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LAD-1, the Caenorhabditis elegans L1CAM homologue, participates in embryonic and gonadal morphogenesis and is a substrate for fibroblast growth factor receptor pathway-dependent phosphotyrosine-based signaling.

Chen L, Ong B, Bennett V - J. Cell Biol. (2001)

Bottom Line: In addition, the ubiquitously expressed LAD-1, which binds to ankyrin-G, colocalizes with the C. elegans ankyrin, UNC-44, in multiple tissues at sites of cell-cell contact.These findings suggest a novel ankyrin-independent role for LAD-1 related to FGFR signaling.Taken together, these results indicate that L1CAMs constitute a family of ubiquitous adhesion molecules, which participate in tissue morphogenesis and maintaining tissue integrity in metazoans.

View Article: PubMed Central - PubMed

Affiliation: Howard Hughes Medical Institute, Department of Cell Biology, and Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA. l.chen@cellbio.duke.edu

ABSTRACT
This study shows that L1-like adhesion (LAD-1), the sole Caenorhabditis elegans homologue of the L1 family of neuronal adhesion molecules, is required for proper development of the germline and the early embryo and embryonic and gonadal morphogenesis. In addition, the ubiquitously expressed LAD-1, which binds to ankyrin-G, colocalizes with the C. elegans ankyrin, UNC-44, in multiple tissues at sites of cell-cell contact. Finally, we show that LAD-1 is phosphorylated in a fibroblast growth factor receptor (FGFR) pathway-dependent manner on a tyrosine residue in the highly conserved ankyrin-binding motif, FIGQY, which was shown previously to abolish the L1 family of cell adhesion molecule (L1CAM) binding to ankyrin in cultured cells. Immunofluorescence studies revealed that FIGQY-tyrosine-phosphorylated LAD-1 does not colocalize with nonphosphorylated LAD-1 or UNC-44 ankyrin but instead is localized to sites that undergo mechanical stress in polarized epithelia and axon-body wall muscle junctions. These findings suggest a novel ankyrin-independent role for LAD-1 related to FGFR signaling. Taken together, these results indicate that L1CAMs constitute a family of ubiquitous adhesion molecules, which participate in tissue morphogenesis and maintaining tissue integrity in metazoans.

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LAD-1 is localized to the plasma membrane at sites of cell–cell contact in all cells throughout development. (A, i) An immunoblot of total C. elegans lysates reveals four major LAD-1 polypeptides (200, 185, 120, and 65 kD) that were detected by a rabbit polyclonal antibody raised against the LAD-1 cytoplasmic domain (lane 2). The lower bands are not LAD-1 related, since they are also recognized by 125 I-labeled protein A (lane 3). (Lane 1) Coomassie blue staining of total C. elegans lysate. Equivalent lysate amounts. (ii) nDf41 homozygous embryos, which contains the lad-1 gene, show LAD-1 immunodetection (green) unlike stDf7 homozygous embryos, which lack the lad-1 gene; only control antibody staining of JAM-1 is seen in red (iii). B and C show immunodetection of LAD-1 in embryos. (B) LAD-1 is localized to sites of cell–cell contact, including the partial plasma membrane of a developing two-cell staged embryo (arrow). A one-cell embryo, which lacks contact sites, does not show LAD-1 localization (arrowhead). (C) LAD-1 is found in the developing nervous system (arrow) with robust LAD-1 staining in the nerve ring, the major C. elegans neuropil (arrowhead). D and E show LAD-1 expression in multiple tissues in a larva and adult, respectively. LAD-1 is present in the nerve ring and ventral nerve cord (D, arrowhead) and in the hypodermis (skin cells) (D, arrows), the plasma membrane of body wall muscles (F, arrow), neuronal cell bodies (G, long arrow), dendrites (G, arrowhead), and the pharynx (G, short arrow). LAD-1 is also present in the syncytial germline where its localization at contact sites is maintained. A schematic of the C. elegans germline is shown in H: arrowheads point to oocytes and arrows point to germ nuclei. The cross section of the cylindrical gonad reveals a single layer of germ nuclei around a cytoplasmic core with T-shaped membranes between each nucleus. In a grazing section of the germline shown in I, LAD-1 is localized at oocyte–oocyte contact (arrowhead) and only the vertical part of the T-shaped membrane, which divides two neighboring germline nuclei (arrows). The top of the T does not show LAD-1 localization. Bars: (A) 20 μm; (B–I) 25 μm.
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fig2: LAD-1 is localized to the plasma membrane at sites of cell–cell contact in all cells throughout development. (A, i) An immunoblot of total C. elegans lysates reveals four major LAD-1 polypeptides (200, 185, 120, and 65 kD) that were detected by a rabbit polyclonal antibody raised against the LAD-1 cytoplasmic domain (lane 2). The lower bands are not LAD-1 related, since they are also recognized by 125 I-labeled protein A (lane 3). (Lane 1) Coomassie blue staining of total C. elegans lysate. Equivalent lysate amounts. (ii) nDf41 homozygous embryos, which contains the lad-1 gene, show LAD-1 immunodetection (green) unlike stDf7 homozygous embryos, which lack the lad-1 gene; only control antibody staining of JAM-1 is seen in red (iii). B and C show immunodetection of LAD-1 in embryos. (B) LAD-1 is localized to sites of cell–cell contact, including the partial plasma membrane of a developing two-cell staged embryo (arrow). A one-cell embryo, which lacks contact sites, does not show LAD-1 localization (arrowhead). (C) LAD-1 is found in the developing nervous system (arrow) with robust LAD-1 staining in the nerve ring, the major C. elegans neuropil (arrowhead). D and E show LAD-1 expression in multiple tissues in a larva and adult, respectively. LAD-1 is present in the nerve ring and ventral nerve cord (D, arrowhead) and in the hypodermis (skin cells) (D, arrows), the plasma membrane of body wall muscles (F, arrow), neuronal cell bodies (G, long arrow), dendrites (G, arrowhead), and the pharynx (G, short arrow). LAD-1 is also present in the syncytial germline where its localization at contact sites is maintained. A schematic of the C. elegans germline is shown in H: arrowheads point to oocytes and arrows point to germ nuclei. The cross section of the cylindrical gonad reveals a single layer of germ nuclei around a cytoplasmic core with T-shaped membranes between each nucleus. In a grazing section of the germline shown in I, LAD-1 is localized at oocyte–oocyte contact (arrowhead) and only the vertical part of the T-shaped membrane, which divides two neighboring germline nuclei (arrows). The top of the T does not show LAD-1 localization. Bars: (A) 20 μm; (B–I) 25 μm.

