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The conditional inactivation of the beta-catenin gene in endothelial cells causes a defective vascular pattern and increased vascular fragility.

Cattelino A, Liebner S, Gallini R, Zanetti A, Balconi G, Corsi A, Bianco P, Wolburg H, Moore R, Oreda B, Kemler R, Dejana E - J. Cell Biol. (2003)

Bottom Line: We found that early phases of vasculogenesis and angiogenesis were not affected in mutant embryos; however, vascular patterning in the head, vitelline, umbilical vessels, and the placenta was altered.These changes paralleled a decrease in cell-cell adhesion strength and an increase in paracellular permeability.We conclude that in vivo, the absence of beta-catenin significantly reduces the capacity of endothelial cells to maintain intercellular contacts.

View Article: PubMed Central - PubMed

Affiliation: FIRC Institute of Molecular Oncology, 16-20139, Milan, Italy.

ABSTRACT
Using the Cre/loxP system we conditionally inactivated beta-catenin in endothelial cells. We found that early phases of vasculogenesis and angiogenesis were not affected in mutant embryos; however, vascular patterning in the head, vitelline, umbilical vessels, and the placenta was altered. In addition, in many regions, the vascular lumen was irregular with the formation of lacunae at bifurcations, vessels were frequently hemorrhagic, and fluid extravasation in the pericardial cavity was observed. Cultured beta-catenin -/- endothelial cells showed a different organization of intercellular junctions with a decrease in alpha-catenin in favor of desmoplakin and marked changes in actin cytoskeleton. These changes paralleled a decrease in cell-cell adhesion strength and an increase in paracellular permeability. We conclude that in vivo, the absence of beta-catenin significantly reduces the capacity of endothelial cells to maintain intercellular contacts. This may become more marked when the vessels are exposed to high or turbulent flow, such as at bifurcations or in the beating heart, leading to fluid leakage or hemorrhages.

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Immunostaining of junctional proteins in β-catenin −/− endothelial cells. Although plakoglobin is correctly organized at cell–cell contacts in β-catenin −/− embryos (compare A and B), α-catenin antibodies give a very faint and discontinuous staining at cell–cell contacts in β-catenin −/−, as compared with control cells (compare C and D). Note the presence of desmoplakin at intracellular junctions only in β-catenin −/− cells (F, arrows), whereas in control cells, the same antibody gives only a faint and diffuse staining (E).
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fig7: Immunostaining of junctional proteins in β-catenin −/− endothelial cells. Although plakoglobin is correctly organized at cell–cell contacts in β-catenin −/− embryos (compare A and B), α-catenin antibodies give a very faint and discontinuous staining at cell–cell contacts in β-catenin −/−, as compared with control cells (compare C and D). Note the presence of desmoplakin at intracellular junctions only in β-catenin −/− cells (F, arrows), whereas in control cells, the same antibody gives only a faint and diffuse staining (E).

Mentions: The expression and distribution of junctional markers was studied by immunofluorescence microscopy. We observed that essentially all the junctional proteins considered (including PECAM, JAM, VE-cadherin, ZO-1, p120, and occludin) were correctly expressed and distributed at intercellular junctions (see Figs. 6–8; unpublished data). The only exceptions were plakoglobin, which presented a slightly brighter staining at intercellular contacts (Fig. 7, A and B), and α-catenin, which was strongly reduced at cell–cell contacts (Fig. 7, C and D). These observations were further confirmed by biochemical analyses. Immunoprecipitation of VE-cadherin followed by Western blot with specific antibodies revealed changes in cadherin–catenin complex composition. α-catenin was strongly reduced (4–5-fold) in the complex and in total amount, whereas plakoglobin was slightly increased (1–1.5-fold; Fig. 8 A). The total level of p120 and VE-cadherin and their level associated to the complex were comparable (Fig. 8 A; unpublished data). Because α-catenin was reduced, plakoglobin could have another partner. Desmoplakin is a preferential binding protein for plakoglobin, but is weakly expressed in vascular endothelium (Franke et al., 1988; Schmelz et al., 1994). We found that desmoplakin was 2–3-fold increased in extracts of β-catenin −/− cells as compared with controls (Fig. 8 B). In addition, desmoplakin was found at intercellular contacts only in β-catenin −/− cells, but not in control cells (Fig. 7, E and F). The same characterization of adherens junctions composition was performed in β-catenin flox endothelial cells treated either with adeno-Cre or the empty vector, and we found essentially the same results (Figs. S1–S3, available at http://www.jcb.org/cgi/content/full/jcb.200212157/DC1).


