title: RTK and TGF-beta signaling pathways genes in the sea urchin genome.
abstract: The Receptor Tyrosine kinase (RTK) and TGF-beta signaling pathways play essential roles during development in many organisms and regulate a plethora of cellular responses. From the genome sequence of Strongylocentrotus purpuratus, we have made an inventory of the genes encoding receptor tyrosine kinases and their ligands, and of the genes encoding cytokines of the TGF-beta superfamily and their downstream components. The sea urchin genome contains at least 20 genes coding for canonical receptor tyrosine kinases. Seventeen of the nineteen vertebrate RTK families are represented in the sea urchin. Fourteen of these RTK among which ALK, CCK4/PTK7, DDR, EGFR, EPH, LMR, MET/RON, MUSK, RET, ROR, ROS, RYK, TIE and TRK are present as single copy genes while pairs of related genes are present for VEGFR, FGFR and INSR. Similarly, nearly all the subfamilies of TGF-beta ligands identified in vertebrates are present in the sea urchin genome including the BMP, ADMP, GDF, Activin, Myostatin, Nodal and Lefty, as well as the TGF-beta sensu stricto that had not been characterized in invertebrates so far. Expression analysis indicates that the early expression of nodal, BMP2/4 and lefty is restricted to the oral ectoderm reflecting their role in providing positional information along the oral-aboral axis of the embryo. The coincidence between the emergence of TGF-beta-related factors such as Nodal and Lefty and the emergence of the deuterostome lineage strongly suggests that the ancestral function of Nodal could have been related to the secondary opening of the mouth which characterizes this clade, a hypothesis supported by functional data in the extant species. The sea urchin genome contains 6 genes encoding TGF-beta receptors and 4 genes encoding prototypical Smad proteins. Furthermore, most of the transcriptional activators and repressors shown to interact with Smads in vertebrates have orthologues in echinoderms. Finally, the sea urchin genome contains an almost complete repertoire of genes encoding extracellular modulators of BMP signaling including Chordin, Noggin, Sclerotin, SFRP, Gremlin, DAN and Twisted gastrulation. Taken together, these findings indicate that the sea urchin complement of genes of the RTK and TGF-beta signaling pathways is qualitatively very similar to the repertoire present in vertebrates, and that these genes are part of the common genetool kit for intercellular signaling of deuterostomes.
authors.affiliation: UMR 7009 CNRS, Université Pierre et Marie Curie-Paris 6, Observatoire Oceanologique, 06230 Villefranche-sur-Mer, France.
authors.forename: François
authors.initials: F
authors.lastname: Lapraz
authors.forename: Eric
authors.initials: E
authors.lastname: Röttinger
authors.forename: Véronique
authors.initials: V
authors.lastname: Duboc
authors.forename: Ryan
authors.initials: R
authors.lastname: Range
authors.forename: Louise
authors.initials: L
authors.lastname: Duloquin
authors.forename: Katherine
authors.initials: K
authors.lastname: Walton
authors.forename: Shu-Yu
authors.initials: SY
authors.lastname: Wu
authors.forename: Cynthia
authors.initials: C
authors.lastname: Bradham
authors.forename: Mariano A
authors.initials: MA
authors.lastname: Loza
authors.forename: Taku
authors.initials: T
authors.lastname: Hibino
authors.forename: Karen
authors.initials: K
authors.lastname: Wilson
authors.forename: Albert
authors.initials: A
authors.lastname: Poustka
authors.forename: Dave
authors.initials: D
authors.lastname: McClay
authors.forename: Lynne
authors.initials: L
authors.lastname: Angerer
authors.forename: Christian
authors.initials: C
authors.lastname: Gache
authors.forename: Thierry
authors.initials: T
authors.lastname: Lepage
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D016678:Genome; D006801:Humans; D010802:Phylogeny; D011505:Protein-Tyrosine Kinases / Q000235:genetics*; D012617:Sea Urchins / Q000235:genetics*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000235:genetics; D016212:Transforming Growth Factor beta / Q000235:genetics*; D014714:Vertebrates / Q000235:genetics
chemical_list: D016212:Transforming Growth Factor beta; D011505:Protein-Tyrosine Kinases