Introduction
Schistosomiasis, caused by the trematode Schistosoma mansoni, is a parasitic disease with a major impact on global health. The sequencing of the parasite genome has provided a basis for functional analyses, but genomic annotation still presents limitations due to the complexity of the transcriptome and splicing signals. The present study used high-depth RNA sequencing (RNA-Seq) to characterize the transcriptome of adult male S. mansoni, allowing the validation of gene predictions and the discovery of novel genes.
Methodology
Polyadenylated (polyA+) RNA was extracted from approximately 200 adult male S. mansoni obtained from infected hamsters. The cDNA library was generated and sequenced using the Roche 454 GS-FLX Titanium platform. RNA-Seq reads were aligned to the S. mansoni genome using the BLAT algorithm, and assembly analysis was performed using Newbler 2.5 p1 software. Stringent parameters were used to validate the presence of previously annotated transcripts and identify novel transcriptionally active regions.
Results
A total of 1,620,432 high-quality EST (Expressed Sequence Tags) sequences were generated, totaling 376 Mb of data. The genomic coverage obtained was 26% higher than that of the public ESTs available at NCBI, allowing the confirmation of the expression of 990 genes previously predicted without experimental evidence, the correction of gene predictions and the identification of 989 new contigs in intergenic regions, suggesting the existence of new protein-coding genes or non-coding RNAs. In addition, 11 new microexon genes (MEGs) were identified, which may be involved in the antigenic variation of the parasite.
Discussion
The use of RNA-Seq has enabled significant advances in the understanding of the S. mansoni transcriptome. The discovery of new genes and adjustments to existing annotations provide critical information for future functional studies, which may contribute to the development of therapeutic strategies. The identification of additional MEGs suggests a possible role of these genes in immune evasion, highlighting their relevance for understanding the parasite-host interaction.
Reference :
ALMEIDA, GT; AMARAL, MS; BECKEDORFF, FCF; KITAJIMA, JP; DEMARCO, R.; VERJOVSKI-ALMEIDA, S. Exploring the Schistosoma mansoni adult male transcriptome using RNA-seq. Experimental Parasitology, v. 132, n. 1, p. 22–31, 2012. Available at: https://doi.org/10.1016/j.exppara.2011.06.010. Accessed: [insert access date].
