MicroRNAs: critical mediators of differentiation, development and disease

MicroRNAs (miRNAs) are small non-coding RNAs that are expressed in higher eukaryoates and have even been found in viral genomes. They usually act as endogenous repressors of target genes by either inhibiting translation, causing mRNA degradation, or by a combination of both mechanisms. More than 850 mature miRNA se-quences have been identified in humans, and al-though this accounts for less than 2 % of human genes, it is predicted that 30 % of mRNAs are tar-geted by miRNAs. miRNAs play critical roles in most cellular processes including development, differentiation, and the homeostasis of both a cell and an organism. Moreover, many disease states, including cancer, occur or are sustained b