| We describe a novel approach for real-time imaging of native mRNAs in living cells. We employed nuclease-resistant molecular beacons, probes that become fluorescent upon hybridization, to image the distribution of maternal mRNAs at different stages in Drosophila melanogaster oogenesis. When introduced into living oocytes, the pattern of observed fluorescence maps the distribution of the target mRNA. We tracked the migration of oskar mRNA in real-time, from the nurse cells where it is produced, to the posterior cortex of the oocyte where it is localized. Our observations reveal the presence of a transient, and heretofore elusive, stage in the transport of oskar mRNA. Direct visualization of specific mRNAs in living cells will accelerate studies of intracellular RNA trafficking and localization, just as green fluorescent protein has stimulated the study of specific proteins in vivo. |
