ABSTRACT

Jamie C Little, Marc Debrunner, Thom de Hoog, Farzad Tadjik, Chiara J Kehl, George Hausmann, Erich Brunner, Konrad Basler

A conserved cohort of signalling pathways orchestrate development and adult homoeostasis. Deregulation of these pathways underlies many diseases. A key set of signals is the family of Wnt ligands. Members of this family are conserved, but a clear understanding of the unique and redundant roles is lacking. Previous efforts to study Wnt ligand function in Drosophila have been hampered by the difficulty of generating , functional transgenes. To address this, we have created a complete set of synthesized constructs in an insulated expression system, integrated into the same genomic location, enabling reliable gain-of-function analyses across multiple tissues. Distinct phenotypic outcomes were observed, reflecting both shared and unique features of individual ligands. To define the canonicity of Wnt signalling, we monitored canonical targets such as Dfz3, notum, and the ‘naked cuticle’ phenotype in developing tissues and the adult gut. Our findings revealed strong evidence of canonical responses from not only wg, but also DWnt6 and DWnt10 in the embryo, wing disc, larval gut, and adult gut. In addition, DWnt2, DWnt4, and WntD produced phenotypes distinct from the control with DWnt2 and DWnt4, showing context-dependent evidence of some canonical activity. While previous studies have suggested regulatory features between wg and DWnt6, our work provides functional evidence that Wg, DWnt6, and DWnt10 each induce expression of canonical signalling reporters in vivo. These findings refine our understanding of redundancy and specificity within the Drosophila Wnt family and demonstrate that multiple Wnt ligands can act similarly within the canonical pathway depending on tissue context.