Five hundred known miRNAs and almost one hundred putative novel vertebrate miRNAs were identified, many of which seem to be teleost-specific, cichlid-specific or tilapia-specific. Abundant miRNA isoforms (isomiRs) were identified with modifications in both 5p and 3p miRNA transcripts. Changes in arm usage (arm switching) of nine miRNAs were detected in early development, adult stage and even between male and female samples. The researchers found an increasing complexity of miRNA expression during ontogenetic development, revealing a remarkable synchronism between the rate of new miRNAs recruitment and morphological changes.
Overall, these results enlarge vertebrate miRNA collection and reveal a notable differential ratio of miRNA arms and isoforms influenced by sex and developmental life stage, providing a better picture of the evolutionary and spatiotemporal dynamics of miRNAs.
Genome organization of miRNAs genes in Nile tilapia genome. Black: known miRNAs. Red: novel miRNAs described in current study. Green: novel miRNAs described previously by Huang et al.36 and Yan et al.40; MiRNAs in brackets: clustered miRNAs.