title: A deep analysis of the small non-coding RNA population in Schistosoma japonicum eggs.
abstract: BACKGROUND
  Schistosoma japonicum is a parasitic flatworm that causes zoonotic schistosomiasis. The typical outcome of schistosomiasis is hepatic granuloma and fibrosis, which is primarily induced by soluble egg-derived antigens. Although schistosomal eggs represent an important pathogenic stage to the host, the biology of this critical stage is largely unknown. We previously investigated the expression profiles of sncRNAs during different developmental stages of this parasite. However, using small RNA extracted from egg-deposited liver tissues generated limited information about sncRNAs in eggs. Here, we characterized the complete small RNAome in this stage of the parasite after optimization of RNA purification.
  
  
  RESULTS
  A library, SjE, was constructed with the small RNA extracted from S. japonicum eggs and subjected to high-throughput sequencing. The data were depicted by comprehensive bioinformatic analysis to explore the expression features of sncRNAs in the egg stage. MicroRNAs accounted for about one quarter of the total small RNA population in this stage, with a strongly biased expression pattern of certain miRNA family members. Sja-miR-71, sja-miR-71-5p, and sja-miR-36-3p were suggested to play important roles in embryo development. A panel of transfer RNA fragments (tRFs) precisely processed from the 5' end of mature tRNAs was identified for the first time, which represented a strong egg stage-biased expression. The tRNA-Ala derived small RNAs were the most highly expressed Sj-tRFs in eggs. Further, the expression of siRNAs from 29 types of well-defined transposable elements (TEs) was observed to be relatively stable among different developmental stages.
  
  
  CONCLUSIONS
  In this study, we characterized the sncRNA profile in the egg stage of S. japonicum. Featured expression of sncRNAs, especially the tRNA-derived small RNAs, was identified, which was further compared with that of other developmental stages. These novel findings would facilitate a deeper understanding of the biology of schistosomal parasites.
authors.affiliation: MOH Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, PR China.
authors.forename: Pengfei
authors.initials: P
authors.lastname: Cai
authors.forename: Xianyu
authors.initials: X
authors.lastname: Piao
authors.forename: Lili
authors.initials: L
authors.lastname: Hao
authors.forename: Shuai
authors.initials: S
authors.lastname: Liu
authors.forename: Nan
authors.initials: N
authors.lastname: Hou
authors.forename: Heng
authors.initials: H
authors.lastname: Wang
authors.forename: Qijun
authors.initials: Q
authors.lastname: Chen
mesh_terms: D000818:Animals; D001483:Base Sequence; D004275:DNA, Ribosomal / Q000235:genetics; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D059014:High-Throughput Nucleotide Sequencing; D035683:MicroRNAs / Q000235:genetics; D010063:Ovum / Q000254:growth & development / Q000378:metabolism*; D058727:RNA, Small Untranslated / Q000235:genetics* / Q000302:isolation & purification; D012343:RNA, Transfer / Q000235:genetics; D012549:Schistosoma japonicum / Q000196:embryology / Q000235:genetics*; D017423:Sequence Analysis, RNA
chemical_list: D004275:DNA, Ribosomal; D035683:MicroRNAs; D058727:RNA, Small Untranslated; D012343:RNA, Transfer