Small RNAs break out: the molecular cell biology of mobile small RNAs.

Small RNAs that function in a non-cell autonomous manner are becoming increasingly recognized as regulatory molecules with the potential to transmit information between cells, organisms and species. In plants and nematodes, small RNA mobility can be genetically dissected to provide information about the nature of the mobile RNA species, their distribution in the organism and inside cells, as well as the cellular machinery required for mobility, including channel proteins and cellular trafficking factors. Mobile RNAs function in antiviral defence, cell signalling and gene expression regulation, and might also mediate transgenerational epigenetic inheritance.