Neuronal sources of hedgehog modulate neurogenesis in the adult planarian brain

Abstract
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Abstract

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 ).

https://www.ncbi.nlm.nih.gov/bioproject/276084
1. Molinaro AM
2. Pearson BJ
(2016) In silico lineage tracing through single cell transcriptomes identifies a neural stem cell population in planarians
Publicly available at the NCBI Gene Expression Omnibus (accession no: GSE79866).

https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE79866

Article and author information

Author details

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.
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.
Bret J Pearson

Program in Developmental and Stem Cell Biology, Hospital for Sick Children, Toronto, Canada

For correspondence
bret.pearson@utoronto.ca

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0002-3473-901X

Funding

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.

Copyright

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.