Developing nodes of Ranvier are defined by ankyrin-G clustering and are independent of paranodal axoglial adhesion

SM Jenkins, V Bennett - Proceedings of the National …, 2002 - National Acad Sciences
SM Jenkins, V Bennett
Proceedings of the National Academy of Sciences, 2002National Acad Sciences
Nodes of Ranvier are excitable regions of axonal membranes highly enriched in voltage-
gated sodium channels that propagate action potentials. The mechanism of protein
clustering at nodes has been a source of controversy. In this study, developmental analysis
of nodes of Ranvier in optic nerve axons reveals that early node intermediates are defined
by ankyrin-G. Other node components, including beta IV spectrin, voltage-gated sodium
channels, and the L1 cell adhesion molecule neurofascin, are subsequently recruited to …
Nodes of Ranvier are excitable regions of axonal membranes highly enriched in voltage-gated sodium channels that propagate action potentials. The mechanism of protein clustering at nodes has been a source of controversy. In this study, developmental analysis of nodes of Ranvier in optic nerve axons reveals that early node intermediates are defined by ankyrin-G. Other node components, including beta IV spectrin, voltage-gated sodium channels, and the L1 cell adhesion molecule neurofascin, are subsequently recruited to sites of ankyrin-G clustering. The role of intact paranodes in protein clustering was examined in the dysmyelinating mouse mutant jimpy. Jimpy mice do not have intact paranodal axoglial contacts, which is indicated by a complete lack of neurexin/contactin-associated protein/paranodin clustering in paranodes. In the absence of intact paranodes, ankyrin-G was still able to cluster, although fewer ankyrin clusters were seen in jimpy optic nerves than in wild-type optic nerves. Recruitment of Nav1.2, Nav1.6, beta IV spectrin, and neurofascin to sites of ankyrin-G clustering is unimpaired in jimpy mice, indicating that node formation occurs independent of intact paranodal axoglial contacts.
National Acad Sciences