Identification and characterization of microRNAs in the pancreatic fluke Eurytrema pancreaticum

BACKGROUND: Eurytrema pancreaticum is one of the most common flukes, which mainly infects ruminants globally and infects human beings accidentally; causing eurytremiasis that has high veterinary and economic importance. MicroRNAs (miRNAs) are small non-coding RNAs and are now considered as a key mechanism of gene regulation at the post-transcription level. METHODS: We investigated the global miRNA expression profile of E. pancreaticum adults using next-generation sequencing technology combined with real-time quantitative PCR. RESULTS: By using the genome of the closely-related species Schistosoma japonicum as reference, we obtained 27 miRNA candidates out of 16.45 million raw sequencing reads, with 13 of them found as known miRNAs in S. japonicum and/or S. mansoni, and the remaining 14 miRNAs were considered as novel. Five out of the 13 known miRNAs coming from one family named as sja-miR-2, including family members from miR-2a to miR-2e. Targets of 19 miRNAs were successfully predicated out of the 17401 mRNA and EST non-redundant sequences of S. japonicum. It was found that a significant high number of targets were related to “chch domain-containing protein mitochondrial precursor” (n = 29), “small subunit ribosomal protein s30e” (n = 21), and “insulin-induced gene 1 protein” (n = 9). Besides, “egg protein cp3842” (n = 2), “fumarate hydratase” (n = 2), “ubiquitin-conjugating enzyme” (n = 2), and “sperm-associated antigen 6” (n = 1) were also found as targets of the miRNAs of E. pancreaticum. CONCLUSIONS: The present study represents the first global characterization of E. pancreaticum miRNAs, which provides novel resources for a better understanding of the parasite, which, in turn, has implications for the effective control of the disease it causes.