The conditional inactivation of the beta-catenin gene in endothelial cells causes a defective vascular pattern and increased vascular fragility.

Cattelino A, Liebner S, Gallini R, Zanetti A, Balconi G, Corsi A, Bianco P, Wolburg H, Moore R, Oreda B, Kemler R, Dejana E - J. Cell Biol. (2003)

Immunostaining of junctional proteins in β-catenin −/− endothelial cells. Although plakoglobin is correctly organized at cell–cell contacts in β-catenin −/− embryos (compare A and B), α-catenin antibodies give a very faint and discontinuous staining at cell–cell contacts in β-catenin −/−, as compared with control cells (compare C and D). Note the presence of desmoplakin at intracellular junctions only in β-catenin −/− cells (F, arrows), whereas in control cells, the same antibody gives only a faint and diffuse staining (E).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2172846&req=5

fig7: Immunostaining of junctional proteins in β-catenin −/− endothelial cells. Although plakoglobin is correctly organized at cell–cell contacts in β-catenin −/− embryos (compare A and B), α-catenin antibodies give a very faint and discontinuous staining at cell–cell contacts in β-catenin −/−, as compared with control cells (compare C and D). Note the presence of desmoplakin at intracellular junctions only in β-catenin −/− cells (F, arrows), whereas in control cells, the same antibody gives only a faint and diffuse staining (E).
Mentions: The expression and distribution of junctional markers was studied by immunofluorescence microscopy. We observed that essentially all the junctional proteins considered (including PECAM, JAM, VE-cadherin, ZO-1, p120, and occludin) were correctly expressed and distributed at intercellular junctions (see Figs. 6–8; unpublished data). The only exceptions were plakoglobin, which presented a slightly brighter staining at intercellular contacts (Fig. 7, A and B), and α-catenin, which was strongly reduced at cell–cell contacts (Fig. 7, C and D). These observations were further confirmed by biochemical analyses. Immunoprecipitation of VE-cadherin followed by Western blot with specific antibodies revealed changes in cadherin–catenin complex composition. α-catenin was strongly reduced (4–5-fold) in the complex and in total amount, whereas plakoglobin was slightly increased (1–1.5-fold; Fig. 8 A). The total level of p120 and VE-cadherin and their level associated to the complex were comparable (Fig. 8 A; unpublished data). Because α-catenin was reduced, plakoglobin could have another partner. Desmoplakin is a preferential binding protein for plakoglobin, but is weakly expressed in vascular endothelium (Franke et al., 1988; Schmelz et al., 1994). We found that desmoplakin was 2–3-fold increased in extracts of β-catenin −/− cells as compared with controls (Fig. 8 B). In addition, desmoplakin was found at intercellular contacts only in β-catenin −/− cells, but not in control cells (Fig. 7, E and F). The same characterization of adherens junctions composition was performed in β-catenin flox endothelial cells treated either with adeno-Cre or the empty vector, and we found essentially the same results (Figs. S1–S3, available at http://www.jcb.org/cgi/content/full/jcb.200212157/DC1).

Bottom Line: We found that early phases of vasculogenesis and angiogenesis were not affected in mutant embryos; however, vascular patterning in the head, vitelline, umbilical vessels, and the placenta was altered.These changes paralleled a decrease in cell-cell adhesion strength and an increase in paracellular permeability.We conclude that in vivo, the absence of beta-catenin significantly reduces the capacity of endothelial cells to maintain intercellular contacts.

View Article: PubMed Central - PubMed

Affiliation: FIRC Institute of Molecular Oncology, 16-20139, Milan, Italy.

ABSTRACT
Using the Cre/loxP system we conditionally inactivated beta-catenin in endothelial cells. We found that early phases of vasculogenesis and angiogenesis were not affected in mutant embryos; however, vascular patterning in the head, vitelline, umbilical vessels, and the placenta was altered. In addition, in many regions, the vascular lumen was irregular with the formation of lacunae at bifurcations, vessels were frequently hemorrhagic, and fluid extravasation in the pericardial cavity was observed. Cultured beta-catenin -/- endothelial cells showed a different organization of intercellular junctions with a decrease in alpha-catenin in favor of desmoplakin and marked changes in actin cytoskeleton. These changes paralleled a decrease in cell-cell adhesion strength and an increase in paracellular permeability. We conclude that in vivo, the absence of beta-catenin significantly reduces the capacity of endothelial cells to maintain intercellular contacts. This may become more marked when the vessels are exposed to high or turbulent flow, such as at bifurcations or in the beating heart, leading to fluid leakage or hemorrhages.

Show MeSH
Related in: MedlinePlus