Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Examining the evidence for extracellular RNA function in mammals

Abstract

The presence of RNAs in the extracellular milieu has sparked the hypothesis that RNA may play a role in mammalian cell–cell communication. As functional nucleic acids transfer from cell to cell in plants and nematodes, the idea that mammalian cells also transfer functional extracellular RNA (exRNA) is enticing. However, untangling the role of mammalian exRNAs poses considerable experimental challenges. This Review discusses the evidence for and against functional exRNAs in mammals and their proposed roles in health and disease, such as cancer and cardiovascular disease. We conclude with a discussion of the forward-looking prospects for studying the potential of mammalian exRNAs as mediators of cell–cell communication.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Fig. 1: Timeline of exRNA discoveries.
Fig. 2: Model of the life cycle of exRNAs.
Fig. 3: Mugshot of exRNA carriers.
Fig. 4: Standards for demonstrating exRNA function.

References

  1. 1.

    Freedman, J. E. et al. Diverse human extracellular RNAs are widely detected in human plasma. Nat. Commun. 7, 11106 (2016).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  2. 2.

    Max, K. E. A. et al. Human plasma and serum extracellular small RNA reference profiles and their clinical utility. Proc. Natl Acad. Sci. USA 115, E5334–E5343 (2018).

    CAS  PubMed  Article  Google Scholar 

  3. 3.

    Godoy, P. M. et al. Large differences in small RNA composition between human biofluids. Cell Rep. 25, 1346–1358 (2018).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  4. 4.

    Palauqui, J. C., Elmayan, T., Pollien, J. M. & Vaucheret, H. Systemic acquired silencing: transgene-specific post-transcriptional silencing is transmitted by grafting from silenced stocks to non-silenced scions. EMBO J. 16, 4738–4745 (1997).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  5. 5.

    Voinnet, O., Vain, P., Angell, S. & Baulcombe, D. C. Systemic spread of sequence-specific transgene RNA degradation in plants is initiated by localized introduction of ectopic promoterless DNA. Cell 95, 177–187 (1998).

    CAS  PubMed  Article  Google Scholar 

  6. 6.

    Voinnet, O. & Baulcombe, D. C. Systemic signalling in gene silencing. Nature 389, 553 (1997).

    CAS  PubMed  Article  Google Scholar 

  7. 7.

    Hamilton, A. J. & Baulcombe, D. C. A species of small antisense RNA in posttranscriptional gene silencing in plants. Science 286, 950–952 (1999).

    CAS  PubMed  Article  Google Scholar 

  8. 8.

    Yoo, B. C. et al. A systemic small RNA signaling system in plants. Plant Cell 16, 1979–2000 (2004).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  9. 9.

    Lucas, W. J. & Lee, J. Y. Plasmodesmata as a supracellular control network in plants. Nat. Rev. Mol. Cell Biol. 5, 712–726 (2004).

    CAS  PubMed  Article  Google Scholar 

  10. 10.

    Vaistij, F. E., Jones, L. & Baulcombe, D. C. Spreading of RNA targeting and DNA methylation in RNA silencing requires transcription of the target gene and a putative RNA-dependent RNA polymerase. Plant Cell 14, 857–867 (2002).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  11. 11.

    Tang, G., Reinhart, B. J., Bartel, D. P. & Zamore, P. D. A biochemical framework for RNA silencing in plants. Genes Dev. 17, 49–63 (2003).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  12. 12.

    Fire, A. et al. Potent and specific genetic interference by double-stranded RNA in Caenorhabditis elegans. Nature 391, 806–811 (1998). A seminal study demonstrating that dsRNA causes systemic gene silencing across tissues and progeny in C. elegans.

    CAS  PubMed  Article  Google Scholar 

  13. 13.

    Smardon, A. et al. EGO-1 is related to RNA-directed RNA polymerase and functions in germ-line development and RNA interference in C. elegans. Curr. Biol. 10, 169–178 (2000).

    CAS  PubMed  Article  Google Scholar 

  14. 14.

    Sijen, T. et al. On the role of RNA amplification in dsRNA-triggered gene silencing. Cell 107, 465–476 (2001).

    CAS  PubMed  Article  Google Scholar 

  15. 15.

