Apoptosis Governs the Elimination of Schistosoma japonicum from the Non-Permissive Host Microtus fortis

Abstract

The reed vole, Microtus fortis, is the only known mammalian host in which schistosomes of Schistosoma japonicum are unable to mature and cause significant pathogenesis. However, little is known about how Schistosoma japonicum maturation (and, therefore, the development of schistosomiasis) is prevented in M. fortis. In the present study, the ultrastructure of 10 days post infection schistosomula from BALB/c mice and M. fortis were first compared using scanning electron microscopy and transmission electron microscopy. Electron microscopic investigations showed growth retardation and ultrastructural differences in the tegument and sub-tegumental tissues as well as in the parenchymal cells of schistosomula from M. fortis compared with those in BALB/c mice. Then, microarray analysis revealed significant differential expression between the schistosomula from the two rodents, with 3,293 down-regulated (by ≥2-fold) and 71 up-regulated (≥2 fold) genes in schistosomula from the former. The up-regulated genes included a proliferation-related gene encoding granulin (Grn) and tropomyosin. Genes that were down-regulated in schistosomula from M. fortis included apoptosis-inhibited genes encoding a baculoviral IAP repeat-containing protein (SjIAP) and cytokine-induced apoptosis inhibitor (SjCIAP), genes encoding molecules involved in insulin metabolism, long-chain fatty acid metabolism, signal transduction, the transforming growth factor (TGF) pathway, the Wnt pathway and in development. TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) and PI/Annexin V-FITC assays, caspase 3/7 activity analysis, and flow cytometry revealed that the percentages of early apoptotic and late apoptotic and/or necrotic cells, as well as the level of caspase activity, in schistosomula from M. fortis were all significantly higher than in those from BALB/c mice.

Comparative characterization of microRNAs in Schistosoma japonicum schistosomula from Wistar rats and BALB/c mice

“…The differential expression of these aforementioned target genes via regulation by miRNAs may result in the abnormal development of the worms. Differentially expressed genes and proteins have been studied among worms collected from different hosts, and genes involved in apoptosis were identified as the cause of growth and development retardation of schistosomes in less susceptible hosts, which is consistent with our previous work (Han et al 2013a;Peng et al 2011a). Calcium signaling pathway molecules may act as key constituents in schistosome development and growth (You et al 2013).…”

“…As a model of a semipermissive host, only a small percentage of the initial cercarial challenge were found to develop into mature adults in the portal mesenteric veins of rats 5 weeks post-infection, and most schistosomes failed to complete their life cycle, as evidenced by the fact that only a few eggs were found in the feces of schistosome-infected rats 6 months post-infection (Peng et al 2011b;Silva-Leitao et al 2009). Based on our previous research, an effective approach to understanding schistosomedefinitive host interplay is to focus on parasite defensive mechanisms and host reactive responses (Han et al 2012;Peng et al 2011a). miRNAs are believed to act as key posttranscriptional regulators of many genes that are involved in a wide variety of biological functions, including cell proliferation, differentiation, apoptosis, metabolism, signal transduction, immunity, and tumorigenesis, by preventing the translation of downstream target mRNAs, thereby ultimately inhibiting the expression of multiple genes (Ambros 2003;Hoefig and Heissmeyer 2008;Xiao et al 2009).…”

“…The target genes were mapped, filtered, and correlated with differentially expressed genes in mice and rats using a S. japonicum oligonucleotide microarray from our previous research (GEO accession no. GSE25728) (Peng et al 2011a). The target genes were analyzed in terms of their Gene Ontology (GO) categories using the Database for Annotation, Visualization, and Integrated Discovery (DAVID) gene annotation tool (http://david.abcc.ncifcrf.gov/) (Huang da et al 2009).…”

Differences in genomic architecture between two distinct geographical strains of the blood fluke Schistosoma japonicum reveal potential phenotype basis

“…All of these more complex probe-design limitations may be addressed in the future through improved re-sequencing, annotation, and particularly the future physical mapping of the S. japonicum genome. In order to determine the effectiveness of the microarray approach for this application, we compared the microarray probes designed from S. japonicum ESTs [32,40] to those of the publicly available S. japonicum genomic sequence [38]. Three or more base pair mismatches are known to dramatically decrease microarray hybridisation efficiency for 60-mer oligos probes [42,43].…”

“…Full details of the microarray design are available (www.ncbi.nlm.nih.gov/geo/; Platform Accession no. GPL9759) and (Supplementary Table 1 [32], series accession no. GSE39329), while the applications of the array for studying different aspects of the biology of S. japonicum have been described [19,33].…”