Comparative analysis of known miRNAs across platyhelminths

Abstract

MicroRNAs (miRNAs) are a subtype of small regulatory RNAs that are involved in numerous biological processes through small RNA-induced silencing networks. In an attempt to explore the phylogeny of miRNAs across five platyhelminths, we integrated annotated miRNAs and their full genomes. We identified conserved miRNA clusters and, in particular, miR-71/2 was conserved from planarian to parasitic flatworms and was expanded in free-living Schmidtea mediterranea. Analysis of 22 miRNA loci provided compelling evidence that most known miRNAs are conserved across platyhelminths. Meanwhile, we also observed alterations of known protein-coding genes flanking miRNA(s), such as transcriptional direction conversion and locus relocation, in around ~ 41% of 22 known miRNA loci. Compared with Echinococcus multilocularis, the majority of these events occurred in evolution-distant Hymenolepis microstoma, Schistosoma japonicum or/and S. mediterranea. These results imply rearrangement events occurred near the known miRNA loci. miRNAs are tiny regulatory RNAs that are involved in regulation of genes. Here we integrated annotated miRNAs and the genomes of platyhelminths, and found that a miR-71/2 cluster was conserved in flatworms. We also observed the transcriptional direction conversion and locus relocation of known protein-coding genes flanking miRNAs. These results imply a potential of rearrangement events occurred near the known miRNA loci. © 2013 FEBS.