Identification of preferential selection of 3p and 5p microRNA transcripts in vertebrates: functional and evolutionary implications

Abstract

MicroRNAs (miRNAs) are a wide class of small (~22nt) non-coding RNAs present in the eukaryotic genome that act directly on the developmental control and homeostasis of these organisms. During miRNA biogenesis, cells generate mature transcripts (miRNAs 5p e 3p) capable of coordinating the modulation of gene expression profile in response to the biological context of the organism. The mechanism of regulation performed by miRNAs occurs canonically through binding to a specific target mRNA, and this specificity is dependent on both nucleotide sequences. Usually, the miRNA-mediated genetic silencing pathway preferentially selects the mature transcripts 3p or 5p that are, commonly, characteristics of a biological group. Endogenous events named arm switching can lead to the shift of the ratio of mature miRNAs 5p or 3p originated by the same primary miRNA, modifying the active miRNA arm and its target genes in different biological pathways. Therefore, arm switching events that lead to the prevalence of functionally distinct miRNA have the potential to contribute to the origin of distinct adaptations through the control of gene expression, thereby contributing to the evolution of novel vertebrate phenotypes. The current project aims to characterize the miRNA arms expression profile in representative species of the living vertebrate groups (Elasmobranchii; Teleostei; Amphibia; Mammalia; Crocodylia; Aves), in order to identify potential differences in the prevalence of functional miRNA arms 5p and 3p mapping potential changes in the pool of genes and biological pathways regulated by them. Towards this goal, bioinformatics tools and microRNome datasets available from open source databases will be scrutinized. We expect to advance in the characterization of miRNA signature of transcripts 3p or 5p in order to contribute to the understanding of the molecular basis of the biological differences between vertebrates and extend our knowledge about miRNA-mediated mechanisms governing function, structure, and evolution of the genome.