Ion channel clustering at the axon initial segment and node of Ranvier evolved sequentially in early chordates
2008
Evolution of Ion Channel Clustering in Neurons
publication
Evidence: high
Author Information
Author(s): Matthew N. Rasband
Primary Institution: Baylor College of Medicine
Hypothesis
How and why did ion channels from two different gene families evolve a common amino acid sequence that mediates their clustering and localization at the AIS and nodes of Ranvier?
Conclusion
The study shows that a distinct axon initial segment (AIS) evolved in basal chordates before the development of myelin and nodes of Ranvier.
Supporting Evidence
- The first Na+ channels with anchor motifs arose in basal chordates, such as amphioxus.
- All orthologous Na+ channel genes in jawed vertebrates contain the anchor motif.
- KCNQ2/3 K+ channel AIS anchor motif arose after lampreys diverged from other vertebrates.
- The unique properties of vertebrate myelinated axons drove the molecular evolution of KCNQ2/3 K+ channels.
Takeaway
This study helps us understand how certain proteins in nerve cells evolved to cluster together, which is important for how signals are sent in our bodies.
Methodology
Phylogenetic analysis of invertebrate and vertebrate Na+ channels to define the evolutionary origins of AIS targeting motifs.
Digital Object Identifier (DOI)
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