title: Cilia are required for asymmetric nodal induction in the sea urchin embryo.
abstract: Left-right (LR) organ asymmetries are a common feature of metazoan animals. In many cases, laterality is established by a conserved asymmetric Nodal signaling cascade during embryogenesis. In most vertebrates, asymmetric nodal induction results from a cilia-driven leftward fluid flow at the left-right organizer (LRO), a ciliated epithelium present during gastrula/neurula stages. Conservation of LRO and flow beyond the vertebrates has not been reported yet.
  
  
  
  Here we study sea urchin embryos, which use nodal to establish larval LR asymmetry as well. Cilia were found in the archenteron of embryos undergoing gastrulation. Expression of foxj1 and dnah9 suggested that archenteron cilia were motile. Cilia were polarized to the posterior pole of cells, a prerequisite of directed flow. High-speed videography revealed rotating cilia in the archenteron slightly before asymmetric nodal induction. Removal of cilia through brief high salt treatments resulted in aberrant patterns of nodal expression. Our data demonstrate that cilia - like in vertebrates - are required for asymmetric nodal induction in sea urchin embryos.
  
  
  
  Based on these results we argue that the anterior archenteron represents a bona fide LRO and propose that cilia-based symmetry breakage is a synapomorphy of the deuterostomes.
authors.affiliation: University of Hohenheim, Institute of Zoology, 70593, Stuttgart, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Tisler
authors.affiliation: University of Hohenheim, Institute of Zoology, 70593, Stuttgart, Germany.
authors.forename: Franziska
authors.initials: F
authors.lastname: Wetzel
authors.affiliation: University of Hohenheim, Institute of Zoology, 70593, Stuttgart, Germany.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Mantino
authors.affiliation: Department of Embryology, Lomonosov Moscow State University, Moscow, Russia.
authors.forename: Stanislav
authors.initials: S
authors.lastname: Kremnyov
authors.affiliation: University of Hohenheim, Institute of Zoology, 70593, Stuttgart, Germany.|Present Address: Centre for Organismal Studies, Im Neuenheimer Feld 230, Heidelberg University, 69120, Heidelberg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Thumberger
authors.affiliation: University of Hohenheim, Institute of Zoology, 70593, Stuttgart, Germany.
authors.forename: Axel
authors.initials: A
authors.lastname: Schweickert
authors.affiliation: University of Hohenheim, Institute of Zoology, 70593, Stuttgart, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Blum
authors.affiliation: University of Hohenheim, Institute of Zoology, 70593, Stuttgart, Germany. philipp.vick@uni-hohenheim.de.
authors.forename: Philipp
authors.identifier: 0000-0002-1430-4561
authors.initials: P
authors.lastname: Vick
mesh_terms: D000818:Animals; D056444:Axonemal Dyneins / Q000378:metabolism; D019521:Body Patterning; D002923:Cilia / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000166:cytology* / Q000378:metabolism; D051858:Forkhead Transcription Factors / Q000378:metabolism; D054262:Gastrulation; D055456:Nodal Signaling Ligands / Q000378:metabolism; D012617:Sea Urchins / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D014741:Video Recording
chemical_list: D051858:Forkhead Transcription Factors; D055456:Nodal Signaling Ligands; D056444:Axonemal Dyneins
keywords: Cilia; Deuterostomes; Left-right asymmetry; Left-right organizer; Nodal; Sea urchin; Symmetry breakage