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Targeted ablation of NrCAM or ankyrin-B results in disorganized lens fibers leading to cataract formation.

Moré MI, Kirsch FP, Rathjen FG - J. Cell Biol. (2001)

Bottom Line: The NgCAM-related cell adhesion molecule (NrCAM) is an immunoglobulin superfamily member of the L1 subgroup that interacts intracellularly with ankyrins.The disorganization of fiber cells becomes histologically distinct during late embryonic development and includes abnormalities of the cytoskeleton and of connexin50-containing gap junctions.Also, these studies provide genetic evidence of an interaction between NrCAM and ankyrin-B.

View Article: PubMed Central - PubMed

Affiliation: Max-Delbrück Center for Molecular Medicine, Robert-Rössle-Strasse 10, D-13092 Berlin, Germany.

ABSTRACT
The NgCAM-related cell adhesion molecule (NrCAM) is an immunoglobulin superfamily member of the L1 subgroup that interacts intracellularly with ankyrins. We reveal that the absence of NrCAM causes the formation of mature cataracts in the mouse, whereas significant pathfinding errors of commissural axons at the midline of the spinal cord or of proprioceptive axon collaterals are not detected. Cataracts, the most common cause of visual impairment, are generated in NrCAM-deficient mice by a disorganization of lens fibers, followed by cellular disintegration and accumulation of cellular debris. The disorganization of fiber cells becomes histologically distinct during late embryonic development and includes abnormalities of the cytoskeleton and of connexin50-containing gap junctions. Furthermore, analysis of lenses of ankyrin-B mutant mice also reveals a disorganization of lens fibers at postnatal day 1, indistinguishable from that generated by the absence of NrCAM, indicating that NrCAM and ankyrin-B are required to maintain contact between lens fiber cells. Also, these studies provide genetic evidence of an interaction between NrCAM and ankyrin-B.

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Expression of NrCAM in lens. (a) Schematic overview of an adult mouse lens as central longitudinal section. The lens has a spheric shape with a symmetry around its rotational axis. It contains primary lens fibers that are formed during early embryonic development and secondary lens fibers that are formed during later embryonic development and throughout life. The anterior end (pointing upwards) has a monolayer of epithelial cells that can divide and migrate towards the sides of the lens, followed by an elongation and maturation process, in which the nucleus and other organelles are lost and characteristics of secondary fiber cells are adopted. For clarity, the capsule, epithelial cells, and lens fibers are not drawn to scale (adapted from Bassnett et al., 1999). (b) Immunoblot of mouse lens proteins using 463 polyclonal antibody against NrCAM. Proteins of lenses from animals aged as indicated are loaded. (c–e) Same magnification. (c) Noncentral longitudinal section through 9-mo-old wild-type mouse secondary lens fibers stained with polyclonal antibodies against NrCAM. (d) E14 chick noncentral longitudinal lens section stained with monoclonal antibody number 3 against chick NrCAM. (e) E14 chick lens longitudinal section stained with polyclonal antibodies against NrCAM. (f and g) Mouse P12 noncentral longitudinal lens sections stained with polyclonal antibodies against NrCAM. ca., capsule; ep., epithelium. (f) side-front region with epithel. The outer edge of the capsule is marked. (g) Posterior edge of the lens. (h and i) Immunoblots of E14 brain (B) and lens (L) lysates reveal that only NrCAM, but no other family members or extracellular NrCAM interaction partner is present in the lens. Since antibodies to anti-CHL1 or anti-RPTPβ/ζ are available only for mouse proteins, these were not tested in chick. For the other proteins, the chick immunoblot is shown for reasons of availability or quality of the antibodies. Molecular weight markers are indicated on the left. (h) Expression of NrCAM, NrCAM homologues NgCAM (species homologue of mouse L1), neurofascin, and CHL1. Note that neurofascin is expressed in several molecular weight forms. (i) Expression of extracellular NrCAM interaction partners F11, axonin-1, and RPTPβ/ζ.
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fig3: Expression of NrCAM in lens. (a) Schematic overview of an adult mouse lens as central longitudinal section. The lens has a spheric shape with a symmetry around its rotational axis. It contains primary lens fibers that are formed during early embryonic development and secondary lens fibers that are formed during later embryonic development and throughout life. The anterior end (pointing upwards) has a monolayer of epithelial cells that can divide and migrate towards the sides of the lens, followed by an elongation and maturation process, in which the nucleus and other organelles are lost and characteristics of secondary fiber cells are adopted. For clarity, the capsule, epithelial cells, and lens fibers are not drawn to scale (adapted from Bassnett et al., 1999). (b) Immunoblot of mouse lens proteins using 463 polyclonal antibody against NrCAM. Proteins of lenses from animals aged as indicated are loaded. (c–e) Same magnification. (c) Noncentral longitudinal section through 9-mo-old wild-type mouse secondary lens fibers stained with polyclonal antibodies against NrCAM. (d) E14 chick noncentral longitudinal lens section stained with monoclonal antibody number 3 against chick NrCAM. (e) E14 chick lens longitudinal section stained with polyclonal antibodies against NrCAM. (f and g) Mouse P12 noncentral longitudinal lens sections stained with polyclonal antibodies against NrCAM. ca., capsule; ep., epithelium. (f) side-front region with epithel. The outer edge of the capsule is marked. (g) Posterior edge of the lens. (h and i) Immunoblots of E14 brain (B) and lens (L) lysates reveal that only NrCAM, but no other family members or extracellular NrCAM interaction partner is present in the lens. Since antibodies to anti-CHL1 or anti-RPTPβ/ζ are available only for mouse proteins, these were not tested in chick. For the other proteins, the chick immunoblot is shown for reasons of availability or quality of the antibodies. Molecular weight markers are indicated on the left. (h) Expression of NrCAM, NrCAM homologues NgCAM (species homologue of mouse L1), neurofascin, and CHL1. Note that neurofascin is expressed in several molecular weight forms. (i) Expression of extracellular NrCAM interaction partners F11, axonin-1, and RPTPβ/ζ.

