ABSTRACT
In the course of an analysis of cell-cell adhesion in the Xenopus embryo, antibodies directed against α and β catenin were applied to investigate their relation to the cadherins occurring early in this system. The results demonstrate that α and β-catenin are provided maternally and increase in amount throughout embryogenesis. Immunoprecipitations indicate that both of the catenins are complexed to U-cadherin in the early phase of embryogenesis and to β-cadherin, when it appears during gastrulation. An excess of α-catenin occurs in free form in the early embryo, whereas all of the catenin seems to be complexed to cadherin. Synthesis of the two components throughout early embryogenesis and their binding to newly synthesized cadherins were demonstrated by metabolic labelling.
The spatial distribution of α-catenin was analysed by immunohistology. During cleavage β-catenin is deposited evenly along the plasma membranes within the embryo, while the cell peripheries at the surface of the embryo remain devoid of α-catenin. At later stages, the pattern of α-catenin distribution becomes more complex. Quantitative differences in the intensity of staining along the plasma membranes in the different regions of the embryo can be distinguished. Particularly the appearance of β-cadherin in the gastrula ectoderm is accompanied by conspicous depositions of α-catenin along the respective plasma membranes in this layer. All cells in the later embryo, apart from the neural crest cells, carry α-catenin on their plasma membranes indicating the universal character of cadherin-mediated cell-cell adhesion in the Xenopus embryo.
