Myths vs. FACS: what do we know about planarian stem cell lineages?
Review | Published: 21 June 2018
Alyssa M. Molinaro1,2 and Bret J. Pearson*,1,2,3
1Hospital for Sick Children, Program in Developmental and Stem Cell Biology, 2Department of Molecular Genetics, University of Toronto and 3Ontario Institute for Cancer Research, Toronto, ON, Canada
Historically, planarian neoblasts were thought to be a homogeneous population of pluripotent stem cells; however, recent population and single-cell level analyses have refuted this idea. Evidence for lineage commitment at the neoblast level has been provided via a number of independent studies using a variety of methods. In situ hybridization experiments first demonstrated the co-expression of lineage-specific markers in neoblasts (marked by piwi-1 expression) isolated by FACS. Subsequently, single cell transcriptomic analyses of FACS-isolated neoblasts uncovered broad lineage-primed neoblast classes based on the clustering of transcriptional profiles and expression of known tissue-specific markers. Additionally, single neoblast pluripotency (and fate restriction) has been demonstrated by single cell transplantation experiments into neoblast-void animals. Here we look to recount the current status of the planarian neoblast field and offer discussion on the caveats of neoblast biology and how to address them experimentally.