title: A one-dimensional model of PCP signaling: polarized cell behavior in the notochord of the ascidian Ciona.
abstract: Despite its importance in development and physiology the planar cell polarity (PCP) pathway remains one of the most enigmatic signaling mechanisms. The notochord of the ascidian Ciona provides a unique model for investigating the PCP pathway. Interestingly, the notochord appears to be the only embryonic structure in Ciona activating the PCP pathway. Moreover, the Ciona notochord as a single-file array of forty polarized cells is a uniquely tractable system for the study of polarization dynamics and the transmission of the PCP pathway. Here, we test models for propagation of a polarizing signal, interrogating temporal, spatial and signaling requirements. A simple cell-cell relay cascading through the entire length of the notochord is not supported; instead a more complex mechanism is revealed, with interactions influencing polarity between neighboring cells, but not distant ones. Mechanisms coordinating notochord-wide polarity remain elusive, but appear to entrain general (i.e., global) polarity even while local interactions remain important. However, this global polarizer does not appear to act as a localized, spatially-restricted determinant. Coordination of polarity along the long axis of the notochord requires the PCP pathway, a role we demonstrate is temporally distinct from this pathway's earlier role in convergent extension and intercalation. We also reveal polarity in the notochord to be dynamic: a cell's polarity state can be changed and then restored, underscoring the Ciona notochord's amenability for in vivo studies of PCP.
authors.affiliation: Department of Molecular, Cell and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106, USA.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Kourakis
authors.affiliation: Department of Molecular, Cell and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106, USA.
authors.forename: Wendy
authors.initials: W
authors.lastname: Reeves
authors.affiliation: Department of Molecular, Cell and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106, USA.
authors.forename: Erin
authors.initials: E
authors.lastname: Newman-Smith
authors.affiliation: Department of Molecular, Cell and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106, USA.
authors.forename: Benoit
authors.initials: B
authors.lastname: Maury
authors.affiliation: Department of Molecular, Cell and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106, USA.
authors.forename: Sarah
authors.initials: S
authors.lastname: Abdul-Wajid
authors.affiliation: Department of Molecular, Cell and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106, USA. Electronic address: william.smith@lifesci.ucsb.edu.
authors.forename: William C
authors.initials: WC
authors.lastname: Smith
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D019521:Body Patterning / Q000235:genetics / Q000502:physiology*; D016764:Cell Polarity / Q000235:genetics / Q000502:physiology; D002938:Ciona intestinalis / Q000196:embryology* / Q000235:genetics / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D018613:Microscopy, Confocal; D008954:Models, Biological; D009672:Notochord / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*; D059008:Time-Lapse Imaging
chemical_list: D049452:Green Fluorescent Proteins
keywords: Cell polarity; Ciona; Notochord development; PCP