    Winston, W. M., Sutherlin, M., Wright, A. J., Feinberg, E. H. & Hunter, C. P. Caenorhabditis elegans SID-2 is required for environmental RNA interference. Proc. Natl Acad. Sci. USA 104, 10565–10570 (2007).

    CAS  PubMed  Article  Google Scholar 

  16. 16.

    Winston, W. M., Molodowitch, C. & Hunter, C. P. Systemic RNAi in C. elegans requires the putative transmembrane protein SID-1. Science 295, 2456–2459 (2002).

    CAS  PubMed  Article  Google Scholar 

  17. 17.

    Sarkies, P. & Miska, E. A. Small RNAs break out: the molecular cell biology of mobile small RNAs. Nat. Rev. Mol. Cell Biol. 15, 525–535 (2014).

    CAS  PubMed  Article  Google Scholar 

  18. 18.

    Bologna, N. G. & Voinnet, O. The diversity, biogenesis, and activities of endogenous silencing small RNAs in Arabidopsis. Annu. Rev. Plant. Biol. 65, 473–503 (2014).

    CAS  PubMed  Article  Google Scholar 

  19. 19.

    Cogoni, C. & Macino, G. Gene silencing in Neurospora crassa requires a protein homologous to RNA-dependent RNA polymerase. Nature 399, 166–169 (1999).

    CAS  PubMed  Article  Google Scholar 

  20. 20.

    Celotto, A. M. & Graveley, B. R. Exon-specific RNAi: a tool for dissecting the functional relevance of alternative splicing. RNA 8, 718–724 (2002).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  21. 21.

    Schwarz, D. S., Hutvagner, G., Haley, B. & Zamore, P. D. Evidence that siRNAs function as guides, not primers, in the Drosophila and human RNAi pathways. Mol. Cell 10, 537–548 (2002).

    CAS  PubMed  Article  Google Scholar 

  22. 22.

    Roignant, J. Y. et al. Absence of transitive and systemic pathways allows cell-specific and isoform-specific RNAi in Drosophila. RNA 9, 299–308 (2003).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  23. 23.

    Tassetto, M., Kunitomi, M. & Andino, R. Circulating immune cells mediate a systemic RNAi-based adaptive antiviral response in Drosophila. Cell 169, 314–325 (2017).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  24. 24.

    Stroun, M. et al. Presence of RNA in the nucleoprotein complex spontaneously released by human lymphocytes and frog auricles in culture. Cancer Res. 38, 3546–3554 (1978).

    CAS  PubMed  Google Scholar 

  25. 25.

    Kolodny, G. M., Culp, L. A. & Rosenthal, L. J. Secretion of RNA by normal and transformed cells. Exp. Cell Res. 73, 65–72 (1972).

    CAS  PubMed  Article  Google Scholar 

  26. 26.

    Stein, P., Svoboda, P., Anger, M. & Schultz, R. M. RNAi: mammalian oocytes do it without RNA-dependent RNA polymerase. RNA 9, 187–192 (2003).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  27. 27.

    Li, W., Koutmou, K. S., Leahy, D. J. & Li, M. Systemic RNA interference deficiency-1 (SID-1) extracellular domain selectively binds long double-stranded RNA and is required for RNA transport by SID-1. J. Biol. Chem. 290, 18904–18913 (2015).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  28. 28.

    Nguyen, T. A. et al. SIDT2 transports extracellular dsRNA into the cytoplasm for innate immune recognition. Immunity 47, 498–509 (2017).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  29. 29.

    Duxbury, M. S., Ashley, S. W. & Whang, E. E. RNA interference: a mammalian SID-1 homologue enhances siRNA uptake and gene silencing efficacy in human cells. Biochem. Biophys. Res. Commun. 331, 459–463 (2005).

    CAS  PubMed  Article  Google Scholar 

  30. 30.

    Elhassan, M. O., Christie, J. & Duxbury, M. S. Homo sapiens systemic RNA interference-defective-1 transmembrane family member 1 (SIDT1) protein mediates contact-dependent small RNA transfer and microRNA-21-driven chemoresistance. J. Biol. Chem. 287, 5267–5277 (2012).

    CAS  PubMed  Article  Google Scholar 

  31. 31.

