title: Repeated, long-term cycling of putative stem cells between niches in a basal chordate.
abstract: The mechanisms that sustain stem cells are fundamental to tissue maintenance. Here, we identify "cell islands" (CIs) as a niche for putative germ and somatic stem cells in Botryllus schlosseri, a colonial chordate that undergoes weekly cycles of death and regeneration. Cells within CIs express markers associated with germ and somatic stem cells and gene products that implicate CIs as signaling centers for stem cells. Transplantation of CIs induced long-term germline and somatic chimerism, demonstrating self-renewal and pluripotency of CI cells. Cell labeling and in vivo time-lapse imaging of CI cells reveal waves of migrations from degrading CIs into developing buds, contributing to soma and germline development. Knockdown of cadherin, which is highly expressed within CIs, elicited the migration of CI cells to circulation. Piwi knockdown resulted in regeneration arrest. We suggest that repeated trafficking of stem cells allows them to escape constraints imposed by the niche, enabling self-preservation throughout life.
authors.affiliation: Institute of Stem Cell Biology and Regenerative Medicine, Departments of Pathology and Developmental Biology, Stanford University School of Medicine, Stanford, CA 94305, USA. ryuval@stanford.edu
authors.forename: Yuval
authors.initials: Y
authors.lastname: Rinkevich
authors.forename: Ayelet
authors.initials: A
authors.lastname: Voskoboynik
authors.forename: Amalia
authors.initials: A
authors.lastname: Rosner
authors.forename: Claudette
authors.initials: C
authors.lastname: Rabinowitz
authors.forename: Guy
authors.initials: G
authors.lastname: Paz
authors.forename: Matan
authors.initials: M
authors.lastname: Oren
authors.forename: Jacob
authors.initials: J
authors.lastname: Douek
authors.forename: Gilad
authors.initials: G
authors.lastname: Alfassi
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Moiseeva
authors.forename: Katherine J
authors.initials: KJ
authors.lastname: Ishizuka
authors.forename: Karla J
authors.initials: KJ
authors.lastname: Palmeri
authors.forename: Irving L
authors.initials: IL
authors.lastname: Weissman
authors.forename: Buki
authors.initials: B
authors.lastname: Rinkevich
mesh_terms: D000818:Animals; D060565:Argonaute Proteins / Q000235:genetics / Q000378:metabolism; D015820:Cadherins / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D005854:Germ Cells / Q000166:cytology* / Q000502:physiology; D007124:Immunoenzyme Techniques; D017403:In Situ Hybridization; D015347:RNA Probes; D012038:Regeneration / Q000502:physiology*; D055153:Stem Cell Niche / Q000502:physiology*; D013234:Stem Cells / Q000166:cytology* / Q000502:physiology; D014561:Urochordata / Q000166:cytology* / Q000235:genetics / Q000378:metabolism
chemical_list: D060565:Argonaute Proteins; D015820:Cadherins; D015347:RNA Probes