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. 2019 Apr 8;10(4):e1535. doi: 10.1002/wrna.1535
Separating RNA signals from waste
Do the same cells release RNA both as a signaling mechanism and a clearance mechanism? Do these involve different ribonucleoprotein complexes of EV subsets?
  • Technological developments are required to separate different extracellular RNA‐containing complexes, including different EV subsets.

  • Careful consideration is required to prevent contaminants, for example, from calf serum used in cell culture experiments.


Linking intracellular and extracellular RNA regulation
Does the up‐ or down‐regulation of RNAs upon infection inside the cell influence extracellular RNA levels? Do passive or active sorting mechanisms dictate what is released? Have viruses evolved to control these processes?
  • Basic research is required to identify the factors required for RNA sorting/export and genetic and synthetic strategies are needed to block these processes for functional interrogation.


Concentration and localization of imported RNA
Is the amount of RNA imported into a cell is sufficient to raise its concentration to a functional level, in particular for RNAs involved in gene silencing?
  • Quantitative data on imported RNA levels under physiological conditions are required, along with new methods to track imported RNAs, including studies of cross‐species RNA transfer.

  • Further understanding on the subcellular localization of imported RNA is required to understand the relationship between its concentration and activity.


Vesicular RNA: When the whole is greater than the sum of the parts
Is RNA the only functional cargo of a given EV population? Does RNA work in concert with the other signaling molecules? How do we interrogate the contribution of the RNA cargo?
  • Further characterization of the complexes in EVs (ribonucleoprotein complexes) will enable more sophisticated reductionist approaches to study extracellular RNA.

  • Strategies to block imported RNA in recipient cells (e.g. synthetic inhibitors) will help distinguish the functions of RNAs from other EV cargos.