Wnt signaling in early zebrafish development

Zebrafish was used as a model organism to investigate the importance of Wnt signaling in early vertebrate development. Three candidate Wnt protein receptors frizzled A, frizzled C, and 10 were cloned. The frizzleds, maternally encoded zebrafish wnt8, and several other Wnt pathway components were overexpressed via synthetic mRNA microinjection. The obtained data indicated that Wnt signaling is sufficient to induce the dorsoventral axis in the early zebrafish embryo. A dominant negative form of maternally expressed frizzled A was constructed and expressed together with dominant negative forms of several wnt pathway members. The experimental results supported the notion that Wnt signaling is required for dorsal mesoderm formation in vertebrates. The possibility of functional interaction between Wnt and Notch signaling pathways was investigated. The preliminary data obtained from the overexpression studies of Notch and members of Wnt pathway indicated that Notch could be a candidate Wnt receptor. An efficient specific gene knockdown technique was developed. The technique uses modified oligonucleotides—morpholino phosphorodiamidate oligonucleotides (morpholinos). Delivery of morpholinos into the early embryos via microinjection specifically inhibits the translation of the gene of interest. This technique was used to knockdown several genes. One of them, VEGF A, is a candidate gene for drug development for cancer treatment.