Manipulating the manipulators: advances in parasitic helminth transgenesis and RNAi

Strongyloides stercoralis: cell- and tissue-specific transgene expression and co-transformation with vector constructs incorporating a common multifunctional 3' UTR

Transgenesis is a valuable methodology for studying gene expression patterns and gene function. It has recently become available for research on some parasitic nematodes, including Strongyloides stercoralis. Previously, we described a vector construct, comprising the promoter and 3' UTR of the S. stercoralis gene Ss era-1 that gives expression of GFP in intestinal cells of developing F1 progeny. In the present study, we identified three new S. stercoralis promoters, which, in combination with the Ss era-1 3' UTR, can drive expression of GFP or the red fluorescent protein, mRFPmars, in tissue-specific fashion. These include Ss act-2, which drives expression in body wall muscle cells, Ss gpa-3, which drives expression in amphidial and phasmidial neurons and Ss rps-21, which drives ubiquitous expression in F1 transformants and in the gonads of microinjected P0 female worms. Concomitant microinjection of vectors containing GFP and mRFPmars gave dually transformed F1 progeny, suggesting that these constructs could be used as co-injection markers for other transgenes of interest. We have developed a vector "toolkit" for S. stercoralis including constructs with the Ss era-1 3' UTR and each of the promoters described above.

An improved and secreted luciferase reporter for schistosomes

Schistosomes are multicellular parasites of humans exhibiting interesting biological adaptations to their parasitic lifestyle. Concerted and in depth analyses of these adaptations and their cell and molecular biology requires further development of molecular genetic tools in schistosomes. In the current study, we demonstrate that a Gaussia luciferase reporter leads to significantly higher levels of luciferase activity in schistosomes compared to other tested luciferases. In addition, Gaussia luciferase can be secreted into culture media enabling non-invasive analysis of reporter activity. The secretion of Gaussia luciferase should allow a variety of new experimental paradigms for schistosome studies. Comparison of biolistic and electroporation transfection methods using luciferase RNA reporters and the luciferase acitivty produced indicates that electroporation of sporocysts and schistosomula is the most efficient transfection method for the four stages analyzed. These data should facilitate additional studies in schistosomes and provide a framework for further development of DNA transfection and gene expression analysis.