title: A transcriptomic analysis of Echinococcus granulosus larval stages: implications for parasite biology and host adaptation.
abstract: BACKGROUND
  The cestode Echinococcus granulosus--the agent of cystic echinococcosis, a zoonosis affecting humans and domestic animals worldwide--is an excellent model for the study of host-parasite cross-talk that interfaces with two mammalian hosts. To develop the molecular analysis of these interactions, we carried out an EST survey of E. granulosus larval stages. We report the salient features of this study with a focus on genes reflecting physiological adaptations of different parasite stages.
  
  
  RESULTS
  We generated ~10,000 ESTs from two sets of full-length enriched libraries (derived from oligo-capped and trans-spliced cDNAs) prepared with three parasite materials: hydatid cyst wall, larval worms (protoscoleces), and pepsin/H(+)-activated protoscoleces. The ESTs were clustered into 2700 distinct gene products. In the context of the biology of E. granulosus, our analyses reveal: (i) a diverse group of abundant long non-protein coding transcripts showing homology to a middle repetitive element (EgBRep) that could either be active molecular species or represent precursors of small RNAs (like piRNAs); (ii) an up-regulation of fermentative pathways in the tissue of the cyst wall; (iii) highly expressed thiol- and selenol-dependent antioxidant enzyme targets of thioredoxin glutathione reductase, the functional hub of redox metabolism in parasitic flatworms; (iv) candidate apomucins for the external layer of the tissue-dwelling hydatid cyst, a mucin-rich structure that is critical for survival in the intermediate host; (v) a set of tetraspanins, a protein family that appears to have expanded in the cestode lineage; and (vi) a set of platyhelminth-specific gene products that may offer targets for novel pan-platyhelminth drug development.
  
  
  CONCLUSIONS
  This survey has greatly increased the quality and the quantity of the molecular information on E. granulosus and constitutes a valuable resource for gene prediction on the parasite genome and for further genomic and proteomic analyses focused on cestodes and platyhelminths.
authors.affiliation: Program in Molecular Structure and Function, Hospital for Sick Children, University of Toronto, Toronto, Canada.
authors.forename: John
authors.initials: J
authors.lastname: Parkinson
authors.forename: James D
authors.initials: JD
authors.lastname: Wasmuth
authors.forename: Gustavo
authors.initials: G
authors.lastname: Salinas
authors.forename: Cristiano V
authors.initials: CV
authors.lastname: Bizarro
authors.forename: Chris
authors.initials: C
authors.lastname: Sanford
authors.forename: Matthew
authors.initials: M
authors.lastname: Berriman
authors.forename: Henrique B
authors.initials: HB
authors.lastname: Ferreira
authors.forename: Arnaldo
authors.initials: A
authors.lastname: Zaha
authors.forename: Mark L
authors.initials: ML
authors.lastname: Blaxter
authors.forename: Rick M
authors.initials: RM
authors.lastname: Maizels
authors.forename: Cecilia
authors.initials: C
authors.lastname: Fernández
mesh_terms: D000818:Animals; D048209:Echinococcus granulosus / Q000235:genetics* / Q000254:growth & development; D020224:Expressed Sequence Tags; D007814:Larva / Q000235:genetics / Q000254:growth & development; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA; D059467:Transcriptome