INDUCTION OF A SECONDARY EMBRYONIC AXIS IN ZEBRAFISH OCCURS FOLLOWING THE OVEREXPRESSION OF BETA-CATENIN

Formation of the vertebrate axis may involve a Wnt signaling cascade similar to the Drosophila wingless pathway. Zebrafish wnt8 is a candidate for involvement in axis specification insofar as it is expressed maternally and when overexpressed it can induce goosecoid, a transcription factor normally expressed in the embryonic shield. In this study we demonstrate that beta-catenin, a cadherin associated protein in the Wnt pathway, is expressed maternally in zebrafish and is widely distributed in the early embryo. Overexpressing beta-catenin in early zebrafish embryos induces goosecoid and nrl, ultimately leading to a duplication of a complete secondary axis. These data are consistent with the involvement of beta-catenin in a Wnt signaling pathway which is involved in mesoderm induction in zebrafish.