A Second Canon Functions and Mechanisms of β-Catenin-Independent Wnt Signaling

AbstractMore is becoming known about so-called noncanonical Wnt pathways that signal independently of β-catenin. Here we review recent developments in both the functions and mechanisms of noncanonical Wnt signaling. We also discuss some unresolved and vexing questions. How many noncanonical Wnt pathways are there? How extensive are the parallels between Drosophila planar polarization and vertebrate convergence and extension? Last, we will outline some challenges and difficulties we foresee for this exciting but still very young field