Identification and Characterization of Novel MicroRNAs from Schistosoma japonicum

Abstract

BackgroundSchistosomiasis japonica remains a major public health problem in China. Its pathogen, Schistosoma japonicum has a complex life cycle and a unique repertoire of genes expressed at different life cycle stages. Exploring schistosome gene regulation will yield the best prospects for new drug targets and vaccine candidates. MicroRNAs (miRNAs) are a highly conserved class of noncoding RNA that control many biological processes by sequence-specific inhibition of gene expression. Although a large number of miRNAs have been identified from plants to mammals, it remains no experimental proof whether schistosome exist miRNAs.Methodology and ResultsWe have identified novel miRNAs from Schistosoma japonicum by cloning and sequencing a small (18–26 nt) RNA cDNA library from the adult worms. Five novel miRNAs were identified from 227 cloned RNA sequences and verified by Northern blot. Alignments of the miRNAs with corresponding family members indicated that four of them belong to a metazoan miRNA family: let-7, miR-71, bantam and miR-125. The fifth potentially new (non conserved) miRNA appears to belong to a previously undescribed family in the genus Schistosome. The novel miRNAs were designated as sja-let-7, sja-miR-71, sja-bantam, sja-miR-125 and sja-miR-new1, respectively. Expression of sja-let-7, sja-miR-71 and sja-bantam were analyzed in six stages of the life cycle, i.e. egg, miracidium, sporocyst, cercaria, schistosomulum, and adult worm, by a modified stem-loop reverse transcribed polymerase chain reaction (RT-PCR) method developed in our laboratory. The expression patterns of these miRNAs were highly stage-specific. In particular, sja-miR-71 and sja-bantam expression reach their peaks in the cercaria stage and then drop quickly to the nadirs in the schistosomulum stage, following penetration of cercaria into a mammalian host.ConclusionsAuthentic miRNAs were identified for the first time in S. japonicum, including a new schistosome family member. The different expression patterns of the novel miRNAs over the life stages of S. japonicum suggest that they may mediate important roles in Schistosome growth and development.

Schistosomiasis in the People's Republic of China: the Era of the Three Gorges Dam

“…The landmark availability of the complete sequences of the S. japonicum (171) and S. mansoni (18) genomes will provide the necessary ancillary information. As well, new approaches in antigen discovery through the generation of a large schistosome transcriptome database, gene finding, and the explosion in postgenome technologies, including DNA microarray profiling, proteomics, glycomics, immunomics, and the application of RNA interference (RNAi) and novel imaging techniques (2,24,25,41,53,72,73,75,76,85,95,109,126,127,179,189,197,205,219,224,230), provide an unprecedented opportunity to identify a new generation of vaccine target molecules that may induce greater potency than the current candidate schistosome antigens (138).…”

microRNAs in parasites and parasite infection

“…Along with let-7, the miRNA bantam that is extraordinarily highly expressed in cercaria is supposed to be active in developmental processes through regulation of a cellular population size. 59 However, a recent study preferably supports the notion that let-7 has other functions rather than controlling developmental timing. 60 It is clear that these presumptions need to be further experimentally tested.…”

Non-coding RNAs in schistosomes: an unexplored world

“…The previously described hammerhead ribozyme RNA (Ferbeyre et al 1998) is the most diverse because it originates from repetitive DNA; tRNAs were found to be the next most diverse ncRNAs encoded in the S. mansoni genome (tRNAscan-SE predicted a total of 713 tRNAs) (Copeland et al 2009). The authors focused on the comparison between tRNA populations in other schistosomes and in a free-living platyhelminth organism (Schmidtea mediterranea); they also confirmed in S. mansoni the first miRNAs described in S. japonicum by Xue et al (Xue et al 2008).…”

“…The first miRNAs characterized in schistosomes were described in 2008 (Xue et al 2008). In that work the authors described 227 cloned microRNAs in S. japonicum.…”