocal microscope, thus confirming the localization of NCAM or PSA detection signals in DiI-labeled TC axons.

Bottom Line: During the early postnatal period, rostrolateral TC axons within the internal capsule along the ventral telencephalon adopted distorted trajectories in the ventral telencephalon and failed to reach the neocortex in NCAM mutant animals.NCAM mutants showed abnormal segregation of layer IV barrels in a restricted portion of the somatosensory cortex.These results indicate a novel role for NCAM in axonal pathfinding and topographic sorting of TC axons, which may be important for the function of specific territories of sensory representation in the somatosensory cortex.

View Article: PubMed Central - PubMed

Affiliation: Instituto de Neurociencias, Consejo Superior de Investigaciones Científicas-Universidad Miguel Hernández San Juan de Alicante, Spain.

ABSTRACT
To study the potential role of neural cell adhesion molecule (NCAM) in the development of thalamocortical (TC) axon topography, wild type, and NCAM mutant mice were analyzed for NCAM expression, projection, and targeting of TC afferents within the somatosensory area of the neocortex. Here we report that NCAM and its α-2,8-linked polysialic acid (PSA) are expressed in developing TC axons during projection to the neocortex. Pathfinding of TC axons in wild type and mutant mice was mapped using anterograde DiI labeling. At embryonic day E16.5, mutant mice displayed misguided TC axons in the dorsal telencephalon, but not in the ventral telencephalon, an intermediate target that initially sorts TC axons toward correct neocortical areas. During the early postnatal period, rostrolateral TC axons within the internal capsule along the ventral telencephalon adopted distorted trajectories in the ventral telencephalon and failed to reach the neocortex in NCAM mutant animals. NCAM mutants showed abnormal segregation of layer IV barrels in a restricted portion of the somatosensory cortex. As shown by Nissl and cytochrome oxidase staining, barrels of the anterolateral barrel subfield (ALBSF) and the most distal barrels of the posteromedial barrel subfield (PMBSF) did not segregate properly in mutant mice. These results indicate a novel role for NCAM in axonal pathfinding and topographic sorting of TC axons, which may be important for the function of specific territories of sensory representation in the somatosensory cortex.

No MeSH data available.


Related in: MedlinePlus