Powerful Drosophila screens that paved the wingless pathway.

The Wnt/Wingless (Wg) signaling cascade controls a number of biological processes in animal development and adult life; aberrant Wnt/Wg signaling can cause diseases. In the 1980s genes were discovered that encode core Wnt/Wg pathway components: their mutant phenotypes were similar and an outline of a signaling cascade emerged. Over the years our knowledge of this important signaling system increased and more components were uncovered that are instrumental for Wnt/Wg secretion and transduction. Here we provide an overview of these discoveries, the technologies involved, with a particular focus on the important role Drosophila screens played in this process.