Armadillo is required for adherens junction assembly, cell polarity, and morphogenesis during Drosophila embryogenesis.

Abstract

Abstract. Morphological and biochemical analyseshave identified a set of proteins which together form a structure known as the adherens junction. Elegant experiments in tissue culture support the idea that adherens junctions play a key role in cell--cell adhesion and in organizing cells into epithelia. During normal embryonic development, cells quickly organize epithelia; these epithelial cells participate in many of the key morphogenetic movements of gastrulation. This prompted the hypothesis that adherens junctions ought to be critical for normal embryonic development.Drosophila Armadillo, the homologue of vertebrate 13-catenin, is a core component of the adherens junction protein complex and has been hypothesized to be essential for adherens junction function in vivo. We have used an intermediate mutant allele of armadillo, armadillo xP33, to test these hypotheses in Drosophila embryos. Adherens junctions cannot assemble in the absence of Armadillo, leading to dramatic defects in cell-cell adhesion. The epithelial ceils of the embryo lose adhesion to each other, round up, and apparently become mesenchymal. Mutant cells also lose their normal cell polarity. These disruptions in the integrity of epithelia block the appropriate morphogenetic movements of gastrulation. These results provide the first demonstration of the effect of loss of adherens junctions on Drosophila embryonic development.

Hepatocyte Growth Factor Alters the Polarity of Madin-Darby Canine Kidney Cell Monolayers

“…The Drosophila cadherin also interacts with catenins, and it is likely that these interactions are also modulated during invertebrate morphogenetic events such as embryonic development. Evidence supporting this hypothesis has been reported by two groups, demonstrating the requirement of the Drosophila ␤-catenin homolog Armadillo for the formation of Drosophila adherens junction and epithelial polarity (28,29).…”

Phenotypic analysis of null mutants for DE‐cadherin and Armadillo in Drosophila ovaries reveals distinct aspects of their functions in cell adhesion and cytoskeletal organization

“…Another difference between shg and arm mutants was that the mis-positioning of the germ cells occurred only in the latter. A similar disarrangement of cells was also observed in the embryonic epithelia of intermediate alleles of arm (Cox et al 1996;Müller & Wiechaus 1996). These arm phenotypes cannot necessarily be explained by a simple loss of cell-cell adhesion, leading us to propose a distinctive role of Armadillo in the cadherin/catenin adhesion system.…”

Molecular regulation of kidney development: is the answer blowing in the Wnt?

“…In other models of branching morphogenesis, it has been suggested that the epithelia reverts to a mesenchymal state during branching [64]. Canonical signaling could be mediating such a transition in the kidney, although this would be contrary to other data, where a loss of β-catenin is correlated with epithelialto-mesenchymal transition [65]. It is possible that Wnt signaling is simply mediating differential adhesiveness between the tips and the stalk, perhaps through regulating the expression or activity of a cell adhesion molecule.…”