Induction of a Secondary Body Axis in Xenopus by Antibodies to -Catenin

We have obtained evidence that a known intracellular component of the cadherin cell-cell adhesion machinery, /3-catenin, contributes to the development of the body axis in the frog Xenopus laevis. Vertebrate/3-catenin is homologus to the Drosophila segment polarity gene product armadillo, and to vertebrate plakoglobin (McCrea, P. D., C. W. Turck, and B. Gumbiner. 1991. Science (Wash. DC). 254: 1359-1361.). ~-Catenin was found present in all Xenopus embryonic stages examined, and associated with C-cadherin, the major cadherin present in early Xenopus embryos. To test/3-catenin's function, affinity purified Fab fragments were injected into ventral blastomeres of developing four-cell Xenopus embryos. A dramatic phenotype, the duplication of the dorsoanterior embryonic axis, was observed. Furthermore, Fab injections were capable of rescuing dorsal features in UV-ventralized embryos. Similar phenotypes have been observed in misexpression studies of the Wnt and other gene products, suggesting that/3-catenin participates in a signaling pathway which specifies embryonic