The Caenorhabditis elegans septin complex is nonpolar

Corinne M. John, Richard K. Hite, Christine S. Weirich, Daniel J. Fitzgerald, Hatim Jawhari, Mahamadou Faty, Dominik Schläpfer, Ruth Kroschewski, Fritz K. Winkler, Tom Walz, Yves Barral, Michel O. Steinmetz

Research output: Contribution to journalArticlepeer-review

108 Scopus citations


Septins are conserved GTPases that form heteromultimeric complexes and assemble into filaments that play a critical role in cell division and polarity. Results from budding and fission yeast indicate that septin complexes form around a tetrameric core. However, the molecular structure of the core and its influence on the polarity of septin complexes and filaments is poorly defined. The septin complex of the nematode Caenorhabditis elegans is formed entirely by the core septins UNC-59 and UNC-61. We show that UNC-59 and UNC-61 form a dimer of coiled-coil-mediated heterodimers. By electron microscopy, this heterotetramer appears as a linear arrangement of four densities representing the four septin subunits. Fusion of GFP to the N termini of UNC-59 and UNC-61 and subsequent electron microscopic visualization suggests that the sequence of septin subunits is UNC-59/UNC-61/UNC-61/UNC-59. Visualization of GFP extensions fused to the extremity of the C-terminal coiled coils indicates that these extend laterally from the heterotetrameric core. Together, our study establishes that the septin core complex is symmetric, and suggests that septins form nonpolar filaments.

Original languageEnglish (US)
Pages (from-to)3296-3307
Number of pages12
JournalEMBO Journal
Issue number14
StatePublished - Jul 25 2007


  • Cell polarity
  • Coiled coil
  • Cytoskeleton
  • Electron microscopy
  • Septin

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)


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