title: Directional migration of neural crest cells in vivo is regulated by Syndecan-4/Rac1 and non-canonical Wnt signaling/RhoA.
abstract: Directed cell migration is crucial for development, but most of our current knowledge is derived from in vitro studies. We analyzed how neural crest (NC) cells migrate in the direction of their target during embryonic development. We show that the proteoglycan Syndecan-4 (Syn4) is expressed in the migrating neural crest of Xenopus and zebrafish embryos. Loss-of-function studies using an antisense morpholino against syn4 show that this molecule is required for NC migration, but not for NC induction. Inhibition of Syn4 does not affect the velocity of cell migration, but significantly reduces the directional migration of NC cells. Furthermore, we show that Syn4 and PCP signaling control the directional migration of NC cells by regulating the direction in which the cell protrusions are generated during migration. Finally, we perform FRET analysis of Cdc42, Rac and RhoA in vitro and in vivo after interfering with Syn4 and PCP signaling. This is the first time that FRET analysis of small GTPases has been performed in vivo. Our results show that Syn4 inhibits Rac activity, whereas PCP signaling promotes RhoA activity. In addition, we show that RhoA inhibits Rac in NC cells. We present a model in which Syn4 and PCP control directional NC migration by, at least in part, regulating membrane protrusions through the regulation of small GTPase activities.
authors.affiliation: Department of Anatomy and Development Biology, University College London, Gower Street, London WC1E 6BT, UK.
authors.forename: Helen K
authors.initials: HK
authors.lastname: Matthews
authors.forename: Lorena
authors.initials: L
authors.lastname: Marchant
authors.forename: Carlos
authors.initials: C
authors.lastname: Carmona-Fontaine
authors.forename: Sei
authors.initials: S
authors.lastname: Kuriyama
authors.forename: Juan
authors.initials: J
authors.lastname: Larraín
authors.forename: Mark R
authors.initials: MR
authors.lastname: Holt
authors.forename: Maddy
authors.initials: M
authors.lastname: Parsons
authors.forename: Roberto
authors.initials: R
authors.lastname: Mayor
mesh_terms: D000818:Animals; D002465:Cell Movement / Q000502:physiology; D016764:Cell Polarity / Q000502:physiology; D004625:Embryo, Nonmammalian / Q000502:physiology; D031541:Fluorescence Resonance Energy Transfer; D009432:Neural Crest / Q000166:cytology* / Q000196:embryology / Q000378:metabolism; D015398:Signal Transduction; D053671:Syndecan-4 / Q000096:biosynthesis / Q000502:physiology*; D051153:Wnt Proteins / Q000502:physiology*; D014981:Xenopus; D015027:Zebrafish; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000502:physiology*; D020742:rhoA GTP-Binding Protein / Q000502:physiology*
chemical_list: D053671:Syndecan-4; D051153:Wnt Proteins; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein