Biogenesis and biological implications of isomirs in mammals-a review

Abstract

Background: IsomiRs, the sequence-variants of microRNA (miRNA), are characterized by variation at the 3′-and/or 5′-end(s) of canonical miRNA-sequence as a result of nucleotide addition or deletion or substitution. These sequence alterations could be created either due to imprecise cleavage of miRNA sequence by drosha or dicer enzymes or through the addition of nucleotides at 3′ end during miRNA-biogenesis. Main body: The present review elaborates the biogenesis vis-à-vis role of isomiRs in disease-related traits in human and animals. The differential expression of isomiRs has been detected in the early and late developmental phases during embryogenesis in fruit fly and halibut (Hippoglossus hippoglossus). Multidimentional role of isomiRs viz. in gene regulation, evolution, RNA interference pathway and differentiation of tumorous cells etc. has attracted researchers to explore the biological significance of isomiRs in different species. Biocomputational identification of isomiRs using suitable online software/tools (miR-isomiRExp, miRPro, isomiRBank, isomiR-SEA etc) has been followed by empirical validation and pathway analyses. Conclusion: IsomiRs have been associated with various disease–pathways and thus could be used as promising disease-related markers in humans and livestock. In addition, the involvement of isomiRs in cancer and other diseases has been the major topic of interest due to the involvement of different biogenesis pathways.