A Transcriptomic Analysis of Echinococcus granulosus Larval Stages: Implications for Parasite Biology and Host Adaptation

Abstract

BackgroundThe 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.Methodology/Principal FindingsWe 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/SignificanceThis 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.

Biology and Systematics of Echinococcus

“…The laminated layer also undoubtedly assists in supporting the cyst and allows an often considerable intracystic tension to develop (Cameron and Webster, 1969;Slais, 1973). It is a remarkable and specialized interface in the intermediate host providing a physiochemical barrier with apparent multi-functionality and a structure whose biosynthesis has become a model system for carbohydrate chemistry (Diaz et al, 2011a,b;Parkinson et al, 2012;. The laminated layer comprises a specialised extracellular matrix unique to Echinococcus (Fig.…”

“…The laminated layer comprises a specialised extracellular matrix unique to Echinococcus (Fig. 7), whose synthesis is a major metabolic activity of the much thinner germinal layer (Diaz et al, 2011a;Lin et al, 2012;Parkinson et al, 2012). It is a carbohydrateeprotein complex of highly glycosylated mucin glycoproteins (Kilejian and Schwabe, 1971).…”

“…Considerable metabolic activity in the germinal layer is required to synthesize and maintain the interfacial barrier of the laminated layer (Parkinson et al, 2012). The role of the laminated layer would appear to be one of protection by modulating the hosteparasite interface, since cyst survival is dependent upon its integrity (Gottstein et al, 2002;Stadelmann et al, 2010).…”

Recent advances in Echinococcus genomics and stem cell research

“…Later, these cestode whole genome sequencing projects were complemented by efforts of a Chinese/Australian consortium, which produced a second E. granulosus draft sequence from a single hydatid cyst (G1 strain) using 454 and Solexa NGS . In all three Echinococcus genome projects, gene finding and annotation was supported by extensive EST-and NGS-transcriptomic analyses (RNAseq) of several life cycle stages such as oncosphere, metacestode, protoscolex and adult worms (Fernandez et al, 2002;Parkinson et al, 2012;Tsai et al, 2013;Zheng et al, 2013).…”

Immunoblotting with Human Native Antigen Shows Stage-Related Sensitivity in the Serodiagnosis of Hepatic Cystic Echinococcosis

“…30 This warrants the evaluation of the transcriptome/proteome from different cyst stages. These differences might be useful in clinical practice to correctly define cyst stages and their viability.…”