MicroRNAs (miRNAs) are endogenous, ca. 22-nucleo-tide, single-strand, non-coding RNAs that regulate gene expression by acting post-transcriptionally through base-pairing between the so called "seed" sequence of the miRNA (nucleotides 2-8 at its 5′ end) and its complementary seed match sequence present in the 3′ untranslated region of the target mRNA. Since the discovery of the first miRNAs in the 1990s, a remarkable diversity of miRNAs has been reported in various organisms, including insects, plants, viruses, and vertebrates. Moreover, computational methods have been developed to find new miRNAs as well as mRNA targets. In insects, most miRNAs are involved in modulating a precise dosage of regulatory proteins, thus fine-tuning biological processes like cell proliferation, apoptosis and growth, oogenesis and embryogenesis, nervous system and muscle differentiation, metamorphosis and other morphogenetic processes, and response to biological stress. The miRNA field is still developing, and many questions remain to be solved. Technologies to determine new miRNAs and miRNA targets still need refinement. Further studies are also needed to elucidate the mechanisms regulating miRNA expression, to validate the miRNA targets in vivo, and to establish the complex networks that connect miRNAs, mRNAs, and proteins, and that govern the development and function of cells and tissues.

Peer reviewed