GSE68581
A mex3 homolog is required for differentiation during planarian stem cell lineage development
Neoblasts are adult stem cells (ASCs) in planarians which sustain cell replacement during homeostasis and regeneration of any missing tissue.  While numerous studies have examined genes underlying neoblast pluripotency, molecular pathways driving the postmitotic fate remain poorly defined.   Here we used transcriptional profiling of irradiation-sensitive and -insensitive cell populations and RNA interference (RNAi) functional screening to uncover markers and regulators of postmitotic progeny.  We identified 32 new markers, which distinguish two epithelial progenitor populations, and a planarian homolog to the MEX3 RNA-binding protein (Smed-mex3-1) as a key regulator of lineage progression.  mex3-1 is required for generating progenitors of epithelial, neural, eye, pharyngeal, and protonephridial lineages, and restricting expansion of the stem cell compartment.  We also demonstrate the utility of using mex3-1(RNAi) animals to identify additional progenitor markers.  These results show that mex3-1 promotes differentiation in multiple, if not all, lineages, and maintains the balance between ASC self-renewal and commitment. Overall design: Sorted and irradiated animals were collected as previously described (Labbe, et al., 2012) and RNAi conditions were triplicated, RNA was purified independently, then each replicate was pooled in equal amounts for sequencing at the timepoint:  1 feed day 12 for control RNAi and mex3-1 RNAi.