Identification of the Schistosoma mansoni TNF-Alpha Receptor Gene and the Effect of Human TNF-Alpha on the Parasite Gene Expression Profile

Abstract

Background Schistosoma mansoni is the major causative agent of schistosomiasis. The parasite takes advantage of host signals to complete its development in the human body. Tumor necrosis factor-alpha (TNF-α) is a human cytokine involved in skin inflammatory responses, and although its effect on the adult parasite's metabolism and egg-laying process has been previously described, a comprehensive assessment of the TNF-α pathway and its downstream molecular effects is lacking.Methodology/Principal FindingsIn the present work we describe a possible TNF-α receptor (TNFR) homolog gene in S. mansoni (SmTNFR). SmTNFR encodes a complete receptor sequence composed of 599 amino acids, and contains four cysteine-rich domains as described for TNFR members. Real-time RT-PCR experiments revealed that SmTNFR highest expression level is in cercariae, 3.5 (±0.7) times higher than in adult worms. Downstream members of the known human TNF-α pathway were identified by an in silico analysis, revealing a possible TNF-α signaling pathway in the parasite. In order to simulate parasite's exposure to human cytokine during penetration of the skin, schistosomula were exposed to human TNF-α just 3 h after cercariae-to-schistosomula in vitro transformation, and large-scale gene expression measurements were performed with microarrays. A total of 548 genes with significantly altered expression were detected, when compared to control parasites. In addition, treatment of adult worms with TNF-α caused a significantly altered expression of 1857 genes. Interestingly, the set of genes altered in adults is different from that of schistosomula, with 58 genes in common, representing 3% of altered genes in adults and 11% in 3 h-old early schistosomula.Conclusions/SignificanceWe describe the possible molecular elements and targets involved in human TNF-α effect on S. mansoni, highlighting the mechanism by which recently transformed schistosomula may sense and respond to this host mediator at the site of cercarial penetration into the skin.

Non-coding RNAs in schistosomes: an unexplored world

“…A set of 755 probes had been identified with a statistically significant (q-value < 0.05) differential expression between TNF-α treated and control early schistosomula (Oliveira et al 2009); with the re-annotation we conclude that 686 unique genes were affected.…”

“…A set of 1,594 probes revealed statistically significant (q-value < 0.05) transient changes in expression (Oliveira et al 2009). With the microarray re-annotation we conclude that there are 1404 unique genes with transient changes induced by TNF-α; 1048 genes have match to S. mansoni gene predictions, 54 match S. japonicum gene predictions, 203 match conserved proteins (GenBank), comprising a total of 1305 known proteincoding genes, and 99 have no match.…”

“…In December 2009 our laboratory published the ortholog gene of TNF-α receptor in S. mansoni and characterized the effect of human TNF-α on the parasite gene expression using a microarray platform of 44k oligonucleotide probes (Oliveira et al 2009). Here, we re-annotated the 44k oligonucleotide array according to gene predictions that appear in the genome publication (Berriman et al 2009) in order to highlight the differentially expressed probes that map to the opposite strand of known proteincoding genes (potentially ncRNAs regulated by TNF-α).…”

“…In adult worms treated during 1 h or 24 h with TNF-α we had identified (Oliveira et al 2009) two distinct expression patterns in treated adult worms: genes with transient expression changes (up-regulated at 1 h treatment and down-regulated at 24 h treatment, or the opposite pattern) and genes with sustained changes (upregulated at 1 h and 24 h treatment, or down-regulated throughout).…”

“…mune system, uptake nutrients for their development and differentiation (Amiri et al 1992, De Mendonca et al 2000, Davies et al 2001, Escobedo et al 2005, and in addition the parasite has many ortholog genes to human receptors (Agboh et al 2004, Osman et al 2006, Khayath et al 2007, Wu et al 2007, Oliveira et al 2009. It is also known that the parasite has a sophisticated alternative splicing mechanism for genes encoding secreted proteins such as micro-exon genes (MEGs) (Demarco et al 2010), polymorphic mucins genes (SmPoMucs) (Roger et al 2008) and venom allergen-like (SmVALs) genes (Chalmers et al 2008).…”