Cellular remodeling and JAK inhibition promote zygotic gene expression in the Ciona germline

Naoyuki Ohta, Lionel Christiaen

Research output: Contribution to journalArticlepeer-review


Transcription control is a major determinant of cell fate decisions in somatic tissues. By contrast, early germline fate specification in numerous vertebrate and invertebrate species relies extensively on RNA-level regulation, exerted on asymmetrically inherited maternal supplies, with little-to-no zygotic transcription. However delayed, a maternal-to-zygotic transition is nevertheless poised to complete the deployment of pre-gametic programs in the germline. Here, we focus on early germline specification in the tunicate Ciona to study zygotic genome activation. We first demonstrate that a peculiar cellular remodeling event excludes localized postplasmic Pem-1 mRNA, which encodes the general inhibitor of transcription. Subsequently, zygotic transcription begins in Pem-1-negative primordial germ cells (PGCs), as revealed by histochemical detection of elongating RNA Polymerase II, and nascent Mef2 transcripts. In addition, we uncover a provisional antagonism between JAK and MEK/BMPRI/GSK3 signaling, which controls the onset of zygotic gene expression, following cellular remodeling of PGCs. We propose a 2-step model for the onset of zygotic transcription in the Ciona germline and discuss the significance of germ plasm dislocation and remodeling in the context of developmental fate specification.

Original languageEnglish (US)
Pages (from-to)2188-2201
Number of pages14
JournalEMBO Reports
Issue number5
StatePublished - May 14 2024


  • Germline Specification
  • Lobe Scission
  • Primordial Germ Cells
  • Transcription Control
  • Tunicate

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Genetics


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