title: Functional evolution of Ets in echinoderms with focus on the evolution of echinoderm larval skeletons.
abstract: Convergent evolution of echinoderm pluteus larva was examined from the standpoint of functional evolution of a transcription factor Ets1/2. In sea urchins, Ets1/2 plays a central role in the differentiation of larval skeletogenic mesenchyme cells. In addition, Ets1/2 is suggested to be involved in adult skeletogenesis. Conversely, in starfish, although no skeletogenic cells differentiate during larval development, Ets1/2 is also expressed in the larval mesoderm. Here, we confirmed that the starfish Ets1/2 is indispensable for the differentiation of the larval mesoderm. This result led us to assume that, in the common ancestors of echinoderms, Ets1/2 activates the transcription of distinct gene sets, one for the differentiation of the larval mesoderm and the other for the development of the adult skeleton. Thus, the acquisition of the larval skeleton involved target switching of Ets1/2. Specifically, in the sea urchin lineage, Ets1/2 activated a downstream target gene set for skeletogenesis during larval development in addition to a mesoderm target set. We examined whether this heterochronic activation of the skeletogenic target set was achieved by the molecular evolution of the Ets1/2 transcription factor itself. We tested whether starfish Ets1/2 induced skeletogenesis when injected into sea urchin eggs. We found that, in addition to ectopic induction of mesenchyme cells, starfish Ets1/2 can activate some parts of the skeletogenic pathway in these mesenchyme cells. Thus, we suggest that the nature of the transcription factor Ets1/2 did not change, but rather that some unidentified co-factor(s) for Ets1/2 may distinguish between targets for the larval mesoderm and for skeletogenesis. Identification of the co-factor(s) will be key to understanding the molecular evolution underlying the evolution of the pluteus larvae.
authors.affiliation: Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, 305-8572, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Koga
authors.forename: Mioko
authors.initials: M
authors.lastname: Matsubara
authors.forename: Haruka
authors.initials: H
authors.lastname: Fujitani
authors.forename: Norio
authors.initials: N
authors.lastname: Miyamoto
authors.forename: Miéko
authors.initials: M
authors.lastname: Komatsu
authors.forename: Masato
authors.initials: M
authors.lastname: Kiyomoto
authors.forename: Koji
authors.initials: K
authors.lastname: Akasaka
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Wada
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000235:genetics; D004447:Echinodermata / Q000196:embryology / Q000235:genetics* / Q000254:growth & development; D004625:Embryo, Nonmammalian / Q000196:embryology / Q000378:metabolism; D019143:Evolution, Molecular; D005260:Female; D018507:Gene Expression Regulation, Developmental; D055785:Gene Knockdown Techniques; D018014:Gene Transfer Techniques; D017403:In Situ Hybridization; D007814:Larva / Q000235:genetics / Q000254:growth & development; D008297:Male; D008648:Mesoderm / Q000166:cytology / Q000378:metabolism; D010802:Phylogeny; D050784:Proto-Oncogene Protein c-ets-1 / Q000145:classification / Q000235:genetics* / Q000502:physiology; D050787:Proto-Oncogene Protein c-ets-2 / Q000145:classification / Q000235:genetics* / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012617:Sea Urchins / Q000196:embryology / Q000235:genetics / Q000254:growth & development; D013215:Starfish / Q000196:embryology / Q000235:genetics / Q000254:growth & development
chemical_list: D050784:Proto-Oncogene Protein c-ets-1; D050787:Proto-Oncogene Protein c-ets-2