Use of small molecule inhibitors of the Wnt and Notch signaling pathways during Xenopus development.

Small molecule inhibitors of growth factor signaling pathways are extremely convenient reagents for investigation of embryonic development. The chemical may be introduced at a precise time, the dose can be altered over a large range and the chemical may be removed simply by replacing the medium surrounding the embryo. Because small molecule modulators are designed to target conserved features of a protein, they are usually effective across species. Ideally the chemicals offer remarkable specificity for a particular signaling pathway and exhibit negligible off-target effects. In this study we examine the use of small molecules to modulate the Wnt and Notch signaling pathways in the Xenopus embryo. We find that IWR-1 and XAV939 are effective inhibitors of the canonical Wnt signaling pathway while BIO is an excellent activator. For Notch signaling, we find that both DAPT and RO4929097 are effective inhibitors, but that RO4929097 is the more potent reagent. This report provides researchers with useful working concentrations of reagents and a small series of genetic and biological assays that may be used to characterize the role of Wnt and Notch signaling during embryonic development.