    Colombo, M., Raposo, G. & Thery, C. Biogenesis, secretion, and intercellular interactions of exosomes and other extracellular vesicles. Annu. Rev. Cell Dev. Biol. 30, 255–289 (2014).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  32. 32.

    Cocucci, E., Racchetti, G. & Meldolesi, J. Shedding microvesicles: artefacts no more. Trends Cell Biol. 19, 43–51 (2009).

    CAS  PubMed  Article  Google Scholar 

  33. 33.

    Raposo, G. & Stoorvogel, W. Extracellular vesicles: exosomes, microvesicles, and friends. J. Cell Biol. 200, 373–383 (2013).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  34. 34.

    Squadrito, M. L. et al. Endogenous RNAs modulate microRNA sorting to exosomes and transfer to acceptor cells. Cell Rep. 8, 1432–1446 (2014).

    CAS  PubMed  Article  Google Scholar 

  35. 35.

    Kariko, K., Ni, H., Capodici, J., Lamphier, M. & Weissman, D. mRNA is an endogenous ligand for Toll-like receptor 3. J. Biol. Chem. 279, 12542–12550 (2004).

    CAS  PubMed  Article  Google Scholar 

  36. 36.

    Fabbri, M. et al. MicroRNAs bind to Toll-like receptors to induce prometastatic inflammatory response. Proc. Natl Acad. Sci. USA 109, E2110–E2116 (2012).

    CAS  PubMed  Article  Google Scholar 

  37. 37.

    Benner, S. A. & Allemann, R. K. The return of pancreatic ribonucleases. Trends Biochem. Sci. 14, 396–397 (1989).

    CAS  PubMed  Article  Google Scholar 

  38. 38.

    Benner, S. A. Extracellular ‘communicator RNA’. FEBS Lett. 233, 225–228 (1988).

    CAS  PubMed  Article  Google Scholar 

  39. 39.

    Arroyo, J. D. et al. Argonaute2 complexes carry a population of circulating microRNAs independent of vesicles in human plasma. Proc. Natl Acad. Sci. USA 108, 5003–5008 (2011). This study demonstrates that a large proportion of extracellular miRNAs are associated with Ago2 and are largely unique relative to those contained in extracellular vesicles.

    CAS  PubMed  Article  Google Scholar 

  40. 40.

    Turchinovich, A., Weiz, L., Langheinz, A. & Burwinkel, B. Characterization of extracellular circulating microRNA. Nucleic Acids Res. 39, 7223–7233 (2011).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  41. 41.

    Jeppesen, D. K. et al. Reassessment of exosome composition. Cell 177, 428–445 (2019). A survey and proposed definitions of extracellular carriers associated with extracellular RNAs.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  42. 42.

    Witwer, K. W. & Thery, C. Extracellular vesicles or exosomes? On primacy, precision, and popularity influencing a choice of nomenclature. J. Extracell. Vesicles 8, 1648167 (2019).

    PubMed  PubMed Central  Article  Google Scholar 

  43. 43.

    Thery, C. et al. Minimal information for studies of extracellular vesicles 2018 (MISEV2018): a position statement of the international society for extracellular vesicles and update of the MISEV2014 guidelines. J. Extracell. Vesicles 7, 1535750 (2018).

    PubMed  PubMed Central  Article  Google Scholar 

  44. 44.

    Baj-Krzyworzeka, M. et al. Tumour-derived microvesicles carry several surface determinants and mRNA of tumour cells and transfer some of these determinants to monocytes. Cancer Immunol. Immunother. 55, 808–818 (2006). Early study demonstrating the presence of mRNAs within extracellular vesicles secreted from cultured human cells.

    CAS  PubMed  Article  Google Scholar 

  45. 45.

    Ratajczak, J. et al. Embryonic stem cell-derived microvesicles reprogram hematopoietic progenitors: evidence for horizontal transfer of mRNA and protein delivery. Leukemia 20, 847–856 (2006). Early study identifying mRNAs within extracellular vesicles secreted from cultured murine and human cultured cells.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  46. 46.

    Valadi, H. et al. Exosome-mediated transfer of mRNAs and microRNAs is a novel mechanism of genetic exchange between cells. Nat. Cell Biol. 9, 654–659 (2007). Pioneering work demonstrating that RNAs are contained within extracellular vesicles, and mRNAs contained within extracellular vesicles retain their ability to be translated.

