Description

Functional Profiling of Planarian Stem Cell Differentiation at Single-Cell Resolution

Mireya Plass^1ߙ, Jordi Solana^1ߙ, Salah Ayoub¹, Christine Kocks¹ and Nikolaus Rajewsky¹*

¹Systems Biology of Gene Regulatory Elements, Berlin Institute for Medical Systems Biology, Max-Delbrück Center for Molecular Medicine, Berlin, Germany

^ߙAuthors contributed equally

*Corresponding author

The planaria Schmidtea mediterranea is a flatworm widely used as an in vivo model for stem cell biology as it contains a large population of pluripotent stem cells. These stem cells -called neoblasts- are able to give rise to all adult cell types and enable the remarkable regeneration capacity characteristic of planarias. In this study, we have profiled thousands of single planarian cells using Drop-seq in order to characterize the different cell populations in the adult worm and understand the gene expression changes responsible for neoblast differentiation. Computational analysis of single-cell transcriptomes has allowed us to identify various neoblast subpopulations and all major differentiated cell types. We have also identified several precursor cell clusters characterized by a low expression of neoblast markers, such as smedwi-1, together with cell-type specific genes. Using histone-2B RNAi, which rapidly and specifically eliminates neoblasts, we have been able to validate these precursor clusters. Upon RNAi treatment, we observe a strong reduction in the amount of neoblasts and precursor cells sequenced. We have further validated the individual identity of these precursor clusters by knocking down the expression of characteristic marker genes with RNAi and analyzing the remaining cell types with Drop-seq and using in-situ hybridizations. Taken together, our results have extensively characterized the different cell types in adult planarias and their differentiation pathways.