Neurofilament-dependent radial growth of motor axons and axonal organization of neurofilaments does not require the neurofilament heavy subunit (NF-H) or its phosphorylation

Mala V. Rao, Megan K. Houseweart, Toni L. Williamson, Thomas O. Crawford, Janet Folmer, Don W. Cleveland

Research output: Contribution to journalArticlepeer-review

Abstract

Neurofilaments are essential for establishment and maintenance of axonal diameter of large myelinated axons, a property that determines the velocity of electrical signal conduction. One prominent model for how neurofilaments specify axonal growth is that the 660-amino acid, heavily phosphorylated tail domain of neurofilament heavy subunit (NF-H) is responsible for neurofilament-dependent structuring of axoplasm through intra-axonal crossbridging between adjacent neurofilaments or to other axonal structures. To test such a role, homologous recombination was used to generate NF-H-null mice. In peripheral motor and sensory axons, absence of NF-H does not significantly affect the number of neurofilaments or axonal elongation or targeting, but it does affect the efficiency of survival of motor and sensory axons. Loss of NF-H caused only a slight reduction in nearest neighbor spacing of neurofilaments and did not affect neurofilament distribution in either large- or small-diameter motor axons. Since postnatal growth of motor axon caliber continues largely unabated in the absence of NF-H, neither interactions mediated by NF-H nor the extensive phosphorylation of it within myelinated axonal segments are essential features of this growth.

Original languageEnglish (US)
Pages (from-to)171-181
Number of pages11
JournalJournal of Cell Biology
Volume143
Issue number1
DOIs
StatePublished - Oct 5 1998

Keywords

  • Axoplasm
  • Motor neurons
  • Neurofilaments
  • Radial growth
  • Sensory neurons

ASJC Scopus subject areas

  • Cell Biology

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