More than one ring to bind them all: Recent insights into the structure of the axon

This brief review outlines recent developments in the understanding of the ultrastructural organization of the axonal and growth cone actin filament cytoskeleton. A novel form of structural organization has arisen as a regulator of the actin cytoskeleton: ring-like structures. Rings may represent a conserved functional theme exhibited by diverse molecular systems and have implications for the understanding of the axon in development, maturity, and disease.