title: Reciprocal signaling between the ectoderm and a mesendodermal left-right organizer directs left-right determination in the sea urchin embryo.
abstract: During echinoderm development, expression of nodal on the right side plays a crucial role in positioning of the rudiment on the left side, but the mechanisms that restrict nodal expression to the right side are not known. Here we show that establishment of left-right asymmetry in the sea urchin embryo relies on reciprocal signaling between the ectoderm and a left-right organizer located in the endomesoderm. FGF/ERK and BMP2/4 signaling are required to initiate nodal expression in this organizer, while Delta/Notch signaling is required to suppress formation of this organizer on the left side of the archenteron. Furthermore, we report that the H(+)/K(+)-ATPase is critically required in the Notch signaling pathway upstream of the S3 cleavage of Notch. Our results identify several novel players and key early steps responsible for initiation, restriction, and propagation of left-right asymmetry during embryogenesis of a non-chordate deuterostome and uncover a functional link between the H(+)/K(+)-ATPase and the Notch signaling pathway.
authors.affiliation: UMR 7009 CNRS, Université de Pierre et Marie Curie (Paris 6), Observatoire Océanologique de Villefranche-sur-Mer, Villefranche-sur-Mer, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Bessodes
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Haillot
authors.forename: Véronique
authors.initials: V
authors.lastname: Duboc
authors.forename: Eric
authors.initials: E
authors.lastname: Röttinger
authors.forename: François
authors.initials: F
authors.lastname: Lahaye
authors.forename: Thierry
authors.initials: T
authors.lastname: Lepage
mesh_terms: D000818:Animals; D019521:Body Patterning / Q000235:genetics; D055396:Bone Morphogenetic Protein 2 / Q000235:genetics / Q000378:metabolism; D004475:Ectoderm / Q000254:growth & development*; D004625:Embryo, Nonmammalian; D047108:Embryonic Development / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D017506:H(+)-K(+)-Exchanging ATPase / Q000235:genetics / Q000378:metabolism; D055458:Left-Right Determination Factors / Q000235:genetics*; D020935:MAP Kinase Signaling System; D051880:Receptors, Notch / Q000235:genetics / Q000378:metabolism; D012617:Sea Urchins / Q000196:embryology / Q000254:growth & development; D015398:Signal Transduction
chemical_list: D055396:Bone Morphogenetic Protein 2; D055458:Left-Right Determination Factors; D051880:Receptors, Notch; D017506:H(+)-K(+)-Exchanging ATPase