FOX and ETS family transcription factors regulate the pigment cell lineage in planarians

Abstract

Many pigment cells acquire unique structural properties and gene expression profiles during animal development. The underlying differentiation pathways have been well characterized in cells formed during embryogenesis, such as the neural crest-derived melanocyte. However, much less is known about the developmental origins of pigment cells produced in adult organisms during tissue homeostasis and repair. Here we report a lineage analysis of ommochrome- and porphyrin-producing cells in the brown, freshwater planarian Schmidtea mediterranea. Using an RNA-sequencing approach, we identified two classes of markers expressed in sequential fashion when new pigment cells are generated during regeneration or in response to pigment cell ablation. We also report roles for FOXF-1 and ETS-1 transcription factors, as well as an FGF Receptor-like molecule, in the specification and maintenance of this cell type. Together, our results provide the first insight into mechanisms of adult pigment cell development in the strikingly colorful Platyhelminthes phylum.