Functional genomic characterization of germinal cells in larval Schistosoma mansoni
RNA-seq experiments to identify gene expression changes following miracidia to sporocyst transformation in Schistosoma mansoni. Schistosomes infect hundreds of millions of people in the developing world. Transmission of these parasites relies on a stem cell-driven, clonal expansion of larvae inside a molluscan intermediate host. How this novel asexual reproductive strategy relates to current models of stem cell maintenance and germline specification is unclear. Here, we demonstrate that this proliferative larval cell population (germinal cells) shares some molecular signatures with stem cells from diverse organisms, in particular neoblasts of planarians (free-living relatives of schistosomes). We identify two distinct germinal cell lineages that differ in their proliferation kinetics and expression of a nanos ortholog. We show that a vasa PL10 homolog is required for proliferation and maintenance of both populations; whereas, argonaute2 and a fibroblast growth factor receptor-encoding gene are required only for nanos-negative cells. Our results suggest that an ancient stem cell-based developmental program may have enabled the evolution of the complex life-cycle of parasitic flatworms. Overall design: Total RNA was purified from ~10,000 freshly hatched miracidia or sporocysts 48 h post-transformation.