Understanding embryogenesis currently relies largely on the control of gene expression via several signaling pathways. Many of the embryonic signaling pathways guiding embryological events are implicated in diseases that lack effective cure or treatment. Because of the large number and size of the eggs, the rapid development of the embryos and the fact they are amenable to pharmacological, surgical and genetic techniques, Xenopus laevis has been successfully used in searching for compounds that target embryonic signaling pathways. Areas covered: Here, the authors address the use of amphibian eggs/embryos in successful chemical screenings; egg extracts as well as embryo phenotypes have been assayed to reveal drug toxicology effects and novel compounds acting in the Wnt/β-catenin signaling pathway. They do not discuss the use of Xenopus oocyte two-electrode voltage clamps or genome editing tools as approaches for drug discovery because they have been discussed elsewhere. Expert opinion: While high-throughput screening is commonly performed in egg extracts, the embryo axes perturbation system is more suited to the refinement and/or the validation of drug discovery targeting embryonic signaling (particularly the Wnt/β-catenin pathway). In addition, Xenopus has also been used in FETAX (frog embryo teratogenesis assay: Xenopus) to address chemical toxic/teratogenic effects. However, further studies are necessary.

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This review highlights the work that my research group has been developing, together with international collaborators, during the last decade. Since we were able to establish Xenopus laevis experimental model in Brazil we have been focused on understanding early embryonic patterns regarding neural induction and axes establishment. In this context, Wnt pathway appears as a major player and has been much explored by us and other research groups. Here we chose to review three published works that we consider landmarks within the history of our research on the developmental biology field and the neural induction and patterning modern findings. We intend to show how our series of discoveries, when painted together, tells a story that covers crucial developmental windows of early differentiation paths of anterior neural tissue. Being those: 1. Establishing Head organizer in contrast to trunk organizer at early gastrula; 2. deciding between neural ectoderm and epidermis ectoderm at the blastula/gastrula stages, and 3. the gathering of prechordal unique properties at late gastrula/early neurula.