title: The disease-associated formin INF2/EXC-6 organizes lumen and cell outgrowth during tubulogenesis by regulating F-actin and microtubule cytoskeletons.
abstract: 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.
authors.affiliation: Howard Hughes Medical Institute, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA. Electronic address: ds451@columbia.edu.
authors.forename: Daniel D
authors.initials: DD
authors.lastname: Shaye
authors.affiliation: Howard Hughes Medical Institute, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA; Department of Biochemistry and Molecular Biophysics, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA; Department of Genetics and Development, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA. Electronic address: isg4@columbia.edu.
authors.forename: Iva
authors.initials: I
authors.lastname: Greenwald
mesh_terms: D008841:Actin Cytoskeleton; D000199:Actins / Q000096:biosynthesis; D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics*; D002462:Cell Membrane / Q000378:metabolism; D002607:Charcot-Marie-Tooth Disease / Q000235:genetics; D003001:Cloning, Molecular; D000080865:Formins; D005923:Glomerulosclerosis, Focal Segmental / Q000235:genetics; D006801:Humans; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D009154:Mutation; D011485:Protein Binding / Q000235:genetics; D017434:Protein Structure, Tertiary; D014404:Tubulin / Q000235:genetics
chemical_list: D000199:Actins; D029742:Caenorhabditis elegans Proteins; C000598635:EXC-6 protein, C elegans; D000080865:Formins; C546959:INF2 protein, human; D008840:Microfilament Proteins; D014404:Tubulin