PUBLICATION

Ncam1a and Ncam1b: Two carriers of polysialic acid with different functions in the developing zebrafish nervous system

Authors
Langhauser, M., Ustinova, J., Rivera-Milla, E., Ivannikov, D., Seidl, C., Slomka, C., Finne, J., Yoshihara, Y., Bastmeyer, M., and Bentrop, J.
ID
ZDB-PUB-110907-37
Date
2012
Source
Glycobiology   22(2): 196-209 (Journal)
Registered Authors
Bastmeyer, Martin, Bentrop, Joachim, Rivera-Milla, Eric, Yoshihara, Yoshihiro
Keywords
polysialic acid, NCAM, zebrafish, nervous system, development
MeSH Terms
  • Animals
  • Axons/metabolism
  • Brain/embryology*
  • Brain/metabolism
  • Carrier Proteins/metabolism
  • Evolution, Molecular
  • Gene Duplication
  • Mesencephalon/embryology
  • Mesencephalon/metabolism
  • Multigene Family
  • Nervous System/embryology*
  • Nervous System/metabolism
  • Neural Cell Adhesion Molecules/metabolism*
  • Prosencephalon/embryology
  • Prosencephalon/metabolism
  • Sialic Acids/metabolism*
  • Spinal Cord/metabolism
  • Zebrafish/embryology*
  • Zebrafish/metabolism
  • Zebrafish Proteins/metabolism*
PubMed
21890892 Full text @ Glycobiology
Abstract

Polysialic acid (polySia) is mainly described as a glycan modification of the neural cell adhesion molecule NCAM1. PolySia-NCAM1 has multiple functions during the development of vertebrate nervous systems including axon extension and fasciculation. Phylogenetic analyses reveal the presence of two related gene clusters, NCAM1 and NCAM2, in tetrapods and fishes. Within the ncam1 cluster, teleost fishes express ncam1a (cam) and ncam1b (pram) as duplicated paralogs which arose from a second round of ray-finned fish-specific genome duplication. Tetrapods, in contrast, express a single NCAM1 gene.

Using the zebrafish model, we identify Ncam1b as a novel major carrier of polysialic acid in the nervous system. PolySia-Ncam1a is expressed predominantly in rostral regions of the developing nervous system whereas polySia-Ncam1b prevails caudally. We show that ncam1a and ncam1b have different expression domains which only partially overlap. Furthermore, Ncam1a and Ncam1b and their polySia modifications serve different functions in axon guidance. Formation of the posterior commissure at the forebrain/midbrain junction requires polySia-Ncam1a on the axons for proper fasciculation, whereas Ncam1b, expressed by midbrain cell bodies, serves as an instructive guidance cue for the dorso-medially directed growth of axons. Spinal motor axons, on the other hand, depend on axonally expressed Ncam1b for correct growth towards their target region.

Collectively, these findings suggest that the genome duplication in the teleost lineage has provided the basis for a functional diversification of polySia carriers in the nervous system.

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