Mentions: Immunoblots of mixed stage worm lysates with an affinity purified antibody generated against the LAD-1 cytoplasmic tail detected a complex pattern of LAD-1 products with apparent molecular weights of 200, 185, 120, and 65 kD. This variety of LAD-1 products suggested a combination of alternative splicing, posttranslational cleavage, and differential glycosylation events, modifications known to occur in the L1CAM family (for review see Hortsch, 1996; Hassel et al., 1997). The polypeptides ranging between 20 and 30 kD that were also detected by immunoblots represent non–LAD-1–related products, since they also reacted with 125I-labeled protein A alone (Fig. 2, A , i).


LAD-1, the Caenorhabditis elegans L1CAM homologue, participates in embryonic and gonadal morphogenesis and is a substrate for fibroblast growth factor receptor pathway-dependent phosphotyrosine-based signaling.

Chen L, Ong B, Bennett V - J. Cell Biol. (2001)

LAD-1 is localized to the plasma membrane at sites of cell–cell contact in all cells throughout development. (A, i) An immunoblot of total C. elegans lysates reveals four major LAD-1 polypeptides (200, 185, 120, and 65 kD) that were detected by a rabbit polyclonal antibody raised against the LAD-1 cytoplasmic domain (lane 2). The lower bands are not LAD-1 related, since they are also recognized by 125 I-labeled protein A (lane 3). (Lane 1) Coomassie blue staining of total C. elegans lysate. Equivalent lysate amounts. (ii) nDf41 homozygous embryos, which contains the lad-1 gene, show LAD-1 immunodetection (green) unlike stDf7 homozygous embryos, which lack the lad-1 gene; only control antibody staining of JAM-1 is seen in red (iii). B and C show immunodetection of LAD-1 in embryos. (B) LAD-1 is localized to sites of cell–cell contact, including the partial plasma membrane of a developing two-cell staged embryo (arrow). A one-cell embryo, which lacks contact sites, does not show LAD-1 localization (arrowhead). (C) LAD-1 is found in the developing nervous system (arrow) with robust LAD-1 staining in the nerve ring, the major C. elegans neuropil (arrowhead). D and E show LAD-1 expression in multiple tissues in a larva and adult, respectively. LAD-1 is present in the nerve ring and ventral nerve cord (D, arrowhead) and in the hypodermis (skin cells) (D, arrows), the plasma membrane of body wall muscles (F, arrow), neuronal cell bodies (G, long arrow), dendrites (G, arrowhead), and the pharynx (G, short arrow). LAD-1 is also present in the syncytial germline where its localization at contact sites is maintained. A schematic of the C. elegans germline is shown in H: arrowheads point to oocytes and arrows point to germ nuclei. The cross section of the cylindrical gonad reveals a single layer of germ nuclei around a cytoplasmic core with T-shaped membranes between each nucleus. In a grazing section of the germline shown in I, LAD-1 is localized at oocyte–oocyte contact (arrowhead) and only the vertical part of the T-shaped membrane, which divides two neighboring germline nuclei (arrows). The top of the T does not show LAD-1 localization. Bars: (A) 20 μm; (B–I) 25 μm.
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Related In: Results  -  Collection

