Biolistic transformation of Schistosoma mansoni: Studies with modified reporter-gene constructs containing regulatory regions of protease genes.

Biolistics of the flatworm parasite Schistosoma mansoni facilitates the accurate spatial expression of transgenes under the control of gene-specific promoter elements. To improve transgene expression, either in the number of positive worms and/or an increased transgene signal per worm, we tested plasmid constructs incorporating 5' and 3' gene-specific genomic fragments, and parts of the open reading frame for two S. mansoni proteases, cathepsins F and D (SmCF and SmCD). GFP-expression was gut-localized, a novel finding for SmCD and consistent with previous data for SmCF. The mCherry fluorescent protein can also operate as a reporter. Though certain constructs imparted stronger and better distributed signals per positive worm, the low yields throughout (1-5% positive per experiment) precluded further quantifications of improvement. Electroporation of the same constructs was also weakly efficient (1-10% positives per experiment). However, reporter signals were found in tissues other than the gut, which may represent dysregulated transcription.