Mentions: NrCAM has been studied so far primarily in the developing nervous system. To investigate its function in the formation of cataracts, we first analyzed the distribution of NrCAM and its extracellular ligands in chick as well as in mouse lenses at various developmental stages by histological methods and Western blotting. Fig. 3 a gives an overview of the lens architecture. Antibodies against NrCAM stain the cell surface of secondary fiber cells in mouse (Fig 3 c) as well as in chick sections (Fig. 3, d and e), showing regular staining patterns depending on the direction and position of the section. The fiber cells are flattened hexagons in cross-section (Fig. 3, c and d), and the radial cell surfaces are highlighted more than the tangential cell surfaces. A longitudinal section of the mouse or chick lens results in a pattern of parallel lines, each line representing the neighboring cell surfaces of two lens fiber cells (Fig. 3 e). The expression of NrCAM in the primary lens fibers was still visible in P12 mouse lenses, but very low in adult mouse lenses (not shown). Interestingly, no NrCAM expression was observed in the lens epithelium or the lens capsule (Fig. 3 f), or the cell surface of fiber cells bordering the capsule (Fig. 3 g), indicating that the contact formation between lens epithelial cells and between lens fiber cells and capsule is not mediated by NrCAM.


Targeted ablation of NrCAM or ankyrin-B results in disorganized lens fibers leading to cataract formation.

Moré MI, Kirsch FP, Rathjen FG - J. Cell Biol. (2001)

Expression of NrCAM in lens. (a) Schematic overview of an adult mouse lens as central longitudinal section. The lens has a spheric shape with a symmetry around its rotational axis. It contains primary lens fibers that are formed during early embryonic development and secondary lens fibers that are formed during later embryonic development and throughout life. The anterior end (pointing upwards) has a monolayer of epithelial cells that can divide and migrate towards the sides of the lens, followed by an elongation and maturation process, in which the nucleus and other organelles are lost and characteristics of secondary fiber cells are adopted. For clarity, the capsule, epithelial cells, and lens fibers are not drawn to scale (adapted from Bassnett et al., 1999). (b) Immunoblot of mouse lens proteins using 463 polyclonal antibody against NrCAM. Proteins of lenses from animals aged as indicated are loaded. (c–e) Same magnification. (c) Noncentral longitudinal section through 9-mo-old wild-type mouse secondary lens fibers stained with polyclonal antibodies against NrCAM. (d) E14 chick noncentral longitudinal lens section stained with monoclonal antibody number 3 against chick NrCAM. (e) E14 chick lens longitudinal section stained with polyclonal antibodies against NrCAM. (f and g) Mouse P12 noncentral longitudinal lens sections stained with polyclonal antibodies against NrCAM. ca., capsule; ep., epithelium. (f) side-front region with epithel. The outer edge of the capsule is marked. (g) Posterior edge of the lens. (h and i) Immunoblots of E14 brain (B) and lens (L) lysates reveal that only NrCAM, but no other family members or extracellular NrCAM interaction partner is present in the lens. Since antibodies to anti-CHL1 or anti-RPTPβ/ζ are available only for mouse proteins, these were not tested in chick. For the other proteins, the chick immunoblot is shown for reasons of availability or quality of the antibodies. Molecular weight markers are indicated on the left. (h) Expression of NrCAM, NrCAM homologues NgCAM (species homologue of mouse L1), neurofascin, and CHL1. Note that neurofascin is expressed in several molecular weight forms. (i) Expression of extracellular NrCAM interaction partners F11, axonin-1, and RPTPβ/ζ.
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Related In: Results  -  Collection

