title: The CCR4-NOT complex mediates deadenylation and degradation of stem cell mRNAs and promotes planarian stem cell differentiation.
abstract: Post-transcriptional regulatory mechanisms are of fundamental importance to form robust genetic networks, but their roles in stem cell pluripotency remain poorly understood. Here, we use freshwater planarians as a model system to investigate this and uncover a role for CCR4-NOT mediated deadenylation of mRNAs in stem cell differentiation. Planarian adult stem cells, the so-called neoblasts, drive the almost unlimited regenerative capabilities of planarians and allow their ongoing homeostatic tissue turnover. While many genes have been demonstrated to be required for these processes, currently almost no mechanistic insight is available into their regulation. We show that knockdown of planarian Not1, the CCR4-NOT deadenylating complex scaffolding subunit, abrogates regeneration and normal homeostasis. This abrogation is primarily due to severe impairment of their differentiation potential. We describe a stem cell specific increase in the mRNA levels of key neoblast genes after Smed-not1 knock down, consistent with a role of the CCR4-NOT complex in degradation of neoblast mRNAs upon the onset of differentiation. We also observe a stem cell specific increase in the frequency of longer poly(A) tails in these same mRNAs, showing that stem cells after Smed-not1 knock down fail to differentiate as they accumulate populations of transcripts with longer poly(A) tails. As other transcripts are unaffected our data hint at a targeted regulation of these key stem cell mRNAs by post-transcriptional regulators such as RNA-binding proteins or microRNAs. Together, our results show that the CCR4-NOT complex is crucial for stem cell differentiation and controls stem cell-specific degradation of mRNAs, thus providing clear mechanistic insight into this aspect of neoblast biology.
authors.affiliation: Centre for Genetics and Genomics, University of Nottingham, Queen's Medical Centre, Nottingham, United Kingdom ; Systems Biology of Gene Regulatory Elements, Max-Delbrück-Center for Molecular Medicine, Berlin, Germany.
authors.forename: Jordi
authors.initials: J
authors.lastname: Solana
authors.affiliation: Department of Biology, McGill University, Montréal, Québec, Canada ; Department of Biology, Concordia University, Montreal, Québec, Canada.
authors.forename: Chiara
authors.initials: C
authors.lastname: Gamberi
authors.affiliation: Centre for Genetics and Genomics, University of Nottingham, Queen's Medical Centre, Nottingham, United Kingdom ; Department of Zoology, University of Oxford, Oxford, United Kingdom.
authors.forename: Yuliana
authors.initials: Y
authors.lastname: Mihaylova
authors.affiliation: Systems Biology of Gene Regulatory Elements, Max-Delbrück-Center for Molecular Medicine, Berlin, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Grosswendt
authors.affiliation: Centre for Genetics and Genomics, University of Nottingham, Queen's Medical Centre, Nottingham, United Kingdom.
authors.forename: Chen
authors.initials: C
authors.lastname: Chen
authors.affiliation: Department of Biology, McGill University, Montréal, Québec, Canada.
authors.forename: Paul
authors.initials: P
authors.lastname: Lasko
authors.affiliation: Systems Biology of Gene Regulatory Elements, Max-Delbrück-Center for Molecular Medicine, Berlin, Germany.
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Rajewsky
authors.affiliation: Centre for Genetics and Genomics, University of Nottingham, Queen's Medical Centre, Nottingham, United Kingdom ; Department of Zoology, University of Oxford, Oxford, United Kingdom.
authors.forename: A Aziz
authors.initials: AA
authors.lastname: Aboobaker
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics*; D002454:Cell Differentiation / Q000235:genetics*; D049109:Cell Proliferation; D018507:Gene Expression Regulation, Developmental; D010932:Planarians / Q000235:genetics* / Q000254:growth & development; D034622:RNA Interference; D020871:RNA Stability / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012038:Regeneration / Q000235:genetics*; D012260:Ribonucleases / Q000235:genetics*; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D012333:RNA, Messenger; D012260:Ribonucleases; C445084:mRNA deadenylase