‘microRNA ’ Review Series The ongoing microRNA revolution and its impact in biology and medicine

First identified more than a decade ago in C. elegans, microRNAs have emerged as key molecular players in virtually all the cellular processes studied to date [1]. The scientific community has witnessed an arguably unparalleled expansion in the number of publications focusing on microRNA biology, from only a handful in 2001 to well over a thousand during the course of last year. In the meantime, the num-ber of experimentally confirmed microRNAs has increased, now exceeding 500 in most studied organisms, including mammals. Many microRNAs exhibit a remark-able degree of evolutionary conservation between birds, rodents and primates, a reflection of their critical importance for fundamental cellular processes. Novel bioinformatic approaches and increasingly advanced cloning technologies could lead to a further enrichment of the microRNAs world in the years to come. Mechanistically, microRNAs interfere with gene expression at post-transcrip-tional level, subsequently to base pairing to partially complementary sites within the 3’UTR of the targets [2]. The early prevailing paradigm divided microRNAs actions along evolutionary lines. Thus, in plants they were thought to interfere wit