Opposing Wnt pathways orient cell polarity during organogenesis.
The orientation of asymmetric cell division contributes to the organization of cells within a tissue or organ. For example, mirror-image symmetry of the C. elegans vulva is achieved by the opposite division orientation of the vulval precursor cells (VPCs) flanking the axis of symmetry. We characterized the molecular mechanisms contributing to this division pattern. Wnts MOM-2 and LIN-44 are expressed at the axis of symmetry and orient the VPCs toward the center. These Wnts act via Fz/LIN-17 and Ryk/LIN-18, which control beta-catenin localization and activate gene transcription. In addition, VPCs on both sides of the axis of symmetry possess a uniform underlying "ground" polarity, established by the instructive activity of Wnt/EGL-20. EGL-20 establishes ground polarity via a novel type of signaling involving the Ror receptor tyrosine kinase CAM-1 and the planar cell polarity component Van Gogh/VANG-1. Thus, tissue polarity is determined by the integration of multiple Wnt pathways.
Green
Jennifer L
JL
Howard Hughes Medical Institute/Division of Biology, California Institute of Technology, Mail Code 156-29, Pasadena, CA 91125, USA.
Inoue
Takao
T
Sternberg
Paul W
PW
D000818:Animals; D017173:Caenorhabditis elegans / Q000196:embryology* / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism*; D016764:Cell Polarity; D005260:Female; D006023:Glycoproteins / Q000378:metabolism; D038081:Organogenesis; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism; D015398:Signal Transduction; D014844:Vulva / Q000196:embryology; D051153:Wnt Proteins / Q000378:metabolism*; D051176:beta Catenin / Q000378:metabolism
D029742:Caenorhabditis elegans Proteins; C117259:Egl-20 protein, C elegans; D006023:Glycoproteins; C101684:LIN-17 protein, C elegans; D043562:Receptors, G-Protein-Coupled; D051153:Wnt Proteins; D051176:beta Catenin; C492691:LIN-18 protein, C elegans; D020794:Receptor Protein-Tyrosine Kinases