Adherens junctions (AJs) are protein complexes that mediate cell adhesion and contribute to tissue homeostasis. Canoe (Cno), the fly orthologue of afadin, is part of a large protein network that regulates the formation of AJs. Cno has five domains, one of which, the Dilute (DIL) domain, is also found in Myosin V (MyoV). However, the function of the DIL domain in Cno is not known. In this study (McParland et al., 2024), Peifer and colleagues perform a structural, biochemical and genetic study into the Cno DIL domain. The authors use AlphaFold to predict the structure of DIL for both Cno and afadin, revealing a 15-amino-acid helical structure which, although similar overall to MyoV, has different conserved surfaces suggesting different binding partners. Like MyoV, the purified DIL domain can dimerize in vitro. To test the functions of the DIL domain, the authors generate a DIL deletion mutant in Drosophila (Cno∆DIL); surprisingly, this does not affect Cno localization or its function at AJs during embryonic development, and adult mutant flies are viable and fertile. However, in a genetic background that reduces Cno mutant protein levels, the authors uncover that the DIL domain is important for morphogenetic events, such as dorsal closure, mesoderm internalisation and pupal eye development, suggesting that the Cno∆DIL protein is not fully functional compared to wild-type protein. Together, this work illustrates the function and surprising dispensability of the Cno DIL domain at AJs, while also highlighting the robustness of AJ–cytoskeletal connections during morphogenesis.
