title: Piwi positive cells that line the vasculature epithelium, underlie whole body regeneration in a basal chordate.
abstract: The colonial tunicate Botrylloides leachi can regenerate functional adults from minute vasculature fragments, in a poorly understood phenomenon termed Whole Body Regeneration (WBR). Using Piwi expression (Bl-Piwi), blood cell labeling and electron microscopy, we show that WBR develops through activation, mobilization and expansion of 'dormant' cells which normally line the internal vasculature epithelium of blood vessels. Following a mechanical insult, these cells express Bl-Piwi de novo, change morphology and invade niches of the vasculature lumen, where they proliferate and differentiate, regenerating a functional organism. Mitomycin C treatments and siRNA knockdown of Bl-Piwi result in deficient cells incapable of expanding or differentiating and to subsequent regeneration arrest. Last, we find similar transient mobilization of Piwi(+) cells recurring every week, as part of normal colony development, and also during acute environmental stress. This recurrent activation of Piwi(+) cells in response to developmental, physiological and environmental insults may have enabled the adaptation of colonial tunicates to the imposed varied conditions in the marine, shallow water environment.
authors.affiliation: Israel Oceanographic and Limnological Research, National Institute of Oceanography, PO Box 8030, Tel Shikmona, Haifa 31080, Israel. yuvalrinkevich@gmail.com
authors.forename: Yuval
authors.initials: Y
authors.lastname: Rinkevich
authors.forename: Amalia
authors.initials: A
authors.lastname: Rosner
authors.forename: Claudette
authors.initials: C
authors.lastname: Rabinowitz
authors.forename: Ziva
authors.initials: Z
authors.lastname: Lapidot
authors.forename: Elithabeth
authors.initials: E
authors.lastname: Moiseeva
authors.forename: Buki
authors.initials: B
authors.lastname: Rinkevich
mesh_terms: D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D001808:Blood Vessels / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000378:metabolism; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D046529:Microscopy, Electron, Transmission; D016685:Mitomycin / Q000494:pharmacology; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D012038:Regeneration; D014561:Urochordata / Q000166:cytology / Q000235:genetics / Q000502:physiology*
chemical_list: D000903:Antibiotics, Antineoplastic; D011506:Proteins; D016685:Mitomycin