a1 Molecular Helminthology Laboratory, Division of Infectious Diseases, Department of Biomedical Sciences, Tufts University, Cummings School of Veterinary Medicine, Grafton, MA 01536, USA
a2 Centro de Biotecnologia, Instituto Butantan, Av. Vital Brasil, 1500, 05503-900 São Paulo, SP, Brazil
RNA interference (RNAi) is a potent gene silencing process that is playing an increasingly important role in investigations of gene function in schistosomes. Here we review what is known about the process in these parasites and provide an update on the methodology and machinery of RNAi. Data are presented to demonstrate that: (1) not all schistosome genes can be suppressed to the same extent, using the methods employed here; (2) while there is variation in the level of suppression achieved for one target gene (SmAP) in adult parasites, all individuals exhibit robust (>80%) suppression; (3) short interfering RNAs (siRNAs) can effect suppression when delivered by soaking (and not just via electroporation, as reported previously); (4) Male/female adult pairs need not be separated prior to siRNA delivery by electroporation for effective gene suppression in both genders and (5) electroporation of siRNAs in medium is as efficient as in commercial electroporation buffer. Regarding the machinery of RNAi in schistosomes, a homologue of the C. elegans multi-membrane spanning, RNA importing protein SID-1 is identified in silico. The gene encoding this protein contains 21 exons and spans over 50 kb to potentially encode a 115,556 Mr protein (SmSID-1). These analyses, and a review of the literature, permit us to derive and present here a draft of potential RNAi pathways in schistosomes.
(Received June 10 2009)
(Revised July 28 2009)
(Accepted July 29 2009)
(Online publication September 21 2009)
c1 Corresponding author: Molecular Helminthology Laboratory, Division of Infectious Diseases, Department of Biomedical Sciences, Tufts University, Cummings School of Veterinary Medicine, Grafton, MA 01536, USA. Tel: 508-887-4348. Fax: 508-839-7911. E-mail: Patrick.Skelly@Tufts.edu