A single target for microRNA regulation

It has generally been believed that microRNAs control biological processes by simultaneously, though modestly, repressing a large number of genes. But in a study published in Developmental Cell, a group of scientists led by Helge Grosshans have now shown that miRNAs can control the development of a roundworm through regulation of a single target. The discovery, some 15 years ago, of the small RNA molecule let-7 opened up a whole new field of research. It became apparent that genes in a wide variety of organisms - from roundworms to humans - are regulated by a host of so-called microRNAs (miRNAs). In the development of the roundworm, let-7 plays a key role: if it is defective, the worm bursts and dies as a result of abnormal development of the sexual organs. Although in the meantime, much has been learned about the molecular mechanisms underlying miRNA function, it remained unclear how this dramatic effect of let-7 was to be explained. An elegant study by a group led by Helge Grosshans at the FMI has now revealed how let-7 controls normal vulval development in the roundworm.