Browsing by Subject "Schistosoma mansoni"
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Item Functional Studies of Stem Cells in the Parasitic Flatworm Schistosoma mansoni(2020-12-01T06:00:00.000Z) Wendt, George R.; Phillips, Margaret A.; Collins, James J.; Mangelsdorf, David J.; Cobb, Melanie H.Schistosomes are parasitic flatworms that infect over 200 million people, primarily in poverty-stricken developing countries, causing extensive morbidity and mortality. Schistosomes have a great deal in common with other parasitic flatworms such as liver flukes and tapeworms. Namely, they are characterized by a syncytial "skin" known as the tegument that is critical for their survival within their hosts, they possess somatic stem cells referred to as neoblasts, and they are incredibly successful parasites. Until now, there has been little appreciation for the interrelationships between the tegument, neoblasts, and successful parasitism. Our recent work, however, suggested that schistosome neoblasts give rise to cells that are associated with the parasite's tegument. In order to determine whether schistosome neoblasts produced the tegument, we developed novel labeling techniques and found that neoblasts give rise to progenitor cells that ultimately maintain the tegument. We also developed a fluorescence activated cell sorting protocol that we used to isolate neoblasts and tegument progenitors and obtain their transcriptomes. With this transcriptome data, we identified two regulators of tegument maintenance, zfp-1 and zfp-1-1, that are functionally conserved in free-living flatworms, suggesting a common molecular program for "skin" production in all flatworms. Additionally, our work suggested that zfp-1-1 specifically and tegument maintenance generally may be valid therapeutic targets. We next wondered whether schistosome neoblasts were responsible for making or maintaining any non-tegumental tissues in the adult parasite. To study this, we employed single cell RNAseq to create a gene expression atlas of 43,642 cells from adult parasites. This atlas gave us molecular markers for 68 distinct clusters of cells ranging from muscles and neurons to reproductive tissues such as the ovary. It also allowed us to identify a previously unknown sub-population of neoblasts that appears to exist at the top of a schistosome gut lineage. In an effort to study these neoblasts, we found that the schistosome homolog of the nuclear receptor hnf4 is required for normal gut homeostasis and that loss-of-function of hnf4 prevents parasite blood feeding and abrogates disease pathology in vivo. Taken together, this work demonstrates how studying basic developmental processes (i.e. stem cell differentiation) in a pathogenic organism can lead to not only insights into evolutionary biology (the machinery that regulates skin production appears to be conserved across flatworms), but it can also suggest novel therapeutic targets (namely zfp-1-1 and tegument maintenance as well as hnf4 and gut homeostasis).Item Nuclear Receptor FTZ-F1 and Downstream Target Gene Meg-8.3 Control Esophageal Gland Function in S. Mansoni(August 2021) Romero, Aracely Alicia; Reese, Michael L.; Collins, James J.; Mangelsdorf, David J.; Phillips, Margaret A.; Kliewer, Steven A.Schistosomes infect over 200 million of the world's poorest people, yet treatment relies on a single drug. Nuclear hormone receptors are ligand-activated transcription factors that regulate diverse processes in metazoans and are known drug targets in humans. However, few nuclear hormone receptors have been characterized functionally in the parasite. During a systematic analysis of nuclear receptor function, we have identified one receptor, an FTZ-F1-like receptor that is essential for parasite survival. Using a combination of transcriptional profiling and chromatin immunoprecipitation we identify the micro-exon gene, meg-8.3, a direct transcriptional target of FTZ-F1 which is also essential for parasite survival. We find that RNAi of either ftz-f1 or meg-8.3 are required for esophageal gland function and maintenance of tissue in the worm head. Together, our data suggest that FTZ-F1 regulates meg-8.3 transcription, and this regulation is essential to esophageal gland function. These data suggest that drugs that alter the activities of proteins in the parasite's esophageal gland could have therapeutic potential.Item STK25 and TAO Regulate Muscle-Specific Transcription and Muscle Function in the Parasitic Flatworm Schistosoma Mansoni(August 2021) Paz, Carlos Alberto; Reese, Michael L.; Collins, James J.; Cobb, Melanie H.; Mangelsdorf, David J.; Phillips, Margaret A.Schistosomiasis, a disease caused by parasitic flatworms called schistosomes, affects 240 million people in developing regions, including large parts of Africa, Asia, and South America. In some of these areas, the disease affects over 50% of the population, making Schistosomiasis second only to Malaria in parasite devastation. To look for functionally important schistosome genes, we performed a large-scale RNAi screen in adult Schistosoma mansoni, and discovered 3 genes that produce an identical type of sickness in the worm. Disruption of the genes thousand-and-one kinase (TAO), serine threonine kinase 25 (STK25), or cerebral cavernous malformations 3 (CCM3) by RNAi in these worms produces a rapid and consistent deterioration consisting of detachment from the culture dish, drastic length reduction, selective paralysis in the worm body, and a distinctive "banana"-shaped morphology. Transplantation of stk25(RNAi) or tao(RNAi)- treated worms into a mouse host results in a significant reduction of worm eggs, and associated liver pathology, compared to healthy worm transplantations. RNA sequencing of stk25(RNAi) and tao(RNAi) worms uncovered that not only do both stk25 and tao cause significant transcriptional changes, but those changes are unusually similar, supporting the model that these genes are interacting as part of a signaling pathway in the worm. RNAi-induced transcriptional changes were heavily biased to worm muscle, a clue to explain loss of movement in these worms. By visualizing gene expression as well as muscle structure in whole worms, we concluded that these worms undergo specific loss of gene expression in the muscle cells of the body, but without significant loss of muscle cells or structure. Additionally, we find that schistosome TAO kinase can directly phosphorylate schistosome STK25 in vitro, and that this phosphorylation occurs at an amino acid (T173) which is known to be required for activation of all homologous STK25 kinases in other organisms. Using a yeast 2-hybrid system, we find that schistosome STK25 and CCM3 can physically interact, in agreement with literature reporting this interaction in other organisms. Altogether, our data supports a model that these genes work together in the parasite to control a muscle-specific transcriptional program that is essential for worm health both in culture and in the host.