GSE66490
The miRNome of Fasciola hepatica juveniles endorse the existence of a reduced set of highly divergent miRNAs in parasitic flatworms.
The liver fluke Fasciola hepatica is a foodborne zoonotic parasite affecting livestock worldwide with increasing relevance in human health. The first developmental stage that the host meets after ingestion of the parasite is the newly excysted juvenile (NEJ), that actively transverse the gut wall and migrates to their final location in the liver. The regulation of the early developmental events in NEJs is still poorly understood and a relevant target for control strategies. Here we investigated the putative involvement of small regulatory RNAs in the invasion process. The small RNA population of the NEJ fall into two classes, one represented by miRNAs and a secondary group of larger (32- 33 nucleotides) tRNA derived sequences. We identified more than 30 different miRNAs most of them belonging to ancient miRNAs conserved in protostomes and metazoans, notably with an miR-125b variant as highly predominant. Remarkably, several protostomian and metazoan conserved families were not detected in consonance with previous reports of drastic miRNome reduction in parasitic flatworms. Additionally, a set of 11 novel miRNAs was identified, probably associated with specific gene regulation expression needs in F. hepatica. While sequence conservation in mature miRNA is high across the metazoan tree, we observed that flatworm miRNAs are more divergent suggesting that mutation rates in parasitic flatworms could be high. Finally, the distinctive presence of tRNA derived sequences, mostly 5'' tRNA halves of selected tRNAs in the small RNA population of NEJs could indicate that this parasite uses both miRNA and tRNA fragments for the regulation of gene expression. Overall design: SmallRNA profile of Fasciola hepatica juvenile stage generated by deep sequencing using illumina GAIIx