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fig2: LAD-1 is localized to the plasma membrane at sites of cell–cell contact in all cells throughout development. (A, i) An immunoblot of total C. elegans lysates reveals four major LAD-1 polypeptides (200, 185, 120, and 65 kD) that were detected by a rabbit polyclonal antibody raised against the LAD-1 cytoplasmic domain (lane 2). The lower bands are not LAD-1 related, since they are also recognized by 125 I-labeled protein A (lane 3). (Lane 1) Coomassie blue staining of total C. elegans lysate. Equivalent lysate amounts. (ii) nDf41 homozygous embryos, which contains the lad-1 gene, show LAD-1 immunodetection (green) unlike stDf7 homozygous embryos, which lack the lad-1 gene; only control antibody staining of JAM-1 is seen in red (iii). B and C show immunodetection of LAD-1 in embryos. (B) LAD-1 is localized to sites of cell–cell contact, including the partial plasma membrane of a developing two-cell staged embryo (arrow). A one-cell embryo, which lacks contact sites, does not show LAD-1 localization (arrowhead). (C) LAD-1 is found in the developing nervous system (arrow) with robust LAD-1 staining in the nerve ring, the major C. elegans neuropil (arrowhead). D and E show LAD-1 expression in multiple tissues in a larva and adult, respectively. LAD-1 is present in the nerve ring and ventral nerve cord (D, arrowhead) and in the hypodermis (skin cells) (D, arrows), the plasma membrane of body wall muscles (F, arrow), neuronal cell bodies (G, long arrow), dendrites (G, arrowhead), and the pharynx (G, short arrow). LAD-1 is also present in the syncytial germline where its localization at contact sites is maintained. A schematic of the C. elegans germline is shown in H: arrowheads point to oocytes and arrows point to germ nuclei. The cross section of the cylindrical gonad reveals a single layer of germ nuclei around a cytoplasmic core with T-shaped membranes between each nucleus. In a grazing section of the germline shown in I, LAD-1 is localized at oocyte–oocyte contact (arrowhead) and only the vertical part of the T-shaped membrane, which divides two neighboring germline nuclei (arrows). The top of the T does not show LAD-1 localization. Bars: (A) 20 μm; (B–I) 25 μm.
Mentions: Immunoblots of mixed stage worm lysates with an affinity purified antibody generated against the LAD-1 cytoplasmic tail detected a complex pattern of LAD-1 products with apparent molecular weights of 200, 185, 120, and 65 kD. This variety of LAD-1 products suggested a combination of alternative splicing, posttranslational cleavage, and differential glycosylation events, modifications known to occur in the L1CAM family (for review see Hortsch, 1996; Hassel et al., 1997). The polypeptides ranging between 20 and 30 kD that were also detected by immunoblots represent non–LAD-1–related products, since they also reacted with 125I-labeled protein A alone (Fig. 2, A , i).

Bottom Line: In addition, the ubiquitously expressed LAD-1, which binds to ankyrin-G, colocalizes with the C. elegans ankyrin, UNC-44, in multiple tissues at sites of cell-cell contact.These findings suggest a novel ankyrin-independent role for LAD-1 related to FGFR signaling.Taken together, these results indicate that L1CAMs constitute a family of ubiquitous adhesion molecules, which participate in tissue morphogenesis and maintaining tissue integrity in metazoans.

View Article: PubMed Central - PubMed

Affiliation: Howard Hughes Medical Institute, Department of Cell Biology, and Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA. l.chen@cellbio.duke.edu

ABSTRACT
This study shows that L1-like adhesion (LAD-1), the sole Caenorhabditis elegans homologue of the L1 family of neuronal adhesion molecules, is required for proper development of the germline and the early embryo and embryonic and gonadal morphogenesis. In addition, the ubiquitously expressed LAD-1, which binds to ankyrin-G, colocalizes with the C. elegans ankyrin, UNC-44, in multiple tissues at sites of cell-cell contact. Finally, we show that LAD-1 is phosphorylated in a fibroblast growth factor receptor (FGFR) pathway-dependent manner on a tyrosine residue in the highly conserved ankyrin-binding motif, FIGQY, which was shown previously to abolish the L1 family of cell adhesion molecule (L1CAM) binding to ankyrin in cultured cells. Immunofluorescence studies revealed that FIGQY-tyrosine-phosphorylated LAD-1 does not colocalize with nonphosphorylated LAD-1 or UNC-44 ankyrin but instead is localized to sites that undergo mechanical stress in polarized epithelia and axon-body wall muscle junctions. These findings suggest a novel ankyrin-independent role for LAD-1 related to FGFR signaling. Taken together, these results indicate that L1CAMs constitute a family of ubiquitous adhesion molecules, which participate in tissue morphogenesis and maintaining tissue integrity in metazoans.

Show MeSH
Related in: MedlinePlus