title: Symmetry breakage in the frog Xenopus: role of Rab11 and the ventral-right blastomere.
abstract: Vertebrates display asymmetric arrangements of inner organs such as heart and stomach. The Nodal signaling cascade in the left lateral plate mesoderm in all cases directs asymmetric morphogenesis and placement during organogenesis. Mechanisms that lead up to left-asymmetric Nodal induction seem to differ between the vertebrates. Cilia produce a leftward extracellular fluid flow in zebrafish, medaka, mouse, rabbit, and Xenopus embryos during neurulation. In Xenopus, earlier asymmetric cues were described. Some, such as Rab11, apparently act in the zygote. Others were efficiently manipulated in ventral-right cells at the four-cell stage, a lineage presumably independent of the ciliated gastrocoel roof plate (GRP) during neurulation. Here, we show that one- and four-cell manipulations of Rab11 showed equal low efficiencies of left-right disturbances. We also reevaluated the lineage of the GRP. By tracing back future ciliated cells from the gastrula to the four-cell stage, we show that ventral cells contribute to ciliated sensory cells at the border of the GRP. Knockdown of the Nodal inhibitor Coco in the ventral right lineage resulted in embryos with ectopic right-sided Nodal and Pitx2c expression. Together, these experiments support a cilia-based mechanism of symmetry breakage in the frog Xenopus.
authors.affiliation: Institute of Zoology, University of Hohenheim, Stuttgart, D-70593, Germany.
authors.forename: Melanie
authors.initials: M
authors.lastname: Tingler
authors.forename: Tim
authors.initials: T
authors.lastname: Ott
authors.forename: Janos
authors.initials: J
authors.lastname: Tözser
authors.forename: Sabrina
authors.initials: S
authors.lastname: Kurz
authors.forename: Maike
authors.initials: M
authors.lastname: Getwan
authors.forename: Matthias
authors.initials: M
authors.lastname: Tisler
authors.forename: Axel
authors.initials: A
authors.lastname: Schweickert
authors.forename: Martin
authors.initials: M
authors.lastname: Blum
mesh_terms: D000818:Animals; D001757:Blastomeres / Q000378:metabolism*; D019521:Body Patterning / Q000502:physiology*; D005775:Gastrula / Q000196:embryology / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D055785:Gene Knockdown Techniques; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D008648:Mesoderm / Q000196:embryology / Q000378:metabolism; D014981:Xenopus / Q000196:embryology*; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D000099193:rab11 GTP-Binding Proteins
chemical_list: D018398:Homeodomain Proteins; D029867:Xenopus Proteins; D020691:rab GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins; C473314:DAND5 protein, Xenopus; C438620:Pitx2c protein, Xenopus
keywords: Coco; Nodal cascade; Rab11; Xenopus; cilia; leftward flow