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fig3: Expression of NrCAM in lens. (a) Schematic overview of an adult mouse lens as central longitudinal section. The lens has a spheric shape with a symmetry around its rotational axis. It contains primary lens fibers that are formed during early embryonic development and secondary lens fibers that are formed during later embryonic development and throughout life. The anterior end (pointing upwards) has a monolayer of epithelial cells that can divide and migrate towards the sides of the lens, followed by an elongation and maturation process, in which the nucleus and other organelles are lost and characteristics of secondary fiber cells are adopted. For clarity, the capsule, epithelial cells, and lens fibers are not drawn to scale (adapted from Bassnett et al., 1999). (b) Immunoblot of mouse lens proteins using 463 polyclonal antibody against NrCAM. Proteins of lenses from animals aged as indicated are loaded. (c–e) Same magnification. (c) Noncentral longitudinal section through 9-mo-old wild-type mouse secondary lens fibers stained with polyclonal antibodies against NrCAM. (d) E14 chick noncentral longitudinal lens section stained with monoclonal antibody number 3 against chick NrCAM. (e) E14 chick lens longitudinal section stained with polyclonal antibodies against NrCAM. (f and g) Mouse P12 noncentral longitudinal lens sections stained with polyclonal antibodies against NrCAM. ca., capsule; ep., epithelium. (f) side-front region with epithel. The outer edge of the capsule is marked. (g) Posterior edge of the lens. (h and i) Immunoblots of E14 brain (B) and lens (L) lysates reveal that only NrCAM, but no other family members or extracellular NrCAM interaction partner is present in the lens. Since antibodies to anti-CHL1 or anti-RPTPβ/ζ are available only for mouse proteins, these were not tested in chick. For the other proteins, the chick immunoblot is shown for reasons of availability or quality of the antibodies. Molecular weight markers are indicated on the left. (h) Expression of NrCAM, NrCAM homologues NgCAM (species homologue of mouse L1), neurofascin, and CHL1. Note that neurofascin is expressed in several molecular weight forms. (i) Expression of extracellular NrCAM interaction partners F11, axonin-1, and RPTPβ/ζ.
Mentions: NrCAM has been studied so far primarily in the developing nervous system. To investigate its function in the formation of cataracts, we first analyzed the distribution of NrCAM and its extracellular ligands in chick as well as in mouse lenses at various developmental stages by histological methods and Western blotting. Fig. 3 a gives an overview of the lens architecture. Antibodies against NrCAM stain the cell surface of secondary fiber cells in mouse (Fig 3 c) as well as in chick sections (Fig. 3, d and e), showing regular staining patterns depending on the direction and position of the section. The fiber cells are flattened hexagons in cross-section (Fig. 3, c and d), and the radial cell surfaces are highlighted more than the tangential cell surfaces. A longitudinal section of the mouse or chick lens results in a pattern of parallel lines, each line representing the neighboring cell surfaces of two lens fiber cells (Fig. 3 e). The expression of NrCAM in the primary lens fibers was still visible in P12 mouse lenses, but very low in adult mouse lenses (not shown). Interestingly, no NrCAM expression was observed in the lens epithelium or the lens capsule (Fig. 3 f), or the cell surface of fiber cells bordering the capsule (Fig. 3 g), indicating that the contact formation between lens epithelial cells and between lens fiber cells and capsule is not mediated by NrCAM.

Bottom Line: The NgCAM-related cell adhesion molecule (NrCAM) is an immunoglobulin superfamily member of the L1 subgroup that interacts intracellularly with ankyrins.The disorganization of fiber cells becomes histologically distinct during late embryonic development and includes abnormalities of the cytoskeleton and of connexin50-containing gap junctions.Also, these studies provide genetic evidence of an interaction between NrCAM and ankyrin-B.

View Article: PubMed Central - PubMed

Affiliation: Max-Delbrück Center for Molecular Medicine, Robert-Rössle-Strasse 10, D-13092 Berlin, Germany.

ABSTRACT
The NgCAM-related cell adhesion molecule (NrCAM) is an immunoglobulin superfamily member of the L1 subgroup that interacts intracellularly with ankyrins. We reveal that the absence of NrCAM causes the formation of mature cataracts in the mouse, whereas significant pathfinding errors of commissural axons at the midline of the spinal cord or of proprioceptive axon collaterals are not detected. Cataracts, the most common cause of visual impairment, are generated in NrCAM-deficient mice by a disorganization of lens fibers, followed by cellular disintegration and accumulation of cellular debris. The disorganization of fiber cells becomes histologically distinct during late embryonic development and includes abnormalities of the cytoskeleton and of connexin50-containing gap junctions. Furthermore, analysis of lenses of ankyrin-B mutant mice also reveals a disorganization of lens fibers at postnatal day 1, indistinguishable from that generated by the absence of NrCAM, indicating that NrCAM and ankyrin-B are required to maintain contact between lens fiber cells. Also, these studies provide genetic evidence of an interaction between NrCAM and ankyrin-B.

Show MeSH
Related in: MedlinePlus