title: Heterochronic activation of VEGF signaling and the evolution of the skeleton in echinoderm pluteus larvae.
abstract: The evolution of the echinoderm larval skeleton was examined from the aspect of interactions between skeletogenic mesenchyme cells and surrounding epithelium. We focused on vascular endothelial growth factor (VEGF) signaling, which was reported to be essential for skeletogenesis in sea urchin larvae. Here, we examined the expression patterns of vegf and vegfr in starfish and brittle stars. During starfish embryogenesis, no expression of either vegfr or vegf was detected, which contrast with previous reports on the expression of starfish homologs of sea urchin skeletogenic genes, including Ets, Tbr, and Dri. In later stages, when adult skeletogenesis commenced, vegfr and vegf expression were upregulated in skeletogenic cells and in the adjacent epidermis, respectively. These expression patterns suggest that heterochronic activation of VEGF signaling is one of the key molecular evolutionary steps in the evolution of the larval skeleton. The absence of vegf or vegfr expression during early embryogenesis in starfish suggests that the evolution of the larval skeleton requires distinct evolutionary changes, both in mesoderm cells (activation of vegfr expression) and in epidermal cells (activation of vegf expression). In brittle stars, which have well-organized skeletons like the sea urchin, vegfr and vegf were expressed in the skeletogenic mesenchyme and the overlying epidermis, respectively, in the same manner as in sea urchins. Therefore, the distinct activation of vegfr and vegf may have occurred in two lineages, sea urchins and brittle stars.
authors.affiliation: Graduate School of Life and Environmental Sciences, University of Tsukuba, 305-8572, Japan. yoshiaki.morino@gmail.com
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Morino
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Koga
authors.forename: Kazunori
authors.initials: K
authors.lastname: Tachibana
authors.forename: Eiichi
authors.initials: E
authors.lastname: Shoguchi
authors.forename: Masato
authors.initials: M
authors.lastname: Kiyomoto
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Wada
mesh_terms: D000818:Animals; D047288:Asterina / Q000196:embryology / Q000254:growth & development / Q000378:metabolism; D005075:Biological Evolution; D004447:Echinodermata / Q000196:embryology / Q000254:growth & development* / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000196:embryology / Q000378:metabolism; D004848:Epithelium / Q000196:embryology / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D007814:Larva / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D008648:Mesoderm / Q000196:embryology / Q000378:metabolism; D050783:Proto-Oncogene Proteins c-ets / Q000235:genetics / Q000378:metabolism; D040262:Receptors, Vascular Endothelial Growth Factor / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D020825:T-Box Domain Proteins / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism*
chemical_list: D050783:Proto-Oncogene Proteins c-ets; D020825:T-Box Domain Proteins; C412283:T-box protein, starfish; D042461:Vascular Endothelial Growth Factor A; D040262:Receptors, Vascular Endothelial Growth Factor