microRNA’s role in germline differentiation

Germline stem cells (GSCs) are unique in that they alone among adult stem cells pass information to the next generation. We here discuss the role of the recently discovered short RNAs called microRNAs in the germline. MicroRNAs are known to function as post-trascriptional regulators of gene expression and in that role to be essential both for development and homeostasis in many, if not all, higher organisms. MicroRNAs are needed for the creation of GSCs during embryogenesis, for the regulation of GSC function in sexually mature adults, and in the developmental programs that lead the daughter cells of GSCs to mature gametes in the course of gametogenesis. We also consider the tantalizing connection between microRNAs and a distinctive organelle of the germline, nuage. This connection is supported both by the presence of microRNA pathway components in nuage,andbythedisruptionofnuageandgermlinefunctionbytheablationofmicroRNApathwaycomponents. This suggests a role for microRNA in regulating the presumptive function of nuage: serving as a clearing house for parental mRNAs that must be either degraded, appropriately localized and stored in an untranslated state for future use, or translated for immediate use.