title: Ephrin-mediated restriction of ERK1/2 activity delimits the number of pigment cells in the Ciona CNS.
abstract: Recent evidence suggests that ascidian pigment cells are related to neural crest-derived melanocytes of vertebrates. Using live-imaging, we determine a revised cell lineage of the pigment cells in Ciona intestinalis embryos. The neural precursors undergo successive rounds of anterior-posterior (A-P) oriented cell divisions, starting at the blastula 64-cell stage. A previously unrecognized fourth A-P oriented cell division in the pigment cell lineage leads to the generation of the post-mitotic pigment cell precursors. We provide evidence that MEK/ERK signals are required for pigment cell specification until approximately 30min after the final cell division has taken place. Following each of the four A-P oriented cell divisions, ERK1/2 is differentially activated in the posterior sister cells, into which the pigment cell lineage segregates. Eph/ephrin signals are critical during the third A-P oriented cell division to spatially restrict ERK1/2 activation to the posterior daughter cell. Targeted inhibition of Eph/ephrin signals results in, at neurula stages, anterior expansion of both ERK1/2 activation and a pigment cell lineage marker and subsequently, at larval stages, supernumerary pigment cells. We discuss the implications of these findings with respect to the evolution of the vertebrate neural crest.
authors: CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer, Observatoire Océanologique, 06230 Villefranche-sur-mer, France; Sorbonne Universités, UPMC Univ Paris 06, Laboratoire de Biologie du Développement de Villefranche-sur-mer, Observatoire Océanologique, 06230 Villefranche-sur-mer, France; Université de Nice Sophia Antipolis, Nice, France.
authors: Nicolas
authors: N
authors: Haupaix
authors: Center for Integrative Genomics, Division of Genetics, Genomics and Development, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
authors: Philip B
authors: PB
authors: Abitua
authors: CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer, Observatoire Océanologique, 06230 Villefranche-sur-mer, France; Sorbonne Universités, UPMC Univ Paris 06, Laboratoire de Biologie du Développement de Villefranche-sur-mer, Observatoire Océanologique, 06230 Villefranche-sur-mer, France.
authors: Cathy
authors: C
authors: Sirour
authors: CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer, Observatoire Océanologique, 06230 Villefranche-sur-mer, France; Sorbonne Universités, UPMC Univ Paris 06, Laboratoire de Biologie du Développement de Villefranche-sur-mer, Observatoire Océanologique, 06230 Villefranche-sur-mer, France.
authors: Hitoyoshi
authors: H
authors: Yasuo
authors: Center for Integrative Genomics, Division of Genetics, Genomics and Development, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
authors: Michael
authors: M
authors: Levine
authors: CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer, Observatoire Océanologique, 06230 Villefranche-sur-mer, France; Sorbonne Universités, UPMC Univ Paris 06, Laboratoire de Biologie du Développement de Villefranche-sur-mer, Observatoire Océanologique, 06230 Villefranche-sur-mer, France. Electronic address: hudson@obs-vlfr.fr.
authors: Clare
authors: C
authors: Hudson
mesh_terms: D000818:Animals; D005075:Biological Evolution; D036703:Blastula / Q000166:cytology; D019521:Body Patterning; D002455:Cell Division; D019070:Cell Lineage; D002490:Central Nervous System / Q000166:cytology*; D002938:Ciona intestinalis / Q000166:cytology / Q000196:embryology*; D004625:Embryo, Nonmammalian / Q000166:cytology; D036342:Ephrins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000096:biosynthesis*; D008544:Melanocytes / Q000166:cytology; D009432:Neural Crest / Q000166:cytology / Q000196:embryology; D010858:Pigmentation; D036081:Receptors, Eph Family / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013234:Stem Cells
chemical_list: D036342:Ephrins; D036081:Receptors, Eph Family; D048049:Extracellular Signal-Regulated MAP Kinases
keywords: Ascidian; Melanocyte; Neural crest; Oriented cell division; Pigment cell