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First published online April 16, 2004
doi: 10.1242/10.1242/jcs.01176

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Sticky worms: adhesion complexes in C. elegans

Department of Zoology, University of Wisconsin, 1117 W. Johnson Street, Madison, WI 53706, USA

View larger version (30K): [in a new window]   Fig. 1. The C. elegans apical junction. (A) Schematic diagram showing epithelial junctional organization in vertebrates, Drosophila and C. elegans. In vertebrates and Drosophila, different junctions are distinguishable by electron microscopy (EM), whereas in C. elegans there is one electron-dense region called the C. elegans apical junction (CeAJ). CeAJs consist of at least three distinct domains, although how these domains correlate to the electron-dense region is currently unclear. Note that the SAR of Drosophila is concentrated at the marginal zone but extends to the apical surface (reviewed by Tepass et al., 2001). Components of the SAR-like region of C. elegans (observed in pharynx and intestine) also localize to both the marginal zone and apical surface (Bossinger et al., 2001). Despite some differences in organization, there is compositional similarity between the regions shown in green (vertebrate tight junction, Drosophila SAR, and C. elegans SAR-like domain), blue (vertebrate, Drosophila, and C. elegans adherens junctions) and red (Drosophila septate junction and the C. elegans DLG-AJM domain) (reviewed by Knust and Bossinger, 2002). (B) TEM image of a CeAJ (arrow indicates the electron-dense region). Bar, 100 nm.

View larger version (92K): [in a new window]   Fig. 2. The cadherin-catenin complex in C. elegans. (A) Diagram of the cadherin-catenin complex in C. elegans. This complex consists of HMR-1A (cadherin), HMP-2 (ß-catenin), HMP-1 (-catenin) and JAC-1 (p120ctn). (B) A time course showing localization of the cadherin-catenin complex during epidermal morphogenesis in C. elegans. Confocal images of a living embryo expressing a JAC-1–GFP fusion protein. During ventral enclosure (a-b), edges of the epidermal cell sheet extend around the embryo, meet at the ventral midline, and seal through the formation of cell junctions. Note that JAC-1–GFP is not present at the leading edge of migrating epidermal cells, but is rapidly recruited to the contact region between cells at the ventral midline. Other adherens junctional components show a similar localization during enclosure. After ventral enclosure, contraction of the epidermis helps to drive the four-fold elongation of the embryo (c,d). Nomarski images of similarly aged embryos are shown for comparison (e-h). A Nomarski movie (Movie 4, http://jcs.biologists.org/supplemental/) showing development of a wild-type embryo is available online. In all images, anterior is left. Bar, 10 µm.

View larger version (18K): [in a new window]   Fig. 3. The structure, homologs and mutant phenotypes of AJM-1, DLG-1 and LET-413. The strongest Drosophila and vertebrate homologs are listed. For the null phenotype, the stage of arrest is indicated and the drawing represents abnormalities in the electrondense region, as observed by TEM (see text for details).

View larger version (76K): [in a new window]   Fig. 4. Dense bodies, M-lines and fibrous organelles. (A) Schematic showing the localization and arrangement of dense bodies and M-lines in C. elegans body wall muscle and fibrous organelles in the epidermis. (Adapted from Mackinnon et al., 2002.) (B) Dense bodies (arrows) and M-lines (arrowheads), visualized with PAT-4–YFP. (Adapted from Mackinnon et al., 2002.) Bar, 5 µm. (C) Fibrous organelles, visualized by MUA-3 staining. Fibrous organelles are shown in regions of epidermal cell contact with body wall muscle (1) and the ALM touch neuron (2). Gaps in fibrous organelles are seen where nerves pass between the epidermis and muscle (3). The image in (b) is an enlargement of (a). (Adapted from Bercher et al., 2001.) Bars, 10 µm.

View larger version (77K): [in a new window]   Fig. 5. Comparison of adhesion complexes in vertebrates and C. elegans. (A) A vertebrate focal adhesion and C. elegans dense body. Only conserved proteins are shown. Focal adhesions contain numerous adaptor and signaling proteins not shown here (refer to Zamir and Geiger, 2001). A few downstream effectors are indicated by the dashed arrows. (B) A vertebrate hemidesmosome and C. elegans fibrous organelles. (For more on hemidesmosome composition, see Nievers et al., 1999; Roper et al., 2002.) Like hemidesmosomes, fibrous organelles anchor IFs through a plectin-family member (VAB-10A). The transmembrane proteins MUA-3 and MUP-4 are located apically and myotactin is located basally. VAB-19 may be located both basally and apically. The protein-protein interactions shown for fibrous organelles are speculative, since it is currently unclear whether myotactin, MUA-3 or MUP-4 interacts directly with VAB-10A or IFs. (C) The dystrophinglycoprotein complex (DGC) in vertebrates and C. elegans. Other proteins are known to associate with the mammalian DGC (reviewed by Ehmsen et al., 2002), but have not been shown for simplicity. C. elegans does not have any clear sarcospan or nNOS homologs (Segalat, 2002). Currently, it is unclear whether the putative C. elegans DGC is present in epidermal, muscle, and/or neuronal tissues (see text for details).

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