title: SMRT analysis of MTOC and nuclear positioning reveals the role of EB1 and LIC1 in single-cell polarization.
abstract: In several migratory cells, the microtubule-organizing center (MTOC) is repositioned between the leading edge and nucleus, creating a polarized morphology. Although our understanding of polarization has progressed as a result of various scratch-wound and cell migration studies, variations in culture conditions required for such assays have prevented a unified understanding of the intricacies of MTOC and nucleus positioning that result in cell polarization. Here, we employ a new SMRT (for sparse, monolayer, round, triangular) analysis that uses a universal coordinate system based on cell centroid to examine the pathways regulating MTOC and nuclear positions in cells plated in a variety of conditions. We find that MTOC and nucleus positioning are crucially and independently affected by cell shape and confluence; MTOC off-centering correlates with the polarization of single cells; acto-myosin contractility and microtubule dynamics are required for single-cell polarization; and end binding protein 1 and light intermediate chain 1, but not Par3 and light intermediate chain 2, are required for single-cell polarization and directional cell motility. Using various cellular geometries and conditions, we implement a systematic and reproducible approach to identify regulators of MTOC and nucleus positioning that depend on extracellular guidance cues.
authors.affiliation: Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218,  USA.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Hale
authors.forename: Wei-Chiang
authors.initials: WC
authors.lastname: Chen
authors.forename: Shyam B
authors.initials: SB
authors.lastname: Khatau
authors.forename: Brian R
authors.initials: BR
authors.lastname: Daniels
authors.forename: Jerry S H
authors.initials: JS
authors.lastname: Lee
authors.forename: Denis
authors.initials: D
authors.lastname: Wirtz
mesh_terms: D000199:Actins / Q000502:physiology; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D015815:Cell Adhesion Molecules / Q000502:physiology; D018797:Cell Cycle Proteins; D002465:Cell Movement; D002467:Cell Nucleus / Q000502:physiology* / Q000648:ultrastructure; D016764:Cell Polarity; D048430:Cell Shape; D002478:Cells, Cultured; D056445:Cytoplasmic Dyneins / Q000037:antagonists & inhibitors / Q000502:physiology*; D034882:Lamins / Q000502:physiology; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000037:antagonists & inhibitors / Q000502:physiology*; D022101:Microtubule-Organizing Center / Q000502:physiology* / Q000648:ultrastructure; D008870:Microtubules / Q000502:physiology; D024462:Myosin Type II / Q000502:physiology
chemical_list: D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D015815:Cell Adhesion Molecules; D018797:Cell Cycle Proteins; C514504:Dynll2 protein, mouse; C405804:EB1 microtubule binding proteins; D034882:Lamins; D008869:Microtubule-Associated Proteins; C115084:Pard3 protein, mouse; C486041:Dync1li1 protein, mouse; D024462:Myosin Type II; D056445:Cytoplasmic Dyneins