1. Cell Biology
  2. Developmental Biology
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Multiple Wnts act synergistically to induce Chk1/Grapes expression and mediate G2 arrest in Drosophila tracheoblasts

  1. Amrutha Kizhedathu
  2. Rose Sebastian Kunnapallill
  3. Archit Bagul
  4. Puja Verma
  5. Arjun Guha  Is a corresponding author
  1. Institute for Stem Cell Biology and Regenerative Medicine (inStem), India
  2. National Center for Biological Sciences, India
  3. Institute of Genetics and Molecular and Cellular Biology, France
  4. Institute for Stem Cell Science and Regenerative Medicine, India
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Cite this article as: eLife 2020;9:e57056 doi: 10.7554/eLife.57056

Abstract

Larval tracheae of Drosophila harbor progenitors of the adult tracheal system (tracheoblasts). We showed previously that thoracic tracheoblasts arrest in the G2 phase of the cell cycle in an ATR-Checkpoint Kinase1(Chk1)-dependent manner prior to division and morphogenesis (Kizhedathu et al., 2018). Here we investigate developmental regulation of Chk1 activation. We report that Wnt signaling is high in tracheoblasts and is necessary for high levels of activated (phosphorylated) Chk1. We find that canonical Wnt signaling facilitates this by transcriptional upregulation of Chk1 in cells that have ATR kinase activity. Wnt signalling is dependent on four Wnts (Wg, Wnt5, 6,10) that are expressed at high levels in arrested tracheoblasts and downregulated at mitotic re-entry. Interestingly, none of the Wnts are dispensable and act synergistically to induce Chk1. Finally, we show that downregulation of Wnt signalling and Chk1 expression leads to mitotic re-entry and the concomitant upregulation of Dpp signalling, driving tracheoblast proliferation.

Data availability

All data generated or analysed during this study are included in the manuscript.

Article and author information

Author details

  1. Amrutha Kizhedathu

    Institute for Stem Cell Biology and Regenerative Medicine (inStem), Bangalore, India
    Competing interests
    The authors declare that no competing interests exist.
  2. Rose Sebastian Kunnapallill

    Neurobiology, National Center for Biological Sciences, Bangalore, India
    Competing interests
    The authors declare that no competing interests exist.
  3. Archit Bagul

    Genetics and Molecular and Cellular Biology, Institute of Genetics and Molecular and Cellular Biology, Illkirch-Graffenstaden, France
    Competing interests
    The authors declare that no competing interests exist.
  4. Puja Verma

    Regulation of Cell Fate, Institute for Stem Cell Science and Regenerative Medicine, Bangalore, India
    Competing interests
    The authors declare that no competing interests exist.
  5. Arjun Guha

    Institute for Stem Cell Biology and Regenerative Medicine (inStem), Bangalore, India
    For correspondence
    arjung@instem.res.in
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-3753-1484

Funding

Department of Biotechnology , Ministry of Science and Technology (inStem Core Grant)

  • Arjun Guha

Department of Biotechnology , Ministry of Science and Technology (InStem Core Grant)

  • Arjun Guha

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Reviewing Editor

  1. Amin S. Ghabrial, Columbia University, United States

Publication history

  1. Received: March 20, 2020
  2. Accepted: August 29, 2020
  3. Accepted Manuscript published: September 2, 2020 (version 1)
  4. Accepted Manuscript updated: September 9, 2020 (version 2)
  5. Version of Record published: September 21, 2020 (version 3)
  6. Version of Record updated: September 24, 2020 (version 4)

Copyright

© 2020, Kizhedathu et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

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Further reading

    1. Developmental Biology
    Amrutha Kizhedathu et al.
    Research Article Updated

    Imaginal progenitors in Drosophila are known to arrest in G2 during larval stages and proliferate thereafter. Here we investigate the mechanism and implications of G2 arrest in progenitors of the adult thoracic tracheal epithelium (tracheoblasts). We report that tracheoblasts pause in G2 for ~48–56 h and grow in size over this period. Surprisingly, tracheoblasts arrested in G2 express drivers of G2-M like Cdc25/String (Stg). We find that mechanisms that prevent G2-M are also in place in this interval. Tracheoblasts activate Checkpoint Kinase 1/Grapes (Chk1/Grp) in an ATR/mei-41-dependent manner. Loss of ATR/Chk1 led to precocious mitotic entry ~24–32 h earlier. These divisions were apparently normal as there was no evidence of increased DNA damage or cell death. However, induction of precocious mitoses impaired growth of tracheoblasts and the tracheae they comprise. We propose that ATR/Chk1 negatively regulate G2-M in developing tracheoblasts and that G2 arrest facilitates cellular and hypertrophic organ growth.

    1. Cell Biology
    2. Stem Cells and Regenerative Medicine
    Anirban Roy et al.
    Research Article Updated

    Skeletal muscle regeneration is regulated by coordinated activation of multiple signaling pathways. The unfolded protein response (UPR) is a major mechanism that detects and alleviates protein-folding stresses in the endoplasmic reticulum. However, the role of individual arms of the UPR in skeletal muscle regeneration remain less understood. In the present study, we demonstrate that IRE1α (also known as ERN1) and its downstream target, XBP1, are activated in skeletal muscle of mice upon injury. Myofiber-specific ablation of IRE1α or XBP1 in mice diminishes skeletal muscle regeneration that is accompanied with reduced number of satellite cells. Ex vivo cultures of myofiber explants demonstrate that ablation of IRE1α reduces the proliferative capacity of myofiber-associated satellite cells. Myofiber-specific ablation of IRE1α dampens Notch signaling and canonical NF-κB pathway in skeletal muscle of adult mice. Finally, targeted ablation of IRE1α also reduces Notch signaling, abundance of satellite cells, and skeletal muscle regeneration in the mdx mice, a model of Duchenne muscular dystrophy. Collectively, our experiments suggest that the IRE1α-mediated signaling promotes muscle regeneration through augmenting the proliferation of satellite cells in a cell non-autonomous manner.