Wnt signaling in axon guidance.

Recent studies have identified Wnt proteins as conserved axon guidance molecules in vertebrates and invertebrates. Wnt proteins are a large family of diffusible factors that play several important roles, both in embryonic development and in adult function. The signaling mechanisms of Wnt proteins are complex and, because Wnts are newly discovered as axon guidance cues, little is known about how Wnt signaling controls the direction of growth cone navigation - a process that is crucial in development of the nervous system. This review summarizes recent work on the role of Wnts in axon guidance and discusses the possible signaling mechanisms involved in growth cone guidance. Understanding how Wnts regulate axon wiring will not only help us to understand how the nervous system is connected but also provide possible tools for axon regeneration.