Species-specific microRNA regulation influences phenotypic variability Perspectives on species-specific microRNA regulation

Phenotypic divergence among animal species may be due in part to species-specific (SS) regulation of gene expression by small, non-coding regulatory RNAs termed microRNAs. This phenomenon can be modulated by several variables. First, microRNA genes vary by their level of conservation, many of them being SS, or unique to a particular evolutionary lineage. Second, microRNA expression levels vary spatially and temporally in different species. Lastly, while microRNAs bind the 3UTR of target genes in order to silence their expression, the binding sites themselves are often non-conserved. The variability of the miRNA-target paradigm between different species is thus multifactorial, and this paradigm has only just started to gain attention from researchers in various fields. Here we present and discuss recent findings regarding the characteristics and implications of SS microRNA regulation.