    CAS  PubMed  Article  Google Scholar 

  47. 47.

    Wei, Z. et al. Coding and noncoding landscape of extracellular RNA released by human glioma stem cells. Nat. Commun. 8, 1145 (2017). A diligent characterization of the different populations of extracellular RNAs contained within extracellular vesicles and RNPs.

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  48. 48.

    Li, Y. et al. Circular RNA is enriched and stable in exosomes: a promising biomarker for cancer diagnosis. Cell Res. 25, 981–984 (2015).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  49. 49.

    Memczak, S., Papavasileiou, P., Peters, O. & Rajewsky, N. Identification and characterization of circular RNAs as a new class of putative biomarkers in human blood. PLoS ONE 10, e0141214 (2015).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  50. 50.

    Chevillet, J. R. et al. Quantitative and stoichiometric analysis of the microRNA content of exosomes. Proc. Natl Acad. Sci. USA 111, 14888–14893 (2014). This study shows that the amount of miRNAs contained within extracellular vesicles is on average less than one miRNA per extracellular vesicle.

    CAS  PubMed  Article  Google Scholar 

  51. 51.

    Williams, Z. et al. Comprehensive profiling of circulating microRNA via small RNA sequencing of cDNA libraries reveals biomarker potential and limitations. Proc. Natl Acad. Sci. USA 110, 4255–4260 (2013). This study demonstrates that extracellular miRNAs are of low abundance within human serum.

    CAS  PubMed  Article  Google Scholar 

  52. 52.

    Zhang, H. et al. Identification of distinct nanoparticles and subsets of extracellular vesicles by asymmetric flow field-flow fractionation. Nat. Cell Biol. 20, 332–343 (2018).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  53. 53.

    Zhang, Q. et al. Transfer of functional cargo in exomeres. Cell Rep. 27, 940–954 (2019).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  54. 54.

    Vickers, K. C., Palmisano, B. T., Shoucri, B. M., Shamburek, R. D. & Remaley, A. T. MicroRNAs are transported in plasma and delivered to recipient cells by high-density lipoproteins. Nat. Cell Biol. 13, 423–433 (2011). This study shows that extracellular miRNAs are associated with lipoproteins, which are altered in disease.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  55. 55.

    Allen, R. M. et al. Bioinformatic analysis of endogenous and exogenous small RNAs on lipoproteins. J. Extracell. Vesicles 7, 1506198 (2018).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  56. 56.

    Harding, C., Heuser, J. & Stahl, P. Receptor-mediated endocytosis of transferrin and recycling of the transferrin receptor in rat reticulocytes. J. Cell Biol. 97, 329–339 (1983).

    CAS  PubMed  Article  Google Scholar 

  57. 57.

    Rimer, J. M. et al. Long-range function of secreted small nucleolar RNAs that direct 2′-O-methylation. J. Biol. Chem. 293, 13284–13296 (2018).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  58. 58.

    Abels, E. R. et al. Glioblastoma-associated microglia reprogramming is mediated by functional transfer of extracellular miR-21. Cell Rep. 28, 3105–3119 (2019).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  59. 59.

    Ridder, K. et al. Extracellular vesicle-mediated transfer of genetic information between the hematopoietic system and the brain in response to inflammation. PLoS Biol. 12, e1001874 (2014).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  60. 60.

    Ridder, K. et al. Extracellular vesicle-mediated transfer of functional RNA in the tumor microenvironment. Oncoimmunology 4, e1008371 (2015).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  61. 61.

    Skog, J. et al. Glioblastoma microvesicles transport RNA and proteins that promote tumour growth and provide diagnostic biomarkers. Nat. Cell Biol. 10, 1470–1476 (2008). An early and thorough characterization of microvesicle-contained exRNAs in primary patient tissue that demonstrates that exRNAs can be used as biomarkers.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  62. 62.

    Tosar, J. P., Cayota, A., Eitan, E., Halushka, M. K. & Witwer, K. W. Ribonucleic artefacts: are some extracellular RNA discoveries driven by cell culture medium components? J. Extracell. Vesicles 6, 1272832 (2017).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  63. 63.

    tom Dieck, S. et al. Direct visualization of newly synthesized target proteins in situ. Nat. Methods 12, 411–414 (2015).

