ABSTRACT
The Xenopus embryo is the organism par excellence in demonstrating how signalling of diffusible inducing factors is coupled to cell-cell adhesion in the process of pattern formation. This becomes most obvious in the double function of β-catenin as stabilizer of the cadherin/catenin adhesion complex and as transducer of the Xwnt signal into the nucleus. Despite this example of a direct molecular link between signalling and cell adhesion more indirect evidence is given considering the activity of mesoderm inducers like activin, TGFβ, bFGF or BMP. It seems, that the two subjects cell-sorting and tissue induction initially studied in amphibians by Townes and Holtfreter (1955) and Spemann and Mangold (1924) are coming together after at least 40 years.
