Purification of Planarian Stem Cells Using a Draq5-Based FACS Approach

Planarians are flatworms that have the remarkable ability to regenerate entirely new animals. This regenerative ability requires abundant adult stem cells called neoblasts, which are relatively small in size, sensitive to irradiation and the only proliferative cells in the animal. Despite the lack of cell surface markers, fluorescence-activated cell sorting (FACS) protocols have been developed to discriminate and isolate neoblasts, based on DNA content. Here, we describe a protocol that combines staining of far-red DNA dye Draq5, Calcein-AM and DAPI, along with a shortened processing time. This profiling strategy can be used to functionally characterize the neoblast population in pharmacologically-treated or gene knockdown animals. Highly purified neoblasts can be analyzed with downstream assays, such as in situ hybridization and RNA sequencing.