    CAS  PubMed  Article  Google Scholar 

  64. 64.

    Wang, C., Han, B., Zhou, R. & Zhuang, X. Real-time imaging of translation on single mRNA transcripts in live cells. Cell 165, 990–1001 (2016).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  65. 65.

    Yan, X., Hoek, T. A., Vale, R. D. & Tanenbaum, M. E. Dynamics of translation of single mRNA molecules in vivo. Cell 165, 976–989 (2016).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  66. 66.

    Lai, C. P. et al. Visualization and tracking of tumour extracellular vesicle delivery and RNA translation using multiplexed reporters. Nat. Commun. 6, 7029 (2015).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  67. 67.

    de Jong, O. G. et al. A CRISPR-Cas9-based reporter system for single-cell detection of extracellular vesicle-mediated functional transfer of RNA. Nat. Commun. 11, 1113 (2020). A thorough study of artificial sgRNA transfer using a CRISPR–Cas reporter system.

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  68. 68.

    Hinger, S. A. et al. Diverse long RNAs are differentially sorted into extracellular vesicles secreted by colorectal cancer cells. Cell Rep. 25, 715–725 (2018).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  69. 69.

    Kosaka, N. et al. Secretory mechanisms and intercellular transfer of microRNAs in living cells. J. Biol. Chem. 285, 17442–17452 (2010).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  70. 70.

    Zhang, Y. et al. Secreted monocytic miR-150 enhances targeted endothelial cell migration. Mol. Cell 39, 133–144 (2010).

    CAS  PubMed  Article  Google Scholar 

  71. 71.

    Ekstrom, K. et al. Characterization of mRNA and microRNA in human mast cell-derived exosomes and their transfer to other mast cells and blood CD34 progenitor cells. J Extracell. Vesicles https://doi.org/10.3402/jev.v1i0.18389 (2012).

    Article  PubMed  PubMed Central  Google Scholar 

  72. 72.

    Mittelbrunn, M. et al. Unidirectional transfer of microRNA-loaded exosomes from T cells to antigen-presenting cells. Nat. Commun. 2, 282 (2011).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  73. 73.

    Nolte-‘t Hoen, E. N. et al. Deep sequencing of RNA from immune cell-derived vesicles uncovers the selective incorporation of small non-coding RNA biotypes with potential regulatory functions. Nucleic Acids Res. 40, 9272–9285 (2012).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  74. 74.

    Montecalvo, A. et al. Mechanism of transfer of functional microRNAs between mouse dendritic cells via exosomes. Blood 119, 756–766 (2012).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  75. 75.

    Ismail, N. et al. Macrophage microvesicles induce macrophage differentiation and miR-223 transfer. Blood 121, 984–995 (2013).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  76. 76.

    Thomou, T. et al. Adipose-derived circulating miRNAs regulate gene expression in other tissues. Nature 542, 450–455 (2017). A study examining tissue to tissue communication via exRNAs, which used an adipose-specific deletion of Dicer to examine adipose to liver transfer of miRNAs.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  77. 77.

    Xu, B. et al. Neurons secrete miR-132-containing exosomes to regulate brain vascular integrity. Cell Res. 27, 882–897 (2017).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  78. 78.

    Zhang, Y. et al. Exosomes derived from mesenchymal stromal cells promote axonal growth of cortical neurons. Mol. Neurobiol. 54, 2659–2673 (2017).

    CAS  PubMed  Article  Google Scholar 

  79. 79.

    Simeoli, R. et al. Exosomal cargo including microRNA regulates sensory neuron to macrophage communication after nerve trauma. Nat. Commun. 8, 1778 (2017).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  80. 80.

    Ashley, J. et al. Retrovirus-like Gag protein Arc1 binds RNA and traffics across synaptic boutons. Cell 172, 262–274 (2018).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  81. 81.

    Pastuzyn, E. D. et al. The neuronal gene arc encodes a repurposed retrotransposon Gag protein that mediates intercellular RNA transfer. Cell 172, 275–288 (2018).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  82. 82.

