Actin, Spectrin, and Associated Proteins Form a Periodic Cytoskeletal Structure in Axons

Axonal Actin

How actin is organized in the axons and dendrites of neurons is largely unknown. Xu et al. (p. 452 , published online 13 December) imaged actin in axons and dendrites using stochastic optical reconstruction microscopy. Surprisingly, while actin in dendrites formed long filaments, the actin in axons was organized into evenly spaced ringlike structures at the axon circumference. Spectrin, which is known to interact with actin to form a membrane cytoskeleton in erythrocytes, formed periodic structures that alternated with those of actin. This actin-spectrin cytoskeletal structure might give mechanical support to axons and could also organize other membrane proteins.