title: The involvement of three signal transduction pathways in botryllid ascidian astogeny, as revealed by expression patterns of representative genes.
abstract: The patterning of the modular body plan in colonial organisms is termed astogeny, as distinct from ontogeny, the development of an individual organism from embryo to adult. Evolutionarily conserved signaling pathways suggest shared roots and common uses for both ontogeny and astogeny. Botryllid ascidians, a widely dispersed group of colonial tunicates, exhibit an intricate modular life form, in which astogeny develops as weekly, highly synchronized growth/death cycles termed blastogenesis, abiding by a strictly regulated plan. In these organisms both astogeny and ontogeny form similar body structures. Working on Botryllus schlosseri, and choosing a representative gene from each of three key Signal Transduction Pathways (STPs: Wnt/β-catenin; TGF-β, MAPK/ERK), we explored and compared gene expression at different stages of ontogeny and blastogenesis. Protein expression was studied via immunohistochemistry, ELISA and Western blotting. Five specific inhibitors and an activator for the selected pathways were used and followed to assess their impact during the blastogenic cycle and the development of distinctive phenotypes. Outcomes show that STPs are activated and function (while not necessarily co-localized) during both ontogeny and astogeny. Cellular patterns in blastogenesis, such as colony architecture, are shaped by these STPs. These results are further supported by administering Wnt agonist and anatagonist, TGF-β receptor antagonists and inhibitors of Mek1/Mek2. Independent of their expression during ontogeny, some of the spatiotemporal patterns of STPs developed within short blastogenic windows. The results support the notion that while the same molecular machinery is functioning in Botryllus schlosseri astogeny and ontogeny, astogenic development is not an ontogenic replicate.
authors.affiliation: Israel Oceanographic and Limnological Research, National Institute of Oceanography, Haifa, Israel. amalia@ocean.org.il.
authors.forename: Amalia
authors.initials: A
authors.lastname: Rosner
authors.forename: Gilad
authors.initials: G
authors.lastname: Alfassi
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Moiseeva
authors.forename: Guy
authors.initials: G
authors.lastname: Paz
authors.forename: Claudette
authors.initials: C
authors.lastname: Rabinowitz
authors.forename: Ziva
authors.initials: Z
authors.lastname: Lapidot
authors.forename: Jacob
authors.initials: J
authors.lastname: Douek
authors.forename: Abraham
authors.initials: A
authors.lastname: Haim
authors.forename: Baruch
authors.initials: B
authors.lastname: Rinkevich
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D005075:Biological Evolution; D015153:Blotting, Western; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D005786:Gene Expression Regulation / Q000187:drug effects*; D007124:Immunoenzyme Techniques; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D008969:Molecular Sequence Data; D010766:Phosphorylation / Q000187:drug effects; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D016212:Transforming Growth Factor beta / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014561:Urochordata / Q000254:growth & development / Q000378:metabolism*; D051153:Wnt Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; D016212:Transforming Growth Factor beta; D051153:Wnt Proteins