The making of a node: a co-production of neurons and glia

- Nodes of Ranvier form by several overlapping mechanisms.
- Node assembly is induced differently by the myelinating glia of the PNS and CNS.
- Axonal barriers drive the assembly of both CNS nodes and the AIS.
- Secreted glial molecules drive the assembly of PNS nodes.

Nodes of Ranvier are specialized axonal domains formed in response to a glial signal. Recent research advances have revealed that both CNS and PNS nodes form by several overlapping molecular mechanisms. However, the precise nature of these mechanisms and the hierarchy existing between them is considerably different in CNS versus PNS nodes. Namely, the Schwann cells of the PNS, which directly contact the nodal axolemma, secrete proteins that cluster axonodal components at the edges of the growing myelin segment. In contrast, the formation of CNS nodes, which are not contacted by the myelinating glia, is surprisingly similar to the assembly of the axon initial segment and depends largely on axonal diffusion barriers.