    Zhou, W. et al. Cancer-secreted miR-105 destroys vascular endothelial barriers to promote metastasis. Cancer Cell 25, 501–515 (2014).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  83. 83.

    Zhang, L. et al. Microenvironment-induced PTEN loss by exosomal microRNA primes brain metastasis outgrowth. Nature 527, 100–104 (2015).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  84. 84.

    Mitchell, P. S. et al. Circulating microRNAs as stable blood-based markers for cancer detection. Proc. Natl Acad. Sci. USA 105, 10513–10518 (2008).

    CAS  PubMed  Article  Google Scholar 

  85. 85.

    Cha, D. J. et al. KRAS-dependent sorting of miRNA to exosomes. eLife 4, e07197 (2015).

    PubMed  PubMed Central  Article  Google Scholar 

  86. 86.

    Dou, Y. et al. Circular RNAs are down-regulated in KRAS mutant colon cancer cells and can be transferred to exosomes. Sci. Rep. 6, 37982 (2016).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  87. 87.

    Halkein, J. et al. MicroRNA-146a is a therapeutic target and biomarker for peripartum cardiomyopathy. J. Clin. Invest. 123, 2143–2154 (2013).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  88. 88.

    Zhao, Z. et al. Peripheral blood circular RNA hsa_circ_0124644 can be used as a diagnostic biomarker of coronary artery disease. Sci. Rep. 7, 39918 (2017).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  89. 89.

    Akat, K. M. et al. Comparative RNA-sequencing analysis of myocardial and circulating small RNAs in human heart failure and their utility as biomarkers. Proc. Natl Acad. Sci. USA 111, 11151–11156 (2014).

    CAS  PubMed  Article  Google Scholar 

  90. 90.

    Hergenreider, E. et al. Atheroprotective communication between endothelial cells and smooth muscle cells through miRNAs. Nat. Cell Biol. 14, 249–256 (2012).

    CAS  PubMed  Article  Google Scholar 

  91. 91.

    Small, J., Roy, S., Alexander, R. & Balaj, L. Overview of protocols for studying extracellular RNA and extracellular vesicles. Methods Mol. Biol. 1740, 17–21 (2018).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  92. 92.

    Srinivasan, S. et al. Small RNA sequencing across diverse biofluids identifies optimal methods for exRNA isolation. Cell 177, 446–462 (2019).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  93. 93.

    Mateescu, B. et al. Obstacles and opportunities in the functional analysis of extracellular vesicle RNA - an ISEV position paper. J. Extracell. Vesicles 6, 1286095 (2017).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  94. 94.

    Shurtleff, M. J., Temoche-Diaz, M. M., Karfilis, K. V., Ri, S. & Schekman, R. Y-box protein 1 is required to sort microRNAs into exosomes in cells and in a cell-free reaction. eLife 5, e19276 (2016).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  95. 95.

    McKenzie, A. J. et al. KRAS-MEK signaling controls Ago2 sorting into exosomes. Cell Rep. 15, 978–987 (2016).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  96. 96.

    Wei, Z., Batagov, A. O., Carter, D. R. & Krichevsky, A. M. Fetal bovine serum RNA interferes with the cell culture derived extracellular RNA. Sci. Rep. 6, 31175 (2016).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  97. 97.

    Rozowsky, J. et al. exceRpt: a comprehensive analytic platform for extracellular RNA profiling. Cell Syst. 8, 352–357 (2019).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  98. 98.

    Bernstein, E. et al. Dicer is essential for mouse development. Nat. Genet. 35, 215–217 (2003).

    CAS  PubMed  Article  Google Scholar 

  99. 99.

    Padron, A., Iwasaki, S. & Ingolia, N. T. Proximity RNA labeling by APEX-Seq reveals the organization of translation initiation complexes and repressive RNA granules. Mol. Cell 75, 875–887 (2019).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  100. 100.

    Christ, L., Raiborg, C., Wenzel, E. M., Campsteijn, C. & Stenmark, H. Cellular functions and molecular mechanisms of the ESCRT membrane-scission machinery. Trends Biochem. Sci. 42, 42–56 (2017).

    CAS  PubMed  Article  Google Scholar 

  101. 101.

    van Niel, G., D’Angelo, G. & Raposo, G. Shedding light on the cell biology of extracellular vesicles. Nat. Rev. Mol. Cell Biol. 19, 213–228 (2018).

