Characterization of microRNAs in Taenia saginata of zoonotic significance by Solexa deep sequencing and bioinformatics analysis

The beef tapeworm Taenia saginata infects human beings with symptoms ranging from nausea, abdominal discomfort to digestive disturbances and intestinal blockage. In the present study, microRNA (miRNA) expressing profile in adult T. saginata was analyzed using Solexa deep sequencing and bioinformatics analysis. A total of 15.8 million reads was obtained by Solexa sequencing, and 13.3 million clean reads (1.73 million unique sequences) was obtained after removing reads smaller than 18 nt. Ten conserved miRNAs corresponding to 607,382 reads were found when matching the reads against known miRNAs of Schistosoma japonicum in miRBase database. The miR-71 had the most abundant expression in T. saginata, followed by miR-219-5p, but some other common miRNAs such as let-7, miR-40, and miR-103 were not identified in T. saginata. Nucleotide bias analysis found that the known miRNAs showed high bias and the uracil was the dominant nucleotide, particularly at the first and 11th positions which were almost at the beginning and middle of conserved miRNAs. One novel miRNA (Tsa-miR-001) corresponding to ten precursors was identified and confirmed by stem-loop RT-PCR. To our knowledge, this is the first report of miRNA profiles in T. saginata, which will contribute to better understanding of the complex biology of this zoonotic trematode. The reported data of T. saginata miRNAs should provide valuable references for miRNA studies of closed related zoonotic Taenia cestodes such as Taenia solium and Taenia asiatica.