title: Wnt/Frizzled signaling controls C. elegans gastrulation by activating actomyosin contractility.
abstract: BACKGROUND
  Embryonic patterning mechanisms regulate the cytoskeletal machinery that drives morphogenesis, but there are few cases where links between patterning mechanisms and morphogenesis are well understood. We have used a combination of genetics, in vivo imaging, and cell manipulations to identify such links in C. elegans gastrulation. Gastrulation in C. elegans begins with the internalization of endodermal precursor cells in a process that depends on apical constriction of ingressing cells.
  
  
  RESULTS
  We show that ingression of the endodermal precursor cells is regulated by pathways, including a Wnt-Frizzled signaling pathway, that specify endodermal cell fate. We find that Wnt signaling has a role in gastrulation in addition to its earlier roles in regulating endodermal cell fate and cell-cycle timing. In the absence of Wnt signaling, endodermal precursor cells polarize and enrich myosin II apically but fail to contract their apical surfaces. We show that a regulatory myosin light chain normally becomes phosphorylated on the apical side of ingressing cells at a conserved site that can lead to myosin-filament formation and contraction of actomyosin networks and that this phosphorylation depends on Wnt signaling.
  
  
  CONCLUSIONS
  We conclude that Wnt signaling regulates C. elegans gastrulation through regulatory myosin light-chain phosphorylation, which results in the contraction of the apical surface of ingressing cells. These findings forge new links between cell-fate specification and morphogenesis, and they represent a novel mechanism by which Wnt signaling can regulate morphogenesis.
authors.affiliation: Department of Biology, University of North Carolina, Chapel Hill, Chapel Hill, North Carolina 27599-3280, USA.
authors.forename: Jen-Yi
authors.initials: JY
authors.lastname: Lee
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Marston
authors.forename: Timothy
authors.initials: T
authors.lastname: Walston
authors.forename: Jeff
authors.initials: J
authors.lastname: Hardin
authors.forename: Ari
authors.initials: A
authors.lastname: Halberstadt
authors.forename: Bob
authors.initials: B
authors.lastname: Goldstein
mesh_terms: D000205:Actomyosin / Q000502:physiology*; D000818:Animals; D017173:Caenorhabditis elegans / Q000196:embryology*; D051157:Frizzled Receptors / Q000378:metabolism*; D005775:Gastrula / Q000502:physiology*; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D009024:Morphogenesis / Q000502:physiology*; D010766:Phosphorylation; D034622:RNA Interference; D015398:Signal Transduction / Q000502:physiology*; D051153:Wnt Proteins / Q000378:metabolism*
chemical_list: D051157:Frizzled Receptors; D051153:Wnt Proteins; D000205:Actomyosin