Adult somatic stem cells in the human parasite Schistosoma mansoni

Howard Hughes Medical Institute and Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
Nature (Impact Factor: 42.35). 02/2013; 494(7438):476-9. DOI: 10.1038/nature11924
Source: PubMed

ABSTRACT Schistosomiasis is among the most prevalent human parasitic diseases, affecting more than 200 million people worldwide. The aetiological agents of this disease are trematode flatworms (Schistosoma) that live and lay eggs within the vasculature of the host. These eggs lodge in host tissues, causing inflammatory responses that are the primary cause of morbidity. Because these parasites can live and reproduce within human hosts for decades, elucidating the mechanisms that promote their longevity is of fundamental importance. Although adult pluripotent stem cells, called neoblasts, drive long-term homeostatic tissue maintenance in long-lived free-living flatworms (for example, planarians), and neoblast-like cells have been described in some parasitic tapeworms, little is known about whether similar cell types exist in any trematode species. Here we describe a population of neoblast-like cells in the trematode Schistosoma mansoni. These cells resemble planarian neoblasts morphologically and share their ability to proliferate and differentiate into derivatives of multiple germ layers. Capitalizing on available genomic resources and RNA-seq-based gene expression profiling, we find that these schistosome neoblast-like cells express a fibroblast growth factor receptor orthologue. Using RNA interference we demonstrate that this gene is required for the maintenance of these neoblast-like cells. Our observations indicate that adaptation of developmental strategies shared by free-living ancestors to modern-day schistosomes probably contributed to the success of these animals as long-lived obligate parasites. We expect that future studies deciphering the function of these neoblast-like cells will have important implications for understanding the biology of these devastating parasites.

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Available from: Phillip A Newmark, Aug 14, 2014
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    • "Wang, Collins and Newmark have now characterized the germinal cell population by profiling gene expression in the cells, validating these findings with fluorescence in situ hybridization, and then using RNA interference to silence individual genes in order to determine their functions. Their results uncovered similarities, at both the molecular and functional level, between these germinal cells and stem cells that have recently been identified in adult parasites (Collins et al., 2013). There were also similarities with pluripotent stem cells known as neoblasts found in non-parasitic free-living flatworms (planarians), and with cells that produce gametes in other multicellular animals. "
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    • "(Tsai et al., 2013), as well as in the bloodfluke Schistosoma mansoni (Gomes et al., 2009), suggesting that parasitic flatworms possess canonical, animal-specific RNAi pathways requiring processing by Drosha. Notably, however, true orthologs of the ubiquitous stem-cell markers Piwi and Vasa are not found in parasitic flatworms, indicating that their 'neoblast' stem cell system may be highly modified (Collins et al., 2013; Tsai et al., 2013). Table 2 Expression of RNA interference pathway components in the Hymenolepis microstoma genome. "
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    ABSTRACT: Background. The selenocysteine(Sec)-containing proteins, selenoproteins, are an important group of proteins present in all three kingdoms of life. Although the selenoproteomes of many organisms have been analyzed, systematic studies on selenoproteins in platyhelminthes are still lacking. Moreover, comparison of selenoproteomes between free-living and parasitic animals is rarely studied. Results. In this study, three representative organisms (Schmidtea mediterranea, Schistosoma japonicum and Taenia solium) were selected for comparative analysis of selenoproteomes in Platyhelminthes. Using a SelGenAmic-based selenoprotein prediction algorithm, a total of 37 selenoprotein genes were identified in these organisms. The size of selenoproteomes and selenoprotein families were found to be associated with different lifestyles: free-living organisms have larger selenoproteome whereas parasitic lifestyle corresponds to reduced selenoproteomes. Five selenoproteins, SelT, Sel15, GPx, SPS2 and TR, were found to be present in all examined platyhelminthes as well as almost all sequenced animals, suggesting their essential role in metazoans. Finally, a new splicing form of SelW that lacked the first exon was found to be present in S. japonicum. Conclusions. Our data provide a first glance into the selenoproteomes of organisms in the phylum Platyhelminthes and may help understand function and evolutionary dynamics of selenium utilization in diversified metazoans.
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