1. Developmental Biology
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Neuronal sources of hedgehog modulate neurogenesis in the adult planarian brain

  1. Ko W Currie
  2. Alyssa M Molinaro
  3. Bret J Pearson  Is a corresponding author
  1. Hospital for Sick Children, Canada
Research Article
  • Cited 27
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Cite this article as: eLife 2016;5:e19735 doi: 10.7554/eLife.19735


The asexual freshwater planarian is a constitutive adult, whose central nervous system (CNS) is in a state of constant homeostatic neurogenesis. However, very little is known about the extrinsic signals that act on planarian stem cells to modulate rates of neurogenesis. We have identified two planarian homeobox transcription factors, Smed-nkx2.1 and Smed-arx, which are required for the maintenance of cholinergic, GABAergic, and octopaminergic neurons in the planarian CNS. These very same neurons also produce the planarian hedgehog ligand (Smed-hh), which appears to communicate with brain-adjacent stem cells to promote normal levels of neurogenesis. Planarian stem cells nearby the brain express core hh signal transduction genes, and consistent hh signaling levels are required to maintain normal production of neural progenitor cells and new mature cholinergic neurons, revealing an important mitogenic role for the planarian hh signaling molecule in the adult CNS.

Data availability

The following previously published data sets were used
    1. Wurtzel
    2. O.
    3. et al.
    (2015) Schmidtea mediterranea Transcriptome or Gene expression
    Publicly available at the NCBI BioProject database (accession no: PRJNA276084 ).

Article and author information

Author details

  1. Ko W Currie

    Program in Developmental and Stem Cell Biology, Hospital for Sick Children, Toronto, Canada
    Competing interests
    The authors declare that no competing interests exist.
  2. Alyssa M Molinaro

    Program in Developmental and Stem Cell Biology, Hospital for Sick Children, Toronto, Canada
    Competing interests
    The authors declare that no competing interests exist.
  3. Bret J Pearson

    Program in Developmental and Stem Cell Biology, Hospital for Sick Children, Toronto, Canada
    For correspondence
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-3473-901X


Natural Sciences and Engineering Research Council of Canada (RGPIN-2016-06354)

  • Ko W Currie
  • Alyssa M Molinaro

Ontario Institute for Cancer Research (IA-026)

  • Bret J Pearson

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

Reviewing Editor

  1. Yukiko M Yamashita, University of Michigan, United States

Publication history

  1. Received: July 17, 2016
  2. Accepted: November 18, 2016
  3. Accepted Manuscript published: November 19, 2016 (version 1)
  4. Version of Record published: December 12, 2016 (version 2)


© 2016, Currie 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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