title: Symmetry Breaking in an Edgeless Epithelium by Fat2-Regulated Microtubule Polarity.
abstract: Planar cell polarity (PCP) information is a critical determinant of organ morphogenesis. While PCP in bounded epithelial sheets is increasingly well understood, how PCP is organized in tubular and acinar tissues is not. Drosophila egg chambers (follicles) are an acinus-like "edgeless epithelium" and exhibit a continuous, circumferential PCP that does not depend on pathways active in bounded epithelia; this follicle PCP directs formation of an ellipsoid rather than a spherical egg. Here, we apply an imaging algorithm to "unroll" the entire 3D tissue surface and comprehensively analyze PCP onset. This approach traces chiral symmetry breaking to plus-end polarity of microtubules in the germarium, well before follicles form and rotate. PCP germarial microtubules provide chiral information that predicts the direction of whole-tissue rotation as soon as independent follicles form. Concordant microtubule polarity, but not microtubule alignment, requires the atypical cadherin Fat2, which acts at an early stage to translate plus-end bias into coordinated actin-mediated collective cell migration. Because microtubules are not required for PCP or migration after follicle rotation initiates, while dynamic actin and extracellular matrix are, polarized microtubules lie at the beginning of a handoff mechanism that passes early chiral PCP of the cytoskeleton to a supracellular planar polarized extracellular matrix and elongates the organ.
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720-3200, USA.
authors.forename: Dong-Yuan
authors.initials: DY
authors.lastname: Chen
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720-3200, USA.
authors.forename: Katherine R
authors.initials: KR
authors.lastname: Lipari
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720-3200, USA.
authors.forename: Yalda
authors.initials: Y
authors.lastname: Dehghan
authors.affiliation: Kavli Institute of Theoretical Physics, University of California, Santa Barbara, Santa Barbara, CA 93106, USA.
authors.forename: Sebastian J
authors.initials: SJ
authors.lastname: Streichan
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720-3200, USA. Electronic address: bilder@berkeley.edu.
authors.forename: David
authors.initials: D
authors.lastname: Bilder
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D015820:Cadherins / Q000378:metabolism*; D016764:Cell Polarity; D029721:Drosophila Proteins / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000166:cytology* / Q000378:metabolism*; D004848:Epithelium / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D010063:Ovum / Q000166:cytology / Q000378:metabolism; D012399:Rotation
chemical_list: D000199:Actins; D015820:Cadherins; D029721:Drosophila Proteins; C546978:kug protein, Drosophila