    PubMed  Article  CAS  Google Scholar 

  102. 102.

    Lu, A. et al. Genome-wide interrogation of extracellular vesicle biology using barcoded miRNAs. eLife 7, e41460 (2018).

    PubMed  PubMed Central  Article  Google Scholar 

  103. 103.

    Lajoie, P. & Nabi, I. R. Lipid rafts, caveolae, and their endocytosis. Int. Rev. Cell Mol. Biol. 282, 135–163 (2010).

    CAS  PubMed  Article  Google Scholar 

  104. 104.

    Crescitelli, R. et al. Distinct RNA profiles in subpopulations of extracellular vesicles: apoptotic bodies, microvesicles and exosomes. J Extracell. Vesicles https://doi.org/10.3402/jev.v2i0.20677 (2013).

    Article  PubMed  PubMed Central  Google Scholar 

  105. 105.

    German, J. B., Smilowitz, J. T. & Zivkovic, A. M. Lipoproteins: when size really matters. Curr. Opin. Colloid Interface Sci. 11, 171–183 (2006).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  106. 106.

    Koppers-Lalic, D. et al. Nontemplated nucleotide additions distinguish the small RNA composition in cells from exosomes. Cell Rep. 8, 1649–1658 (2014).

    CAS  PubMed  Article  Google Scholar 

  107. 107.

    Villarroya-Beltri, C. et al. Sumoylated hnRNPA2B1 controls the sorting of miRNAs into exosomes through binding to specific motifs. Nat. Commun. 4, 2980 (2013).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  108. 108.

    Shurtleff, M. J. et al. Broad role for YBX1 in defining the small noncoding RNA composition of exosomes. Proc. Natl Acad. Sci. USA 114, E8987–E8995 (2017).

    CAS  PubMed  Article  Google Scholar 

  109. 109.

    Temoche-Diaz, M. M. et al. Distinct mechanisms of microRNA sorting into cancer cell-derived extracellular vesicle subtypes. eLife 8, e47544 (2019).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

Download references

Acknowledgements

The authors thank C. Hunter, J. Patton, S. Oberlin, H. Valadi, K. Vickers, M. Tewari, X. Breakfield, A. Krichevsky, M. Gruner, K. Weller and D. Knupp for their helpful feedback on the manuscript. This work was supported by grants to M.T.M.: U19CA179513, U01CA217882 and U42OD026647.

Author information

Affiliations

Authors

Contributions

The authors contributed equally to all aspects of the article.

Corresponding author

Correspondence to Michael T. McManus.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Peer review information

Nature Reviews Genetics thanks B. Mateescu, J. G. Patton and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

“Extraordinary claims require extraordinary evidence.”

Carl Sagan

Glossary

Extracellular RNAs

(exRNAs). RNAs that are transcribed within a donor cell that are released into the extracellular space.

Extracellular vesicles

Spheres of phospholipids and proteins secreted from the cell, including small and large extracellular vesicles, that contain various molecular cargoes such as RNA and proteins.

Ribonucleoprotein

(RNP). A complex consisting of an RNA-binding protein that is bound to an RNA that is often recognized by an RNA-binding domain.

Lipoproteins

Particles of proteins and lipids that bind RNA, which are divided into different subtypes based on density, such as high-density lipoprotein and low-density lipoprotein.

RNA interference

(RNAi). A process resulting in small RNAs binding to complementary RNA sequences to suppress their translation or direct their degradation.

microRNAs

(miRNAs). Small non-coding single-stranded RNAs that often regulate gene expression by binding to the 3′ untranslated region of mRNAs to induce translational repression, destabilization or cleavage of the transcript.

Ribonucleases

(RNases). Enzymes that cleave RNA, which are often found in the extracellular environment where they efficiently degrade RNAs that are not protected by other factors such as extracellular vesicles or proteins.

Locked nucleic acids

Artifical nucleoside analogues that are more resistant to degradation than endogenous RNA.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Gruner, H.N., McManus, M.T. Examining the evidence for extracellular RNA function in mammals. Nat Rev Genet (2021). https://doi.org/10.1038/s41576-021-00346-8

Download citation

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing