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EP-cadherin in muscles and epithelia of Xenopus laevis embryos.
Levi G
,
Ginsberg D
,
Girault JM
,
Sabanay I
,
Thiery JP
,
Geiger B
.
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EP-cadherin is a novel Xenopus Ca+2-dependent adhesion molecule, which shares comparable homology with mouse E- and P-cadherins (Ginsberg, De Simone and Geiger; 1991, Development 111, 315-325). We report here the patterns of expression of this molecule in Xenopus laevis embryos at different developmental stages ranging from cleavage to postmetamorphic. EP-cadherin is already expressed in the oocyte and egg and can then be detected in close association with the membrane of all blastomeres up to late blastula stages. Starting at late gastrula stages, the level of EP-cadherin expression increases sharply in non-neural ectodermal cells, in the somites and in the notochord; it persists in endodermal cells and decreases rapidly in all migratory cells. During neurulation the level of EP-cadherin expression declines gradually in the nervous system and is undetectable here throughout later development except in the optic nerve and in the neural part of the olfactory organ. This pattern continues during later development so that in the tailbud stage and up to metamorphosis the most prominent staining is detected in the epidermis and skeletal muscle. After metamorphosis, the molecule gradually disappears from the muscletissue and the major site of expression remains the skin. EP-cadherin is invariably present in close association with the cell membrane. In the muscle it is associated with the sarcolemma at regions of myoblast-myoblast or myotube-myotube contact. In epidermal cells, EP-cadherin is usually coexpressed with E-cadherin. Yet, while E-cadherin staining is always restricted to the basolateral aspects of the cells, EP-cadherin is often distributed throughout the plasmalemma including the apical surface.
Fig. 1. Characterization of anti-EP-cadherin antibodies. (A) Western blot analysis of extracts of CHO cells stably
transfected with either EP-cadherin cDNA (lanes 1,3) or the neomycin-resistance vector only (lanes 2,4) and of A6
Xenopus epithelial cells (lanes 5,6); the blots were reacted either with the pan-cadherin serum R-156 (lanes 1,2,5) or with
anti-EP-cadherin antiserum R-827 (lanes 3,4,6). (B) Western blot analysis of extracts from eggs (lane 1), stage 8 blastulas
(lane 2) and stage 17 neurulas (lane 3) performed with R-827 antiserum. (C and D) Immunofluorescence staining of CHO
cells stably transfected with either EP-cadherin cDNA (B) or the neomycin-resistance vector only (C). EP-cadherin
immunostaining is evident at the region of contact of the epithelioid polygonal transfected cells.
Fig. 2. Distribution of EP-cadherin during early embryogenesis.
Immunoperoxidase labeling of early blastula with anti-EP-cadherin (R-827).
Bar=20um.
Fig. 3. Immunofluorescent labeling of section of Xenopus larva using anti-EP-cadherin R-827 antibodies. Sections from
stage 22 (A-E) and stage 41 (F) embryos. The positively labeled structures include: the cement gland and underlying
endoderm (A), the lateral epidermis and underlying mesoderm and endoderm (B), the somites (C), the endoderm (D) and
the notochord (E and F). ce, cement gland; e, epidermis; en, endoderm; me, mesoderm; n, notochord; s, somite; ph,
pharynx. Bar=15/xm (A,B,E); 25/an (C,D); 40um (F).
Fig. 4. Distribution of anti-EP-cadherin immunoreactivity in the skin. (A,B) Double staining with R-827 anti-EP-cadherin
antibody (A) and a monoclonal anti Xenopus E-cadherin (B) of larval skin (stage 41) showing distinct distribution of the
two molecules. Premetamorphic skin (C) and forelimb of a stage 51 animal (D) stained with R-827. Note that only the
newly formed epidermis of the limb is stained for EP-cadherin while the degenerating epidermis of the body (sk) is not. fl,
forelimb; g, gland; ol, outerlayer of the epidermis; sk, degenerating skin of the body; si, sensory layer of the epidermis.
Bar=30um.
Fig. 5. Expression of EP-cadherin in Xenopus muscles. Single immunolabeling of sections of stage 34 (A), 45 (B) and 53
(C) with R-827 anti-EP-cadherin antibody. Sections were from either the tail (A,B) o r the head (C). Double
immunofluorescence labeling of stage 53 animals for EP-cadherin (D,F) and E-cadherin (E,G). Areas shown in D and E
are from the head region while F and G are from the tail. Immunoblots of dissected tail axial muscles (H) and tail
epidermis (I) with R-8327 corresponding to specimens shown in F. c, cartilage; e, epidermis; i, iris; m, muscles; r, retina.
Bar=10/im (A,B); 25/an (C); 50jan (D-G).
Fig. 6. Vinculin immunolabeling (A) and electron
microscopy analysis (B) of Xenopus tail muscles. The
arrows indicate electron-dense close contacts between the
sarcolemma of adjacent myotubes.