Catenins of the p120 subclass display an array of intracellular localizations and functions. Although the genetic knockout of mouse δ-catenin results in mild cognitive dysfunction, we found severe effects of its depletion in Xenopus. δ-catenin in Xenopus is transcribed as a full-length mRNA, or as three (or more) alternatively spliced isoforms designated A, B and C. Further structural and functional complexity is suggested by three predicted and alternative translation initiation sites. Transcript analysis suggests that each splice isoform is expressed during embryogenesis, with the B and C transcript levels varying according to developmental stage. Unlike the primarily neural expression of δ-catenin reported in mammals, δ-catenin is detectable in most adult Xenopus tissues, although it is enriched in neural structures. δ-catenin associates with classical cadherins, with crude embryo fractionations further revealing non-plasma-membrane pools that might be involved in cytoplasmic and/or nuclear functions. Depletion of δ-catenin caused gastrulation defects, phenotypes that were further enhanced by co-depletion of the related p120-catenin. Depletion was significantly rescued by titrated p120-catenin expression, suggesting that these catenins have shared roles. Biochemical assays indicated that δ-catenin depletion results in reduced cadherin levels and cell adhesion, as well as perturbation of RhoA and Rac1. Titrated doses of C-cadherin, dominant-negative RhoA or constitutively active Rac1 significantly rescued δ-catenin depletion. Collectively, our experiments indicate that δ-catenin has an essential role in amphibian development, and has functional links to cadherins and Rho-family GTPases.
ASJC Scopus subject areas
- Cell Biology