Germ lineage properties in the urochordate Botryllus schlosseri - From markers to temporal niches

Amalia Rosner, Elizabeth Moiseeva, Claudette Rabinowitz, Baruch Rinkevich

Research output: Contribution to journalArticlepeer-review


The primordial germ cells (PGCs) in the colonial urochordate Botryllus schlosseri are sequestered in late embryonic stage. PGC-like populations, located at any blastogenic stage in specific niches, inside modules with curtailed lifespan, survive throughout the life of the colony by repeated weekly migration to newly formed buds. This cyclical migration and the lack of specific markers for PGC-like populations are obstacles to the study on PGCs. For that purpose, we isolated the Botryllus DDX1 (BS-DDX1) and characterized it by normal expression patterns and by specific siRNA knockdown experiments. Expression of BS-DDX1 concurrent with BS-Vasa, γ-H2AX, BS-cadherin and phospho-Smad1/5/8, demarcate PGC cells from soma cells and from more differentiated germ cells lineages, which enabled the detection of additional putative transient niches in zooids. Employing BS-cadherin siRNA knockdown, retinoic acid (RA) administration or β-estradiol administration affirmed the BS-Vasa+BS-DDX1+BS-cadherin+γ-H2AX+phospho-Smad1/5/8+ population as the B. schlosseri PGC-like cells. By striving to understand the PGC-like cells trafficking between transient niches along blastogenic cycles, CM-DiI-stained PGC-like enriched populations from late blastogenic stage D zooids were injected into genetically matched colonial ramets at blastogenic stages A or C and their fates were observed for 9 days. Based on the accumulated data, we conceived a novel network of several transient and short lived 'germ line niches' that preserve PGCs homeostasis, protecting these cells from the weekly astogenic senescence processes, thus enabling the survival of the PGCs throughout the organism's life.

Original languageEnglish
Pages (from-to)356-374
Number of pages19
JournalDevelopmental Biology
Issue number2
StatePublished - 15 Dec 2013
Externally publishedYes

Bibliographical note

Funding Information:
We thank G. Paz for his drawings and artistic work. This study was supported by a grant from the Israel Academy of Sciences ( 68/10 ).


  • BS-DDX1
  • BS-Vasa
  • BS-cadherin
  • Botryllus schlosseri
  • Germ cells
  • Niche
  • PGC
  • Phospho-Smad1/5/8
  • RNA helicase
  • Urochordata
  • γ-H2AX

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology
  • Developmental Biology


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