The disease-associated formin INF2/EXC-6 organizes lumen and cell outgrowth during tubulogenesis by regulating F-actin and microtubule cytoskeletons

Dev Cell. 2015 Mar 23;32(6):743-55. doi: 10.1016/j.devcel.2015.01.009. Epub 2015 Mar 12.


We investigate how outgrowth at the basolateral cell membrane is coordinated with apical lumen formation in the development of a biological tube by characterizing exc-6, a gene required for C. elegans excretory cell (EC) tubulogenesis. We show that EXC-6 is orthologous to the human formin INF2, which polymerizes filamentous actin (F-actin) and binds microtubules (MTs) in vitro. Dominant INF2 mutations cause focal segmental glomerulosclerosis (FSGS), a kidney disease, and FSGS+Charcot-Marie-Tooth neuropathy. We show that activated INF2 can substitute for EXC-6 in C. elegans and that disease-associated mutations cause constitutive activity. Using genetic analysis and live imaging, we show that exc-6 regulates MT and F-actin accumulation at EC tips and dynamics of basolateral-localized MTs, indicating that EXC-6 organizes F-actin and MT cytoskeletons during tubulogenesis. The pathology associated with INF2 mutations is believed to reflect misregulation of F-actin, but our results suggest alternative or additional mechanisms via effects on MT dynamics.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Actin Cytoskeleton
  • Actins / biosynthesis
  • Animals
  • Caenorhabditis elegans / genetics*
  • Caenorhabditis elegans Proteins / genetics*
  • Cell Membrane / metabolism
  • Charcot-Marie-Tooth Disease / genetics
  • Cloning, Molecular
  • Formins
  • Glomerulosclerosis, Focal Segmental / genetics
  • Humans
  • Microfilament Proteins / genetics
  • Microfilament Proteins / metabolism*
  • Microtubules / metabolism*
  • Mutation
  • Protein Binding / genetics
  • Protein Structure, Tertiary
  • Tubulin / genetics


  • Actins
  • Caenorhabditis elegans Proteins
  • EXC-6 protein, C elegans
  • Formins
  • INF2 protein, human
  • Microfilament Proteins
  • Tubulin