title: Coordination by Cdc42 of Actin, Contractility, and Adhesion for Melanoblast Movement in Mouse Skin.
abstract: The individual molecular pathways downstream of Cdc42, Rac, and Rho GTPases are well documented, but we know surprisingly little about how these pathways are coordinated when cells move in a complex environment in vivo. In the developing embryo, melanoblasts originating from the neural crest must traverse the dermis to reach the epidermis of the skin and hair follicles. We previously established that Rac1 signals via Scar/WAVE and Arp2/3 to effect pseudopod extension and migration of melanoblasts in skin. Here we show that RhoA is redundant in the melanocyte lineage but that Cdc42 coordinates multiple motility systems independent of Rac1. Similar to Rac1 knockouts, Cdc42 null mice displayed a severe loss of pigmentation, and melanoblasts showed cell-cycle progression, migration, and cytokinesis defects. However, unlike Rac1 knockouts, Cdc42 null melanoblasts were elongated and displayed large, bulky pseudopods with dynamic actin bursts. Despite assuming an elongated shape usually associated with fast mesenchymal motility, Cdc42 knockout melanoblasts migrated slowly and inefficiently in the epidermis, with nearly static pseudopods. Although much of the basic actin machinery was intact, Cdc42 null cells lacked the ability to polarize their Golgi and coordinate motility systems for efficient movement. Loss of Cdc42 de-coupled three main systems: actin assembly via the formin FMNL2 and Arp2/3, active myosin-II localization, and integrin-based adhesion dynamics.
authors.affiliation: CRUK Beatson Institute, University of Glasgow, Switchback Road, Bearsden, Glasgow G61 1BD, UK.
authors.forename: Emma F
authors.initials: EF
authors.lastname: Woodham
authors.affiliation: CRUK Beatson Institute, University of Glasgow, Switchback Road, Bearsden, Glasgow G61 1BD, UK.
authors.forename: Nikki R
authors.initials: NR
authors.lastname: Paul
authors.affiliation: CRUK Beatson Institute, University of Glasgow, Switchback Road, Bearsden, Glasgow G61 1BD, UK.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Tyrrell
authors.affiliation: CRUK Beatson Institute, University of Glasgow, Switchback Road, Bearsden, Glasgow G61 1BD, UK.
authors.forename: Heather J
authors.initials: HJ
authors.lastname: Spence
authors.affiliation: CRUK Beatson Institute, University of Glasgow, Switchback Road, Bearsden, Glasgow G61 1BD, UK.
authors.forename: Karthic
authors.initials: K
authors.lastname: Swaminathan
authors.affiliation: CRUK Beatson Institute, University of Glasgow, Switchback Road, Bearsden, Glasgow G61 1BD, UK.
authors.forename: Michelle R
authors.initials: MR
authors.lastname: Scribner
authors.affiliation: CRUK Beatson Institute, University of Glasgow, Switchback Road, Bearsden, Glasgow G61 1BD, UK.
authors.forename: Evangelos
authors.initials: E
authors.lastname: Giampazolias
authors.affiliation: CRUK Beatson Institute, University of Glasgow, Switchback Road, Bearsden, Glasgow G61 1BD, UK.
authors.forename: Ann
authors.initials: A
authors.lastname: Hedley
authors.affiliation: CRUK Beatson Institute, University of Glasgow, Switchback Road, Bearsden, Glasgow G61 1BD, UK.
authors.forename: William
authors.initials: W
authors.lastname: Clark
authors.affiliation: Division of Molecular Cell Biology, Zoological Institute, Technische Universität Braunschweig, Spielmannstrasse 7, 38106 Braunschweig, Germany; Molecular Cell Biology Group, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany.
authors.forename: Frieda
authors.initials: F
authors.lastname: Kage
authors.affiliation: Department of Pharmacology, University of North Carolina, Chapel Hill, NC 27599, USA; Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27514, USA.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Marston
authors.affiliation: Department of Pharmacology, University of North Carolina, Chapel Hill, NC 27599, USA; Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27514, USA.
authors.forename: Klaus M
authors.initials: KM
authors.lastname: Hahn
authors.affiliation: CRUK Beatson Institute, University of Glasgow, Switchback Road, Bearsden, Glasgow G61 1BD, UK.
authors.forename: Stephen W G
authors.initials: SW
authors.lastname: Tait
authors.affiliation: Institute Curie, CNRS UMR3347, INSERM U1021, Bat 110, Centre Universitaire, 91405 Orsay Cedex, France.
authors.forename: Lionel
authors.initials: L
authors.lastname: Larue
authors.affiliation: Biotech Research Center, University of Copenhagen, Ole Maaløes Vej 5, Copenhagen 2200, Denmark.
authors.forename: Cord H
authors.initials: CH
authors.lastname: Brakebusch
authors.affiliation: CRUK Beatson Institute, University of Glasgow, Switchback Road, Bearsden, Glasgow G61 1BD, UK.
authors.forename: Robert H
authors.initials: RH
authors.lastname: Insall
authors.affiliation: CRUK Beatson Institute, University of Glasgow, Switchback Road, Bearsden, Glasgow G61 1BD, UK. Electronic address: l.machesky@beatson.gla.ac.uk.
authors.forename: Laura M
authors.initials: LM
authors.lastname: Machesky
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D002448:Cell Adhesion; D019070:Cell Lineage; D002465:Cell Movement; D008544:Melanocytes / Q000378:metabolism*; D051379:Mice / Q000196:embryology; D009479:Neuropeptides / Q000235:genetics / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000235:genetics* / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D020742:rhoA GTP-Binding Protein
chemical_list: D000199:Actins; D009479:Neuropeptides; C484602:Rac1 protein, mouse; C526380:RhoA protein, mouse; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein; D020741:rho GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein
keywords: Cdc42; Rho GTPases; actin; actin cytoskeleton; adhesion; cell motility; integrin; melanocyte; migration; myosin