Tubular excretory canal structure depends on intermediate filaments EXC-2 and IFA-4 in caenorhabditis elegans

Hikmat Al-Hashimi, David H. Hall, Brian D. Ackley, Erik A. Lundquist, Matthew Buechner

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


The excretory canals of Caenorhabditis elegans are a model for understanding the maintenance of apical morphology in narrow single-celled tubes. Light and electron microscopy shows that mutants in exc-2 start to form canals normally, but these swell to develop large fluid-filled cysts that lack a complete terminal web at the apical surface, and accumulate filamentous material in the canal lumen. Here, whole-genome sequencing and gene rescue show that exc-2 encodes intermediate filament protein IFC-2. EXC-2/IFC-2 protein, fluorescently tagged via clustered regularly interspaced short palindromic repeats/Cas9, is located at the apical surface of the canals independently of other intermediate filament proteins. EXC-2 is also located in several other tissues, though the tagged isoforms are not seen in the larger intestinal tube. Tagged EXC-2 binds via pulldown to intermediate filament protein IFA-4, which is also shown to line the canal apical surface. Overexpression of either protein results in narrow but shortened canals. These results are consistent with a model whereby three intermediate filaments in the canals—EXC-2, IFA-4, and IFB-1—restrain swelling of narrow tubules in concert with actin filaments that guide the extension and direction of tubule outgrowth, while allowing the tube to bend as the animal moves.

Original languageEnglish (US)
Pages (from-to)637-652
Number of pages16
Issue number2
StatePublished - Oct 2018


  • Epithelium
  • Excretory canal
  • Intermediate filament
  • Lumen
  • Tubulogenesis

ASJC Scopus subject areas

  • Genetics


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