title: Planar Cell Polarity Breaks the Symmetry of PAR Protein Distribution prior to Mitosis in Drosophila Sensory Organ Precursor Cells.
abstract: During development, cell-fate diversity can result from the unequal segregation of fate determinants at mitosis. Polarization of the mother cell is essential for asymmetric cell division (ACD). It often involves the formation of a cortical domain containing the PAR complex proteins Par3, Par6, and atypical protein kinase C (aPKC). In the fly notum, sensory organ precursor cells (SOPs) divide asymmetrically within the plane of the epithelium and along the body axis to generate two distinct cells. Fate asymmetry depends on the asymmetric localization of the PAR complex. In the absence of planar cell polarity (PCP), SOPs divide with a random planar orientation but still asymmetrically, showing that PCP is dispensable for PAR asymmetry at mitosis. To study when and how the PAR complex localizes asymmetrically, we have used a quantitative imaging approach to measure the planar polarization of the proteins Bazooka (Baz, fly Par3), Par6, and aPKC in living pupae. By using imaging of functional GFP-tagged proteins with image processing and computational modeling, we find that Baz, Par6, and aPKC become planar polarized prior to mitosis in a manner independent of the AuroraA kinase and that PCP is required for the planar polarization of Baz, Par6, and aPKC during interphase. This indicates that a "mitosis rescue" mechanism establishes asymmetry at mitosis in PCP mutants. This study therefore identifies PCP as the initial symmetry-breaking signal for the planar polarization of PAR proteins in asymmetrically dividing SOPs.
authors.affiliation: Institut Pasteur, rue du Dr Roux, 75015 Paris, France; CNRS, URA2578, rue du Dr Roux, 75015 Paris, France; UPMC, Cellule Pasteur, rue du Dr Roux, 75015 Paris, France.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Besson
authors.affiliation: Institut Pasteur, rue du Dr Roux, 75015 Paris, France; CNRS, URA2578, rue du Dr Roux, 75015 Paris, France.
authors.forename: Fred
authors.initials: F
authors.lastname: Bernard
authors.affiliation: Institut Pasteur, rue du Dr Roux, 75015 Paris, France.
authors.forename: Francis
authors.initials: F
authors.lastname: Corson
authors.affiliation: Institut Pasteur, rue du Dr Roux, 75015 Paris, France; CNRS, URA2578, rue du Dr Roux, 75015 Paris, France.
authors.forename: Hervé
authors.initials: H
authors.lastname: Rouault
authors.affiliation: Institut Pasteur, rue du Dr Roux, 75015 Paris, France; CNRS, URA2578, rue du Dr Roux, 75015 Paris, France.
authors.forename: Elodie
authors.initials: E
authors.lastname: Reynaud
authors.affiliation: Institut Pasteur, rue du Dr Roux, 75015 Paris, France; CNRS, URA2578, rue du Dr Roux, 75015 Paris, France.
authors.forename: Alyona
authors.initials: A
authors.lastname: Keder
authors.affiliation: Institut Pasteur, rue du Dr Roux, 75015 Paris, France; CNRS, URA2578, rue du Dr Roux, 75015 Paris, France.
authors.forename: Khalil
authors.initials: K
authors.lastname: Mazouni
authors.affiliation: Institut Pasteur, rue du Dr Roux, 75015 Paris, France; CNRS, URA2578, rue du Dr Roux, 75015 Paris, France. Electronic address: fschweis@pasteur.fr.
authors.forename: François
authors.initials: F
authors.lastname: Schweisguth
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000818:Animals; D002455:Cell Division / Q000502:physiology*; D016764:Cell Polarity / Q000502:physiology*; D004330:Drosophila / Q000166:cytology; D029721:Drosophila Proteins / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D008938:Mitosis / Q000502:physiology*; D011493:Protein Kinase C / Q000378:metabolism*; D012679:Sense Organs / Q000166:cytology*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D029721:Drosophila Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C400774:baz protein, Drosophila; C115015:PKC-3 protein; D011493:Protein Kinase C