Ankyrin recruits a fleet

Axon initial segments are specialized microdomains that integrate neuronal inputs and initiate action potentials. On page 739, Jenkins and Bennett demonstrate that the ankyrin-G adaptor protein is required to coordinate the assembly of the initial segment during early development, and suggest that related mechanisms may regulate the assembly of other microdomains in a variety of cell types.Concentrated in axon initial segments are both voltage-gated sodium channels and several proteins that have been hypothesized to direct the assembly of the microdomain. In the new work, the authors examined protein localization in Purkinje neuron initial segments during development in wild-type and ankyrin-G mutant mice. Ankyrin-G and βIV spectrin appear at axon initial segments by postnatal day 2, but the sodium channels and adhesion molecules are not fully assembled in the microdomain until seven days later. In mice...