title: Nodal and BMP expression during the transition to pentamery in the sea urchin Heliocidaris erythrogramma: insights into patterning the enigmatic echinoderm body plan.
abstract: The molecular mechanisms underlying the development of the unusual echinoderm pentameral body plan and their likeness to mechanisms underlying the development of the bilateral plans of other deuterostomes are of interest in tracing body plan evolution. In this first study of the spatial expression of genes associated with Nodal and BMP2/4 signalling during the transition to pentamery in sea urchins, we investigate Heliocidaris erythrogramma, a species that provides access to the developing adult rudiment within days of fertilization.
  
  
  
  BMP2/4, and the putative downstream genes, Six1/2, Eya, Tbx2/3 and Msx were expressed in the earliest morphological manifestation of pentamery during development, the five hydrocoele lobes. The formation of the vestibular ectoderm, the specialized region overlying the left coelom that forms adult ectoderm, involved the expression of putative Nodal target genes Chordin, Gsc and BMP2/4 and putative BMP2/4 target genes Dlx, Msx and Tbx. The expression of Nodal, Lefty and Pitx2 in the right ectoderm, and Pitx2 in the right coelom, was as previously observed in other sea urchins.
  
  
  
  That genes associated with Nodal and BMP2/4 signalling are expressed in the hydrocoele lobes, indicates that they have a role in the developmental transition to pentamery, contributing to our understanding of how the most unusual body plan in the Bilateria may have evolved. We suggest that the Nodal and BMP2/4 signalling cascades might have been duplicated or split during the evolution to pentamery.
authors.affiliation: School of Medical Science and Bosch Institute, The University of Sydney, Sydney, NSW, 2006, Australia. demian.koop@sydney.edu.au.
authors.forename: Demian
authors.identifier: 0000-0003-3248-6298
authors.initials: D
authors.lastname: Koop
authors.affiliation: School of Medical Science and Bosch Institute, The University of Sydney, Sydney, NSW, 2006, Australia.
authors.forename: Paula
authors.initials: P
authors.lastname: Cisternas
authors.affiliation: School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW, 2006, Australia.
authors.forename: Valerie B
authors.initials: VB
authors.lastname: Morris
authors.affiliation: School of Mathematics and Statistics, The University of Sydney, Sydney, NSW, 2006, Australia.
authors.forename: Dario
authors.initials: D
authors.lastname: Strbenac
authors.affiliation: School of Mathematics and Statistics, The University of Sydney, Sydney, NSW, 2006, Australia.
authors.forename: Jean Yee Hwa
authors.initials: JY
authors.lastname: Yang
authors.affiliation: Department of Biology and Center for Genomic and Computational Biology, Duke University, Durham, NC, 27708, USA.
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Wray
authors.affiliation: School of Medical Science and Bosch Institute, The University of Sydney, Sydney, NSW, 2006, Australia.|School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW, 2006, Australia.
authors.forename: Maria
authors.initials: M
authors.lastname: Byrne
mesh_terms: D000818:Animals; D047329:Anthocidaris / Q000235:genetics* / Q000254:growth & development*; D019521:Body Patterning / Q000235:genetics*; D019485:Bone Morphogenetic Proteins / Q000235:genetics* / Q000378:metabolism; D004475:Ectoderm / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D055457:Nodal Protein / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D019485:Bone Morphogenetic Proteins; D055457:Nodal Protein
keywords: Coelomogenesis; Deuterostome; Direct development; Echinoid; Evolution; Sea urchin body plan development