Possible role for microRNAs as inter-species mediators of epigenetic information in disease pathogenesis: Is the non-coding dark matter of the genome responsible for epigenetic interindividual or interspecies communication?

MicroRNAs are short non-coding RNA molecules involved in the posttranscriptional epigenetic regulation of gene expression. Recent data show that microRNAs can be found in body fluids, and these microRNAs might enter cells giving rise to a hormone like way of action. MicroRNAs released in body fluids might affect other individuals, and there are some data of potential cross-species action of microRNAs, as well. Here, the authors discuss hypotheses concerning the potential pathogenic relevance of interindividual and cross-species action of microRNAs including food-derived microRNAs. Supposing that microRNAs might traverse the gastrointestinal tract, microRNAs might wander via the food-chain and even master regulatory microRNAs might be envisaged that could influence gene expression in a wide range of species and might thereby link different species via common gene expression signatures. Since many microRNA genes are located in the non-protein coding “dark matter” of the genome, a novel function of this “dark matter” is raised regarding interindividual and cross-species epigenetic communication via information transfer by gene products coded by the non-protein coding part of the genome.